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A commercial comsat is being retired after thirty-two years. The original design life was five. Space hardware tends to be overdesigned, but I wonder how they had enough propellant to go that long?


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Josh Reiter wrote:

Best I can tell from reading the blogs from the researchers at the South Pole is that Marisat-F2's Geosynchronous orbit had decayed somewhat from a 3 degree inclination over the equator to a 13 degree inclination. At this higher inclination orbit it found a new life as a comm sat for shipping and research around the South Pole. From what the South Pole researchers were saying is that they often inherit aging comm sats that are low of fuel and left to drift into higher inclination orbits. I am assuming this means that Geosynchronous orbits do not require so much of a re-boost in terms of altitude but more so in steering.

tom wrote:

A bunch of things come together on the older commsats that are inapplicable to newer ones. First, it was a spinner. So no fuel required for inertial orientation.

Second, since they were unsure where in GEO this thing would spend its life, they had to design to worst case, as far as posible from the two geo stable points of 75 deg east and 225 east. As it turns out, according to astronautix, Marisat 2 spent most of it's time at 79 East, so it really never had to fight the perturbative pull of the earth's bulges.

Third, the Delta II had more capacity than the satellite mission required, so they over built it for serice life. This would have allowed the satellite to help reach a good orbit even if the delta II underperformed for some reason. Add the three together, you get a big fuel surplus enabling long life.

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This page contains a single entry by Rand Simberg published on November 4, 2008 5:59 AM.

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