The BBC are running the video on their website

http://news.bbc.co.uk/1/hi/science_and_environment/10150614.stm

73 Trevor M5AKA

--- On Tue, 25/5/10, David - KG4ZLB [email protected] wrote:

The "dead-but-alive" telecommunications satellite, Galaxy-15 http://www.orbital.com/SatellitesSpace/Communications/PanAmSat/, has begun to enter the space of neighbouring craft, and their operators are planning evasive action.

"Zombie-sat" has captured the imagination of the internet space forums these past few weeks. It's probably the nickname that's done it.

When we sit on the sofa skipping across the smorgasbord of channels with our remote-controls, we don't usually give much thought to the "bent pipes" that sit 36,000km above our heads, delivering the televisual feast.

Intelsat's Galaxy-15 http://www.intelsat.com/resources/galaxy-15/operational-status.asp satellite was put in geostationary orbit five years ago to re-distribute TV services to cable companies across North America, and also to send navigation data to aeroplanes to improve the accuracy of their GPS receivers.

But the "bird" experienced a major hiccup at the beginning of April.

It's not known precisely what happened. One possibility is that it was damaged by high-speed particles billowing off the Sun in a solar storm - an ever-present danger for orbiting electronics.

The satellite is still operational: it's still "on", but Intelsat cannot control it. Any signal it receives, it re-transmits at high power. It's a very unusual situation.

What doesn't help is the fact that Galaxy-15, which is supposed to sit at 133 degrees West (over the eastern Pacific), is drifting slowing eastwards by about 0.05 degrees a day. This will take it into the path of other satellites, and first to have an issue is AMC-11 http://www.ses-worldskies.com/worldskies/satellites/01_amc-fleet/amc-11/index.php, another TV services spacecraft operated by SES World Skies http://www.ses-worldskies.com/worldskies/index.php.

If SES were to do nothing, Zombie-sat would soon start picking up and retransmitting signals sent to AMC 11. To users on the ground who depend on AMC 11 for their daily dose of MTV, this could lead to a horrendous mash-up.

It would be like trying to listen to two people who are shouting the same conversation at you.

So, SES World Skies will today begin a delicate orbital dance, in which they will allow AMC 11 to drift in tandem with Galaxy-15 while at the same time sneaking up another satellite behind the pair.

The plan is for the SES controllers to then leapfrog many of the services on AMC-11 across to this other satellite, known as SES-1, thereby minimising the disruption to customers.

The manoeuvres are unprecedented, says Alan Young, the chief technology officer with SES World Skies.

"The closest AMC-11 and Galaxy-15 will come is measured in    kilometres, and in space terms that's quite close. But the risk here    is not one of collision; we're not at all concerned about that. The    problem is that they're so close when viewed from Earth that it's    not easy to distinguish between the two satellites and seeing as    they both operate in the same frequency band, there will be    interference if we're not careful.

"We've gone to a number of measures, including moving customers on    AMC-11 on to a very large uplink antenna. This means we can very    finely discriminate between the two spacecraft so that we can direct    all of the energy into AMC-11 and as little energy as possible into    Galaxy-15. If you don't put anything into Galaxy-15, you won't get    anything out."

AMC-11 will eventually be moved back to its orbital slot to resume normal operations once the zombie has passed through, which should be 7 June.

All satellite operators and comms companies will have to work out what Galaxy-15 means to them. Here at the BBC, we've had to consider how some of our international services like the BBC World News channel http://www.bbcworldnews.com might be affected.

This channel is fed through Intelsat's Galaxy-13 platform. The most recent calculations suggest everything should be fine.

Anyone sitting on their sofa in North America should be oblivious to the space waltz that is about to take place.

There are some wider issues, however. For satellite manufacturers, there will be keen interest in understanding exactly what happened to Galaxy-15.

Satellites have redundant, or back-up systems http://news.bbc.co.uk/1/hi/sci/tech/8458203.stm; and when they have major upsets, there are usually modes that will completely re-boot the spacecraft automatically after a period of time.

Galaxy-15 was made by Orbital Sciences http://www.orbital.com/, but Patrick Wood, the chief technical officer for EADS Astrium satellites http://www.astrium.eads.net/, told me the entire industry had an interest in finding out what went wrong:

"Part of our design review process is to check through the    architecture to ensure there isn't a single point that, were it to    fail, we'd lose complete control of the spacecraft. Clearly    Galaxy-15 has had a major event and most organisations will want to    understand what happened. From an industrial point of view, the    surprising thing is that Galaxy-15 is locked on full power. This    tends to suggest the control/tele-command side of the spacecraft has    failed and left the spacecraft in whatever mode it was in when it    was last commanded. It's a very unusual case."

And, of course, the whole episode raises once again the issue of orbital space debris http://news.bbc.co.uk/1/hi/sci/tech/7916582.stm. Galaxy 15 will likely end its days in one of the two great "garbage patches" in the sky.

These libration points http://en.wikipedia.org/wiki/Geostationary_orbit#Earth_orbital_libration_points, as they are known, are located at roughly 105 degrees West and 75 degrees East. They are gravitational "sweet-spots" where drifting objects will naturally coalesce.

The two libration points now contain more than 150 defunct satellites [395Kb PDF] http://www.secureworldfoundation.org/siteadmin/images/files/file_460.pdf.

Satellite operators are urged to put their geostationary spacecraft in a "graveyard orbit" once their missions are complete. This usually means pushing the platforms even higher into the sky.

But of the 21 spacecraft which reached end of life in 2009, only 11 were disposed of in accordance with the Inter-Agency Space Debris Coordination Committee's (IADC) re-orbiting guidelines [99 Kb PDF] http://www.iadc-online.org/Documents/Docu/IADC_Mitigation_Guidelines_Rev1_Sep07.pdf.

We may all love our satellite TV, but we're starting to build a problem for ourselves.

Watch this space.

-----Inline Attachment Follows-----

---

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On May 25, 2010, at 2:27 PM, Luc Leblanc wrote:

...

The BBC are running the video on their website

http://news.bbc.co.uk/1/hi/science_and_environment/10150614.stm

73 Trevor M5AKA

They will need a space fly swatter... More seriously some kind of solution will have to be found to discard useless space debris and junk.

It's all in the delta-V. If you can apply enough to put the perigee in the upper atmosphere, the orbit will eventually decay to where the object deorbits. Everything in LEO encounters enough drag to end up in the atmosphere sooner or later, whether it's within a year, within ten years, or within a hundred years, sooner or later it will fall out. HEO and above, you pretty much have to apply external delta-V to get the perigee down far enough.

The problem with dead HEO and GEO sats, and a lot of the GTO booster stages that got them there, and all the loose bits of shrouds, interstage thrust structures, and so on, is that their perigees are far enough above the atmosphere that if left completely alone, they'll still be there tends of thousands of years from now, because there just aren't any forces acting on them that are strong enough to either deorbit them or kick them up to escape velocity and out into solar orbit, and the immediate problem with *that* is that at $36k-$550k/ kilogram, it's still too expensive to launch much more than new working sats to GEO.

If the cost comes down to where it's practical to launch a semi- autonomous deorbiting "tug" of some sort to grapple junk and push it to a low enough perigee, with some kind of propulsion that can supply large amounts of delta-V for a relatively small onboard fuel load, then a lot can be done about HEO/GEO junk. But all of those are big ifs, and doing anything like that with our current propulsion tech just isn't feasible due to diminishing returns. You're pretty much looking at some kind of antimatter rocket to be able to do that kind of job.

"A process cannot be understood by stopping it. Understanding must move with the flow of the process, must join it and flow with it." -- the First Law of Mentat

At 02:03 PM 5/25/2010 -0400, [email protected] wrote:

The "dead-but-alive" telecommunications satellite, Galaxy-15 http://www.orbital.com/SatellitesSpace/Communications/PanAmSat/, has begun to enter the space of neighbouring craft, and their operators are planning evasive action.

"Zombie-sat" has captured the imagination of the internet space forums these past few weeks. It's probably the nickname that's done it.

When we sit on the sofa skipping across the smorgasbord of channels with our remote-controls, we don't usually give much thought to the "bent pipes" that sit 36,000km above our heads, delivering the televisual feast.

Intelsat's Galaxy-15 http://www.intelsat.com/resources/galaxy-15/operational-status.asp satellite was put in geostationary orbit five years ago to re-distribute TV services to cable companies across North America, and also to send navigation data to aeroplanes to improve the accuracy of their GPS receivers.

But the "bird" experienced a major hiccup at the beginning of April.

It's not known precisely what happened. One possibility is that it was damaged by high-speed particles billowing off the Sun in a solar storm - an ever-present danger for orbiting electronics.

The satellite is still operational: it's still "on", but Intelsat cannot control it. Any signal it receives, it re-transmits at high power. It's a very unusual situation.

What doesn't help is the fact that Galaxy-15, which is supposed to sit at 133 degrees West (over the eastern Pacific), is drifting slowing eastwards by about 0.05 degrees a day. This will take it into the path of other satellites, and first to have an issue is AMC-11 http://www.ses-worldskies.com/worldskies/satellites/01_amc-fleet/amc-11/index.php, another TV services spacecraft operated by SES World Skies http://www.ses-worldskies.com/worldskies/index.php.

If SES were to do nothing, Zombie-sat would soon start picking up and retransmitting signals sent to AMC 11. To users on the ground who depend on AMC 11 for their daily dose of MTV, this could lead to a horrendous mash-up.

It would be like trying to listen to two people who are shouting the same conversation at you.

So, SES World Skies will today begin a delicate orbital dance, in which they will allow AMC 11 to drift in tandem with Galaxy-15 while at the same time sneaking up another satellite behind the pair.

The plan is for the SES controllers to then leapfrog many of the services on AMC-11 across to this other satellite, known as SES-1, thereby minimising the disruption to customers.

The manoeuvres are unprecedented, says Alan Young, the chief technology officer with SES World Skies.

"The closest AMC-11 and Galaxy-15 will come is measured in kilometres, and in space terms that's quite close. But the risk here is not one of collision; we're not at all concerned about that. The problem is that they're so close when viewed from Earth that it's not easy to distinguish between the two satellites and seeing as they both operate in the same frequency band, there will be interference if we're not careful.

"We've gone to a number of measures, including moving customers on AMC-11 on to a very large uplink antenna. This means we can very finely discriminate between the two spacecraft so that we can direct all of the energy into AMC-11 and as little energy as possible into Galaxy-15. If you don't put anything into Galaxy-15, you won't get anything out."

AMC-11 will eventually be moved back to its orbital slot to resume normal operations once the zombie has passed through, which should be 7 June.

All satellite operators and comms companies will have to work out what Galaxy-15 means to them. Here at the BBC, we've had to consider how some of our international services like the BBC World News channel http://www.bbcworldnews.com might be affected.

This channel is fed through Intelsat's Galaxy-13 platform. The most recent calculations suggest everything should be fine.

Anyone sitting on their sofa in North America should be oblivious to the space waltz that is about to take place.

There are some wider issues, however. For satellite manufacturers, there will be keen interest in understanding exactly what happened to Galaxy-15.

Satellites have redundant, or back-up systems http://news.bbc.co.uk/1/hi/sci/tech/8458203.stm; and when they have major upsets, there are usually modes that will completely re-boot the spacecraft automatically after a period of time.

Galaxy-15 was made by Orbital Sciences http://www.orbital.com/, but Patrick Wood, the chief technical officer for EADS Astrium satellites http://www.astrium.eads.net/, told me the entire industry had an interest in finding out what went wrong:

"Part of our design review process is to check through the architecture to ensure there isn't a single point that, were it to fail, we'd lose complete control of the spacecraft. Clearly Galaxy-15 has had a major event and most organisations will want to understand what happened. From an industrial point of view, the surprising thing is that Galaxy-15 is locked on full power. This tends to suggest the control/tele-command side of the spacecraft has failed and left the spacecraft in whatever mode it was in when it was last commanded. It's a very unusual case."

And, of course, the whole episode raises once again the issue of orbital space debris http://news.bbc.co.uk/1/hi/sci/tech/7916582.stm. Galaxy 15 will likely end its days in one of the two great "garbage patches" in the sky.

These libration points http://en.wikipedia.org/wiki/Geostationary_orbit#Earth_orbital_libration_points, as they are known, are located at roughly 105 degrees West and 75 degrees East. They are gravitational "sweet-spots" where drifting objects will naturally coalesce.

The two libration points now contain more than 150 defunct satellites [395Kb PDF] http://www.secureworldfoundation.org/siteadmin/images/files/file_460.pdf.

Satellite operators are urged to put their geostationary spacecraft in a "graveyard orbit" once their missions are complete. This usually means pushing the platforms even higher into the sky.

But of the 21 spacecraft which reached end of life in 2009, only 11 were disposed of in accordance with the Inter-Agency Space Debris Coordination Committee's (IADC) re-orbiting guidelines [99 Kb PDF] http://www.iadc-online.org/Documents/Docu/IADC_Mitigation_Guidelines_Rev1_Sep07.pdf.

We may all love our satellite TV, but we're starting to build a problem for ourselves.

Watch this space.

Sometimes I wonder, as AO-40's AOP precesses over time if it won't become a hazard to other satellites some day.

KB7ADL

On 25 May 2010 at 19:36, Greg D. wrote:

I wonder... Has anyone at SES considered just turning off their transmitter, while Galaxy-15 crosses their path, and using it instead?

G-15 and AMC-11 are opposite polarity, and most of the AMC-11 transponders are pretty wide, and the main carrier freq of each transponder is right at the null between the transponders on G-15. It should work on narrow signals that don't have carriers at the nulls, but I don't think it would work for most of the wide transponders.

If Galaxy 15's transponders are all of opposite polarities, then wouldn't the potential interference be cancelled-out by around -60dB due to the polarisation mis-match on both the uplink and downlink paths?

Auke ----- Original Message -----

...

From: [email protected] To: [email protected] Date: Wed, 26 May 2010 09:35:54 -0400 Subject: [amsat-bb] Re: 'Zombie-sat' and the clever orbital dance

On 25 May 2010 at 19:36, Greg D. wrote:

...

I wonder... Has anyone at SES considered just turning off their transmitter, while Galaxy-15 crosses their path, and using it instead?

G-15 and AMC-11 are opposite polarity, and most of the AMC-11 transponders are pretty wide, and the main carrier freq of each transponder is right at the null between the transponders on G-15. It should work on narrow signals that don't have carriers at the nulls, but I don't think it would work for most of the wide transponders.

---

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---

The New Busy is not the too busy. Combine all your e-mail accounts with Hotmail. http://www.windowslive.com/campaign/thenewbusy?tile=multiaccount&ocid=PI... _______________________________________________ Sent via [email protected]. 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

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Where does one find this information?

On 27-May-10 11:44, Bill Jones wrote:

I think the transponders on both sats are 36MHz wide, spaced every 40 MHz. AMC-11 has vertical transponders at 3720, 3760,.....4120,4160 and horizontal from 3740,3780,...4140,4180. There is about a 4 MHz gap between each transponder, but I am not sure just how sharp the dropoff of the bands are, and how effective this 4 MHz gap really is. The Galaxy 15 transponders are at the same places, but the vertical are where the AMC11 horizontal are, and visa-versa. For narrower signals which aren't centered at the transponder center, are within the bandwidth of both horizontal and vertical transponders. For example the QVC shopping channel is an approximately 15 MHz wide vertical signal centered at 3928. It's on the 3902-3938 "3920" transponder on AMC-11, but would also almost fit into the 3922-3958 "3940" transponder on Galaxy-15. Most of AMC-11's transponders however are centered on the nulls between the Galaxy-15s transponders. I am not at all clear with respect to what this would do to the signal. Sort of seems like the 4 MHz gaps would be like a notch filter, and would be somewhat similar to removing the carrier when generating a SSB signal. These digital signals look very broad and rectangular in a spectrum analyzer. Most are 20 or 30 MHz wide, and if you remove a 4 MHz wide segment from the middle, I assume that it would result in significant distortion, regardless of whether you leave the AMC-11 transponders on or off, but I really don't understand much at all about how removing part of the envelope of a broad digital signal like this affects the reception. Since these are mostly QPSK an 8PSK signals, it doesn't take much interference from similar symbol rate signals to mess up the reception of these things, particularly because the phases will be different from G-15.

At 03:44 AM 5/27/2010, Bill Jones wrote:

On 26 May 2010 at 23:06, Auke de Jong wrote:

...

If Galaxy 15's transponders are all of opposite polarities, then wouldn't the potential interference be cancelled-out by around -60dB due to the polarisation mis-match on both the uplink and downlink paths?

Auke

I think the transponders on both sats are 36MHz wide, spaced every 40 MHz. AMC-11 has vertical transponders at 3720, 3760,.....4120,4160 and horizontal from 3740,3780,...4140,4180. There is about a 4 MHz gap between each transponder, but I am not sure just how sharp the dropoff of the bands are, and how effective this 4 MHz gap really is. The Galaxy 15 transponders are at the same places, but the vertical are where the AMC11 horizontal are, and visa-versa. For narrower signals which aren't centered at the transponder center, are within the bandwidth of both horizontal and vertical transponders. For example the QVC shopping channel is an approximately 15 MHz wide vertical signal centered at 3928. It's on the 3902-3938 "3920" transponder on AMC-11, but would also almost fit into the 3922-3958 "3940" transponder on Galaxy-15. Most of AMC-11's transponders however are centered on the nulls between the Galaxy-15s transponders. I am not at all clear with respect to what this would do to the signal. Sort of seems like the 4 MHz gaps would be like a notch filter, and would be somewhat similar to removing the carrier when generating a SSB signal. These digital signals look very broad and rectangular in a spectrum analyzer. Most are 20 or 30 MHz wide, and if you remove a 4 MHz wide segment from the middle, I assume that it would result in significant distortion, regardless of whether you leave the AMC-11 transponders on or off, but I really don't understand much at all about how removing part of the envelope of a broad digital signal like this affects the reception. Since these are mostly QPSK an 8PSK signals, it doesn't take much interference from similar symbol rate signals to mess up the reception of these things, particularly because the phases will be different from G-15.

Bill Jones N3JLQ Sweden Maine [email protected] http://www.megalink.net/~wejones

303rdBG page http://www.eskerridge.com/bj/303rdbg/wwii.html

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What I recall from installing c-band dishes in the mid-1980's is that adjacent satellites were parked in orbit spaced approx. 4 degrees apart. They then polarized even numbered channels 90-degrees from odd numbered channels. The early satellite receivers had to be programmed for each satellite and polarity adjusted for best even and odd channel. If you had polarity off, the receiver could pick up a transponder (channel) from an adjacent satellite. It would not be clear but it would show a blurry picture and even sound. Usually, once you adjusted the polarity and were pointed dead on a satellite the correct channel for that satellite would be received. In some cases satellites had inactive channels and there would be bleed-over from an adjacent channel in the same satellite. Most of these satellites had individual transponder amplifiers that could be individually adjusted in power by ground station commands. If you had a smaller home dish that sometimes meant not all channels would be received clearly.

However, the polarity angle of one satellite would not be the same as another so even if they had opposite polarity channel schemes they might only be 45 or 60-degrees vs 90-degrees. At 45-degrees the signal is only 3-dB down vs about 20-dB at 90-degrees.

Here in Alaska, the first satellite dishes had to be 14 to 16 foot for good reception. Initially, only Galaxy-V "Aurora" was available with two channels: the RATNET (Rural Alaska TV Net) and an educational net. Most rural schools put up 16-foot dishes to receive this (my 16-foot eme dish is a surplus one of these). By mid 1980's commercial home dishes became widely available and new satellites were launched with enough signal in AK for 10-12 foot dishes. In 1985 HBO was first to scramble (encoded) their programs requiring a subscription and descrambler box. In the mid-1990's Ku-band satellite service (Direct-TV, Dish-Net) became available but not for HI or AK. But enterprising AK dealers offered 6-foot dishes to receive the weak signal at the edge of the footprint. Today, a 30-inch dish is standard in AK though many opt for 1m (39-in) or 1.2m (4-ft) dishes to minimize rain fade.

The 4-MHz gaps in the channels were guard bands and not notched to my knowledge. Often narrow-band subcarriers carried commercial data not viewed by home customers.

A standard tool in a satellite installer's kit back in those days was a chainsaw, since trees did not pass c-band microwaves. I figure that I installed somewhere about 50-70 dishes from 1985-1991. The Exxon-Valdez Oil Spill in 1989 gave me 13 months of work and I did not go back to TV dishes full-time after that. I just retired after 15 years as a comm tech for an AK Oil Spill Recovery Org.

73, Ed - KL7UW, WD2XSH/45 ====================================== BP40IQ 500 KHz - 10-GHz www.kl7uw.com EME: 144-600w, 432-100w, 1296-60w, 3400-fall 2010 DUBUS Magazine USA Rep [email protected] ======================================