ANS-199 AMSAT News Service Special Bulletin - AMSAT Fox-1C Launch Opportunity Announced
AMSAT NEWS SERVICE ANS-199
The AMSAT News Service bulletins are a free, weekly news and infor- mation service of AMSAT North America, The Radio Amateur Satellite Corporation. ANS publishes news related to Amateur Radio in Space including reports on the activities of a worldwide group of Amateur Radio operators who share an active interest in designing, building, launching and communicating through analog and digital Amateur Radio satellites.
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In this edition:
* AMSAT Fox-1C Launch Opportunity Announced
SB SAT @ AMSAT $ANS-199.01 ANS-199 AMSAT News Service Special Bulletin
AMSAT News Service Bulletin 199.01
From AMSAT HQ KENSINGTON, MD.
DATE July 18, 2014 To All RADIO AMATEURS BID: $ANS-199.01
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AMSAT Fox-1C Launch Opportunity Announced
AMSAT is excited to announce a launch opportunity for the Fox-1C Cubesat. AMSAT has teamed with Spaceflight Inc. for integration and launch utilizing Spaceflight's SHERPA system to a sun-synchronous orbit in the third quarter of 2015.
Fox-1C is the third of four Fox-1 series satellites under development, with Fox-1A and RadFXsat/Fox-1B launching through the NASA ELANA program. Fox-1C will carry an FM repeater system for amateur radio for use by radio hams and listeners worldwide. Further details on the satellite and launch will be made available as soon as released.
AMSAT has an immediate need to raise funds to cover both the launch contract and additional materials for construction and testing for Fox-1C. We have set a fundraising goal of $125,000 dollars to cover these expenses over the next 12 months, and allow us to continue to keep amateur radio in space.
Donations may be made through the AMSAT webpage at www.amsat.org, by calling (888) 322-6728 or by mail to the AMSAT office at 10605 Concord Street, Kensington, MD 20895, USA.
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[ANS Thanks AMSAT Board of Directors for the above information]
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/EX
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73, This week's ANS Editor, Joe Spier, K6WAO k6wao at amsat dot org
On 07/18/2014 12:08 PM, Joseph Spier wrote:
Fox-1C is the third of four Fox-1 series satellites under development, with Fox-1A and RadFXsat/Fox-1B launching through the NASA ELANA program. Fox-1C will carry an FM repeater system for amateur radio for use by radio hams and listeners worldwide.
YET ANOTHER analog satellite?
I'm not interested.
Are FM repeater satellites what we all want in orbit? No. Personally, I'd like a Mode J linear transponder in a sun synchronous circular orbit of about 2,000km (if we can't get anything to HEO).
However, the Fox-1A, Fox-1B, Fox-1C, and Fox-1D satellites will eventually lead to the Fox-2 series of satellites. The software designed transponders on board the Fox-2 series will be capable of operating in any number of digital communications modes as well as operating as linear transponders.
AO-51's V/U FM repeater was probably the most popular amateur satellite ever launched. Since the loss of AO-51, AMSAT-NA membership has been declining and is at the point where membership dues alone do not sustain the operating costs of the organization.
Right now, those who are mildly interested in amateur satellites have one satellite to try with a minimal investment: SO-50, which is a satellite that for about half the days of each month is not convenient for most people who work 9-5 and sleep 10-6 and has a weak downlink that is often very difficult for newcomers to hear. Even experienced satellite operators are at times heard to transmit without being able to hear the satellite. With EO-80 (QB50p2), Fox-1A, and Fox-1C hopefully in orbit and operational next year, there will be three easily heard FM satellites (the 9 dB advantage of the 2m downlinks on these satellites will be quite welcome) - two in sun synchronous orbits with relatively consistent pass times. Having those satellites in orbit will mean that more hams get bitten by the satellite bug, join AMSAT, and progress to improving their stations to operate on the linear transponders and, potentially, on digital satellites.
Bottom line - an AMSAT with more satellites in orbit means an AMSAT with more members and that's how we are eventually going to get our ideal satellites in orbit.
73,
Paul, N8HM
On Sat, Jul 19, 2014 at 2:54 PM, Phil Karn karn@ka9q.net wrote:
On 07/18/2014 12:08 PM, Joseph Spier wrote:
Fox-1C is the third of four Fox-1 series satellites under development, with Fox-1A and RadFXsat/Fox-1B launching through the NASA ELANA program. Fox-1C will carry an FM repeater system for amateur radio for use by radio hams and listeners worldwide.
YET ANOTHER analog satellite?
I'm not interested.
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
On 07/19/2014 12:28 PM, Paul Stoetzer wrote:
Are FM repeater satellites what we all want in orbit? No. Personally, I'd like a Mode J linear transponder in a sun synchronous circular orbit of about 2,000km (if we can't get anything to HEO).
Getting a launch opportunity is difficult and expensive. Going digital is not.
However, the Fox-1A, Fox-1B, Fox-1C, and Fox-1D satellites will eventually lead to the Fox-2 series of satellites.
I've been hearing that for years, so please forgive my skepticism. Tony AA2TX himself told me that the analog Fox-1 would be followed by the digital Fox-2. Now we have Fox-1B, Fox-1C, etc, that will also be analog. Forgive me if I feel a little like Achilles racing the tortoise.
I originally joined AMSAT as a technical volunteer in mid 1980, shortly after the Phase III-A launch failure. At the time, AMSAT was doing some very impressive things. Many weren't even being done (or were just starting to be done) in the commercial world: the use of digital command and telemetry links, the use of onboard computers, even the use of ground computers to steer antennas. AMSAT had shown how to locate an emergency beacon by measuring its Doppler shift through a LEO transponder -- which eventually became the SARSAT (Search and Rescue Satellite) payload on many US and Russian LEO weather satellites.
And AMSAT was showing how to do it all on a low budget, with resourcefulness replacing brute force bucks. I was blown away by clever little tricks like spinning a satellite by painting one side of its antennas black and the other side white. This was ham radio at its best.
But that was 1980. It's now 34 years later and we're still doing the same old thing. Meanwhile, mobile phones and the Internet have gone from the exotic to the commonplace -- and I don't have to tell you that they're 100% digital. TV broadcasting is also now digital, few cable TV systems still carry analog signals, and FM and shortwave broadcasting are in a digital transition.
When AMSAT showed how to use an inexpensive hand-held radio to communicate with a satellite, no one had ever seen such a thing. Now digital satellite broadcasting and GPS are nearly universal in cars, hikers and boaters carry SPOT units, and you can buy handheld Iridium phones that will work anywhere on the globe. All digital, of course.
Yet AMSAT continues to fly one analog satellite after another. Why?
All these outside developments have rendered FCC Part 97.1, the Basis and Purpose of the Amateur Service, almost completely obsolete with the singular exception of personal technical education and possibly (some) emergency communications. You want to further international goodwill by talking to people in other countries? Get on the Internet. You want to call your wife to see if she needs anything? Pick up your mobile phone. Further the technical art? Go work for a communications R&D company, because it isn't happening in ham radio anymore.
How are we justifying our spectrum by doing the same thing over and over again, while the world passes us by?
Appealing to "what the members want" doesn't fly with me, because "the members" are a tiny fraction of our potential audience. AMSAT keeps wondering why it can't seem to grow beyond a tiny niche; it need look no further for the reason.
Nor does an appeal to "simplicity" and "cost" carry any weight. Mobile phones, GPS units and Sirius/XM receivers may not be "simple" but that doesn't keep them from being cheap and easy to use. It's their very "complexity" (if you consider "digital" to be complex -- which I don't) that makes them cheap and easy to use.
But by design they are impossible to take apart and learn from. That's where the amateur service can still play a big role. For those who want to learn communications technology by hands-on experimentation there is still simply nothing like it. But where are the amateur digital voice satellite systems to take apart and study? At least a linear transponder could repeat an efficient digital signal, but with the trend to FM even that is no longer possible. If an amateur satellite carries any digital links at all, they are slow and generally limited to telemetry and command, not user-to-user communications. Many don't even use modern modulation and error-correction methods, making them that much harder to access with the small antennas to which most hams are now limited because of CC&Rs and other restrictions.
Far from being "elitist" or "hard to use", digital represents the *only* way forward. It's time to move into the 21st century.
--Phil
Getting a launch opportunity is difficult and expensive. Going digital is
not.
The Fox satellites each have four designated experiment cards. Assemble a team and pitch a proposal for 1D, or 1C if you can do it in a hurry.
73, Drew KO4MA
Hey, this sounds like a terrific opportunity. Not only did AMSAT work on securing our new launch opportunities ... but we are in a position to offer a launch opportunity for a mode/radio/experiment for those who can contribute to amateur radio in space instead of complain about it.
-- 73 de JoAnne K9JKM k9jkm@amsat.org
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Andrew Glasbrenner Sent: Saturday, July 19, 2014 15:43 To: 'Phil Karn'; 'Paul Stoetzer' Cc: amsat-bb@amsat.org Subject: Re: [amsat-bb] ANS-199 AMSAT News Service Special Bulletin - AMSAT Fox-1C Launch Opportunity Announced
Getting a launch opportunity is difficult and expensive. Going
digital is not.
The Fox satellites each have four designated experiment cards. Assemble a team and pitch a proposal for 1D, or 1C if you can do it in a hurry.
73, Drew KO4MA
_______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
On 07/19/2014 01:42 PM, Andrew Glasbrenner wrote:
Getting a launch opportunity is difficult and expensive. Going digital is
not.
The Fox satellites each have four designated experiment cards. Assemble a team and pitch a proposal for 1D, or 1C if you can do it in a hurry.
73, Drew KO4MA
I see no reason to consider a digital satellite an "experiment". Not in 2014, anyway.
Besides, there are several other critical technical hurdles AMSAT must first overcome if we are to do anything interesting with a cubesat. First and foremost among them is
ATTITUDE CONTROL!
Passive bar magnets (or nothing at all, as on ARISSat-1) no longer cut it.
The lack of attitude control forces us to use simple omnidirectional antennas, which in turn keeps us on the crowded and narrow VHF/UHF bands. Worse, there's really no such thing as an "omnidirectional antenna" so our links are plagued by frequent deep fades of unlimited (or at least unknown) duration. Fading has driven every one of my modulation/coding designs for AMSAT telemetry links -- at the expense of making them much less power-efficient.
And "power efficient" means smaller ground antennas, and that means a cheaper and more accessible ground station for the average ham. And THAT means a much larger potential AMSAT membership.
With attitude control, our satellite could use directional antennas on the microwave bands. Directional antennas on higher frequencies mean much better link budgets. You could easily do MEGABITS PER SECOND between LEO and small ground antennas!
A lack of attitude control also plagues thermal design. I learned this from Dick Janssen KD1K's talk at the Symposium a few years ago when he said Fox-1 was the most difficult thermal design he'd ever done for AMSAT. And he's done many.
The problem is that without attitude control you have to cover every available surface with solar cells to guarantee power in any attitude, and solar cells are excellent thermal radiators. Those not facing the earth or the sun face dark sky, radiating away much of the spacecraft's heat. I think he found the equilibrium temperature of a 1U cubesat to be something like -30 or -40 C! The team had no choice but to add resistance heaters to keep the payload (especially the batteries) warm. I can't think of a more painful use of scarce, hard-earned, expensive DC power in space.
Attitude control would completely solve this problem too. In LEO the most common form of attitude control is "local vertical/local horizontal", the mode the ISS uses most of the time. You'd designate one face as nadir-pointing; here you would mount antennas and earth observation cameras. With circularly polarized antennas, you'd still have a degree of freedom around the yaw axis, i.e., you could rotate around the local vertical with no effect on the RF links.
The opposite (zenith-facing) side would have a solar cell, as would one of the four remaining sides. The remaining three would be covered with thermal blankets to insulate the spacecraft from the dark sky they'd face all the time. (Not being a thermal designer I haven't calculated what the new equilibrium temperature would be. But it would obviously solve Dick's problem. He might even have to leave part of those surfaces exposed to radiate excess heat!)
You see how this works? At low beta angles, when the sun is in or near the orbital plane, you point the side with the solar cell forward at local sunrise. At local noon you yaw 180 degrees so the cell faces the sun as it sets behind you. At higher beta angles you simply yaw to track the sun as it passes off to one side; in the limiting case of a beta angle of 90 degrees (continuous sunlight) you'd simply keep the spacecraft yawed at a constant +90 or -90 degrees.
And you only need to buy two expensive solar cells instead of (nearly) six.
Attitude control systems for cubesats already exist. You can buy one for $200,000 from suppliers serving the burgeoning cubesat community (most of which considers ham radio completely irrelevant except as a source of free spectrum). But that's not the AMSAT way. I am sure that if we brought enough clever minds together (along with some good mechanical engineers and craftsmen) we could design and build our own attitude control system for far less.
But to attract all those people to do all these new (in AMSAT) things, you have to stop doing the same old thing over and over. You have to make a conscious choice to stand back and actually innovate at the systems level instead of relegating digital to the status of an "experiment" on the same old primitive spacecraft bus.
Look at all the attention and excitement generated by the ISEE-3 Reboot project. That's because they're actually doing something new and challenging. They say they've gotten donations from many people far outside the usual "space groupie" segment of the population. It's also caught the imagination of at least a few hams, including the AMSAT-DL gang which has been using their 20m Bochum dish to receive telemetry. And me, as I wrote the software they're using to demodulate and FEC-decode the ISEE-3 signal.
Pose a really interesting technical challenge and make it clear you really want it to happen, and the necessary technical volunteers will come out of the woodwork. Do the same old thing over and over, and you'll find it hard to even pay people to do the work.
--Phil
The lack of attitude control forces us to use simple omnidirectional
antennas, which in turn keeps us on the crowded and narrow VHF/UHF bands. Worse, there's really no such thing as an "omnidirectional antenna" so our links are plagued by frequent deep fades of unlimited (or at least unknown) duration. Fading has driven every one of my modulation/coding designs for AMSAT telemetry links -- at the expense of making them much less power-efficient.
And "power efficient" means smaller ground antennas, and that means a cheaper and more accessible ground station for the average ham. And THAT means a much larger potential AMSAT membership.
With attitude control, our satellite could use directional antennas on the microwave bands. Directional antennas on higher frequencies mean much better link budgets.
Yes, but with who? 95% of everyone in view is more than 45 degrees OUT of the main beam. Directional antennas have zero value on LEO birds that need to serve everyone in view at the same time. And if you only serve those in the main beam, then the duration is under 1 minute.
A lack of attitude control also plagues thermal design.... I think he found the equilibrium temperature of a 1U cubesat to be something like -30 or -40 C!
I cannot believe that. The equilibrium of a nominally black (solar panels on all sides) spacecraft is something like about 0 to 30 C (32F to 90F) a very benign operational range. The only time you DO have thermal issues is when you DO have attitude control and have things that are not equally over time seeing the sun and dark sky.
PCSAT is now 13 years in orbit and the above range is what it sees. And that range is over a 2 month period. THe orbit-by-orbit temperature changes are less than +/- 10 degrees C. The extremes are due to the "seasons" of the orbit. When it is seeing eclipses it averages to about 10C and when it is in full sun for weeks at a time, it gets up to 30 C (90F)
I do agree that attitude control is nice to have, but my point is that it only makes the thermal problem much worse and that "gain" is of no value for a LEO where it must see everyone in a footprint at the same time. (Remmebr you cannot have wide beamwidth and gain at the same time).
Gain for HEO's of course is another matter! (think AO-10, AO-13 and AO-40)
Bob, WB4APR
On 07/19/2014 09:23 PM, Robert Bruninga wrote:
I cannot believe that. The equilibrium of a nominally black (solar panels on all sides) spacecraft is something like about 0 to 30 C (32F to 90F) a very benign operational range. The only time you DO have thermal issues is when you DO have attitude control and have things that are not equally over time seeing the sun and dark sky.
See Dick's paper for the details; I'm just quoting his results. I know the basic physics of heat transfer in space but I would never call myself an expert. He is.
But I can do a back-of-the-envelope calculation that tells me he's right.
The solar cells they're using have an absorptivity and emissivity that is both 0.98, as I recall, so a cubesat covered with them is essentially a perfect blackbody.
A blackbody cube with one face normal to the sun at 1 AU will reach an equilibrium temperature of -21.35 C. The problem is that the ratio of radiating area to absorbing area for a cube is 6:1 (with the sun normal to one surface). A sphere would be warmer because its ratio of radiating to absorbing area is only 4:1. A thin flat plate normal to the sun (like a solar wing) would be even warmer -- 2:1.
And that -21.35 C figure is for continuous sunlight. Throw in eclipses and things get much worse. Yes, it would be a little better when the sun shines on a corner rather than normal to a face, and Earth albedo and IR radiation will warm things a little, but not enough to matter.
--Phil
PS: Temperature of 10 cm blackbody cube at 1 AU:
Area facing sun: .01 m^2 Solar constant: 1367.5 W/m^2 Absorbed power = 13.675 W
Total radiating area: .06 m^2 Emissivity = 1.0 (perfect blackbody) Stefan-Boltzmann constant = 5.6703e-8 W/(m^2K^4)
T = (13.675 W / (5.6703e-8 * 1.0 * .06)) ** (1/4) = 251.8K == -21.35 C
Hi All,
I could start writing all kinds of angry E-mails, but I have always resisted to reply on these kind of threads.
I'm glad the AMSAT-BB is not reflecting the great community that is amateur radio and the many exciting things we are doing for our community to keep communications alive.
I will go back to work on SDR transponders, D-ATV cubesats, CODEC2 speech downlinks and FUNcube linear transponder improvements, but you guys are not interested I hear, so I will shut up.
Wouter PA3WEG
On Sun, Jul 20, 2014 at 12:59 PM, Phil Karn karn@ka9q.net wrote:
On 07/19/2014 09:23 PM, Robert Bruninga wrote:
I cannot believe that. The equilibrium of a nominally black (solar
panels
on all sides) spacecraft is something like about 0 to 30 C (32F to 90F) a very benign operational range. The only time you DO have thermal issues
is
when you DO have attitude control and have things that are not equally
over
time seeing the sun and dark sky.
See Dick's paper for the details; I'm just quoting his results. I know the basic physics of heat transfer in space but I would never call myself an expert. He is.
But I can do a back-of-the-envelope calculation that tells me he's right.
The solar cells they're using have an absorptivity and emissivity that is both 0.98, as I recall, so a cubesat covered with them is essentially a perfect blackbody.
A blackbody cube with one face normal to the sun at 1 AU will reach an equilibrium temperature of -21.35 C. The problem is that the ratio of radiating area to absorbing area for a cube is 6:1 (with the sun normal to one surface). A sphere would be warmer because its ratio of radiating to absorbing area is only 4:1. A thin flat plate normal to the sun (like a solar wing) would be even warmer -- 2:1.
And that -21.35 C figure is for continuous sunlight. Throw in eclipses and things get much worse. Yes, it would be a little better when the sun shines on a corner rather than normal to a face, and Earth albedo and IR radiation will warm things a little, but not enough to matter.
--Phil
PS: Temperature of 10 cm blackbody cube at 1 AU:
Area facing sun: .01 m^2 Solar constant: 1367.5 W/m^2 Absorbed power = 13.675 W
Total radiating area: .06 m^2 Emissivity = 1.0 (perfect blackbody) Stefan-Boltzmann constant = 5.6703e-8 W/(m^2K^4)
T = (13.675 W / (5.6703e-8 * 1.0 * .06)) ** (1/4) = 251.8K == -21.35 C _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
I must quickly point out some real data:
www.warehouse.funcube.org.uk
Which shows an equilibrium of around +20 degrees after 64 minutes of sunlight. Black solar cells on a black surface but some polished Aluminium in the structure.
During eclipse, The Earth facing side begins to increase in temperature at around -16 degrees, but then cools down rapidly as the cube rotates. The temperature is still heading down rapidly as it exits eclipse after 34 minutes and at around -24C on the outside surfaces.
Thanks
David
-----Original Message----- From: Phil Karn karn@ka9q.net To: amsat-bb amsat-bb@amsat.org Sent: Sun, 20 Jul 2014 11:59 Subject: Re: [amsat-bb] ANS-199 AMSAT News Service Special Bulletin - AMSAT Fox-1C Launch Opportunity Announced
On 07/19/2014 09:23 PM, Robert Bruninga wrote:
I cannot believe that. The equilibrium of a nominally black (solar panels on all sides) spacecraft is something like about 0 to 30 C (32F to 90F) a very benign operational range. The only time you DO have thermal issues is when you DO have attitude control and have things that are not equally over time seeing the sun and dark sky.
See Dick's paper for the details; I'm just quoting his results. I know the basic physics of heat transfer in space but I would never call myself an expert. He is.
But I can do a back-of-the-envelope calculation that tells me he's right.
The solar cells they're using have an absorptivity and emissivity that is both 0.98, as I recall, so a cubesat covered with them is essentially a perfect blackbody.
A blackbody cube with one face normal to the sun at 1 AU will reach an equilibrium temperature of -21.35 C. The problem is that the ratio of radiating area to absorbing area for a cube is 6:1 (with the sun normal to one surface). A sphere would be warmer because its ratio of radiating to absorbing area is only 4:1. A thin flat plate normal to the sun (like a solar wing) would be even warmer -- 2:1.
And that -21.35 C figure is for continuous sunlight. Throw in eclipses and things get much worse. Yes, it would be a little better when the sun shines on a corner rather than normal to a face, and Earth albedo and IR radiation will warm things a little, but not enough to matter.
--Phil
PS: Temperature of 10 cm blackbody cube at 1 AU:
Area facing sun: .01 m^2 Solar constant: 1367.5 W/m^2 Absorbed power = 13.675 W
Total radiating area: .06 m^2 Emissivity = 1.0 (perfect blackbody) Stefan-Boltzmann constant = 5.6703e-8 W/(m^2K^4)
T = (13.675 W / (5.6703e-8 * 1.0 * .06)) ** (1/4) = 251.8K == -21.35 C _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Hi Phil,
The reality is, even with no battery heater on FUNcube-1 we seem to have an acceptable battery temperature of between 0 and +5C. The temp sensor is, of course, actually external to the battery itself.
Our orbit is sun synchronous so we "suffer" eclipses for approx 33% of the orbit ..but then we are relatively close to the earth!
I would also comment that any active attitude control system will consume power...which we don't have much of..
Probably, if you need continuous operation of the radio system, then a 2U with deployable solar panels is the minimum configuration for a CubeSat operating on microwave bands with an active attitude control system.
best 73
Graham G3VZV
-----Original Message----- From: g0mrf@aol.com Sent: Sunday, July 20, 2014 3:41 PM To: karn@ka9q.net ; amsat-bb@amsat.org ; bruninga@usna.edu Subject: Re: [amsat-bb] ANS-199 AMSAT News Service Special Bulletin - AMSAT Fox-1C Launch Opportunity Announced
I must quickly point out some real data:
www.warehouse.funcube.org.uk
Which shows an equilibrium of around +20 degrees after 64 minutes of sunlight. Black solar cells on a black surface but some polished Aluminium in the structure.
During eclipse, The Earth facing side begins to increase in temperature at around -16 degrees, but then cools down rapidly as the cube rotates. The temperature is still heading down rapidly as it exits eclipse after 34 minutes and at around -24C on the outside surfaces.
Thanks
David
-----Original Message----- From: Phil Karn karn@ka9q.net To: amsat-bb amsat-bb@amsat.org Sent: Sun, 20 Jul 2014 11:59 Subject: Re: [amsat-bb] ANS-199 AMSAT News Service Special Bulletin - AMSAT Fox-1C Launch Opportunity Announced
On 07/19/2014 09:23 PM, Robert Bruninga wrote:
I cannot believe that. The equilibrium of a nominally black (solar panels on all sides) spacecraft is something like about 0 to 30 C (32F to 90F) a very benign operational range. The only time you DO have thermal issues is when you DO have attitude control and have things that are not equally over time seeing the sun and dark sky.
See Dick's paper for the details; I'm just quoting his results. I know the basic physics of heat transfer in space but I would never call myself an expert. He is.
But I can do a back-of-the-envelope calculation that tells me he's right.
The solar cells they're using have an absorptivity and emissivity that is both 0.98, as I recall, so a cubesat covered with them is essentially a perfect blackbody.
A blackbody cube with one face normal to the sun at 1 AU will reach an equilibrium temperature of -21.35 C. The problem is that the ratio of radiating area to absorbing area for a cube is 6:1 (with the sun normal to one surface). A sphere would be warmer because its ratio of radiating to absorbing area is only 4:1. A thin flat plate normal to the sun (like a solar wing) would be even warmer -- 2:1.
And that -21.35 C figure is for continuous sunlight. Throw in eclipses and things get much worse. Yes, it would be a little better when the sun shines on a corner rather than normal to a face, and Earth albedo and IR radiation will warm things a little, but not enough to matter.
--Phil
PS: Temperature of 10 cm blackbody cube at 1 AU:
Area facing sun: .01 m^2 Solar constant: 1367.5 W/m^2 Absorbed power = 13.675 W
Total radiating area: .06 m^2 Emissivity = 1.0 (perfect blackbody) Stefan-Boltzmann constant = 5.6703e-8 W/(m^2K^4)
T = (13.675 W / (5.6703e-8 * 1.0 * .06)) ** (1/4) = 251.8K == -21.35 C _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
_______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Yes, that is exactly the temperatures of PCSAT in similar eclipse periods.
IE, anything more or less uniformly BLACK (solar panels) no matter the shape and size will assume that average temperature with 35% eclipses. This is because the absorbtivity and emissivity of "black" are both 0.9. (assuming there is some thermal communication within the spacecraft to move the heat evenly (such as an aluminum frame)...
If it ever gets into a 0% eclipse period (full sun) those average temps will rise to about 30-40C. Still safe for most electronics.
Bob, WB4APR
On Sun, Jul 20, 2014 at 11:09 AM, Graham Shirville < g.shirville@btinternet.com> wrote:
Hi Phil,
The reality is, even with no battery heater on FUNcube-1 we seem to have an acceptable battery temperature of between 0 and +5C. The temp sensor is, of course, actually external to the battery itself.
Our orbit is sun synchronous so we "suffer" eclipses for approx 33% of the orbit ..but then we are relatively close to the earth!
I would also comment that any active attitude control system will consume power...which we don't have much of..
Probably, if you need continuous operation of the radio system, then a 2U with deployable solar panels is the minimum configuration for a CubeSat operating on microwave bands with an active attitude control system.
best 73
Graham G3VZV
-----Original Message----- From: g0mrf@aol.com Sent: Sunday, July 20, 2014 3:41 PM To: karn@ka9q.net ; amsat-bb@amsat.org ; bruninga@usna.edu Subject: Re: [amsat-bb] ANS-199 AMSAT News Service Special Bulletin - AMSAT Fox-1C Launch Opportunity Announced
I must quickly point out some real data:
www.warehouse.funcube.org.uk
Which shows an equilibrium of around +20 degrees after 64 minutes of sunlight. Black solar cells on a black surface but some polished Aluminium in the structure.
During eclipse, The Earth facing side begins to increase in temperature at around -16 degrees, but then cools down rapidly as the cube rotates. The temperature is still heading down rapidly as it exits eclipse after 34 minutes and at around -24C on the outside surfaces.
Thanks
David
-----Original Message----- From: Phil Karn karn@ka9q.net To: amsat-bb amsat-bb@amsat.org Sent: Sun, 20 Jul 2014 11:59 Subject: Re: [amsat-bb] ANS-199 AMSAT News Service Special Bulletin - AMSAT Fox-1C Launch Opportunity Announced
On 07/19/2014 09:23 PM, Robert Bruninga wrote:
I cannot believe that. The equilibrium of a nominally black (solar panels
on all sides) spacecraft is something like about 0 to 30 C (32F to 90F) a very benign operational range. The only time you DO have thermal issues is when you DO have attitude control and have things that are not equally over time seeing the sun and dark sky.
See Dick's paper for the details; I'm just quoting his results. I know the basic physics of heat transfer in space but I would never call myself an expert. He is.
But I can do a back-of-the-envelope calculation that tells me he's right.
The solar cells they're using have an absorptivity and emissivity that is both 0.98, as I recall, so a cubesat covered with them is essentially a perfect blackbody.
A blackbody cube with one face normal to the sun at 1 AU will reach an equilibrium temperature of -21.35 C. The problem is that the ratio of radiating area to absorbing area for a cube is 6:1 (with the sun normal to one surface). A sphere would be warmer because its ratio of radiating to absorbing area is only 4:1. A thin flat plate normal to the sun (like a solar wing) would be even warmer -- 2:1.
And that -21.35 C figure is for continuous sunlight. Throw in eclipses and things get much worse. Yes, it would be a little better when the sun shines on a corner rather than normal to a face, and Earth albedo and IR radiation will warm things a little, but not enough to matter.
--Phil
PS: Temperature of 10 cm blackbody cube at 1 AU:
Area facing sun: .01 m^2 Solar constant: 1367.5 W/m^2 Absorbed power = 13.675 W
Total radiating area: .06 m^2 Emissivity = 1.0 (perfect blackbody) Stefan-Boltzmann constant = 5.6703e-8 W/(m^2K^4)
T = (13.675 W / (5.6703e-8 * 1.0 * .06)) ** (1/4) = 251.8K == -21.35 C _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
On 07/20/2014 08:09 AM, Graham Shirville wrote:
Hi Phil,
The reality is, even with no battery heater on FUNcube-1 we seem to have an acceptable battery temperature of between 0 and +5C. The temp sensor is, of course, actually external to the battery itself.
You must be using different solar cells, or perhaps you don't fully cover the exterior with them. I did wonder why Dick didn't consider the same thing for Fox-1; if you're going to dissipate some of the electricity they generate in resistance heaters, you might consider covering less than 100% of the surface with them and cover the remainder with thermal blankets. I haven't worked out this alternative, and as I said I'm not a thermal design expert.
At the time I believe Dick said he was considering gold plating the inside surfaces of the cells to isolate them from the interior, since there was little or no room for any other kind of insulation. In that case you would no longer have thermal equilibrium and my back of the envelope calculation would not apply.
There's one additional factor to make things worse, though I haven't quantified it. Space-rated solar cells are getting good enough that the spacecraft as a whole actually converts a non-insignificant amount of the sunlight hitting it into transmitted RF, and that power is no longer available to keep the spacecraft warm. So it gets even colder.
That's right, turn on the transmitter and the spacecraft cools down -- at least if the solar cells are not thermally isolated from the interior.
Our orbit is sun synchronous so we "suffer" eclipses for approx 33% of the orbit ..but then we are relatively close to the earth!
Yes, and you do pick up longwave IR from the earth even on the night side. According to my copy of "Spacecraft Thermal Control Handbook Vol 1", this is only about 150 W/m^2 in LEO, so it doesn't seem to help that much. Albedo is greater (about 250 W/m^2) but only over the subsolar point so again it doesn't help much on average.
It *would* help a lot if you could insulate those sides facing dark sky, and that's where attitude control comes in.
During his after-dinner talk at the AMSAT Symposium a couple of years ago, astronaut Sam Durrance described just how cold that dark sky is. He flew with Ron Parise on the Astro-1 and -2 shuttle missions. Because these were astronomy missions, the shuttle payload bay spent long periods pointed at dark sky, as opposed to its usual practice (when not docked to the ISS) of keeping the payload bay toward earth. He said it got so cold near the orbiter's overhead windows that they had to don sweaters.
But the real issue that Dick drove home to me in his talk was just how variable the thermal situation was when you can't control your attitude and when eclipse durations and beta angles vary so drastically over a year. Even if you could design for acceptable equilibrium temperatures under one set of conditions you can't maintain them as they vary so much.
I would also comment that any active attitude control system will consume power...which we don't have much of..
Yes, but active attitude control lets you keep those panels pointed at the sun to produce much more power on average. Only two of the six surfaces of a 1U cubesat even need solar cells with my stabilized design. You can do much better with deployable, steerable panels -- which pretty much demands active attitude control.
The fact that virtually every military, commercial and scientific spacecraft launched today is three-axis stabilized should settle the question: active attitude control is the way to go, if you can do it.
--Phil
Thanks for the FOX-1 thermal data! (36 C variation per orbit)
PCSAT (10" cubesat) has less than 15C variation on its sides with its 0.6 RPM spin and 35% eclipses, but this is because the sides are made of 1/8" aluminum and have a huge 1/8" center deck that is thermally connected to the center of each face, providing great communication from the sun side to the other sides. Notice, this was a HEAVY satellite because we just overbuilt it to make sure the heat was evenly distributed.
On Sun, Jul 20, 2014 at 10:41 AM, g0mrf@aol.com wrote:
I must quickly point out some real data:
www.warehouse.funcube.org.uk
Which shows an equilibrium of around +20 degrees after 64 minutes of sunlight. Black solar cells on a black surface but some polished Aluminium in the structure.
During eclipse, The Earth facing side begins to increase in temperature at around -16 degrees, but then cools down rapidly as the cube rotates. The temperature is still heading down rapidly as it exits eclipse after 34 minutes and at around -24C on the outside surfaces.
Thanks
David
-----Original Message----- From: Phil Karn karn@ka9q.net To: amsat-bb amsat-bb@amsat.org Sent: Sun, 20 Jul 2014 11:59 Subject: Re: [amsat-bb] ANS-199 AMSAT News Service Special Bulletin - AMSAT Fox-1C Launch Opportunity Announced
On 07/19/2014 09:23 PM, Robert Bruninga wrote:
I cannot believe that. The equilibrium of a nominally black (solar panels on all sides) spacecraft is something like about 0 to 30 C (32F to 90F) a very benign operational range. The only time you DO have thermal issues is when you DO have attitude control and have things that are not equally over time seeing the sun and dark sky.
See Dick's paper for the details; I'm just quoting his results. I know the basic physics of heat transfer in space but I would never call myself an expert. He is.
But I can do a back-of-the-envelope calculation that tells me he's right.
The solar cells they're using have an absorptivity and emissivity that is both 0.98, as I recall, so a cubesat covered with them is essentially a perfect blackbody.
A blackbody cube with one face normal to the sun at 1 AU will reach an equilibrium temperature of -21.35 C. The problem is that the ratio of radiating area to absorbing area for a cube is 6:1 (with the sun normal to one surface). A sphere would be warmer because its ratio of radiating to absorbing area is only 4:1. A thin flat plate normal to the sun (like a solar wing) would be even warmer -- 2:1.
And that -21.35 C figure is for continuous sunlight. Throw in eclipses and things get much worse. Yes, it would be a little better when the sun shines on a corner rather than normal to a face, and Earth albedo and IR radiation will warm things a little, but not enough to matter.
--Phil
PS: Temperature of 10 cm blackbody cube at 1 AU:
Area facing sun: .01 m^2 Solar constant: 1367.5 W/m^2 Absorbed power = 13.675 W
Total radiating area: .06 m^2 Emissivity = 1.0 (perfect blackbody) Stefan-Boltzmann constant = 5.6703e-8 W/(m^2K^4)
T = (13.675 W / (5.6703e-8 * 1.0 * .06)) ** (1/4) = 251.8K == -21.35 C _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Hummh,
We get an equilibrium of a cube to be about 55F (13C) when exposed to the sun on one side and all the other sides radiating to cold space. (assuming they are thermally connected).
I wonder why the big difference between our calculations? Bob, WB4aPR
On Sun, Jul 20, 2014 at 6:59 AM, Phil Karn karn@ka9q.net wrote:
On 07/19/2014 09:23 PM, Robert Bruninga wrote:
I cannot believe that. The equilibrium of a nominally black (solar
panels
on all sides) spacecraft is something like about 0 to 30 C (32F to 90F) a very benign operational range. The only time you DO have thermal issues
is
when you DO have attitude control and have things that are not equally
over
time seeing the sun and dark sky.
See Dick's paper for the details; I'm just quoting his results. I know the basic physics of heat transfer in space but I would never call myself an expert. He is.
But I can do a back-of-the-envelope calculation that tells me he's right.
The solar cells they're using have an absorptivity and emissivity that is both 0.98, as I recall, so a cubesat covered with them is essentially a perfect blackbody.
A blackbody cube with one face normal to the sun at 1 AU will reach an equilibrium temperature of -21.35 C. The problem is that the ratio of radiating area to absorbing area for a cube is 6:1 (with the sun normal to one surface). A sphere would be warmer because its ratio of radiating to absorbing area is only 4:1. A thin flat plate normal to the sun (like a solar wing) would be even warmer -- 2:1.
And that -21.35 C figure is for continuous sunlight. Throw in eclipses and things get much worse. Yes, it would be a little better when the sun shines on a corner rather than normal to a face, and Earth albedo and IR radiation will warm things a little, but not enough to matter.
--Phil
PS: Temperature of 10 cm blackbody cube at 1 AU:
Area facing sun: .01 m^2 Solar constant: 1367.5 W/m^2 Absorbed power = 13.675 W
Total radiating area: .06 m^2 Emissivity = 1.0 (perfect blackbody) Stefan-Boltzmann constant = 5.6703e-8 W/(m^2K^4)
T = (13.675 W / (5.6703e-8 * 1.0 * .06)) ** (1/4) = 251.8K == -21.35 C _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
On 07/20/2014 04:58 PM, Robert Bruninga wrote:
Hummh,
We get an equilibrium of a cube to be about 55F (13C) when exposed to the sun on one side and all the other sides radiating to cold space. (assuming they are thermally connected).
I wonder why the big difference between our calculations?
Well, here's mine again:
Stefan-Boltzmann law:
P = A*e*s*T^4, where
P = radiated thermal power in watts A = radiating area in m^2 e = emissivity (dimensionless) s = Stefan-Boltzmann constant: 5.6703e-8 W/(m^2 K^4) T = absolute temperature, kelvins
Solving for T:
T = (P / (A*e*s)) ** (1/4)
The solar constant at 1 AU is 1367.5 W/m^2.
For a 10 cm cube with a = e = 1.0 (blackbody) at 1 AU, with the sun normal on one surface, the absorbed solar thermal power is 1367.5 * .01 = 13.675 W. The radiating surface is six times the absorbing area, or .06 m^2, because it radiates from all six sides (including the side facing the sun).
Plugging into the previous formula:
T = (13.675 / (.06 * 1.0 * 5.6703e-8)) ** (1/4) = 251.8 K = -21.4 C.
Shape matters a very great deal. If you have a blackbody sphere instead of a cube, then the ratio of radiating to absorbing area is only 4:1 instead of 6:1 and the equilibrium temperature rises to 278.7K = +5.5C. A thin flat plate (normal to the sun) is only 2:1 so it's even warmer: 331.38K = +58.2 C (quite toasty).
Here's why we may get different answers. If the sun shines on an edge of the cube instead of normal to one surface, the effective absorbing area increases to sqrt(2) times that of a single face. In that case, the equilibrium temperature increases to 274.5K = +1.4C.
And if the sun shines directly on a corner, the absorbing area becomes (3/4) * sqrt(3) times the area of a single face and the equilibrium temperature is 268.8 K = -4.3C.
But without active attitude control you can't count on *any* specific orientation with respect to the sun, and that's precisely the problem. Even a random average is not necessarily useful if the cube is small (with a low thermal mass) and turning very slowly. Add the ~90 min periodic changes due to eclipses and the much slower periodic changes with the seasons and you can see why the thermal design of a 1U unstabilized cubesat is such a challenging problem.
It's much less of a problem on a larger spacecraft because you don't have to cover every surface with solar cells to maximize power generation, you have a much greater thermal mass to smooth out eclipse (but not seasonal) variations, and you have room for insulation to thermally isolate the external surfaces from the interior components.
--Phil
On 07/19/2014 09:23 PM, Robert Bruninga wrote:
Yes, but with who? 95% of everyone in view is more than 45 degrees OUT of the main beam. Directional antennas have zero value on LEO birds that need to serve everyone in view at the same time. And if you only serve those in the main beam, then the duration is under 1 minute.
Run the link budgets. With reasonable numbers (transmit power 100 mW, range 1,000 km, Rx T = 50K) you only need a few dB of transmit gain to get megabits/sec into a 60 cm DBS dish at 10 GHz. A few dB can easily cover an entire hemisphere, though you might want to squash the pattern to cover it more uniformly (as the GPS satellites do).
The big reason to use attitude control isn't high on-axis antenna gain, it's AVOIDING ANTENNA NULLS. Fading was the major factor in every one of the modulation/coding schemes I've designed for AMSAT. It forces me to use noncoherent (DBPSK) modulation, which even with FEC can cost as much as 4-5dB over coherent BPSK. And that's WITHOUT fading.
Fading is a major headache in coding design because you need to know how long a fade will last to know how long to make your interleaver, and you simply don't know when the spacecraft is unstabilized.
At least I had a good idea with AO-40 because the fading was caused by the spacecraft spin so it was quite predictable. But ARISSat-1 was completely unstabilized and I didn't even have an antenna pattern, so I basically had to pull a maximum fade duration out of my butt.
Same with FOX-1, although it's somewhat less severe in the data-under-voice mode since it's the fade duration relative to the data rate that matters, and the data rate in that mode is so extremely low. But it's a serious problem in the high speed (data only) mode.
And for truly interesting data rates (hundreds of kilobits/sec and up), slow fading is simply intolerable. Attitude stabilized antennas are the only way.
--Phil
On 7/19/2014 3:24 PM, Phil Karn wrote:
However, the Fox-1A, Fox-1B, Fox-1C, and Fox-1D satellites will eventually lead to the Fox-2 series of satellites.
I've been hearing that for years, so please forgive my skepticism. Tony AA2TX himself told me that the analog Fox-1 would be followed by the digital Fox-2. Now we have Fox-1B, Fox-1C, etc, that will also be analog. Forgive me if I feel a little like Achilles racing the tortoise.
Ah, but the plan always was to build four of the Fox-1 series, which is a series of FM analog transponders. Initially, one had a launch and the other three would be "ready to fly" if other opportunities came up. If you're going to spend the time developing them, why not partner for free launches (ELaNa) for more than one? The opportunities for an FM transponder and educational outreach are good. I still have universities looking to partner.
Look at it this way... we are "clearing the shelves" with 3 out of 4 of the intended Fox-1 going to orbit, that really means that we can pretty much call it a day with Fox-1 and move on to Fox-2 now. We will build them all and be done with them all by next May. There will be more than one flying soon, so that we can learn how well they work and apply those lessons to Fox-2 while we're working out the design. It's only the beginning!
Jerry Buxton, NØJY
On 07/19/2014 02:04 PM, Jerry Buxton wrote:
other three would be "ready to fly" if other opportunities came up. If you're going to spend the time developing them, why not partner for free launches (ELaNa) for more than one? The opportunities for an FM transponder and educational outreach are good. I still have universities looking to partner.
Ah, because launches are scarce and expensive, and (re)developing even "the same old thing" consumes much of AMSAT's limited resources. And they're limited because we have yet to interest more than a tiny niche in what we're doing.
It's great to have universities looking to partner, but what do they bring to the table, really? Are we sure they're not just looking for free spectrum?
one flying soon, so that we can learn how well they work and apply those lessons to Fox-2 while we're working out the design.
We already know how well they'll work because we've done the same thing many times before. I hate to say it, but this is no longer "rocket science". The physics is well understood, and those same physics tell us how we could accomplish so much more with our (currently) limited resources.
--Phil
On 7/19/2014 4:50 PM, Phil Karn wrote:
Ah, because launches are scarce and expensive, and (re)developing even "the same old thing" consumes much of AMSAT's limited resources. And they're limited because we have yet to interest more than a tiny niche in what we're doing.
But you arguing about something that has already happened. That makes no sense. Arguing for doing something different, as you also did just a bit ago today, makes sense. Why did the U.S. go back to the moon so many times? I don't know. But we did, and that is done. You could argue now that it had been done before, why did we do it over and over, it was the same old thing. That doesn't change the facts. There is an audience for these FM satellites.
It's great to have universities looking to partner, but what do they bring to the table, really? Are we sure they're not just looking for free spectrum?
Both universities that I am working with are building amateur radio ground stations and interesting the students in becoming hams. We all benefit from that. And some other universities want to fly an ADAC system. We may benefit from that on Fox-2.
one flying soon, so that we can learn how well they work and apply those lessons to Fox-2 while we're working out the design.
We already know how well they'll work because we've done the same thing many times before. I hate to say it, but this is no longer "rocket science". The physics is well understood, and those same physics tell us how we could accomplish so much more with our (currently) limited resources.
We have already learned a great deal from an engineering process perspective, as well as about cramming a lot into a little cubesat. Not rocket science, but certainly for a large all volunteer group a valuable step toward what it will take to build something more complex. I think you over estimate the ability of an all-volunteer workforce, in terms of churning out satellites akin to how a business does it. Amateur radio is a hobby!
You see lemons. I see lemonade. But by all means, let's go for pink lemonade and keep on talking about Fox-2 opportunities while people enjoy what we have already done with the Fox-1 series!
Jerry Buxton, NØJY
On 07/19/2014 03:32 PM, Jerry Buxton wrote:
But you arguing about something that has already happened. That makes no sense.
None of the Fox satellites have yet flown, so they haven't "already happened".
Why did the U.S. go back to the moon so many times? I don't know. But we did, and that is done. You could argue now that it had been done before, why did we do it over and over, it was the same old thing. That doesn't change the facts.
Good analogy, actually. They returned to the moon six times (succeeding on five) because they had excess hardware originally built in the expectation that the first attempts would fail.
And when they did return, they began to do some serious scientific exploration that made it worthwhile. Unfortunately, the public *did* see this as "the same old thing" and Congress quickly withdrew support. As everyone knows, NASA canceled the last three Apollo lunar missions and humans haven't left earth orbit since Apollo 17. (Strictly speaking, even Apollo never left earth orbit, since the moon orbits the earth.)
Yet NASA has always managed to find support for new and interesting things in space even without a human presence. The two keys to public interest have always been 1) exploration and 2) photography.
Apollo certainly did that in its time. More recently, stunning pictures from the surface of Mars and of the moons and backlit rings of Saturn have done much to keep NASA going even as it flails aimlessly in its human program. Sure, the ISS returns some pretty good pictures of earth but so do many robotic spacecraft. And the ISS certainly isn't exploring much of space from only 400 km up. That's why most people don't find it very exciting.
Both universities that I am working with are building amateur radio ground stations and interesting the students in becoming hams. We all benefit from that. And some other universities want to fly an ADAC system. We may benefit from that on Fox-2.
I'm hearing privately that many university groups really are after us for only our spectrum. Or our spectrum plus a ready-made telecommunications system they can use for their purposes without having to worry about the details. I actually don't oppose this categorically as some do, but I insist on *some* benefit back to the amateur service, such as an interesting new communications system to experiment with and to learn from. Some aren't even willing to go that far.
--Phil
I was not going to post but since no one else has, I thought there needs to be a correction to a statement made in case some younger people are reading the thread.
Phil said: "Good analogy, actually. They returned to the moon six times (succeeding on five) because they had excess hardware originally built in the expectation that the first attempts would fail."
There were actually seven manned missions to the moon. Six succeeded. Apollo 13 never landed on the moon and returned to earth safely. Apollo 11,12,14,15,16, and 17 landed. 12 American astronauts walked on the moon.
Sent from Rick's iPad2
I need to receive the foot in mouth award. The key word I read past was "They RETURNED to the moon six..." I'll just go back to the my radios and hide.
Sent from Rick's iPad2
On Jul 20, 2014, at 9:27 AM, Rick Walter wb3csy@gmail.com wrote:
I was not going to post but since no one else has, I thought there needs to be a correction to a statement made in case some younger people are reading the thread.
Phil said: "Good analogy, actually. They returned to the moon six times (succeeding on five) because they had excess hardware originally built in the expectation that the first attempts would fail."
There were actually seven manned missions to the moon. Six succeeded. Apollo 13 never landed on the moon and returned to earth safely. Apollo 11,12,14,15,16, and 17 landed. 12 American astronauts walked on the moon.
Sent from Rick's iPad2
On 07/20/2014 06:27 AM, Rick Walter wrote:
I was not going to post but since no one else has, I thought there needs to be a correction to a statement made in case some younger people are reading the thread.
Phil said: "Good analogy, actually. They returned to the moon six times (succeeding on five) because they had excess hardware originally built in the expectation that the first attempts would fail."
There were actually seven manned missions to the moon. Six succeeded. Apollo 13 never landed on the moon and returned to earth safely. Apollo 11,12,14,15,16, and 17 landed. 12 American astronauts walked on the moon.
That's exactly what I said. They *returned* to the moon (i.e., after landing the first time on Apollo 11) six times, succeeding on five.
Three missions went to the moon without landing: Apollos 8, 10 and 13, for a total of nine Apollo lunar missions. Two more (7 & 9) remained in earth orbit.
--Phil
Hi,
AMSAT can open a Project at KICKSTARTER in technology tag. https://www.kickstarter.com/discover/categories/technology
I saw a lot of project getting 300, 400% more than originally goal. Some of then looks like a stupid idea, but that´s no matter they get the found´s, and what make no sense for me can be a good deal to others :)
Already donated via PAYPAL today, but in my opinion would be great if AMSAT-NA use this way also to get founds for the project!
Please think about it, I believe that donations don´t need to come only from amateur radio satellite operators, but also from everyone who likes electronics, science and technology.
73 Fabiano Moser CT7ABD PY5RX
On Sat, Jul 19, 2014 at 10:50 PM, Phil Karn karn@ka9q.net wrote:
On 07/19/2014 02:04 PM, Jerry Buxton wrote:
other three would be "ready to fly" if other opportunities came up. If you're going to spend the time developing them, why not partner for free launches (ELaNa) for more than one? The opportunities for an FM transponder and educational outreach are good. I still have universities looking to partner.
Ah, because launches are scarce and expensive, and (re)developing even "the same old thing" consumes much of AMSAT's limited resources. And they're limited because we have yet to interest more than a tiny niche in what we're doing.
It's great to have universities looking to partner, but what do they bring to the table, really? Are we sure they're not just looking for free spectrum?
one flying soon, so that we can learn how well they work and apply those lessons to Fox-2 while we're working out the design.
We already know how well they'll work because we've done the same thing many times before. I hate to say it, but this is no longer "rocket science". The physics is well understood, and those same physics tell us how we could accomplish so much more with our (currently) limited resources.
--Phil
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Is there some reason why a digital signal cannot be passed thru an analog/linear transponder? What goes in is what comes out. It seems the lack of transponder bandwidth limits the digital signal experimenter... Maybe that is why commercial transponders on satellites are linear. They can take any modulation and retransmit it : AM, FM, PM or CB
The biggest problem would be the taxi-cabs etc
-----Original Message----- From: Phil Karn Sent: Saturday, July 19, 2014 4:24 PM To: Paul Stoetzer Cc: amsat-bb@amsat.org Subject: Re: [amsat-bb] ANS-199 AMSAT News Service Special Bulletin - AMSAT Fox-1C Launch Opportunity Announced
On 07/19/2014 12:28 PM, Paul Stoetzer wrote:
Are FM repeater satellites what we all want in orbit? No. Personally, I'd like a Mode J linear transponder in a sun synchronous circular orbit of about 2,000km (if we can't get anything to HEO).
Getting a launch opportunity is difficult and expensive. Going digital is not.
John,
If both side have good Doppler correction then it can be done, but you have to choose the correct mode as there are other issues even if the Doppler correction is perfect, especially when the range is changing at its maximum, for example as the satellite passes overhead.
Simon Brown G4ELI http://v2.sdr-radio.com
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of John / NS1Z Sent: 20 July 2014 11:46 To: Phil Karn; Paul Stoetzer Cc: amsat-bb@amsat.org Subject: Re: [amsat-bb] going digital
Is there some reason why a digital signal cannot be passed thru an analog/linear transponder? What goes in is what comes out. It seems the lack of transponder bandwidth limits the digital signal experimenter... Maybe that is why commercial transponders on satellites are linear. They can take any modulation and retransmit it : AM, FM, PM or CB
The biggest problem would be the taxi-cabs etc
-----Original Message----- From: Phil Karn Sent: Saturday, July 19, 2014 4:24 PM To: Paul Stoetzer Cc: amsat-bb@amsat.org Subject: Re: [amsat-bb] ANS-199 AMSAT News Service Special Bulletin - AMSAT Fox-1C Launch Opportunity Announced
On 07/19/2014 12:28 PM, Paul Stoetzer wrote:
Are FM repeater satellites what we all want in orbit? No. Personally, I'd like a Mode J linear transponder in a sun synchronous circular orbit of about 2,000km (if we can't get anything to HEO).
Getting a launch opportunity is difficult and expensive. Going digital is not.
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On 07/20/2014 06:13 AM, Simon Brown wrote:
John,
If both side have good Doppler correction then it can be done, but you have to choose the correct mode as there are other issues even if the Doppler correction is perfect, especially when the range is changing at its maximum, for example as the satellite passes overhead.
Correct, but Doppler actually gets much easier to deal with as the data rate increases. What matters is the *ratio* of the Doppler to the data rate (actually the channel symbol rate, which is usually higher).
At the very high rates possible from LEO on the microwave bands, Doppler on a BPSK signal can be easily tracked by a Costas loop even without orbit prediction steering (though it's still a good idea).
E.g., a relative velocity of 3 km/s at 10 GHz is a Doppler of 100 kHz, considerably less than the symbol rates possible from LEO with even small transmitter powers and antenna gains. Compare this with the numbers for current amateur satellites on VHF and UHF.
--Phil
On 07/20/2014 03:45 AM, John / NS1Z wrote:
Is there some reason why a digital signal cannot be passed thru an analog/linear transponder? What goes in is what comes out. It seems the lack of transponder bandwidth limits the digital signal experimenter... Maybe that is why commercial transponders on satellites are linear. They can take any modulation and retransmit it : AM, FM, PM or CB
You certainly can, and as you point out there are a lot of commercial satellite transponders that do just that. But the most common practice there is to drive the transponder power amplifier into nonlinear saturation to increase its efficiency, and that limits you to a single signal at a time.
Some transponders are shared among multiple simultaneous ground transmitters, and to avoid intermodulation distortion they have to back off on their uplink powers to keep the transponder linear. So besides having to divide the transponder power by N users, the transponder converts DC to RF much less efficiently.
Linear power amplifiers are inherently much less efficient than nonlinear (constant envelope) amplifiers. AMSAT (specifically AMSAT-DL) has done quite a bit of work to increase linear amplifier efficiency, but the techniques tend to be inherently limited in bandwidth (a few hundred kHz max). Much wider bandwidths are available at microwave, and since the link budgets in LEO support them we'd like to use them.
The transponder also repeats a certain amount of uplink noise, though in LEO it isn't hard to saturate the uplink receiver so this isn't much of a factor. But again you tend to be limited to a single user at a time.
So there are considerable advantages to making the satellite itself digital. It can emit a digital modulation designed to be maximally power efficient, and it can do so continuously and at full power (solar panels and batteries permitting). This makes it easy to acquire and track at the ground station.
Spacecraft power efficiency is our prime consideration, as it determines the size and cost of the satellite and the required size of the ground station antenna. And we're trying to minimize that to make our satellite appeal to many more hams.
Multiuser satellite uplinks and downlinks are fundamentally different problems, and in a digital satellite with onboard processing the uplink can easily use a different modulation optimized for the problem. There are several good options: FDMA as in the PACSATs, CDMA (spread spectrum), and TDMA. You can even use more than one in combination, e.g., FDMA or TDMA for the continuous high volume users and CDMA for the intermittent low volume users. The user data streams can be easily multiplexed onto the single downlink stream along with data generated within the satellite itself, such as telemetry, camera images and scientific instruments, or stored for later transmission over a different part of the earth.
--Phil
On 07/20/2014 03:45 AM, John / NS1Z wrote:
Is there some reason why a digital signal cannot be passed thru an analog/linear transponder? What goes in is what comes out.
I forgot to mention that a FM repeater is not a linear transponder. Although FM is constant envelope and a FM RF power amplifier can therefore be made pretty efficient, it will not support a power-efficient modulation mode like coherent BPSK.
Single channel FM is about the worst possible choice for a multiple access satellite uplink. Not only is it analog and noncoherent, but because it's noncoherent it has a capture effect. For a signal to come through at all, it must capture the channel over all noise and interference. This also severely limits the power improvement that can be attained with forward error correction; if the demodulator is below threshold, coding can't help you.
Depending on the demodulator design the capture ratio is somewhere around 10 dB or slightly less, which means that the capturing signal must be at least 10 times as strong as *all* of the interferers combined. This makes it more or less useless unless there's only one user (in which case it's no longer multiple access) or the users are highly disciplined (which is hardly the case in the amateur service).
--Phil
I'm all in favour of new modes and new technology. Pushing the boundaries should be a primary goal. But before any new bird is put in the sky, surely the target audience must be considered?
I'd hazard to guess that the 'average' shack has multi-mode HF capability, along with VHF/UHF FM. Some lesser number of 'average' shacks will have multi-mode VHF/UHF, or could readily acquire that capability without too much expenditure in resources (time, effort, money).
Accept that we want to launch boundary-expanding, technologically advanced satellites if possible. What sort of equipment should we expect to find in the shacks of those hams who are the target audience for these new satellites? How big is this suitably equipped target audience? Big enough to justify having their own satellite? How much time, effort and money will it take to upgrade an 'average' shack (like mine) to meet the requirements of being a part of the target audience?
I'm really pro- and not anti- here. But it may be that any new, digital satellite will have to be developed in parallel with readily available ground station modules (Funcube Dongle Deluxe?) that provide the 'average' ham a path to participation.
Again: Interested to hear roughly what capabilities would be needed to join the gang working the new digital birds, when they fly.
On 07/20/2014 08:00 PM, Gus wrote:
I'd hazard to guess that the 'average' shack has multi-mode HF capability, along with VHF/UHF FM. Some lesser number of 'average' shacks will have multi-mode VHF/UHF, or could readily acquire that capability without too much expenditure in resources (time, effort, money).
When DirecTV designed their satellite broadcast system, did they worry about backward compatibility with the multitude (or so it probably seemed) of existing C-band BUD (Big Ugly Dish) owners? All of whom were then receiving analog FM, I might add.
If not, then why are they still in business?
--Phil
On 07/21/2014 01:57 AM, Phil Karn wrote:
On 07/20/2014 08:00 PM, Gus wrote:
I'd hazard to guess that the 'average' shack has multi-mode HF capability, along with VHF/UHF FM. Some lesser number of 'average' shacks will have multi-mode VHF/UHF, or could readily acquire that capability without too much expenditure in resources (time, effort, money).
When DirecTV designed their satellite broadcast system, did they worry about backward compatibility with the multitude (or so it probably seemed) of existing C-band BUD (Big Ugly Dish) owners? All of whom were then receiving analog FM, I might add.
If not, then why are they still in business?
Probably because they didn't design a satellite. They designed an entire system including ground station components as well as flight hardware. The ground system components were made available such that their target audience was able to upgrade their BUD installations with only reasonable expenditures of time, effort and money. But that's just a guess in my part.
I'd love to chat with you on the new digital hamsat, but if it's going to require I spend $5k+ on hard-to-source, esoteric components and cobble them together with duct tape, then it'll be a while before I'm QRV. So, the first few days after launch those 60 DV channels may be a little quiet.
On 07/21/2014 06:00 AM, Gus wrote:
Probably because they didn't design a satellite. They designed an entire system including ground station components as well as flight hardware. The ground system components were made available such that their target audience was able to upgrade their BUD installations with only reasonable expenditures of time, effort and money. But that's just a guess in my part.
Bingo!
I'd love to chat with you on the new digital hamsat, but if it's going to require I spend $5k+ on hard-to-source, esoteric components and cobble them together with duct tape, then it'll be a while before I'm QRV. So, the first few days after launch those 60 DV channels may be a little quiet.
Next questions:
Does a DirecTV receiving station cost $5K? Are its components hard to source or esoteric?
If not, what makes you think that a digital ground station for an AMSAT satellite should be?
--Phil
On 07/21/2014 01:00 PM, Phil Karn wrote:
Next questions:
Does a DirecTV receiving station cost $5K?
Actually, DirecTV is not available for purchase in my neck of the woods. I can get a system installed, but it wouldn't be my system to fiddle with.
Are its components hard to source or esoteric?
Well, I know where I could nick one, but I'd rather not. Otherwise, I guess I could source one overseas, ship it in, then bow down before the Customs & Excise godlings..... ham gear is 10 + 17.5% but there's no way they'd pass that as ham gear, so probably 115 + 17.5% or worse. That might satisfy Rx needs, but wouldn't include a transmitter.... Does that sound hard to source or esoteric?
If not, what makes you think that a digital ground station for an
AMSAT satellite should be?
Phil, I'm not saying it /should/ be, but that if it is, you won't get many users on the system. So, part of the system design for any such bird had better include design of low cost, easy to find, simple to use hardware that will allow me -- or any other doofus like me -- to get QRV without too much hardship.
I'm not totally unsympathetic to Phil's ideas. They have quite a bit of merit, but clearly AMSAT would also have to develop the ground station equipment in order for it to get a user base that would make it worthwhile. I know this was planned for Eagle, but that was for a HEO which would have many hours a day of visibility for everyone. It's difficult to rationalize spending money on equipment good for a single LEO satellite at this point, especially one that would be as complex as is contemplated here.
I am intrigued by digital operations. My current operating situation prevents me from doing much in that field (I have to carry the radios and hold the antenna, no more hands for a computer). I followed the unsuccessful FreeDV via FO-29 trials between W0DHB and NX9G last year. When the DSTAR parrot repeater that was recently launched is activated, I will certainly borrow a DSTAR radio to try it out. Maybe I'll even buy one!
AMSAT's limiting factors are money and volunteer time. Unfortunately, neither money nor people's time grow on trees. I do think that multiple launches by AMSAT-NA will lead to a resurgence of interest in North America, especially when people realize just how easy Fox is going to be to hear. The launches are also going to occur at a time when solar activity is falling, those with limited antenna situations might look to other aspects of amateur radio while conditions on the higher HF bands are poor. Hopefully those factors will help to provide the resources for more complex projects!
73,
Paul, N8HM
On Mon, Jul 21, 2014 at 5:00 PM, Gus gus@8p6sm.net wrote:
On 07/21/2014 01:00 PM, Phil Karn wrote:
Next questions:
Does a DirecTV receiving station cost $5K?
Actually, DirecTV is not available for purchase in my neck of the woods. I can get a system installed, but it wouldn't be my system to fiddle with.
Are its components hard to source or esoteric?
Well, I know where I could nick one, but I'd rather not. Otherwise, I guess I could source one overseas, ship it in, then bow down before the Customs & Excise godlings..... ham gear is 10 + 17.5% but there's no way they'd pass that as ham gear, so probably 115 + 17.5% or worse. That might satisfy Rx needs, but wouldn't include a transmitter.... Does that sound hard to source or esoteric?
If not, what makes you think that a digital ground station for an AMSAT
satellite should be?
Phil, I'm not saying it /should/ be, but that if it is, you won't get many users on the system. So, part of the system design for any such bird had better include design of low cost, easy to find, simple to use hardware that will allow me -- or any other doofus like me -- to get QRV without too much hardship.
-- Gus 8P6SM The Easternmost Isle
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On 07/21/2014 02:53 PM, Paul Stoetzer wrote:
I'm not totally unsympathetic to Phil's ideas. They have quite a bit of merit, but clearly AMSAT would also have to develop the ground station equipment in order for it to get a user base that would make it worthwhile.
Absolutely. About 14 years ago (i.e., at the beginning of the 21st century) I made a donation to AMSAT earmarked for the development and initial production of the low-cost ground station hardware absolutely necessary to the success of a new digital satellite mode.
I didn't specify any particular digital mode. ANY new satellite mode would qualify as long as it's digital and requires new ground station hardware.
As far as I know (the AMSAT treasurer can comment), my donation is still sitting there.
AMSAT's limiting factors are money and volunteer time. Unfortunately, neither money nor people's time grow on trees.
I think you'll find that the supply of both money and volunteer time depends strongly on what that time and money will be used for. If you think the supply is limited, you might consider being a little more imaginative and ambitious in your goals.
--Phil
Look at what the FunCube guys did!
On 7/21/2014 5:00 PM, Gus wrote:
On 07/21/2014 01:00 PM, Phil Karn wrote:
Next questions:
Does a DirecTV receiving station cost $5K?
Actually, DirecTV is not available for purchase in my neck of the woods. I can get a system installed, but it wouldn't be my system to fiddle with.
Are its components hard to source or esoteric?
Well, I know where I could nick one, but I'd rather not. Otherwise, I guess I could source one overseas, ship it in, then bow down before the Customs & Excise godlings..... ham gear is 10 + 17.5% but there's no way they'd pass that as ham gear, so probably 115 + 17.5% or worse. That might satisfy Rx needs, but wouldn't include a transmitter.... Does that sound hard to source or esoteric?
If not, what makes you think that a digital ground station for an
AMSAT satellite should be?
Phil, I'm not saying it /should/ be, but that if it is, you won't get many users on the system. So, part of the system design for any such bird had better include design of low cost, easy to find, simple to use hardware that will allow me -- or any other doofus like me -- to get QRV without too much hardship.
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On 07/21/2014 06:34 PM, Jim Sanford wrote:
Look at what the FunCube guys did!
Absolutely. Which is why I said in my initial post on this subject:
...any new, digital satellite will have to be developed in parallel
with readily available
ground station modules (Funcube Dongle Deluxe?) that provide the
'average' ham
a path to participation.
Specifically referencing the FCD as an example. The proposal for Phil's 10GHz digital sat would best to include a suitable 10GHz module for ground station use.
On 7/21/2014 5:00 PM, Gus wrote:
On 07/21/2014 01:00 PM, Phil Karn wrote:
Next questions:
Does a DirecTV receiving station cost $5K?
Actually, DirecTV is not available for purchase in my neck of the woods. I can get a system installed, but it wouldn't be my system to fiddle with.
Are its components hard to source or esoteric?
Well, I know where I could nick one, but I'd rather not. Otherwise, I guess I could source one overseas, ship it in, then bow down before the Customs & Excise godlings..... ham gear is 10 + 17.5% but there's no way they'd pass that as ham gear, so probably 115 + 17.5% or worse. That might satisfy Rx needs, but wouldn't include a transmitter.... Does that sound hard to source or esoteric?
If not, what makes you think that a digital ground station for an
AMSAT satellite should be?
Phil, I'm not saying it /should/ be, but that if it is, you won't get many users on the system. So, part of the system design for any such bird had better include design of low cost, easy to find, simple to use hardware that will allow me -- or any other doofus like me -- to get QRV without too much hardship.
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On 07/21/2014 02:00 PM, Gus wrote:
Actually, DirecTV is not available for purchase in my neck of the woods. I can get a system installed, but it wouldn't be my system to fiddle with.
Sorry about that, I was primarily thinking of AMSAT-NA members when I said that. Forget the DirecTV receiver itself and consider their offset-fed Ku-band dishes and 0.7 dB NF LNBs that are readily available on the surplus market. Since DirecTV isn't available in Barbados, paint the dish with the logo of whatever DBS provider you like. Nobody will know the difference.
Phil, I'm not saying it /should/ be, but that if it is, you won't get many users on the system. So, part of the system design for any such bird had better include design of low cost, easy to find, simple to use hardware that will allow me -- or any other doofus like me -- to get QRV without too much hardship.
And here I am with you 100%. So many hams seem to automatically assume, for no good reason, that getting on any new digital mode must necessarily require exotic, expensive and hard to find components and a PhD to use. But the required hardware is now very common, and nearly all of the "complexity" that defines any particular digital communication system these days is implemented almost entirely in software that costs nothing to copy and distribute once written.
The hardware to run said software already exists in virtually every ham shack. Even a low-end general purpose PC is a very capable DSP engine, and this has been true for almost 20 years since Intel introduced MMX, their first set of DSP instructions for the x86 CPU. Since then there has been SSE, SSE2, SSE3, SSSE3, SSE4 and now AVX and AVX2, Advanced Vector Extensions 2.
Here's an example of how far consumer DSP has come just in the time I've been involved with AMSAT. I wrote the demodulation and decoding software now used by the ISEE-3 Reboot Project. It takes the A/D output of an Ettus USRP software defined radio, tracks the RF carrier, demodulates the phase modulation, tracks and demodulates the binary symbols, and performs error correction to produce raw telemetry frames.
ISEE-3 uses a rate 1/2 constraint length k=24 convolutional error correction code. When it was launched in 1978, decoding it took highly specialized, dedicated hardware. Someone here who worked for Linkabit, the manufacturer of that decoding hardware, can probably jump in with the exact cost in millions of dollars and the number of 6' equipment racks it filled.
I am doing all these functions on my laptop using not only the Fano algorithm used by that original Linkabit hardware, but also the Viterbi algorithm, which is better at correcting errors in noise.
The Viterbi algorithm is traditionally used with much shorter codes (k=7, first used on the Voyagers, is still common) because its complexity doubles each time you increase it by one. Had I suggested, in 1978, using it for a k=24 code (taking 131,072 times as much effort as k=7) NASA would have laughed me out of the room.
The same reaction would still have been justified in 1985 when they renamed it ICE and sent it out of earth orbit to the first-ever comet rendezvous, requiring Herculean efforts to overcome the extra path loss.
Now I'm doing it all on my 2-year-old Sony laptop.
That's how much computing power we hams now have in front of us. All we need is a little imagination and vision as to what it makes possible. Instead there seems to be a contest to see who can produce the most objections, valid or otherwise. Is this what the amateur service (or AMSAT) has become?
--Phil
Circumstances in the launch business have driven many groups, including AMSAT, to select the cubesat path to space. Arguing about an on-going project isn't productive but I find discussions about future possibilities interesting. These discussions don't have come at the expense of the current project plan (such as why use FM when this project is already 2 years in progress). We do have future satellites still on the drawing board however!
On the digital radio front Phil makes a very good point ...
So many hams seem to automatically assume, for no good reason, that getting on any new digital mode must necessarily require exotic, expensive and hard to find components and a PhD to use. But the required hardware is now very common, and nearly all of the "complexity" that defines any particular digital communi- cation system these days is implemented almost entirely in soft- ware that costs nothing to copy and distribute once written.
I used free software, my FT-857, small yagis at fixed elevation on a TV rotor to decode Delfi, ARISSat, FUNcube, and 2-way with ISS packet. The computer that does this is a bargain e-machine box with the only modification being additional memory.
The software tools for digital modes on these satellites were a free download. The key to getting the software and your computer to do this requires one additional piece of hardware if you use an external radio. If you use one of the various flavors of Dongles on your computer you only need to add a software audio path (another download).
When thinking of projects to enter into the digital communication world plan on building or buying that digital interface to connect your radio to the soundcard. A few days or weeks spent on the soundcard interface is the key link to enter this exciting other half of satellite operating.
There are many paths to soundcard digital interfaces. Google is your friend. I bet a local dealer would love to sell you a RigBlaster (which many have had good luck with).
I used a less expensive off-the-shelf digital interface from a place called Donner Digital Interfaces. He sells it on the web:
http://www.donnerstore.org/ ... the page is quite an entrepreneur operation, select digital interfaces from the menu on the left side.
http://www.youtube.com/watch?v=34dy21z2I8Y ... shows how to set up a Donner interface to your rig. More good news ... the setup for the digital interface is the same for HF, VHF, or UHF. Once installed you have digital modes on all bands. (On HF I use the JT-65 software which often decodes DX signals so weak I cannot hear them by ear - it was just another software download.) PSK and SSTV were more downloads. But ya gotta install that Soundcard interface to get to this good stuff!
http://www.eham.net/reviews/detail/2073 ... some reviews and discussion to help your research.
-- 73 de JoAnne K9JKM k9jkm@amsat.org Editor, AMSAT Journal
On 07/22/2014 07:27 AM, JoAnne Maenpaa wrote:
When thinking of projects to enter into the digital communication world plan on building or buying that digital interface to connect your radio to the soundcard.
Soundcard interfaces to existing voice radios were a good start, but it's time to move past them. I've designed several modulation and coding schemes to fit existing radios, and their inherently limited bandwidth is a major pain. For ARISSat-1 I agreed to cram everything through a SSB filter, and I'm not doing that again.
Not only does the narrow bandwidth often limit the data rate to much less than what the link budget could actually support, but it enormously aggravates the Doppler problem. It doesn't help that there are no industry-wide standards for SSB phase response or computer tuning, or that every time you retune one (which is often) there is a poorly characterized phase jump.
Doppler is much easier to handle at high data rates because it's the ratio of the symbol rate to the Doppler that matters, not the absolute amount of Doppler.
Now that we have a variety of "pure digital" radio front ends to choose from, it's time to set aside the voice radio + soundcard model. Not only do the SDRs support wider bandwidths but they tend to be considerably smaller, lighter and easier to work with in software. Some, like the Funcube dongle, are even considerably cheaper than conventional radios.
--Phil
This rotor is less than a year old. It works perfectly and is in very good condition. Works with any of the ST series interfaces (ST-1 and ST-3). Selling the rotor, control box, Satellite serial port interfaces ST-3 and SAT668. It really is Plug and Play
$450 plus shipping
Thanks
-----Original Message----- From: Phil Karn Sent: Sunday, July 27, 2014 1:12 AM To: amsat-bb@amsat.org Subject: Re: [amsat-bb] going digital
On 07/22/2014 07:27 AM, JoAnne Maenpaa wrote:
When thinking of projects to enter into the digital communication world plan on building or buying that digital interface to connect your radio to the soundcard.
Soundcard interfaces to existing voice radios were a good start, but it's time to move past them. I've designed several modulation and coding schemes to fit existing radios, and their inherently limited bandwidth is a major pain. For ARISSat-1 I agreed to cram everything through a SSB filter, and I'm not doing that again.
Not only does the narrow bandwidth often limit the data rate to much less than what the link budget could actually support, but it enormously aggravates the Doppler problem. It doesn't help that there are no industry-wide standards for SSB phase response or computer tuning, or that every time you retune one (which is often) there is a poorly characterized phase jump.
Doppler is much easier to handle at high data rates because it's the ratio of the symbol rate to the Doppler that matters, not the absolute amount of Doppler.
Now that we have a variety of "pure digital" radio front ends to choose from, it's time to set aside the voice radio + soundcard model. Not only do the SDRs support wider bandwidths but they tend to be considerably smaller, lighter and easier to work with in software. Some, like the Funcube dongle, are even considerably cheaper than conventional radios.
--Phil
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Which is exactly what the FunCube guys did, and look at what they've wrought!! 73, Jim wb4gcs@amsat.org
When DirecTV designed their satellite broadcast system, did they worry
about backward compatibility with the multitude (or so it probably seemed) of existing C-band BUD (Big Ugly Dish) owners? All of whom were then receiving analog FM, I might add.
If not, then why are they still in business?
Probably because they didn't design a satellite. They designed an entire _/*system*/_ including ground station components as well as flight hardware. The ground system components were made available such that their target audience was able to upgrade their BUD installations with only reasonable expenditures of time, effort and money. But that's just a guess in my part.
I'd love to chat with you on the new digital hamsat, but if it's going to require I spend $5k+ on hard-to-source, esoteric components and cobble them together with duct tape, then it'll be a while before I'm QRV. So, the first few days after launch those 60 DV channels may be a little quiet.
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Since I think it so apropos to our discussion of old vs new technology in AMSAT, I hereby quote in full today's "Borowitz Report" from the New Yorker. Rarely does an item cause me to laugh and feel pain at the same time, but this is one of those cases.
--Phil
[Picture of Buzz Aldrin saluting the flag on the moon during Apollo 11]
MINNEAPOLIS (The Borowitz Report)—Historians studying archival photographs from four decades ago have come to the conclusion that the U.S. must have believed in science at some point.
According to the historian Davis Logsdon, who has been sifting through mounds of photographic evidence at the University of Minnesota, the nation apparently once held the view that investing in science and even math could yield accomplishments that would be a source of national pride.
While Logsdon has not developed a complete theory to explain the United States’ pro-science stance during that era, he attributes some of it to the liberal views of the President at that time, Richard M. Nixon.
Source: http://www.newyorker.com/humor/borowitz-report/nation-apparently-believed-sc...
a different slant-not wanting to enter the fm vs linear ongoing debate or the "easy sat" concept-I started satellites not because it was easy, but because it was hard, and at times still is! This was back in the days of the RS satellites. I believe if you present the challenge they will come. Unfortunately we need the money upfront not after the fact. Perhaps this "incremental" effort toward HEO or MEO is required, however we (AMSAT's) have been doing this for a long time and I think should have had our "ducks lined up" by now. We're a bunch of cleaver people and should develop a method getting the necessary funds for launches. Everything is now "bottom line" driven. We should "just do it". 73 Bob W7LRD Seattle
----- Original Message -----
From: "Paul Stoetzer" n8hm@arrl.net To: "Phil Karn" karn@ka9q.net Cc: amsat-bb@amsat.org Sent: Saturday, July 19, 2014 12:28:12 PM Subject: Re: [amsat-bb] ANS-199 AMSAT News Service Special Bulletin - AMSAT Fox-1C Launch Opportunity Announced
Are FM repeater satellites what we all want in orbit? No. Personally, I'd like a Mode J linear transponder in a sun synchronous circular orbit of about 2,000km (if we can't get anything to HEO).
However, the Fox-1A, Fox-1B, Fox-1C, and Fox-1D satellites will eventually lead to the Fox-2 series of satellites. The software designed transponders on board the Fox-2 series will be capable of operating in any number of digital communications modes as well as operating as linear transponders.
AO-51's V/U FM repeater was probably the most popular amateur satellite ever launched. Since the loss of AO-51, AMSAT-NA membership has been declining and is at the point where membership dues alone do not sustain the operating costs of the organization.
Right now, those who are mildly interested in amateur satellites have one satellite to try with a minimal investment: SO-50, which is a satellite that for about half the days of each month is not convenient for most people who work 9-5 and sleep 10-6 and has a weak downlink that is often very difficult for newcomers to hear. Even experienced satellite operators are at times heard to transmit without being able to hear the satellite. With EO-80 (QB50p2), Fox-1A, and Fox-1C hopefully in orbit and operational next year, there will be three easily heard FM satellites (the 9 dB advantage of the 2m downlinks on these satellites will be quite welcome) - two in sun synchronous orbits with relatively consistent pass times. Having those satellites in orbit will mean that more hams get bitten by the satellite bug, join AMSAT, and progress to improving their stations to operate on the linear transponders and, potentially, on digital satellites.
Bottom line - an AMSAT with more satellites in orbit means an AMSAT with more members and that's how we are eventually going to get our ideal satellites in orbit.
73,
Paul, N8HM
On Sat, Jul 19, 2014 at 2:54 PM, Phil Karn karn@ka9q.net wrote:
On 07/18/2014 12:08 PM, Joseph Spier wrote:
Fox-1C is the third of four Fox-1 series satellites under development, with Fox-1A and RadFXsat/Fox-1B launching through the NASA ELANA program. Fox-1C will carry an FM repeater system for amateur radio for use by radio hams and listeners worldwide.
YET ANOTHER analog satellite?
I'm not interested.
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Getting the $125,000 to launch a 1U cubesat into LEO should be plenty doable, but raising $10-$15 million for a launch to HEO?
AMSAT-DL has been raising funds for P3E now for nearly a decade. If they thought they had a chance of success, I'm sure there'd be a much more public push to raise those funds.
Unfortunately, there are not enough amateur radio operators interested in the amateur satellite program to put up that kind of money. Million dollar DXpeditions are doable because of the broad interest among the amateur radio community in funding those projects. A good number of amateur radio operators are only vaguely aware of the amateur satellite program and consider it to be quite esoteric. Heck, on the extremely rare occasion that the amateur satellite program merits a mention in a QST column these days, it's often in WB8IMY's "Eclectic Technology" column. That, unfortunately, shows you how the amateur radio community as a whole views the amateur satellite program.
The bottom line is that AMSAT-NA needs a significant boost in membership and visibility and that boost needs to be soon. Putting two satellites into orbit that nearly every single ham will be able to easily hear (even a $30 Baofeng and it's stock duck should hear high passes of the Fox-1 satellites) along with the accompanying publicity should provide that boost. ARISSat-1 and the heavy publicity in QST and other amateur radio news sources is what got me involved in amateur satellites, though it would take me another two years before I really got into it seriously. Now I've really been bitten by the bug: 293 grids, 48 states, 4 Canadian provinces, and 27 DXCCs in my log plus I've done two public demonstrations of amateur satellites and assisted the AMSAT booth and demo station at Dayton. That's all because of a project derided by many on this board as a waste of AMSAT's time and resources!
73,
Paul, N8HM
On Sun, Jul 20, 2014 at 12:42 PM, Bob- W7LRD w7lrd@comcast.net wrote:
a different slant-not wanting to enter the fm vs linear ongoing debate or the "easy sat" concept-I started satellites not because it was easy, but because it was hard, and at times still is! This was back in the days of the RS satellites. I believe if you present the challenge they will come. Unfortunately we need the money upfront not after the fact. Perhaps this "incremental" effort toward HEO or MEO is required, however we (AMSAT's) have been doing this for a long time and I think should have had our "ducks lined up" by now. We're a bunch of cleaver people and should develop a method getting the necessary funds for launches. Everything is now "bottom line" driven. We should "just do it". 73 Bob W7LRD Seattle
From: "Paul Stoetzer" n8hm@arrl.net
To: "Phil Karn" karn@ka9q.net Cc: amsat-bb@amsat.org Sent: Saturday, July 19, 2014 12:28:12 PM Subject: Re: [amsat-bb] ANS-199 AMSAT News Service Special Bulletin - AMSAT Fox-1C Launch Opportunity Announced
Are FM repeater satellites what we all want in orbit? No. Personally, I'd like a Mode J linear transponder in a sun synchronous circular orbit of about 2,000km (if we can't get anything to HEO).
However, the Fox-1A, Fox-1B, Fox-1C, and Fox-1D satellites will eventually lead to the Fox-2 series of satellites. The software designed transponders on board the Fox-2 series will be capable of operating in any number of digital communications modes as well as operating as linear transponders.
AO-51's V/U FM repeater was probably the most popular amateur satellite ever launched. Since the loss of AO-51, AMSAT-NA membership has been declining and is at the point where membership dues alone do not sustain the operating costs of the organization.
Right now, those who are mildly interested in amateur satellites have one satellite to try with a minimal investment: SO-50, which is a satellite that for about half the days of each month is not convenient for most people who work 9-5 and sleep 10-6 and has a weak downlink that is often very difficult for newcomers to hear. Even experienced satellite operators are at times heard to transmit without being able to hear the satellite. With EO-80 (QB50p2), Fox-1A, and Fox-1C hopefully in orbit and operational next year, there will be three easily heard FM satellites (the 9 dB advantage of the 2m downlinks on these satellites will be quite welcome) - two in sun synchronous orbits with relatively consistent pass times. Having those satellites in orbit will mean that more hams get bitten by the satellite bug, join AMSAT, and progress to improving their stations to operate on the linear transponders and, potentially, on digital satellites.
Bottom line - an AMSAT with more satellites in orbit means an AMSAT with more members and that's how we are eventually going to get our ideal satellites in orbit.
73,
Paul, N8HM
On Sat, Jul 19, 2014 at 2:54 PM, Phil Karn karn@ka9q.net wrote:
On 07/18/2014 12:08 PM, Joseph Spier wrote:
Fox-1C is the third of four Fox-1 series satellites under development, with Fox-1A and RadFXsat/Fox-1B launching through the NASA ELANA program. Fox-1C will carry an FM repeater system for amateur radio for use by radio hams and listeners worldwide.
YET ANOTHER analog satellite?
I'm not interested.
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
On 7/20/2014 12:00 PM, Paul Stoetzer wrote: IN PART
The bottom line is that AMSAT-NA needs a significant boost in membership and visibility and that boost needs to be soon.
I gave up on AMSAT when it seemed that the main afford was put into FM in and FM out satellites. Membership ran out many (15) years ago.
John
The Fox-1 series of satellites will lead to the Fox-2 series with many more interesting modes and capabilities. Yes, the priority is on building and launching the Fox-1 series, but a good portion of that work will be done by next year and then the lessons learned can be applied to constructing and launching the Fox-2 series.
The reality is, of course, that FM satellites are extremely popular. I have read through much of the AMSAT-BB archives and I find a ton more posts about grid and country activations from back when AO-51 was alive than what you see now. Getting on the linear satellites is not expensive or complicated at all, but for whatever reason, we just have not been able to communicate that it's both fun, extremely rewarding, and that won't break the bank doing it to the amateur radio community as a whole, so for those of us who enjoy chasing grids, states, provinces, DX, etc, we do rely on the availability of FM satellites to activate those areas.
Also remember that AMSAT is a membership organization. If members are not happy with the direction of the organization, they are free to select directors who prioritize what the membership desires. Non-members, however, have no voice in the proceedings.
73,
Paul, N8HM
On Sun, Jul 20, 2014 at 1:19 PM, John Becker w0jab@big-river.net wrote:
On 7/20/2014 12:00 PM, Paul Stoetzer wrote: IN PART
The bottom line is that AMSAT-NA needs a significant boost in membership and visibility and that boost needs to be soon.
I gave up on AMSAT when it seemed that the main afford was put into FM in and FM out satellites. Membership ran out many (15) years ago.
John
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On 07/20/2014 10:00 AM, Paul Stoetzer wrote:
A good number of amateur radio operators are only vaguely aware of the amateur satellite program and consider it to be quite esoteric.
Precisely. Huge az/el yagi arrays don't help that image either.
Nor does an occasional, brief, noisy pass of an FM voice-only satellite carrying 1 QSO at a time do much to impress a young person with a mobile phone in his pocket that he can use to talk or message anywhere in the world. The term "easysat" doesn't seem appropriate when said FM voice satellite requires pointing an ungainly-looking 2m antenna at the sky even if that antenna is very small by usual ham satellite standards. Most mobile phones don't even have visible external antennas anymore.
I'm not trying to make ham radio into a utility to compete with either the Internet or mobile phones. That's not what it's for. But for those who'd like to learn, hands-on, about modern communication technology -- for which ham radio *IS* still uniquely suited -- you have to offer something that's actually halfway modern!
I can't do anything about the occasional, brief passes of a LEO without going to a higher altitude orbit. But I certainly *can* do far better with a LEO satellite and a ~1/2 meter ground antenna by:
1. Adding 3-axis attitude control to the spacecraft. 2. Moving up to the microwave bands. 3. Going digital.
Instead of one voice conversation (interrupted by deep, noisy fades) you could support many. Although the LEO passes would still be occasional and brief, alternatives to real-time voice would be available. Bulk data (including recorded and possibly lengthy voice messages) could be sent up and delivered to an entirely different part of the globe. For those who don't really care to talk, satellite-generated data (e.g., telemetry, imagery) can be multiplexed with the downlink data.
The bottom line is that AMSAT-NA needs a significant boost in membership and visibility and that boost needs to be soon. Putting two satellites into orbit that nearly every single ham will be able to easily hear (even a $30 Baofeng and it's stock duck should hear high passes of the Fox-1 satellites) along with the accompanying publicity should provide that boost.
Suppose it were just as easy and cheap to build or buy an amateur digital microwave satellite earth terminal? In this age of mobile microprocessors that would at one time have been considered supercomputers; handheld GPS receivers; Sirius/XM receivers with postage-stamp antennas; and direct broadcast satellite dishes -- just to mention a few now-widespread consumer items -- do you really think it so impossible to set our sights as hams just a little higher than 1960s technology?
--Phil
On 7/19/2014 1:54 PM, it was wrote:
YET ANOTHER analog satellite? I'm not interested.
I hear yeah !
This is great news.
I thank all the AMSAT volunteers, past and present for this opportunity.
GO FOX, GO!
73 Clayton W5PFG On Jul 18, 2014 2:11 PM, "Joseph Spier" wao@vfr.net wrote:
AMSAT NEWS SERVICE ANS-199
The AMSAT News Service bulletins are a free, weekly news and infor- mation service of AMSAT North America, The Radio Amateur Satellite Corporation. ANS publishes news related to Amateur Radio in Space including reports on the activities of a worldwide group of Amateur Radio operators who share an active interest in designing, building, launching and communicating through analog and digital Amateur Radio satellites.
The news feed on http://www.amsat.org publishes news of Amateur Radio in Space as soon as our volunteers can post it.
Please send any amateur satellite news or reports to: ans-editor at amsat.org.
In this edition:
- AMSAT Fox-1C Launch Opportunity Announced
SB SAT @ AMSAT $ANS-199.01 ANS-199 AMSAT News Service Special Bulletin
AMSAT News Service Bulletin 199.01
From AMSAT HQ KENSINGTON, MD.
DATE July 18, 2014 To All RADIO AMATEURS BID: $ANS-199.01
AMSAT Fox-1C Launch Opportunity Announced
AMSAT is excited to announce a launch opportunity for the Fox-1C Cubesat. AMSAT has teamed with Spaceflight Inc. for integration and launch utilizing Spaceflight's SHERPA system to a sun-synchronous orbit in the third quarter of 2015.
Fox-1C is the third of four Fox-1 series satellites under development, with Fox-1A and RadFXsat/Fox-1B launching through the NASA ELANA program. Fox-1C will carry an FM repeater system for amateur radio for use by radio hams and listeners worldwide. Further details on the satellite and launch will be made available as soon as released.
AMSAT has an immediate need to raise funds to cover both the launch contract and additional materials for construction and testing for Fox-1C. We have set a fundraising goal of $125,000 dollars to cover these expenses over the next 12 months, and allow us to continue to keep amateur radio in space.
Donations may be made through the AMSAT webpage at www.amsat.org, by calling (888) 322-6728 or by mail to the AMSAT office at 10605 Concord Street, Kensington, MD 20895, USA.
Please consider a recurring, club, or corporate donation to maximize our chance of success with this mission. Also watch our website at www.amsat.org,follow us on Twitter at "AMSAT", or on Facebook as "The Radio Amateur Satellite Corporation" for continuing news and opportunities for support. AMSAT is a 501(c)3 non-profit corporation and donations may be tax-deductible.
[ANS Thanks AMSAT Board of Directors for the above information]
/EX
In addition to regular membership, AMSAT offers membership in the President's Club. Members of the President's Club, as sustaining donors to AMSAT Project Funds, will be eligible to receive addi- tional benefits. Application forms are available from the AMSAT Office.
Primary and secondary school students are eligible for membership at one-half the standard yearly rate. Post-secondary school students enrolled in at least half time status shall be eligible for the stu- dent rate for a maximum of 6 post-secondary years in this status. Contact Martha at the AMSAT Office for additional student membership information.
73, This week's ANS Editor, Joe Spier, K6WAO k6wao at amsat dot org
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participants (19)
-
Andrew Glasbrenner -
Bob- W7LRD -
Clayton Coleman -
Fabiano Moser -
g0mrf＠aol.com -
Graham Shirville -
Gus -
Jerry Buxton -
Jim Sanford -
JoAnne Maenpaa -
John / NS1Z -
John Becker -
Joseph Spier -
Paul Stoetzer -
Phil Karn -
Rick Walter -
Robert Bruninga -
Simon Brown -
Wouter Weggelaar