[X] My Assistant

[deglr6328]

What is up with the tiny Ulysses spacecraft that was launched in 1990 to study the solar whatever at high lattitudes? Last I heard it was in danger of dying because the RTG power was running low and at aphelion there was a risk of the hydrazine freezing/exploding in its propulsion system. Well that was like a year ago and I haven't heard anything since. It looks like it should've passed aphelion by now and should be out of danger.....

Its been going up there for over a full solar cycle, is it one of the missions on the chopping block because of the new humans on moon/mars thing?

[edstrick]

Remember that Ulysses needs to periodically re-orient it's high-gain antenna to point toward Earth. Though it's now irrelevant, the X-band beam is several times narrower than the S-band beam due to the diffraction limit of the dish antenna. We're moving out of the S-band beam, I presume, and data rates will drop to useless levels. There may be an omni antenna (I'd presume there is) for tracking immediately post-launch, but data rates would be like the raw data rate (before heroic efforts) of Galileo at Jupiter or worse, and depending on spacecraft orientation, might drop to zero for months or years. The spacecraft might well continue to transmit for some more years, but it's mission is essentially about to end.

[mcaplinger]

Remember that Ulysses needs to periodically re-orient it's high-gain antenna to point toward Earth. Though it's now irrelevant, the X-band beam is several times narrower than the S-band beam due to the diffraction limit of the dish antenna. We're moving out of the S-band beam, I presume, and data rates will drop to useless levels.

Certainly once the s/c loses attitude control the mission is essentially over.
The S-band and X-band both go through the high-gain antenna, but the S-band output power is only 5 watts compared to 20 on X-band, so the maximum data rate is pretty limited (I believe 128 bps compared to 1024 bps on X-band through DSN 34m).

Presumably, if they didn't have the power problem as well, they'd keep the mission going on S-band.

Lots of good info at
http://ulysses-ops.jpl.esa.int/ulsfct/spac...ft/scframe.html