Remaining Mer Solar Power Extrapolation, helvick's Power Chart :) Options

[Nirgal]

some time ago, helvick posted the following excellent analysis of the
MER solar power situation as an extrapolation of a diagram showing Watts/hours
against Sols.

http://www.unmannedspaceflight.com/index.p...ype=post&id=580
(originally posted in: http://www.unmannedspaceflight.com/index.p...722&#entry10722)

What makes this chart (let's call it Helvick's Power Chart, HPC so useful, is it's taking into account all relevant factors contributing to the remaining power life time of the rovers: seasonal solar input, gradual attenuation by dust accumulation, and (last not least the "pushing" of the cleaning events.

So here is my suggestion to use this thread/topic for updating this chart
whenever new power figures (watts/hours) and/or new cleaning events are
reported by JPL.

This would be a great way to always get an overview of the best guess of the maximum remaining rover life time (i.e. the limit imposed by the solar power...
which, of course does not take into account failure for other reasons, but would be a nice estimate of the maximum expected lifetime of our little heros

The latest JPL power report

The rover's power team reported a dust-cleaning event on Opportunity between sols 524 and 526. Daily power output from solar panels increased from about 500 watt hours to about 650 watt hours.

underlines the remarkable accuracy of the HPC:
helvick posted the chart on May 18 (aronud Sol 460) predicting the 500 Watts/hour for around Oppy-Sol 540 (note, that the chart shows Spirit-Sols),
which is very well in agreement with the new JPL report !

Now, with 650 Watts at Sol 530 after the cleaning event, the "critical-below-300-Watt-drop" would be deferred from (approx) Sol 680 to Sol 750, in other words:
about 70 extra Sols as a gift from the cleaning event ;-)

[Cugel]

Would it be possible for the power output to reach some sort of balanced state?
I mean, you have dust setting and dust removing powers at work here. So, if the cleaning events come in a regular enough fashion, it would mean that the power output would remain above a certain level.... for ever???
Or do the solar cells degenerate anyway, regardless of dust? (But in a much lower rate I would guess).

[Bob Shaw]

Would it be possible for the power output to reach some sort of balanced state?
I mean, you have dust setting and dust removing powers at work here. So, if the cleaning events come in a regular enough fashion, it would mean that the power output would remain above a certain level.... for ever???
Or do the solar cells degenerate anyway, regardless of dust? (But in a much lower rate I would guess).

The batteries have a limited number of discharge/recharge cycles, and thermal stresses may eventually cause dry joints in circuits etc, but in principle a solar-powered spacecraft which is protected from the worst ravages of the sun and has no attitude control issues can last a l-o-o-n-g time. Whether or not it'd be doing much, though...

...still, we've heard elsewhere on this forum that DODGE is still alive, and the old Pioneer solar orbiters also lasted an extraordinary amount of time, so who knows!

[djellison]

I think it'll be like gambling. Sometimes you win, sometimes you loose,but eventually, the house will always win and the output drops below a critical level.


Doug

[tedstryk]

I think it'll be like gambling. Sometimes you win, sometimes you loose,but eventually, the house will always win and the output drops below a critical level.
Doug

Well, depends how you look at it. Spirit and Oppy might win in the power situation category in the sense that this cleaning is efficient enough to allow them to live until they fall victim to some other kind of component failure that ends the mission. I will add that I really hope that these things continue their extended lives long enough to take full advantage of MRO...otherwise it seems that its communications package may go to waste, other than the Phoenix interlude, if MSL keeps getting pushed back.

[helvick]

Update to the original chart.

I'm stuck down at the bottom of a net free zone updating over GPRS so I'm just dipping in briefly. This is my current "best" guess based on the very few sample points we've been given. I also cleaned up my earlier data somewhat however it is now more obvious that the two main factors I didn't take into account, Tau and Rover Orientation, played a significant part in the very healthy Power state in the Sol 350-Sol 500 timeframe. Very slick orientation gave Oppy better than 100% of the theoretical level I calculated for it from Sol 275 to Sol 340 or so. The benefits of finding a nice sheltered Sun facing slope in mid winter are pretty clear.

Anyway - I'd love more data and really want to work this out a bit better but here's where i'm at so far

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[ToSeek]

The charts are great, but you might consider adding something to them to indicate when they were made. Right now there's no easy way of telling the difference between actual values and predicted values just from looking at the charts.

[deglr6328]

Oppy exceeds maximum power estimate? Is this because it was resting on the slopes of endurance crater at a favorable angle?

[djellison]

Just a thought - is there some whr info in the mobility reports?

Doug

[dvandorn]

I think it'll be like gambling. Sometimes you win, sometimes you loose,but eventually, the house will always win and the output drops below a critical level.
Doug

I'm reminded of the lyric to the song "The Gambler" -- I should write up a whole lyric, but the line that springs to mind is:

"And somewhere in the darkness,
Ol' Spirit, she broke even..."

-the other Doug

[mars loon]

Well this power chart is outstanding, exactly what's needed for presentations.

may I suggest adding a few real time earth dates (month/yr), perhaps every 100 to 150 Sols, at bottom.

Also, Martian seasons on top to correlate with estimated max power


thanks.

[helvick]

Another variation..

Added a table for Martian Seasons in Mission Year 1\2 (Solstice\Equinox) and Landing anniversary date.
Changed X-Axis to reflect Earth Date (M\D\YY) & Spirit sol
Added shading to indicate the current date (split between "known" data and extrapolated data)

I'm still looking for more precise data on the actual power and want to work on building a better model for the "Estimated Max Power" data - I got the data for this by lifting some values from an insolation chart I found online and making some outrageous assumptions but really want to recalculate that based on actual orbital data\lattitude.

The pointing data that Michael Howard has put together for MMB makes me think that I should be able to get sufficiently accurate information on the actual orientation\inclination of the Rovers to work out pretty accurate "maximum theoretical power"

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[Nirgal]

Thanks again, Helvick for this great analysis !

I bet, even JPL's own models couldn't hardly be more elaborated than your's

speaking of the JPL team: have you considered mailing them for more accurate solar power data ?

maybe someone of them is reading this forum

[helvick]

speaking of the JPL team: have you considered mailing them for more accurate solar power data ?

maybe someone of them is reading this forum 

Well if they are reading - Pretty please?

I don't want to bug anyone about it but if someone is reading this who can publish the data or point me to it if it's already online then I'd be very appreciative.

[djellison]

You may get more info my dredging thru all the workbook sol-by-sol documentation.

Doug