[X] My Assistant

[kenny]

Any idea when we will get a picture of the summit of Mount Sharp? One of the tantalising parts of the local view we have yet to see...

[charleski]

I remember hearing in a podcast a month or so ago that there were some concerns about possible contamination of the SAM suite with lubricants from the drill, but they were working on ways to mitigate that. The contaminants were teflon and Molybdenum (?disulfide), and I would expect the Molybdenum is the biggest issue, not least because it's linked to historical oxidation states (ref).

Anyone know of any further news, or is it too early? They won't be drilling for a month or two still, so there's still a reasonable amount of time.

[Marc]

I haven't heard any further word regarding REMS from NASA or JPL this week. However, on August 9 the Centro De Astrobiologia moved a press release that suggests to me (I don’t read Spanish) that the parameter problem had been identified and resolved, although doesn’t set out a timetable for future observations.

According to the press relase the problem was due to a misunderstanding between the rover and the instrument, which caused that the data could not be recorded properly. The problem was quickly identified and corrected by the REMS team.

[MahFL]

Hopefully the REMS will run as normal, especially if the R10 installation is successful. Remember after landing the surface obs were preset and pretty limited.

[B Bernatchez]

Ah yes, I was thinking about that; it was literally the last thing left to do before launch because of the heat it emits.

I think that it has more to do with minimizing the thermocouple's exposure to radiation. IIRC, degredation of the thermocouple is the reason that RTG's don't last as long as the halflife of Pu238.

[craigmcg]

Anyone heard how the sw update is progressing? Should be mostly done by now.

[Stellingwerff]

As input for the discussion about the geology of Gale, (mods: Maybe a seperate thread for that discussion?) I've prepared a layman's graphic about the history of the crater as I understand it. I'm definitely no geologist, this is just my interpretation of what I've read uptill now. (mostly the Anderson and Bell paper) It is a necessary simplification and highly based on speculation and I definitely would welcome the (probably well-deserved) critique on it or any questions that might pop-up. What I find mind-boggling in any geological context is the sheer duration of the processes: 3.5 Billion years since the crater formed!

In the graphic, north is to the left, south to the right. The rover landed on the left side of the mount.

Grz,
Ludo.

[Edit: All the usual disclaimers: no, the graphic is not to scale, don't base any conclusions on it, etc., etc.]

[RoverDriver]

...
Imagine if Spirit could have rotated the RF wheel

She would not have made the discoveries she did!

In one of the last attempts she managed to rotate it again briefly if I'm no mistaken? But maybe only intermittent?

Yes the RF actuator worked and then the RR drive actuator stopped working and then both of them stopped working :-(
You should really ask/review these questions on the appropriate thread.

Paolo

[centsworth_II]

As impressive as Mount Sharp is, it is easy to see it as just a remnant of layers which once covered the region.


http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA15958

[craigmcg]

Great way of putting things in context.

[Airbag]

MSL drive actuators can be back driven, so in case of a failure the affected wheel can rotate (almost) freely.

Really - against a very high gear ratio? If so, better watch out when you park her on a slope :-)

Airbag

[mcaplinger]

Any idea when we will get a picture of the summit of Mount Sharp?

Now that the daily press conferences are over I'm not sure what the plan is for discussing the activity timeline. Alas, I'm not authorized to share the details. On the general topic of doing more imaging, you can rest assured that the team is just as interested (for example, I'd love to see some 100mm imaging!) and we'll be doing it as soon as we can subject to all the constraints.

[tuomio]

This is teh first time I heard about Spirit RF drive actuator loss being related to trenching. I was there at the meeting and unless I was asleep I heard nothing to that effect. Spirit RF (and RR) drive actuators were attributed to "napping motors". Apparently an insulating coat had built up on the commutator of those motors preventing good contact between the brushes and the commutator. It had been observed during testing on Earth but never been able to reproduce and analyze. For Opportunity we do not have a reliable theory of the high wheel currents on the RF drive actuator, we just observed that driving backwards prevents it from happening. AFAIK we did not observe high wheel currents on any other drive/steer actuator. The loss of the RF steer actuator had been attributed to a magnetic detent coming loose, preventing the motor to rotate.
MSL drive actuators can be back driven, so in case of a failure the affected wheel can rotate (almost) freely.

What am I doing? I'm talking MER on an MSL thread!

Paolo

I would imagine the rover motors being brushless. If so, only way to have overcurrent is overtorque (rotor lock).

[mcaplinger]

Really - against a very high gear ratio?

I'm not sure exactly what happened on MER or what the gear ratio is in the MSL drive train (for the teeny brushless motors in the cameras back-driving them is indeed very hard) but since MER had a commutator issue and brushless motors don't have commutators or brushes, we shouldn't need to worry about that. I'm not sure, but I assume that MSL has redundant windings also.

[Kaputnik]

I think that it has more to do with minimizing the thermocouple's exposure to radiation. IIRC, degredation of the thermocouple is the reason that RTG's don't last as long as the halflife of Pu238.

I'm no authority on this but I believe that heat rejection is indeed the reason for late loading of the RTG.
When in space the cruise stage had a cooling system which coped with the RTG's heat output, but during ascent they had a limited time before overheating woul occur- hence the RTG was loaded through a hatch in the aeroshell.

Degradation of the thermocouples is an issue, but only in the context of exposure over many years. A few days extra prior to launch would make no difference.