Whr Figures, From various sources Options

[djellison]

I've been looking at the new entries at the PDS for WHR quotes, to compile as good a list of actual quoted Whr values as I can......so if you find one, add it to this thread and I'll update this post with figures....any source as long as it's an actual figure and an actual sol.


B0515 - 418 Whrs
B0522 - 462 Whrs

[jamescanvin]

Helvick.

One thing that struck me last night. The amount of incident sunlight absorbed by dust on the panels must be quite inclination dependent. (Think of the size of the shadow of a dust grain, or the path length through a thin dust film as the the angle varies) Maybe this is the reason for the power falling off faster than expected?

If this is the case then as we appoach the solstice the rate of change of this effect should decrease and even better, give more power than expected as spring arrives.

Does this make any sense?

James

[helvick]

Helvick.
One thing that struck me last night. The amount of incident sunlight absorbed by dust on the panels must be quite inclination dependent. (Think of the size of the shadow of a dust grain, or the path length through a thin dust film as the the angle varies) Maybe this is the reason for the power falling off faster than expected?

Interesting idea - this certainly would make sense for beam insolation. The assumption that I made was that the "loss" in power due to dust could be described by a simple efficiency percentage as that seemed to be what the mission planners had thought. Now that I think about it it doesn't make a lot of sense to think it could be so simple.

I think I need to try to model this to see how it might effect power throughout the day and as the Sun's altitude changes from Sol to Sol.

Diffuse light (which accounts for around 30% of power generated at the moment) is definitely not affected in the same way - by definition it comes from all incident angles after all.

[Nirgal]

Hi Helvick,

do you also have current dust accumulation loss rate estimates for Opportunity ?

(see also my former posting above)

[helvick]

Hi Helvick,
do you also have current dust accumulation loss rate estimates for Opportunity ?

The problem with Opportunity is that there is very little data - the last update I can find that mentions power was the 400whr number at the end of May.
Using the same assumptions as for Spirit above I get the following for Opportunity at the moment. Power has just about hit its lowest level for this winter (~370) and will stay around there for a while (say around Sol 925\930) and then will slowly creep up to ~420 at around Sol 1080 and then begin to decline back to 300 whr as Tau increases with SH Spring\Summer. Any cleaning events will significantly change that of course.

[Nirgal]

The problem with Opportunity is that there is very little data - the last update I can find that mentions power was the 400whr number at the end of May.
Using the same assumptions as for Spirit above I get the following for Opportunity at the moment. Power has just about hit its lowest level for this winter (~370) and will stay around there for a while (say around Sol 925\930) and then will slowly creep up to ~420 at around Sol 1080 and then begin to decline back to 300 whr as Tau increases with SH Spring\Summer. Any cleaning events will significantly change that of course.

Thanks Helvick !

It's encouraging, that even with your conservative estimate and even without cleaning events,
there seems to be sufficient power for Oppy until at least around Sol 1150

BTW.: I really love those excellent diagrams of yours

[helvick]

More good news on the power front, this time for Oppy - from todays JPL update:

Over the past 50 sols the team noticed a gradual cleaning of the solar panels similar to a more-sudden cleaning event experienced one Mars-year ago in "Endurance Crater." Removal of some of the accumulated dust on the panels allows greater production of electricity from sunlight. Opportunity's solar panels are now producing just over 500 watt-hours per sol.

So Oppy is in very good shape and getting better. The following chart shows that even without any further cleaning Opportunity should have enough power generating capability to last through to next winter.

I think I'm going to break out the Laphroaig and have a wee dram to celebrate.

Spirit hasn't been so lucky (yet) but they have confirmed that her power generating capability is not expected to fall below 275 watt hours which is very good news.

[dilo]

Great news, helvick. I think we definitively need another mission extention, something like another earth year (up to sol 1350). This would allow Opportunity to complete Victoria Crater exploration and, hopefully, Spirit will be able to climb the Mc Cool hill (but probably we need a cleaning event too!).

[Nirgal]

Great news, helvick. I think we definitively need another mission extention, something like another earth year (up to sol 1350). This would allow Opportunity to complete Victoria Crater exploration and, hopefully, Spirit will be able to climb the Mc Cool hill (but probably we need a cleaning event too!).

yes: comleting Victoria exploration and Mc Cool Summit - that would be the absolute dream of the perfect mission !


so let's just pray that the hardware will last long enough ...
<sol 1350 vision>
Oppy is dragging its broken IDD on 3 wheels accross the bottm of Victoria while Spirit finishes a one-eyed McCool Summit Panorama after having creeped to the top at a pace of 2-meters-per day
</sol 1350 vision>