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Spirit - 2010 Winter@Troy, The first stationary science campaign
Poolio
post Feb 4 2010, 04:22 PM
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He might have been alluding to Ashley's comment found in the latest TPS report:
QUOTE
"The strategy we have for Spirit getting the tilt better [takes us] through a couple of days of it getting worse before a turn around," Stroupe explained.

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Tesheiner
post Feb 4 2010, 05:44 PM
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I haven't seen any decrease in northern tilt for the time being.
And again. That 182Wh figure is from a week ago, sol 2158, before the last drive during sol 2161 where we saw an increase of the northern tilt.

Better wait for the next status report.
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serpens
post Feb 5 2010, 04:10 AM
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Indeed Poolio. From that report quote
'Spirit was slated to drive on 2161 (January 30, 2010) but the results were not available by presstime. The latest data clearly indicate the tilt to the north has degraded or gotten worse. "Before we started driving backwards, we were roughly at 4 degrees southerly tilt. Now, we're roughly in about 10 degrees southerly tilt," Matijevic informed last Friday. But this was expected and should be temporary.'
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Guest_Sunspot_*
post Feb 12 2010, 12:05 PM
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How low do they expect power levels to drop in terms of watts. Didn't Opportunity drop below 100W during the dust storm a year or so ago?
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tanjent
post Feb 12 2010, 12:36 PM
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With regard to the liquid/solid core question, that seems like something really fundamental and important that Spirit can accomplish in her remaining days. I'm not clear on all the details, but I understand that if the rover remains absolutely stationary for a long enough period, very precise measurements can be taken of the planet's rate of spin and precession of the spin axis, and from these conclusions can be drawn about what's going on inside. For a better understanding, I'd be interested to hear informed opinions on the following issues:

A. How long is "long enough"? Do I recall having seen an estimate of "six months" somewhere on the web?
B. Within that time period, does the experiment require a series of observations at regular intervals, or just one "before" and one "after" with no rover movement in between?
C. How will the rover's precise position be determined? Optically, with the use of Hi-Rise, or by some triangulation procedure involving the three working orbiters? Or is there some way to do it from Earth?
D. Just how much precision can be obtained with whatever method is to be used? It sounds like probably a resolution of centimeters is required, but even earth-based military grade GPS is not that accurate, is it?
E. Does the rover have to cease all other activities and remain perfectly motionless during the entire observation period for fear of introducing spurious motions into the experiment?
F. If the rover doesn't make it through the winter, can the experiment be concluded passively by a "dead" rover?

(Sorry about that last one everybody, but really, what more could any of us wish for than to be able to continue doing worthwhile work in the afterlife...)

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djellison
post Feb 12 2010, 12:51 PM
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A - Six months is what I have seen as well
B - A series, I believe.
C - DDOR from the DSN. It's accurate to an extraordinary degree (and is nothing like GPS)
D - Centimetres is what they need, and what they'll get.
E - It's a case of not moving. The arm and camera past can, I presume, still be used.
F - No. It's a case of tracking the radio signal it's transmitting. No transmission, no experiment.
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tanjent
post Feb 12 2010, 01:10 PM
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I remember in grade school, we learned to spin the Easter Eggs on the table to determine if they were hard-boiled or not. This must be a planetary-scale variant of the same technique. (All you out-reachers take note!)
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elakdawalla
post Feb 12 2010, 02:38 PM
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One small correction -- I've been told Spirit can actually roll a few centimeters while the experiment is still going on, so there could be motion first thing in spring when power levels start going back up.


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Poolio
post Feb 12 2010, 03:25 PM
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Spirit had an all time low of 86 whr during the regional dust storm of November 2008. That's an unsustainable level of course, but it only lasted for a few days and Spirit was able to live off her batteries until the situation improved.

I think Opportunity's lowest power level was around 128 whr during the global storm in July 2007.

I don't know how low they expect the power levels to get for Spirit this winter, but I would imagine it doesn't matter that much. Whether the batteries take three days or three weeks to drain, she will still need to endure some lengthy period of being subjected to the unmitigated chill of winter.
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Poolio
post Feb 12 2010, 03:55 PM
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Thinking about the "hibernation" period for Spirit some more, I have a couple questions. Forgive me if these have been covered before; I don't recall seeing anything...

Once she has "shut down" and is hibernating, is it correct to assume that Spirit will not be consuming any power? If so, wouldn't that mean that what little power the panels do generate each day (whether its 10 whr or 100) would go into charging the batteries? And if that's the case, could we expect Spirit to wake up periodically throughout the winter and try to make contact? (Even though the simple act of waking up may prompt her to trip a low-power fault again.)

During any brief periods of wakefulness, would the computers generate enough heat to provide some warmth to the WEB? And (finally!) would such temperature cycles be helpful or harmful to her chances of long term survival?

Sorry for all the hypotheticals. I know that the hibernation period has been discussed, but I don't recall seeing anything about the possible effects of cyclic sleeping and waking.
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djellison
post Feb 12 2010, 05:04 PM
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QUOTE (Poolio @ Feb 12 2010, 03:55 PM) *
is it correct to assume that Spirit will not be consuming any power? .......would the computers generate enough heat to provide some warmth to the WEB? And (finally!) would such temperature cycles be helpful or harmful to her chances of long term survival?


Back in the pre-Victoria entry power crisis, but that was nearly 3 years ago, so I'm working off unreliable memories here...

These documents may help :
http://trs-new.jpl.nasa.gov/dspace/handle/2014/13037
http://trs-new.jpl.nasa.gov/dspace/handle/2014/13105
http://trs-new.jpl.nasa.gov/dspace/handle/2014/37750
http://trs-new.jpl.nasa.gov/dspace/handle/2014/17736

in particular
QUOTE
The response to low batteries or power faults does not use the scheduled communication windows. If the rover is awake when a low battery situation occurs, the flight software has 60 seconds to quickly shut down before the BCB removes the batteries from the power bus. If it is nighttime when the BCB detects a low battery condition, the BCB takes the battery offline and the power bus crashes. Eventually, when the sun rises, the solar array power supports the bus and the BCB. As the batteries charge back up, the BCB puts them back online to support the bus. At the next solar wakeup, the flight software schedules one LGA communication window at a predetermined hour (11:00 LST) to report to Earth. No UHF windows are attempted because these usually occur in the early morning or late afternoon, when the available solar power is low. The vehicle remains in this configuration (with autonomous shutdown mode active, in receive mode via the LGA, performing one DTE window per day) until the operations team reconfigures the vehicle to resume normal operations


As I understand it, the Rover Battery Control Board ( RBCB / BCB ) remains on - managing and measuring the power generated by the arrays and the battery, and issuing wakeup to the main computer based on either a specific power being generated or a timer.

How, exactly, this will tie in to brown outs, low power faults etc, I don't know

Also - there are RHU's within the WEB to generate a certain ammount of heat.

As for thermal cycles, every single day-night cycle is a thermal cycle and every single one runs the risk of a solder fracturing or a wire breaking.
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fredk
post Feb 12 2010, 08:32 PM
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QUOTE (Sunspot @ Feb 12 2010, 01:05 PM) *
How low do they expect power levels to drop in terms of watts. Didn't Opportunity drop below 100W during the dust storm a year or so ago?

Another point to always keep in mind is that previous lows during dust storms were during the warm summer, when the heating power requirements were less than during winter. So 100 Whrs for Spirit this winter isn't the same as 100 Whrs for her in the summer.
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fredk
post Feb 12 2010, 08:42 PM
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Some details in this update. It looks like preparations for the winter, and the stationary science campaign have begun:
QUOTE
This week the rover team is uploading schedules to Spirit for when to communicate with Earth or with the orbiting Mars Odyssey during the rest of this year and into 2011. Spirit will use these schedules whenever it has adequate power to wake up. Spirit will take a set of "before" images of surroundings from the parked position this week, for comparison with images in the Martian spring to study effects of wind. Images toward the south will also aid preparations for possible future drives... Other preparations for winter will include putting the robotic arm into a position for studies of atmospheric composition when power is available and changing the stow positions of the high-gain antenna and panoramic camera to minimize shadowing of the solar panels.
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Stu
post Feb 12 2010, 09:16 PM
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Guess that's it, then; our girl is hunkering down for the long, hard winter. But we'll keep her company here, on UMSF, that's for sure.

The rubbing sound you can hear is the sound of thousands and thousands of fingers around the world being crossed.


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marsophile
post Feb 12 2010, 10:40 PM
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I assume there is no danger of the flash memory anomaly returning while Spirit is incommunicado?
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