NASASpaceFlight.com Forum
General Discussion => Q&A Section => Topic started by: kevin-rf on 12/09/2012 02:42 pm
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Since I did not notice a Q/A for Communications satellites I thought I would start one to ask a question that has me curious.
In light of the latest Proton Briz-M under performance placing Yamal-402 in an orbit with a lower perigee than planned (I believe the apogee is on or close to target so it is not a "lower" orbit so to speak) I was wondering the following.
How many GEO com satellites have been saved by the on-board propulsion system when the launcher under-performed?
Does anyone has a list?
HGS-1 by looping around the moon in the late 90's
AMC-14 using it's propulsion system
AEHF-1 using it's propulsion system
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Artemis (http://telecom.esa.int/telecom/www/object/index.cfm?fobjectid=31170).
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I am looking for a source that lists which Globalstar satellites are in which plane.
Google is not too helpful today in this regard.
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Here's one that was not an LV underperformance, but is still interesting. Superbird 6, launched into a very high supersynchronous orbit in 15 April 2004. Gravitational effect of the moon had not been properly accounted for. Result was a loss of spacecraft perigee altitude and a scramble by the S/C company to regain proper orbit. most Centaur upper stages on GTO flights take a few years to re-enter. IIRC, this one came down in less than 5 orbits.
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I am looking for a source that lists which Globalstar satellites are in which plane.
Celestrak has the orbital elements:
http://www.celestrak.com/NORAD/elements/globalstar.txt
You could try to figure it out from those TLEs directly by looking at the RAAN, or possibly the COSPAR ID (same rocket, same plane). Or plug them into Xephem, OVT, STK (they now have a free version) etc.
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How would a com sat in areosynchronous orbit (at Mars) have to differ from one in GEO? It'd need larger solar panels and ability to communicate all the way to Earth which is sometimes 400,000,000 km away. Would this require a completely different design, or could an ordinary com sat be upgraded for use at Mars? The delta-v difference between GEO and Mars orbit doesn't seem to be very large.
The main purpose would be to allow almost real time remote control of rovers on the surface of Mars, massively increasing their productivity.
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How would a com sat in areosynchronous orbit (at Mars) have to differ from one in GEO? It'd need larger solar panels and ability to communicate all the way to Earth which is sometimes 400,000,000 km away. Would this require a completely different design, or could an ordinary com sat be upgraded for use at Mars? The delta-v difference between GEO and Mars orbit doesn't seem to be very large.
The main purpose would be to allow almost real time remote control of rovers on the surface of Mars, massively increasing their productivity.
I've heard the APL scientist presenting the Red Dragon saying that it usually looks like it, but once you get into the details, you need pretty much a new space craft. I understand that you could start from a commercial sat bus. But then you'd have to redo the avionics, GNC, station keeping, power system and payload. Oh! And control is done with really weak signal, with a 40 minute latency and has nobody on surface to input actual tracking data.
But MOM does uses a GSO bus (granted, a small one).
In any case , until they perfect a high throughput optical link, I don't believe they'll consider such a craft. Station keeping might be more difficult due to perturbations from Fobos.