Opportunity General Health |
Opportunity General Health |
Aug 15 2013, 10:25 AM
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Member Group: Members Posts: 102 Joined: 8-August 12 Member No.: 6511 |
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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Jun 3 2017, 01:09 PM
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Member Group: Admin Posts: 976 Joined: 29-September 06 From: Pasadena, CA - USA Member No.: 1200 |
The wear and tear on the brushes is proportional to each actuator use. If you take the current rover odometer, divide by one wheel circumference and multiply by 1500 (the gear ratio) you get a decent number (100 million revs) which is not too shabby but not too out of specs.
Oppy RF steering actuator if I remember correctly (it happened close to 14 years ago!) the most likely theory was that the magnetic detent came unglued and got jammed into the motor. Spirit RF (and at the end the RR) drive actuators instead were suffering from what appeared to be a contact failure between the brush and commutator as if there was a non-conductive layer deposited over time. We called that "napping motor". This is also different from the Joint 1 actuator on Oppy's IDD. That one was attributed to a broken winding wire due to fatigue caused by thermal expansion/contraction ultimately due to the stuck shoulder heater. All actuators on MER are brushed motors, except the stepper used on the MI dust cover mechanism. That one was built as an open loop control. Open loop is now also used on the three RAT actuators, but that is due to the loss of signal from the encoders due to wear and tear on the IDD flex cable). Now you know almost as much as what we tell to new rover driver trainees. Paolo PS: questions... longevity... incept date... Eyes, I only do eyes! -------------------- Disclaimer: all opinions, ideas and information included here are my own,and should not be intended to represent opinion or policy of my employer.
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