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Opportunity General Health
Doug M.
post Aug 15 2013, 10:25 AM
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I've been clicking around for a general health status for Opportunity, but haven't been able to find one.


Power -- The solar panels seem to be showing signs of degradation over time but it's not clear how much. NASA reports regularly on power output, tau/opacity and dust levels, but not on the status of the panels themselves. They did clock well over 500 watt-hours as recently as May, so it doesn't look like their performance is a serious issue. As for non-solar power, the radioisotope heaters seem to be fine; they're Pu-238, so they would only have lost about 10% of their power since launch. So the WEB is still toasty.

Motors and joints -- I know we've got one bad wheel motor (which means we spend a lot of time driving backwards) and the bad arm azimuth joint and the separate issue with the arm potentiometer.

Electronics -- There was the flash memory issue earlier this year but I don't know if that was a one-off or a sign of age.

Instruments -- The Mossbauer spectrometer is done because its radioactive cobalt source ran out. MiniTES got dust on its mirror after the big 2007 dust storm and stopped working. AFAICT the other instruments are okay? Pancam, Navcam, Hazcams, and the APXS all seem to be working fine. There was a NASA press release last month that said "Opportunity imaged the Rock Abrasion Tool (RAT) bit to assess remaining bit life", but it didn't say anything about what they saw and I haven't been able to find any more information. Clearly the RAT is still working, at least for now.

What else?


Doug M.

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fredk
post Aug 15 2013, 02:45 PM
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If you mean would the panels still provide the power they did at landing if they were clear of dust (and the illumination was the same), I don't recall any mention of that. My guess would be that the battery's ability to charge would be more of a problem, but again I don't recall any mention of its status. Remember that Spirit hit over 900 Whr at around sol 2000.

I don't think you mentioned the frozen steering actuator. Probably not fair to call it a "bad" driving motor, since it works but just gets a little hot sometimes.

Probably the best source to find lots of detail about all of these problems is the PS updates.
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Doug M.
post Aug 15 2013, 07:39 PM
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QUOTE (fredk @ Aug 15 2013, 03:45 PM) *
If you mean would the panels still provide the power they did at landing if they were clear of dust (and the illumination was the same), I don't recall any mention of that.


Well, all solar panels degrade gradually over time, and in space they go faster. The ISS arrays have a 15 year nominal lifespan; it's expected to be longer than that in practice, but OTOH the ISS arrays were designed and built with a large margin over the ISS' actual power needs. But given that nobody seems to be mentioning it, I suspect that it hasn't been a significant issue yet, or at least not as compared to dust, opacity, et al.

Your point about the batteries is a good one -- I hadn't thought of that. Googling turns up a number of papers from the rovers' first few years, basically saying "wow -- these lithium-ion batteries are holding up great!" Not seeing anything since 2010 one way or the other.


Doug M.
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djellison
post Aug 15 2013, 08:25 PM
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Note - on the surface, under an atmosphere and, for half the time, in the dark - those solar arrays are not getting the same level of abuse they would be getting if they were in free space.
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fredk
post Aug 15 2013, 08:44 PM
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Yeah, a better comparison than the ISS might be the Mars orbiters. Maybe someone knows something quantitative about those.

In the absence, 900 Whr at sol 2000 is pretty good. And the panels weren't completely free of dust at that time.
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djellison
post Aug 15 2013, 08:56 PM
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FWIW - I'd expect that the 'dust factor' value inherently includes solar array degradation. It's simply the ratio between predicted solar power from new, clean arrays given known atmospheric opacity - and the actual power generated.
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Aldebaran
post Dec 30 2013, 11:03 PM
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(Long term lurker here)

It's quite amazing how much is still working, given that Opportunity will have been on the surface of Mars for 10 years as of next month.
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pospa
post Jul 8 2015, 08:50 AM
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Hi, yesterday was 12th anniversary of Oppy's launch from Earth (2003-07-07). Its amazing what she has achieved.
Would anybody know actual status of rover battery pack (available capacity after n-thousands of cycles) and estimation of today's RHU's heat output?
Eventually any update about other component / equipment / tool / instrument degradation or lost vs. remaining functionality.
Many thanks
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craigmcg
post Aug 14 2015, 02:52 PM
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Just curious - has anyone created a log of the decrease in MER capability over time? For example, loss of various instruments, loss of solid state memory, etc? Has there been any planning about what loss of future capability would push it past the line where the cost/benefit ration of running the mission was too low?
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fredk
post Aug 14 2015, 04:05 PM
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There are so many things that could go wrong or partially wrong that once you got into their combinations and permutations it seems to me that the cost/benefit ratio of doing such planning would be pretty high. The benefits to continuing the mission would also depend on the scientific interest at the site she was located at the time.
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TheAnt
post Aug 15 2015, 02:08 PM
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Fredk already covered the question well. IMO opinion the cost/benefit hardly will apply unless the cost is as high as for sending another rover = hugely expensive.

Yet even if all instruments and cameras are dead (The radio has to be working else no mission right? tongue.gif) - there's one thing that Opportunity can do, and which actually were one task planned for Spirit if it had survived that last winter - and that is for the rover to use the radio as a stationary platform that could give hints of Mars interior and perhaps even Mars-quakes - which could be indirectly detected by a change in the planet rotational period.
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MoreInput
post Aug 15 2015, 05:43 PM
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QUOTE (Doug M. @ Aug 15 2013, 09:39 PM) *
Your point about the batteries is a good one -- I hadn't thought of that. Googling turns up a number of papers from the rovers' first few years, basically saying "wow -- these lithium-ion batteries are holding up great!" Not seeing anything since 2010 one way or the other.


Here is an older paper about the performance of the batteries of the rover (only until sol 670): http://www.researchgate.net/publication/23...loration_Rovers
Here is the link to the battery manufacturer: http://yardney.com/

I couldn't find any newer material about this.


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serpens
post Aug 15 2015, 11:13 PM
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One has to give full credit and plaudits to the JPL engineers that designed the battery control board. However, after 4000 odd cycles since landing the battery storage capacity must have dropped significantly (around 50%?). The reducing capacity between maximum charge and minimum voltage cutoff means an increasing risk over those long winter nights. Given that these Li-ion batteries are pretty much first generation post production their longevity is nothing short of amazing.
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nprev
post Aug 16 2015, 05:56 AM
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"Amazing" is not too strong a word at all re Oppy's battery performance. I'm surprised that nobody's published any more recent studies at this point; surely there are MANY good lessons to be learned here.


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A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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craigmcg
post Aug 17 2015, 11:34 AM
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> Yet even if all instruments and cameras are dead...

So some value comes if the only parts left working are the power system and the radio

The other part of my original question was about a "log" that documented the various failure dates of key components. I was thinking about creating some kind of timeline that showed this visually.
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