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Posted by: JayB Jul 1 2009, 07:11 PM

I've just finished re-reading Roving Mars for the 3rd or 4th time and it's still a brilliant insight on to all the hard work and crazy things that went wrong and right to get the girls to Mars and then their story for the first sols on Mars. It's fun to read about the debate on how long to keep Oppy in Eagle (6 or 10 days... they chose 6 since 10 was 1/4 of the science mission available after standup and the worries about cracking the beam splitter on miniTES with deep sleep. How dust would kill them both by sol 200...

I thought is might be a good idea to take an inventory of the girls as Spirit approaches 2000 sols (1953 at time of post)

To take a quote from one of my favorite movies

"Let's look at this thing from a... um, from a standpoint of status. What do we got on the spacecraft that's good?" (Gene Kranz/Ed Harris Apollo 13)

(we have an amazing amount that IS)


MI - seems pretty good on both rovers. Little or no dust contamination
RAT - Main grinding tool unusable on both. Brushes?
APXS - ???
miniTES - OK on Spirit, unusable on Oppy due to dust contamination of mirror in periscope (currently trying to clear by leaving open to elements)
Mossbauer - Approaching half life of radiation source so sensing takes twice as long (?)
IDD - Spirit OK, Oppy has shoulder seizure, stuck heater switch
Pancam - Both OK
Navcam - Spirit OK, Oppy seems to have some dust
FHaz Cam - Both a bit dusty (?)
Rhaz Cam - Both a bit dusty (?)
Wheels - Spirit RF seized, Oppy RF elevated currents moderated by rest and backward driving.
Power- Spirit ~900whr Oppy ~450whr

Please correct mistakes and update as you can...

oh..btw as of this post Spirit is stuck at Troy. I'm betting we'll be roving again by 2000

Posted by: climber Jul 1 2009, 07:36 PM

Good idea JayB.

Sundial - Still OK on both

Posted by: alan Jul 1 2009, 07:57 PM

The half life is 271 days, it now takes a couple of weeks to do what initially took part of a sol.

Posted by: djellison Jul 1 2009, 08:32 PM

Spirit RAT is just brushing. Oppy RAT as far as I know, can still drill (given that it's spent it's life drilling into cottage cheese rather than basalt)

All Haz, Nav and Pan have dust - Oppy Pancam is probably the worst.

And, one issue we don't often mention. Spirit X-Band channel clashes with MRO.

Posted by: SFJCody Jul 1 2009, 09:13 PM

Imagine the status updates in a couple of years! August 2011: Continued mossbauer integration. September 2011: Continued mossbauer integration. October 2011: Continued mossbauer integration...

Posted by: JayB Jul 1 2009, 10:44 PM

hmm.. guess i didn't mention it because I've not heard of it.... Can you elaborate

Posted by: Tesheiner Jul 2 2009, 06:01 AM

Both Spirit and MRO X-band links with the DSN are at the same frequency. The reason was that it was never thought to have both machines alive at the same time.

Another issue with Opportunity is the RF wheel steering actuator which is stuck.

Posted by: nprev Jul 2 2009, 06:13 AM

One articulating component we don't hear much about is the HGA; I assume that no news is good news for both MERs!

Posted by: RoverDriver Jul 2 2009, 11:21 AM

That is correct. I never heard of any issues with that. One problem we have on Spirit, is the IMU (Inertial Measurement Unit). The IMU has gyros and accelerometers. There seems to be about 4 degrees difference between the gyros and the accelerometer data. It seems that the accelerometers are OK ut gyros are off.

Also, amazingly enough in spite of the loss of azimuth actuator on Opportunity we can still use all the instruments and do all the observations, including MI mosaics. The IDD can reach only a narrow strip in front of the rovers but we are getting good at positioning the rover accurately enough to get to the science targets.

Regarding the RAT:

Spirit: grinding bit are worn out, we can only do brushing
Opportunity: grinding bits are still OK, brush is bent and therefore it does not clean very well.

This is an excellent summary!

Paolo

Posted by: JayB Jul 2 2009, 02:54 PM

My knowledge of radio communications can be seen here _> . <_ however, I have to ask why they would choose exactly the same freq even given the thought that the rovers wouldn't last. Is the useful X band that tight?

Are future missions (ie: MSL) planning for mission overlap? I'd hope given the longevity of some missions (Happy 5th in orbit Cassini!) that there would be a general goal of avoiding such problems

Posted by: ElkGroveDan Jul 2 2009, 02:56 PM

You left off:

Rover DRIVERS - Older but wiser, still functioning within normal parameters. Various components subject to balky performance and occasional mood swings, however these conditions were present at launch and deemed to fall within established tolerances.

Posted by: MahFL Jul 2 2009, 03:03 PM

Jay, I would imagine cost was involved.

Posted by: fredk Jul 2 2009, 04:07 PM

Brilliant, Dan!

The APXS uses curium-244 sources, which have a half-life of just over 18 years. So they should be fine for a few more sols.

One other moving part no-one has mentioned is in the Mossbauer. It works by modulating the signal with a periodic Doppler shift, by vibrating the source. It must be working since they're still using it.

Posted by: Fran Ontanaya Jul 2 2009, 04:11 PM

I've read they built a backup radio for MER that finally they didn't use, so they put it in MRO.

Posted by: JayB Jul 2 2009, 04:27 PM

Wasn't it this vibrating mechanism on both these that had an anomaly during cruise which mysteriously fixed itself on landing?

Posted by: stewjack Jul 2 2009, 04:53 PM

I've heard that it was a spare transmitter from the MER program.

Just in case someone wants to criticize the above action -

Imagine that if you spend a million more on a space program that your grandparents will die one year earlier. I have no knowledge of the truth of that statement, but I am quite certain that over a short time span society has only a finite amount of resources, and money is more than symbolically related to societies resources.

IMO: MER has got a lot of "bang for the buck," and even saved MRO money.

Jack

Posted by: nprev Jul 2 2009, 05:03 PM

That's extremely interesting; could somebody provide more details on this problem & the MER IMUs, if possible?

Most IMUs I've dealt with have 3 accelerometers & 3 gyros mounted on a single platform that aligns to local vertical prior to use. A significant angular offset of any of these components would almost have to mean that it was whacked out of its original position somehow...but, don't know how these particular IMUs are built.

Posted by: climber Jul 2 2009, 08:01 PM

I guess that computers are both ok. Any issues on heaters or other critical but "less" mechanical parts?