Increasing range from LEO.
In a message dated 03/09/2009 08:09:09 GMT Standard Time, kd6ozh@comcast.net writes:
P3E is a HEO with the same engine as P3D and no benefactor funding a launch. It seems more reasonable to focus on projects that we can pay to launch or
where someone has already donated the launch.
73,
John KD6OZH Wacky idea No 357
Perhaps a longer term piece of AMSAT research could be to develop a subsystem for LEO satellites that detects and then connects users between passing LEOs. This would allow short term intersatellite communication. Very tricky, but a nice project where boards are made available to anyone who would like to add this facility to their LEO Sat.
Thanks
David
To get good coverage you need as many LEO satellites as possible so they should each be as small as possible. Intersatellite linking could be done via automated ground stations. This eliminates the need for high-power transmtters and/or high-gain antennas on the satellites for interlinkng. It's better to put that gain and power consumption on earth. Eveything on the satellite costs more than its weight in gold as launch costs are $700 per ounce.
73,
John KD6OZH ----- Original Message ----- From: G0MRF@aol.com To: kd6ozh@comcast.net ; amsat-bb@AMSAT.Org Sent: Thursday, September 03, 2009 18:16 UTC Subject: Increasing range from LEO.
In a message dated 03/09/2009 08:09:09 GMT Standard Time, kd6ozh@comcast.net writes: P3E is a HEO with the same engine as P3D and no benefactor funding a launch. It seems more reasonable to focus on projects that we can pay to launch or where someone has already donated the launch.
73,
John KD6OZH Wacky idea No 357
Perhaps a longer term piece of AMSAT research could be to develop a subsystem for LEO satellites that detects and then connects users between passing LEOs. This would allow short term intersatellite communication. Very tricky, but a nice project where boards are made available to anyone who would like to add this facility to their LEO Sat.
Thanks
David
To get good coverage you need as many LEO satellites as possible so they should each be as small as possible. Intersatellite linking could be done via automated ground stations. This eliminates the need for high-power transmtters and/or high-gain antennas on the satellites for interlinkng.
Yep, that is what we have been trying to do now for 8 years with the APRS satellites on 145.825. We just need several of them in orbit at the same time. We have demonstrated dual-hops several times whenever two or more of the APRS satellites (and ARISS) are operational at the same time. If we could get 6 to 10 of the University cubesats to simply carry the 3.4" square APRS transponder (Byonics TinyTrck-4), then we would have a constellation providing nearly continuous connectivity via these satellites from any handheld or mobile APRS radio. With 6, you might have to wait 30 minutes or so to make yoru contacts. With 10 or so, you might have to wit no more than 5 to 10 minutes for connectivity.
See www.aprs.org/cubesat-comms.html
It's better to put that gain and power consumption on earth.
The advantage of the APRS satellite concept and Packet, is that we can use a 5 Watt transmitter on the satellite to be able to hit any mobile or HT using its existing omni antenna because the packet has a low dutycycle. So running 5 watts on a cubesat is easy, because the transmitter dutycycle is only on less than say 5% of the whole-orbit time. (average power 1/4 Watt)
Whereas ECHO which is on all the time, has to be set at 1/4 watt TX power because it is on all the time.
Also, EVERY APRS satellite would be on the same frequency 145.825 with no doppler to track, and since every one of them does the same generic relay, independent of callsign, then the user on the ground just operates... He does not have to do anything to go from one satellite to another...
Bob, WB4APR
Why is pcsat having so much trouble carrying its 5 watts then? Even when the satellite is in full sun? Even on the Z panel? I'm not complaining, I just want to understand what went wrong.
73 de KA9SCF.
On Sep 3, 2009, at 17:34, "Robert Bruninga" bruninga@usna.edu wrote:
To get good coverage you need as many LEO satellites as possible so they should each be as small as possible. Intersatellite linking could be done via automated ground stations. This eliminates the need for high-power transmtters and/or high-gain antennas on the satellites for interlinkng.
Yep, that is what we have been trying to do now for 8 years with the APRS satellites on 145.825. We just need several of them in orbit at the same time. We have demonstrated dual-hops several times whenever two or more of the APRS satellites (and ARISS) are operational at the same time. If we could get 6 to 10 of the University cubesats to simply carry the 3.4" square APRS transponder (Byonics TinyTrck-4), then we would have a constellation providing nearly continuous connectivity via these satellites from any handheld or mobile APRS radio. With 6, you might have to wait 30 minutes or so to make yoru contacts. With 10 or so, you might have to wit no more than 5 to 10 minutes for connectivity.
See www.aprs.org/cubesat-comms.html
It's better to put that gain and power consumption on earth.
The advantage of the APRS satellite concept and Packet, is that we can use a 5 Watt transmitter on the satellite to be able to hit any mobile or HT using its existing omni antenna because the packet has a low dutycycle. So running 5 watts on a cubesat is easy, because the transmitter dutycycle is only on less than say 5% of the whole-orbit time. (average power 1/4 Watt)
Whereas ECHO which is on all the time, has to be set at 1/4 watt TX power because it is on all the time.
Also, EVERY APRS satellite would be on the same frequency 145.825 with no doppler to track, and since every one of them does the same generic relay, independent of callsign, then the user on the ground just operates... He does not have to do anything to go from one satellite to another...
Bob, WB4APR
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the APRS satellites on 145.825. We just need several of them in orbit at the same time.
SpaceX has just scored a large contract with ORBCOMM to put their next gen birds in orbit (using the Falcon1E)...a small APRS generic satellite might just substitute for ballast
Robert WB5MZO
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http://space.skyrocket.de/index_frame.htm?http://space.skyrocket.de/doc_sdat...
it looks like the orbcomm will go up three at a time...six launches multiple planes...
Robert WB5MZO
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On 3 Sep 2009 at 20:12, Rocky Jones wrote:
the APRS satellites on 145.825. We just need several of them in orbit at the same time.
SpaceX has just scored a large contract with ORBCOMM to put their next gen birds in orbit (using the Falcon1E)...a small APRS generic satellite might just substitute for ballast
Robert WB5MZO
The digipeat APRS/text signal on multiple LEO'S is could be an alternative solution to a HEO but i will go a bit further and is it possible to have DSTAR FM transponder on multiple LEO'S? With the new small size transponder made by William PE1RAH it will be something to investigate. DSTAR can even send APRS data D-PRS and digital audio in the same transmission.
Do not forget that any analog FM repeater which does not filter CTCSS tone (audio taken at the discriminator directly) can transmit D-Star signal.
Since my first experience with DSTAR i firmly believe a small cube sat will be soon be possible and with the fabulous linking capabilities of DSTAR communication protocole it will also be possible to have of some sort of intersatellite linking system.
Remain to see how to have a wide FM transponder.
As DSTAR is quite in advance in Japan i will not be surprised to see something coming out there. With the new JAXA H-II transfer vehicule did we overlooked a launch opportunity? again our Japanese friends seems to be quite impress with William pico transponder! did they have something in mind?
Here is some link of interest.
http://www.qsl.net/pe1rah/HAMSAT-info.htm http://www.qsl.net/pe1rah/ http://www.pe1rah.observations.biz/ http://www.aprs-is.net/ http://www.jaxa.jp/projects/rockets/h2a/index_e.html http://www.jaxa.jp/projects/rockets/htv/index_e.html
P.S. I am looking for someone with DSTAR capabilities to try some DSTAR satellite transmission as the AO-27 first DSTAR test in 2007. I already have Robin AA4RC in my urcall list and i can see his amsat.org text message passing in my screen!!! Just put my call sign in your urcall list the next step is to find a common footprint. Just go on http://www.ao27.org/AO27/index.shtml at the bottom of the page you will have all you need to program your DSTAR radio parameters.
SSTV text chat and file transfer is also possible on DSTAR too.
"-"
Luc Leblanc VE2DWE Skype VE2DWE www.qsl.net/ve2dwe WAC BASIC CW PHONE SATELLITE
Luc Leblanc VE2DWE Skype VE2DWE www.qsl.net/ve2dwe WAC BASIC CW PHONE SATELLITE
Luc those are good thoughts. I went to a mindset of more PCSAT satellites with the SpaceX thing...but of course the theory is just a platform to carry a small payload.
The small transponder you mention is indeed amazing.
I wonder as well if there are some opportunities with the Japanese in terms of their transfer vehicle (interesting to see the differences between that vehicle and the European one).
There are massive changes coming in "how" space is done in the US. If Falcon 1E and 9 are success...hang on to your hats.
Robert WB5MZO
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Luc...I would add this.
What is firmly missing in the amateur satellite effort is something "repeatable" that encourages solid commercial gear to be available to people who want to use the sats.
Wayne Green (w2nsd who I think is still with us)...had some pretty "wild" stuff in the startup of the repeater movement...but he also had some pretty good musings about what it would take to take the repeater movement from the "techies" to "ordinary" hams... He came and spoke to us while I was in college and we had a chance to have some "one on one" and he more or less nailed what it was going to take to get the repeater movement "mainstream".
It is going to take about the same thing for hamsats...and one of those is a continued supply of hamsats which encourage more communicating and less experimenting....
Thats what is intriguing about the SpaceX "launch" campaign...and indeed about the entire changes that are occurring now with the Augustine commission there is a chance for things developing like geo synch "rafts" where very large satellite complexes etc are built. But ham radio will not in my view have a seat at that table unless and until there is some "normalcy" in the mode.
I spent part of the afternoon talking with a condo owner on Clear Lake about the Club moving its APRS/voice machine to the top of his 14 story building (a virtual skyscraper in this part of Houston)...it was amazing how fast he came around, all he could think of was what went on in Hurricane Ike.
Robert WB5MZO
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If all you want to do is "communicate" with no experimenting or technical involvement then forget amateur radio and sit at your computer and use the internet. It even now works throughout the world via easy to set up satellite links using "solid commercial gear".
Rocky Jones wrote:
Luc...I would add this.
What is firmly missing in the amateur satellite effort is something "repeatable" that encourages solid commercial gear to be available to people who want to use the sats.
Wayne Green (w2nsd who I think is still with us)...had some pretty "wild" stuff in the startup of the repeater movement...but he also had some pretty good musings about what it would take to take the repeater movement from the "techies" to "ordinary" hams... He came and spoke to us while I was in college and we had a chance to have some "one on one" and he more or less nailed what it was going to take to get the repeater movement "mainstream".
It is going to take about the same thing for hamsats...and one of those is a continued supply of hamsats which encourage more communicating and less experimenting....
Thats what is intriguing about the SpaceX "launch" campaign...and indeed about the entire changes that are occurring now with the Augustine commission there is a chance for things developing like geo synch "rafts" where very large satellite complexes etc are built. But ham radio will not in my view have a seat at that table unless and until there is some "normalcy" in the mode.
I spent part of the afternoon talking with a condo owner on Clear Lake about the Club moving its APRS/voice machine to the top of his 14 story building (a virtual skyscraper in this part of Houston)...it was amazing how fast he came around, all he could think of was what went on in Hurricane Ike.
Robert WB5MZO
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On Fri, Sep 4, 2009 at 10:41 PM, Rocky Jonesorbitjet@hotmail.com wrote:
Luc...I would add this.
What is firmly missing in the amateur satellite effort is something "repeatable" that encourages solid commercial gear to be available to people who want to use the sats.
Rocky --
With respect, I wish once again to take issue with your view that there is a dearth of both useful satellites and of commercial equipment. Previously, you have represented this as a sort of negative feedback loop, with useful satellites (and I understand to you this means those equipped with SSB/CW linear transponder) dwindling in number while commercial equipment becoming more scarce.
I would contend that on both sides you are incorrect. On the equipment side, we have the IC-910H and the new all-in-one Icom rig, over which this list has drooled. I myself use the TS-2000 with great enjoyment. Sure, there are other models that have come and gone, but price-for-performance, we're in satellite appliance-operator heaven these days. (An aside for anyone new to this work who already has an all-in-one rig that will work 144 and 435 in SSB and CW: another option these days is to buy a second-hand FT-817 and, with clever use of computer control you can have full doppler tuning with this arrangement.)
It is going to take about the same thing for hamsats...and one of those is a continued supply of hamsats which encourage more communicating and less experimenting....
Setting aside the contention that communication is the basis of this branch of the hobby, note that we do have a very healthy assembly line of LEO SSB/CW birds: KiwiSat's website has videos of them milling their spaceframe, and they'll take your money to help launch the thing at http://www.kiwisat.org.nz/funding.html; XW-1 from China is going to be fun; SSETI-ESEO will have an S-band linear transponder; Delfi n3xt; the next Indian Hamsat, and *anyone* that wants to cart PE1RAH's little board into space for the relatively minor price of a cubesat launch.
Moreover, in my experience, the majority of 'communicating' -- like it or not -- is done on FM birds, again with a great deal of excellent commercial equipment built for the purpose. Exhibit A: my trusty Arrow Antenna, and SumbandilaSat will give us another target at which to shoot our Arrows :-) in a couple of weeks. http://www.southgatearc.org/news/september2009/sumbandilasat_launch_on_track...
Thats what is intriguing about the SpaceX "launch" campaign...and indeed about the entire changes that are occurring now with the Augustine commission there is a chance for things developing like geo synch "rafts" where very large satellite complexes etc are built. But ham radio will not in my view have a seat at that table unless and until there is some "normalcy" in the mode.
Perhaps more tendentiously, I would finally contend that we amateur satellite folks have indeed created a new normalcy: the steady flow of cubesats and their launches. Until recently, it has been hard for us to capitalize on this situation for two-way communication purposes, but with Delfi C3 and, now, FunCube, I think we're well on our way. As Bob has persistently argued, maybe we should just shoot for 1200 bps and provide a real and workable service through a LEO network.
I spent part of the afternoon talking with a condo owner on Clear Lake about the Club moving its APRS/voice machine to the top of his 14 story building (a virtual skyscraper in this part of Houston)...it was amazing how fast he came around, all he could think of was what went on in Hurricane Ike.
That's great work! Thanks for doing it.
73, Bruce VE9QRP
Hi All! if the subject of this post call attention on you is because that sounds familiar to you on these last days QSO's on the birds, before I continue with this post I will type some words that shows the enthusiasm of a person to success!
It's better to try and fail than to never try at all..... because sometimes you don't fail! those are the words sent to me on an email, from KG6NUB Sawson, I sure that most people here know him very well, for me he has been a great help since I started working satellites, I remember my self asking him to send me an email because I was not able to copy his call, and he did just after the satellite go down on the horizon, he also helped me to set up for ISS APRS, send me the schematics to make my first sound card interface, and he makes arrangements to help me work Hawaii for the first time on a very low elevation on SO-50, he reply on emails so fast, and he is always with a solution when you have a problem. And he stay late on the night.something different the the rest of us is that he is not hunting QSL Cards nor he's in a hurry to get any awards, but more in the hearth of this hobby the technical part, I ask him once about using a preamp and he told me that he will spend that money buying more aluminium to make a bigger antenna.On recent days I was able to purchase an HT so I added to my satellite station and finally I was able to listen to my self and free from the little 10W duplexer on my arrow antenna, so been able to cennetct both radios my mobile and my HT I was ready to power up with 50W on my uplink!!! (OH YEAH every body will listen to KI6YAA and I will step on them jejejej!)and just when I was about to become a satellite hog, Sawson get out working with 50mw on his arrow antenna, he also worked the same power on a whip, and if that is not much he contacted Hawaii with the same settings. That teach me a good lesson and remains me of what I learned a few moths ago by studying for my ham exam, use as low power as necessary to complete your contact, Below is a copy of his recent email sent to me with details of his so famous "50mW on an arrow" work.Thakns Sawson for all your Help! KI6YAA From:Sawson -KG6NUB (sawson@w6yx.stanford.edu)Sent:Sun 9/06/09 10:23 PMTo:Larry Teran (satvader@hotmail.com)>Earlier in the week on AO27, there was 4.35 degrees peak. I only had
my AL800 whip with me and didn't even want to try working NH7WN. Robert convinced me to try. To my amazement, I was getting in so loud on 5W, I lowered it to 0.5W and still got in! I tried 50mW but was too weak. This convinced me on a quiet pass 50mW + whip is possible. Two days later I worked Hawaii on 50mW. See the attached files. So the lesson learned is.... it's better to try and fail than to never try at all..... because sometimes you don't fail!
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Hi FO-29 Guys
This is FO-29 status from JARL command team. This was written in Japanese and I translated to English.
----------------------------------------------------------- FO-29 status in 2009
FO-29 launched in August 1996 and has been working 14 years.
FO-29 is planning to operate the consecutive use with the analog transponder until the end of August 2009, but it was confirmed that a transponder stopped on August 25.
In the later pass, the transponder operation is confirmed when we sent a command of transponder ON from the control station, but we stopped transponder temporarily now.
We had the a similar symptom of stopping the transponder in the spring of 2007 .
FO-29 is in the "high shade rate period" now. Both of the transponder stop in the spring of 2007 and this time are thought that by this "high shade rate" and by the rise of the internal resistance of the deterioration of the battery and by the influence of the temperature of the battery.
The power control system FO-29 (PCU) watches a terminal voltage of the battery and turns off the power supply of the transmitter automatically if it becomes less than the setting voltage. In addition, When FO-29 enters the sunshine area and it recovers to the setting voltage by sun battery power, it is designed to turn on a transmitter automatically. However malfunction occurred for this function in 2007.
Because of transmitter was not turned on automatically, We made an operation schedule plan from the summer of 2007 and managed 1-2 times on in a day. This management operation worked well. The electricity income and expenditure restored or it was cured spontaneously.The transponder has been worked without control command from control station from summer of 2008.
The power supply circumstances of current FO-29 is almost same situation as stop period spring of 2007, scheduled operation period, the consecutively operative period from the summer of 2008 and it is in a "high shade rate". This transponder off is supposed to be a similar situation as when transponder stopped in the spring of 2007.
From this , We decided that we make the operation schedule plan, and manage the limit of the operative number of times in one day like last time to keep the electricity income and expenditure untill improve the "shade rate" which is in January, 2010.
----------------------------------------------------------------------- Thanks control team
JA1COU Yutaka Murata
Larry,
My congratulations to you and Sawson on your recent satellite work using very low power levels. This is something I also have enjoyed very much over the past year, using my Yaesu-VX-7R at .05-watt (50 mW) with a variety of antennas, including the AL-800, to log contacts with stations in 30 states, plus Canada, Mexico and Venezuela. My location will not permit me to work all states on the FM satellites, but I suspect that either of you have the opportunity to do that using 50 mW out. It will, indeed, be a challenge for you, but I believe it is one you can achieve. If you decide to pursure such a goal, I wish you the very best in your efforts.
I will begin listening for you and Sawson on passes to my west, and hope that we can complete a contact with each of us transmitting only 50 mW. I suspect it is a very rare contact when each ground station is transmitting far less power than the satellites they are working through!
73 to all,
Tim - N3TL Athens, Ga. - EM84ha
________________________________ From: Larry Teran satvader@hotmail.com To: amsat-bb@amsat.org Sent: Monday, September 7, 2009 3:55:47 AM Subject: [amsat-bb] 50mW on an Arrow
Hi All! if the subject of this post call attention on you is because that sounds familiar to you on these last days QSO's on the birds, before I continue with this post I will type some words that shows the enthusiasm of a person to success!
It's better to try and fail than to never try at all..... because sometimes you don't fail! those are the words sent to me on an email, from KG6NUB Sawson, I sure that most people here know him very well, for me he has been a great help since I started working satellites, I remember my self asking him to send me an email because I was not able to copy his call, and he did just after the satellite go down on the horizon, he also helped me to set up for ISS APRS, send me the schematics to make my first sound card interface, and he makes arrangements to help me work Hawaii for the first time on a very low elevation on SO-50, he reply on emails so fast, and he is always with a solution when you have a problem. And he stay late on the night.something different the the rest of us is that he is not hunting QSL Cards nor he's in a hurry to get any awards, but more in the hearth of this hobby the technical part, I ask him once about using a preamp and he told me that he will spend that money buying more aluminium to make a bigger antenna.On recent days I was able to purchase an HT so I added to my satellite station and finally I was able to listen to my self and free from the little 10W duplexer on my arrow antenna, so been able to cennetct both radios my mobile and my HT I was ready to power up with 50W on my uplink!!! (OH YEAH every body will listen to KI6YAA and I will step on them jejejej!)and just when I was about to become a satellite hog, Sawson get out working with 50mw on his arrow antenna, he also worked the same power on a whip, and if that is not much he contacted Hawaii with the same settings. That teach me a good lesson and remains me of what I learned a few moths ago by studying for my ham exam, use as low power as necessary to complete your contact, Below is a copy of his recent email sent to me with details of his so famous "50mW on an arrow" work.Thakns Sawson for all your Help! KI6YAA From:Sawson -KG6NUB (sawson@w6yx.stanford.edu)Sent:Sun 9/06/09 10:23 PMTo:Larry Teran (satvader@hotmail.com)>Earlier in the week on AO27, there was 4.35 degrees peak. I only had
my AL800 whip with me and didn't even want to try working NH7WN. Robert convinced me to try. To my amazement, I was getting in so loud on 5W, I lowered it to 0.5W and still got in! I tried 50mW but was too weak. This convinced me on a quiet pass 50mW + whip is possible. Two days later I worked Hawaii on 50mW. See the attached files. So the lesson learned is.... it's better to try and fail than to never try at all..... because sometimes you don't fail!
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The sporadic thing about amateur satellites is free launch opportunuities. If hams were paying customers launches would be repeatable. Cubesats provide the standard form factor that fits many launchers and costs are less than 1% of a HEO launch.
73,
John KD6OZH
----- Original Message ----- From: "Rocky Jones" orbitjet@hotmail.com To: lucleblanc6@videotron.ca; "Amsat BB" amsat-bb@amsat.org Cc: eu-amsat@yahoogroups.com Sent: Saturday, September 05, 2009 01:41 UTC Subject: [amsat-bb] Re: Increasing range from LEO/SpaceX/APRS
Luc...I would add this.
What is firmly missing in the amateur satellite effort is something "repeatable" that encourages solid commercial gear to be available to people who want to use the sats.
Wayne Green (w2nsd who I think is still with us)...had some pretty "wild" stuff in the startup of the repeater movement...but he also had some pretty good musings about what it would take to take the repeater movement from the "techies" to "ordinary" hams... He came and spoke to us while I was in college and we had a chance to have some "one on one" and he more or less nailed what it was going to take to get the repeater movement "mainstream".
It is going to take about the same thing for hamsats...and one of those is a continued supply of hamsats which encourage more communicating and less experimenting....
Thats what is intriguing about the SpaceX "launch" campaign...and indeed about the entire changes that are occurring now with the Augustine commission there is a chance for things developing like geo synch "rafts" where very large satellite complexes etc are built. But ham radio will not in my view have a seat at that table unless and until there is some "normalcy" in the mode.
I spent part of the afternoon talking with a condo owner on Clear Lake about the Club moving its APRS/voice machine to the top of his 14 story building (a virtual skyscraper in this part of Houston)...it was amazing how fast he came around, all he could think of was what went on in Hurricane Ike.
Robert WB5MZO
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Is there a ham radio equivalent ?
http://agrg.cogs.nscc.ca/node/81
---------------------------------------------------------- Andrew Rich Airways Technical Officer Grade 4 Surveillance - RADAR ADS-B Amateur Radio Callsign VK4TEC email: vk4tec@tech-software.net web: www.tech-software.net
The amateur satellites are included. Once you load Google Earth and it in turn downloads the data you can turn off those satellites you don't want but first go to the bottom of the alphabetic data and un-check the debris, rocket bodies and inactive satellites to reduce the clutter.
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Andrew Rich (Home) Sent: September 3, 2009 9:08 PM To: amsat-bb@amsat.org Subject: [amsat-bb] Satellite tracking in google earth
Is there a ham radio equivalent ?
http://agrg.cogs.nscc.ca/node/81
---------------------------------------------------------- Andrew Rich Airways Technical Officer Grade 4 Surveillance - RADAR ADS-B Amateur Radio Callsign VK4TEC email: vk4tec@tech-software.net web: www.tech-software.net
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Why is pcsat having so much trouble carrying its 5 watts then? Even when the satellite is in full sun? Even on the Z panel? ...what went wrong.
Error in design. Since it was our first satellite, and the first time that hamtronics TX and RX were flown in space, we put in multiple redundancy. Two identical RX=>TNC=>TX systems. We thought the most important thing was the command link.
To make sure we could still access both TNC systems even with a TX or RX failure we added a second UHF RX to both systems. In additionl we had a relay to CROSS-CONNECT the transmitters.
THen we made the mistake. We assumed that to recover from an anomoly, the most important thing was to regain the command link. Hence, from cold-boot, the spare UHF receivers would both come on AND the transmitters would be cross-connected. This assured we could access either TNC even if we had lost one RX or one TX.
The mistake was assuming that in such a recovery effort, the first thing we would then do is TURN OFF the extra receivers and DISCONNNECT the cross conneced transmitters once we had command.
Well... DUH.... If the reason the spacecraft crashed back to defaults was because it was low on power, then the last thing you want to do is QUADRUPLE the power budget by having the recovery-defaults turn on double the number of receivers and double the number of transmitters!
So we need FOUR times the average power just to get command and that only happens during mid-day passes during maximum eclipse periods, and sometimes right at the beginning of full sun periods in the southern hemisphere. Our first commmand then IN SEQUENCE is 1) LOGON 2) Send command to separate the transmitters 3) Send command to turn off the two spare UHF reciverss
If those are successful, AND PCSAT then has a full orbit in full sun, then we can recover. But the loggon password challenge from the satellite is the LONGEST packet in the command sequence, and if is not successful on the FIRST try, then the battery is exhausted and you loose the pass.
Bob, Wb4APR
On Sep 3, 2009, at 17:34, "Robert Bruninga"
bruninga@usna.edu wrote:
To get good coverage you need as many LEO satellites as possible so they should each be as small as possible. Intersatellite linking could be done via automated ground stations. This eliminates the need for high-power transmtters and/or high-gain antennas on the satellites for interlinkng.
Yep, that is what we have been trying to do now for 8 years
with
the APRS satellites on 145.825. We just need several of
them in
orbit at the same time. We have demonstrated dual-hops
several
times whenever two or more of the APRS satellites (and
ARISS)
are operational at the same time. If we could get 6 to 10
of
the University cubesats to simply carry the 3.4" square APRS transponder (Byonics TinyTrck-4), then we would have a constellation providing nearly continuous connectivity via
these
satellites from any handheld or mobile APRS radio. With 6,
you
might have to wait 30 minutes or so to make yoru contacts.
With
10 or so, you might have to wit no more than 5 to 10 minutes
for
connectivity.
See www.aprs.org/cubesat-comms.html
It's better to put that gain and power consumption on earth.
The advantage of the APRS satellite concept and Packet, is
that
we can use a 5 Watt transmitter on the satellite to be able
to
hit any mobile or HT using its existing omni antenna because
the
packet has a low dutycycle. So running 5 watts on a cubesat
is
easy, because the transmitter dutycycle is only on less than
say
5% of the whole-orbit time. (average power 1/4 Watt)
Whereas ECHO which is on all the time, has to be set at 1/4
watt
TX power because it is on all the time.
Also, EVERY APRS satellite would be on the same frequency 145.825 with no doppler to track, and since every one of
them
does the same generic relay, independent of callsign, then
the
user on the ground just operates... He does not have to do anything to go from one satellite to another...
Bob, WB4APR
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:
Thank you Bob...
You always have a refreshing, clear, informative response for any inquiry into your systems.
The fact that you recognize a design error publicly reassures us neophytes that new designs are built considering past events.
It's always a pleasure hearing one of your explanations.
Roger WA1KAT
----- Original Message ----- From: "Robert Bruninga" bruninga@usna.edu To: "'Patrick Green'" pagreen@gmail.com Cc: amsat-bb@amsat.org Sent: Friday, September 04, 2009 9:44 AM Subject: [amsat-bb] Why PCSAT is hard to recover
Why is pcsat having so much trouble carrying its 5 watts then? Even when the satellite is in full sun? Even on the Z panel? ...what went wrong.
Error in design. Since it was our first satellite, and the first time that hamtronics TX and RX were flown in space, we put in multiple redundancy. Two identical RX=>TNC=>TX systems. We thought the most important thing was the command link.
To make sure we could still access both TNC systems even with a TX or RX failure we added a second UHF RX to both systems. In additionl we had a relay to CROSS-CONNECT the transmitters.
THen we made the mistake. We assumed that to recover from an anomoly, the most important thing was to regain the command link. Hence, from cold-boot, the spare UHF receivers would both come on AND the transmitters would be cross-connected. This assured we could access either TNC even if we had lost one RX or one TX.
The mistake was assuming that in such a recovery effort, the first thing we would then do is TURN OFF the extra receivers and DISCONNNECT the cross conneced transmitters once we had command.
Well... DUH.... If the reason the spacecraft crashed back to defaults was because it was low on power, then the last thing you want to do is QUADRUPLE the power budget by having the recovery-defaults turn on double the number of receivers and double the number of transmitters!
So we need FOUR times the average power just to get command and that only happens during mid-day passes during maximum eclipse periods, and sometimes right at the beginning of full sun periods in the southern hemisphere. Our first commmand then IN SEQUENCE is
- LOGON
- Send command to separate the transmitters
- Send command to turn off the two spare UHF reciverss
If those are successful, AND PCSAT then has a full orbit in full sun, then we can recover. But the loggon password challenge from the satellite is the LONGEST packet in the command sequence, and if is not successful on the FIRST try, then the battery is exhausted and you loose the pass.
Bob, Wb4APR
On Sep 3, 2009, at 17:34, "Robert Bruninga"
bruninga@usna.edu wrote:
To get good coverage you need as many LEO satellites as possible so they should each be as small as possible. Intersatellite linking could be done via automated ground stations. This eliminates the need for high-power transmtters and/or high-gain antennas on the satellites for interlinkng.
Yep, that is what we have been trying to do now for 8 years
with
the APRS satellites on 145.825. We just need several of
them in
orbit at the same time. We have demonstrated dual-hops
several
times whenever two or more of the APRS satellites (and
ARISS)
are operational at the same time. If we could get 6 to 10
of
the University cubesats to simply carry the 3.4" square APRS transponder (Byonics TinyTrck-4), then we would have a constellation providing nearly continuous connectivity via
these
satellites from any handheld or mobile APRS radio. With 6,
you
might have to wait 30 minutes or so to make yoru contacts.
With
10 or so, you might have to wit no more than 5 to 10 minutes
for
connectivity.
See www.aprs.org/cubesat-comms.html
It's better to put that gain and power consumption on earth.
The advantage of the APRS satellite concept and Packet, is
that
we can use a 5 Watt transmitter on the satellite to be able
to
hit any mobile or HT using its existing omni antenna because
the
packet has a low dutycycle. So running 5 watts on a cubesat
is
easy, because the transmitter dutycycle is only on less than
say
5% of the whole-orbit time. (average power 1/4 Watt)
Whereas ECHO which is on all the time, has to be set at 1/4
watt
TX power because it is on all the time.
Also, EVERY APRS satellite would be on the same frequency 145.825 with no doppler to track, and since every one of
them
does the same generic relay, independent of callsign, then
the
user on the ground just operates... He does not have to do anything to go from one satellite to another...
Bob, WB4APR
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
I would like to reiterate the sentiment Roger states. This list is occasionally overtaken by emotionally charged "shoulda-woulda-coulda" threads. Bob's clear and concise posts, that are understandable by those of us that are not satellite experts, continue to make the Amsat-bb list worthy of a daily read.
Randy KI4LMR
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Roger Kolakowski Sent: Friday, September 04, 2009 9:22 AM To: bruninga@usna.edu; 'Patrick Green' Cc: amsat-bb@amsat.org Subject: [amsat-bb] Re: Why PCSAT is hard to recover
Thank you Bob...
You always have a refreshing, clear, informative response for any inquiry into your systems.
The fact that you recognize a design error publicly reassures us neophytes that new designs are built considering past events.
It's always a pleasure hearing one of your explanations.
Roger WA1KAT
----- Original Message ----- From: "Robert Bruninga" bruninga@usna.edu To: "'Patrick Green'" pagreen@gmail.com Cc: amsat-bb@amsat.org Sent: Friday, September 04, 2009 9:44 AM Subject: [amsat-bb] Why PCSAT is hard to recover
Why is pcsat having so much trouble carrying its 5 watts then? Even when the satellite is in full sun? Even on the Z panel? ...what went wrong.
Error in design. Since it was our first satellite, and the first time that hamtronics TX and RX were flown in space, we put in multiple redundancy. Two identical RX=>TNC=>TX systems. We thought the most important thing was the command link.
To make sure we could still access both TNC systems even with a TX or RX failure we added a second UHF RX to both systems. In additionl we had a relay to CROSS-CONNECT the transmitters.
THen we made the mistake. We assumed that to recover from an anomoly, the most important thing was to regain the command link. Hence, from cold-boot, the spare UHF receivers would both come on AND the transmitters would be cross-connected. This assured we could access either TNC even if we had lost one RX or one TX.
The mistake was assuming that in such a recovery effort, the first thing we would then do is TURN OFF the extra receivers and DISCONNNECT the cross conneced transmitters once we had command.
Well... DUH.... If the reason the spacecraft crashed back to defaults was because it was low on power, then the last thing you want to do is QUADRUPLE the power budget by having the recovery-defaults turn on double the number of receivers and double the number of transmitters!
So we need FOUR times the average power just to get command and that only happens during mid-day passes during maximum eclipse periods, and sometimes right at the beginning of full sun periods in the southern hemisphere. Our first commmand then IN SEQUENCE is
- LOGON
- Send command to separate the transmitters
- Send command to turn off the two spare UHF reciverss
If those are successful, AND PCSAT then has a full orbit in full sun, then we can recover. But the loggon password challenge from the satellite is the LONGEST packet in the command sequence, and if is not successful on the FIRST try, then the battery is exhausted and you loose the pass.
Bob, Wb4APR
On Sep 3, 2009, at 17:34, "Robert Bruninga"
bruninga@usna.edu wrote:
To get good coverage you need as many LEO satellites as possible so they should each be as small as possible. Intersatellite linking could be done via automated ground stations. This eliminates the need for high-power transmtters and/or high-gain antennas on the satellites for interlinkng.
Yep, that is what we have been trying to do now for 8 years
with
the APRS satellites on 145.825. We just need several of
them in
orbit at the same time. We have demonstrated dual-hops
several
times whenever two or more of the APRS satellites (and
ARISS)
are operational at the same time. If we could get 6 to 10
of
the University cubesats to simply carry the 3.4" square APRS transponder (Byonics TinyTrck-4), then we would have a constellation providing nearly continuous connectivity via
these
satellites from any handheld or mobile APRS radio. With 6,
you
might have to wait 30 minutes or so to make yoru contacts.
With
10 or so, you might have to wit no more than 5 to 10 minutes
for
connectivity.
See www.aprs.org/cubesat-comms.html
It's better to put that gain and power consumption on earth.
The advantage of the APRS satellite concept and Packet, is
that
we can use a 5 Watt transmitter on the satellite to be able
to
hit any mobile or HT using its existing omni antenna because
the
packet has a low dutycycle. So running 5 watts on a cubesat
is
easy, because the transmitter dutycycle is only on less than
say
5% of the whole-orbit time. (average power 1/4 Watt)
Whereas ECHO which is on all the time, has to be set at 1/4
watt
TX power because it is on all the time.
Also, EVERY APRS satellite would be on the same frequency 145.825 with no doppler to track, and since every one of
them
does the same generic relay, independent of callsign, then
the
user on the ground just operates... He does not have to do anything to go from one satellite to another...
Bob, WB4APR
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
_______________________________________________ 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
At 11:44 PM 9/4/2009, Robert Bruninga wrote:
Well... DUH.... If the reason the spacecraft crashed back to defaults was because it was low on power, then the last thing you want to do is QUADRUPLE the power budget by having the recovery-defaults turn on double the number of receivers and double the number of transmitters!
Oops, yes, you live and learn. Sometimes it's hard to guess which scenario is going to be the most troublesome, when you first try your hand at something new. I'm sure future APRS satellites won't have this problem, thanks to your experience. And well explained too.
73 de VK3JED / VK3IRL http://vkradio.com
participants (16)
-
Alan VE4YZ -
Andrew Rich (Home) -
Armour, Randy (ITS) -
Bruce Robertson -
G0MRF＠aol.com -
John B. Stephensen -
Larry Teran -
Luc Leblanc -
Nigel Gunn G8IFF/W8IFF -
Patrick Green -
Robert Bruninga -
Rocky Jones -
Roger Kolakowski -
Tim - N3TL -
Tony Langdon -
Yutaka Murata