Re: geo stationary bird
In a message dated 04/11/2007 15:41:26 GMT Standard Time, richard@g3rwl.demon.co.uk writes:
Does anyone know if retired birds are switched ON or OFF once they get boosted into a retirement orbit ? Could still be useful to us even from there.
73 Richard Limebear G3RWL
Hi Richard.
After the 15 year (ish) period, the satellite is normally switched off as it can no longer point its high gain antennas at the correct point on the earth after the station keeping fuel has run out.
For us it just means we need switchable antennas that can be swapped 15 years after launch.
In every day use I suspect there could well be some loss of service during eclipse. On GEO sats the DC power required to run the transponders normally is a little less than the power from the solar array.
However, when the satellite enters eclipse, the TV etc transponders are run from the batteries. I suspect that at this point, AMSAT would be switched off or into some low power mode until the eclipse has passed. The extra battery power needed for operation of AMSAT and the commercial transponder during eclipse would require a significant mass increase of the on-board batteries.
73
David
Thanks for the replies
Does anyone know if retired birds are switched ON or OFF once they get boosted into a retirement orbit ? Could still be useful to us even from there.
For us it just means we need switchable antennas that can be swapped 15 years after launch.
Accepted. We don't yet know what antenna assemblies will be permissible.
However, when the satellite enters eclipse, the TV etc transponders are run from the batteries. I suspect that at this point, AMSAT would be switched off or into some low power mode until the eclipse has passed. The extra battery power needed for operation of AMSAT */_and_/* the commercial transponder during eclipse would require a significant mass increase of the on-board batteries.
But thats the whole point of this exercise (piggy-backing inside a geo bird); there *is* extra mass availability due to the launch configuration.
Good concept and has my full support as long as P3E doesn't become a victim of fund diversion.
Another thing to remember is once attitude control is turned off, there is also no way to keep the solar arrays pointed at the sun. Once this happens the on board computer will "Load Shed" and shut down everything not needed to regain attitude control. Switchable antennas would not be a help.
For satellites that are out of expendables (loss of too much redundancy, or almost out of fuel). They may be kept as a spare if they are usable at all, or like on bird our company owns just held in the slot until a replacement can be launched. FCC and ITU require us to maintain the bird in the slot or we loose the slot. Once we stop doing maneuvers the birdwill start drifting and become a hazard for other spacecraft. The operator will once this happens "SuperSync" it, kicking it up about 300 miles above the geo-stationary or "Clark Belt", and permanently shutting off all electronics.
In my experience most satellites have enough solar array power and battery capacity to run through eclipse long past end of life due to fuel exhaustion or some other catastrophic problem. You can however count on the AMSAT Payload being a lower priority than the revenue producing payloads, and will be turned off first if there is a power problem.
I would support AMSAT investigating this and seeing if there is a possibility of it becoming a project. I would however like to see P3E finished first.
Mark
On 11/5/07, Richard Limebear Richard@g3rwl.demon.co.uk wrote:
Thanks for the replies
Does anyone know if retired birds are switched ON or OFF once they get boosted into a retirement orbit ? Could still be useful to us even from there.For us it just means we need switchable antennas that can be swapped 15 years after launch.
Accepted. We don't yet know what antenna assemblies will be permissible.
However, when the satellite enters eclipse, the TV etc transponders are run from the batteries. I suspect that at this point, AMSAT would be switched off or into some low power mode until the eclipse has passed. The extra battery power needed for operation of AMSAT */_and_/* the commercial transponder during eclipse would require a significant mass increase of the on-board batteries.
But thats the whole point of this exercise (piggy-backing inside a geo bird); there *is* extra mass availability due to the launch configuration.
Good concept and has my full support as long as P3E doesn't become a victim of fund diversion.
-- 73 Richard W L Limebear G3RWL g3rwl@amsat.org FOC # 1188
So many beautiful girls ... (sob) so little time
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