Ulysses Update

The Ulysses spacecraft is slowly dying, but its not quite finished yet! Its demise was slated for July 1, 2008, but even without its primary X-Band transmitter whose heatsink doubles as the heater for the fuel lines, its been surviving. Here’s the latest update on the health of the only spacecraft ever to explore the polar regions of the Sun.

Dear Ulysses colleagues,

Yesterday was mission day 6712 and we surpassed 400 days of S-band mission operations. Given that we thought the spacecraft would only survive a few months after the X-band transmitter failure on 15 January 2008, that’s pretty good going! The last month or so has seen a dramatic increase in data return. This is due in part to a request by NASA HQ for additional DSN coverage and also due to the fact that we can record and play back data again on board the spacecraft. That’s possible because the spacecraft-Earth distance is low enough to support a 1024 bps telemetry data rate at the moment (this situation will last until sometime in mid-March). I’ve attached a plot of our weekly data return percentages which clearly shows the recent improvements.

As far as the hydrazine is concerned, it’s obviously not frozen yet, but there can’t be very much left. Our estimate is that we have almost no fuel left even using our best-case estimates. However, it’s very difficult to get an exact figure of fuel usage over the mission given that we have had about 3 years of closed-loop conscan operations to control nutation when the spacecraft fired the thruster autonomously. During those periods, we had to estimate the number of pulses fired by monitoring the increase in catalyst bed temperature after each period of thruster activity which is not the easiest thing
to do. So the bad news is that we don’t have an exact estimate of how much fuel is left but the good news is that it’s still above zero! We hope that the data returned is continuing to excite you as the solar activity slowly begins to increase.

Best regards,

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