http://qt.exploratorium.edu/mars/opportuni...PDP2996M2M1.JPG

Looks like they are not only operating the imager, but also the RAT ... Am I right?

I'm not entirely sure what you mean.

If your talking about the indentation in the ground in that image - that is from the Mössbauer

Yeah, thank you! That's why I enjoy being here

Glad to be of help.

Talking of the RAT, is anybody else worried to see a sequence of identical pancams and fhazcams of the RAT on 1764. I assume it should have been moving between those shots.

http://qt.exploratorium.edu/mars/opportuni...BBP2137R1M1.JPG
http://qt.exploratorium.edu/mars/opportuni...BBP2137R1M1.JPG
http://qt.exploratorium.edu/mars/opportuni...BBP2137R1M1.JPG

http://qt.exploratorium.edu/mars/opportuni...BBP1148R0M1.JPG
http://qt.exploratorium.edu/mars/opportuni...BBP1148R0M1.JPG
http://qt.exploratorium.edu/mars/opportuni...BBP1148R0M1.JPG

Yes, it should have. We will repeat the sequence on Monday and this time it should work. It seems we have lost the RAT_Z encoder, which was sort of expected. Unfortunately, at this time we do not have a working testbed so we will have to postpone all RAT activities on Mars until we can verify in the sandbox the new procedure to grind and brush rocks. It should not be a major issue, but we need to test it on the ground before we do it on Mars. So in the meantime it will be and and . What a bummer.

Paolo

Nice

Floyd

Stretch her legs!

Paolo, what's the anticipated work-around for the encoder loss? I assume it's used just for position monitoring telemetry, not for active positional feedback in the control loop?

Looking forward to the continuation of the drive

Hey, folks!

This one... this one!

http://qt.exploratorium.edu/mars/opportuni...BBP2629L6M3.JPG

Take a look. Quickly!

PS: I Posted a colorified version of the upper photo. Hope you liked it!

We believe that the loss of RAT grind and revolve encoders are due to damage to the flex cable of the IDD. The damage is presumably due to wear caused by friction and/or thermal cycles. Since the next trace was the RAT Z position encoder we did a test that was aimed at correlating the RAT Z position to particular values of voltage and time. Therefore the workaround is very similar to the revolve and grind actuators: disable the encoder and stall detection, and apply a predefined voltage for a fixed time assuming the actuator will move for an approximate amount. Careful monitoring of the motors current should allow to determine when interaction with the rock occurs. The sequence will allow for a large inaccuracy in position knowledge, but should nonetheless work.

Since the keyword here is "should" we need to test it first on Earth before attempting its execution on Mars.

Paolo

Open-loop operation based on operational experience; got it, thanks, Paolo!

More curiosity: I'm assuming that you guys built a table of the observed RAT-Z position vs. applied motor voltage/time. What sort of angular resolution did you get within your confidence/comfort level? Has the motor response changed over time as well? (I'm also assuming that it's still pretty linear, though).

A lot of these engineering details are pure gold for future mission designs given the MERs' longevity.

EDIT: Oops, think I meant something like 'distance resolution' instead of 'angular resolution': the Z-axis is forward/back, right?

As I was saying we did it pretty recently (in the Sol 1600s I think) for the first time. It might be that Honeybee had done it during development or ATLO, but I don't think we monitored this particular behavior. I do not recall exactly the test, but I believe we measured the response for ~1mm RAT_Z travel assuming the response being linear with voltage (= speed) and time. I'm afriaid this is all the details I have for the moment.

Yes, MER is an engineering mine, one aspect of this mission that has not been pointed out too often!

Paolo

No driving to-sol it seems. More diagnostics.

Correct. We need to retract the RAT-Z before driving. Last time we did not succeed, so we try and try again ;-) This time it should work.

Paolo

In today's download I noticed a sequence of 4 pancams which appeared to show an extension followed by a retraction of the RAT along what I assume is the Z axis direction. It took place on sol 1768 over a period of about 6 minutes shortly before local noon.

Was that the result we were hoping to see?

Not entirely. The initial extension was not expected, at least not to me which I am not an expert on the RAT flight software. Still the retraction maneuver was successful so we are good to go to drive.

Paolo

Thanks a lot for your prompt updates, Paolo ... those are well appreciated



-> Yeah ! Next stop: Endeavour Crater

I'm sure we will stumble into some cobbles along the way and deploy the IDD which now should be renamed Increasing Delay Device. (for those without sense of humor I mean: )

Paolo

Is the robotic arm still extended?

I'm not sure what you mean by "extended". We no longer do the regular IDD stow on MER-B. We keep it like an elephant's trunk, dangling in front of the hazcams, sort of like a carrot to run faster. If you were asking if the IDD is still in the the same position during the RAT-Z tests, I believe the answer is yes. We will be "stowing" the IDD right before the next drive.

Paolo

Yeah! I really like these words.

LOL

I'll second that laugh, Nirgal. The 'carrot on a stick' is a metaphor we can all appreciate as Opportunity embarks on her latest colossal endeavor.

It's a good thing the carrot is dangling in front of the hazcams, rather than the elevated navcams.

... and Opportunity has finally left Santorini's vicinity during sol 1770. There are still very few images from the new site (fhaz, rhaz, nav), not enough (for me) to determine the new position, but I would say we are near the southern end of the "Conjunction Road".

Woo-hoo! And it will be time for a map shift soon. Double woo-hoo!

A polar view of Opportunity's current partial panorama. North at the top.

Phil

Click to view attachment

It's been a long road...

Click to view attachment

I just was logging off UMSF when I did a last quick stop off at this topic. I know that some people find it hard to see 3 D in analglyphs but for me I could have just stepped in through the screen and started walking .... at least until my blood boiled off. I love the way you go for the depth. One day when I get a bit of time away from work, I'm definitely going to email you Stu and get some advice off you as to how you get such good results! Until then I will just keep walking until my blood boils!!

Drive Direction mosaic after the sol 1770 drive.



James

The Beacon's still visible on the right

Yeah, she's still hanging in there... guess she's loathe to give up the limelight, eh?

Given the tilt of Victoria's rim, it will still be visible from Endeavour!

Phil

Well really, it wouldn't be worthy of the name Beacon if it wasn't visible for miles around, would it?

We'll only be able to see the beacon from the two or three highest points on the rim of Endevour. Remember that that's all we could see of Endevour from the north rim of Victoria.

Oh well, the last ridge before Endeavour, then! Point is - it will be visible for quite a way. Actually its small size will be the limiting factor. But Victoria itself might show up on the horizon for quite a distance, long after the tiny beacon is smaller than a pixel.

Phil

Why did Oppy spend 2 months going no where ?
I think I missed something.......?

Conjunction, Science, RAT issues.

The following quote from Steve Squyres leads me to expect that Opportunity will stay in one location for up to one month after every one or two km of its journey to Endeavor:

In the final weeks of December, Opportunity has checked out a rock and soil sample, as part of what is to become a systematic sampling of the chemistry and bedrock of the terrain. “It’s something we’ve decided we should do every so often – like every kilometer or two as we work our way south – to see if there are any trends,” said Squyres. “So we finished with Santorini, did a little bump forward to get into position to where we could take some measurements of rock and soil and we’re making APXS measurements and MI imaging there.” Once that task is finished, Opportunity will rove on, he said, “and we’ll start driving fast again.”

http://www.planetary.org/news/2008/1231_Ma..._Update_As.html

Just to get this back into the discussion thread...

A month seems like a long time to stop for these scratch and sniff sessions. I certainly hope they won't be that long. They could be spending more time on science than driving. That's just... plain wrong!

(I moved this here from the "route-map" thread)



This would mean spending about one year (!) of the remaining rover lifetime for routine rock sampling alone...
But I still hope that the plan is to invest the bulk of the remaining life time in studies at Endeavour Crater, which is the main and highest priority scientific target, if I understood Steve S. correctly
The intermediate routine sampling stops will likely be significantly shorter in the future (1-2 weeks) with the potential for longer stops only in the case that we discover something entirely new along the way (BTW it is this latter possibility, that makes driving larger distances to new horizons so important IMHO

So I for myself rather take the last part of Steves quote:

How long is that again?

Yeah, actually I hope this is right, but given that Victoria's rim slopes down towards the south (as Phil illustrated beautifully a while ago), we may be able to see slightly into the interior of Victoria once we get far enough south/southeast. It may be a very prominent sight, especially when the capes are casting long shadows. It should be a very different view than what we had on approach to Victoria.

Don't forget that because radioisotope degradation, spectrometry readings that took a few hours years ago now take days... and days. I think this was a special case. Since Opportunity was going to be stopped for conjunction anyway, they decided to thoroughly analyze Santorini. I don't think this is going to be the case for most other stops along the way.

Remember, part of the Endeavour justification was that it was the right way to go anyway.....that only remains true if you do science along the way

Do the "sensing" devices have a shorter expected life span than the "imagers" ?
Or are they all in the How-long-will-your-toaster-work? category?

Of course It's not about the exact amount of time, which could be another 4 years or it could be over tomorrow ...

But the fact that it is limited and that it's expected value (in a probability theory sense) decreases with time, seems to warrant some prioritization of goals ...



That's True. With the unknown/small probability of reaching Endeavour in the first place it wouldn't make sense to do no stops at all until reaching the target. So I too interpret the "Endevaour Goal" as this kind of "imgainary" horizon that gives the direction (think "The journey is the reward." )

But nevertheless I would interpret the shift in strategy after Victoria to put more more priority to driving with less routine observations in order to open the opportunity for science studies of entirely new discoveries encountered along the way.

Maybe we are just a couple of kilometres away from the discovery of some completely new type of rock/terrain (something completely new as the blueberries were when we first encountered them)

The more aggressive driving opens the potential (no guarantee of course) for this kind of discoveries

This is certainly a problem for the Mössbauer spectrometer, where the half-life of its Cobalt 57 source is only 271.74 days, but for the Alpha Particle X-ray Spectrometer (APXS) the source is Curium 244, with a half-life of 18.1 years. I imagine the planners will not schedule much use of the Mössbauer (except at the next conjunction ) but the APXS shouldn't cause much of a problem.

Steve M

Is there something about the Mössbauer process that requires a radiation source with such a short life-span? Or will it be possible to build a unit with a longer useful life for the next mission that requires a Mössbauer spectrometer?

TTT

'Fraid so. To Mössbauer 57Fe, you need a Gamma-ray source emitted from 57Fe atoms decaying for resonance to occur, which basically restricts you to 57Co...