According to a daily briefing note made available to SpaceDaily.com NASA's Mars Exploration Rover A - Spirit - is having communication problems. The current information available suggests the problems are not overly critical and can probably be fixed. However the root cause of the problem remains unknown.
Briefing Note:
Sol 119 was not a good sol for Spirit (and others). We attempted to uplink our daily loads as planned, but we received the off-nominal beep at 10 LSTA. Investigation revealed that we uplinked at 500 bps, but the comm window was a 1K bps window. So the sol 119 master sequence load never made it on board.
The ramification of this was that Spirit would stay awake until 12:00 LSTA and then shutdown for the day. To add insult to injury, we did not execute our e0010 daily mod comm. window sequence.
On sol 119 we had a 13:05 afternoon MGS pass communication window scheduled as well as a 14:10 to 15:00 DTE pass scheduled. Spirit would have shutdown at noon and awoken at 12:58 to support the MGS pass. The spacecraft would then have stayed awake through the 14:00 - 15:00 DTE because it would have been solar groovy.
So we would have:
1. Not executed sol 119 as planned
2. Supported two afternoon communication sessions that we did not need, including 50 minutes of SSPA powered on time
3. Not slept through the afternoon as was the default run out plan
4. Substantially depleted our batteries
With the help of TDL (Chris Lewicki) and SIE (Sharon Laubach) and ACE (Bill Currie) we created and uplinked a standalone ae0010 mod comm window SCMF with its accompanying real-time activate command. This sequence deleted the afternoon MGS and DTE comm windows on sol 119.
We also created and uplinked the real-time delete ae0010 sequence command to clean up after ourselves. We completed command radiation with about five minutes to spare, so the commands should execute before the spacecraft shuts down at noon.
We also got the real-time stop comm command ready and the ACE will uplink it once at 15 bps to be received by the spacecraft at 14:06, during the prep time for the afternoon comm window, and once more at 1000 bps to be received by the spacecraft at 14:15 during the comm window. This last action is just a backup in case we did not get the mod comm window sequence up earlier.
We also uplinked a SET_UPLOSS command before the spacecraft shutdown.
On the positive side, if we were successful in deleting the two afternoon comm sessions, Spirit's batteries should have a very good day charging, and the plan for sol 120 is very close to being done (repeat the sol 119 plan, only get the uplink rate correct).
Some other notes for the uplink planning team, we have not performed data management activities since sol 117. DM pulled their sequence just before uplink on sol 118 and you know what happened on sol 119. Also Spirit has only one more morning DFE comm window, on sol 120, loaded.
We had reviewed and bundled a new strategic comm window load, ae0050, that would have loaded comm windows through sol 127, and it have been executed on sol 119 but it did not make it. So there is added urgency to get it up on sol 120.
A quick note on the uplink data rate, when we switched to HGA uplink sessions, we were initially told to stay at 500 bps to ensure adequate margin on the uplink. The latest strategic comm window delivery (sol 121 - 127) has the morning uplink rate set to 1K bps.
I requested that the TDL question Telecom and verify that in-fact there is sufficient margin to uplink at 1K bps. The answer was 1K bps uplink is fine. So we expected the uplink rate to increase from 500 on sol 120, to 1000 bps on sol 121. Also adding to the confusion, we have not had a complete downlinked comm window data product dump since sol 115.
As it turns out sol 118's uplink data rate was 500 bps, sol 119's data rate was 1K bps, sol 120's data rate is 500 bps, and sols 121 and on will be 1K bps. We should avoid data rate oscillations in the future.
Another point is that even through the comm window was set to 1K bps, we only had a 34 meter DSN antenna this morning and our ACE doesn't believe that a 34 meter dish can support 1K bps uplink.
Pasadena (JPL) May 04, 2004
