An Xtra leg for Xtra power for Xtra imaging !, Tilting Phoenix for Xtra weeks of activity before winter... Options

[djellison]

Compare the charts on post 12 of this thread. At Sol 250, the difference would be negligable. If the vehicle is still alive then, with or without a tilt ( and don't compare MER power requirements with Phoenix- there's a reason it's gettgin 2kWh now...it needs it ) it would be a miracle.

Doug

[MahFL]

One of the Phoenix team said they will see frost build up near the end of the mission, I think he was hinting sol 120 -150 or so.....

[vikingmars]

Compare the charts on post 12 of this thread. At Sol 250, the difference would be negligable. If the vehicle is still alive then, with or without a tilt ( and don't compare MER power requirements with Phoenix- there's a reason it's gettgin 2kWh now...it needs it ) it would be a miracle. Doug

Agree w/you that if the frost arrives only at sol 250, the difference is negligable for power.
BUT we may witness also some Ls variations : there were an Ls 8.5 difference between the 2 winters witnessed by VL2. It could have been bigger : Ls 15...
So, if the thick frost really built-up earlier (let's say at sol 200), then the Xtra juice will really make the difference for having a continuous monitoring of several interesting spots at the surface...
Anyway, the RA will be no longer useful for trenching. Why not then park it being useful for another purpose, i.e. to tilt the lander and receive an Xtra energy ?

2nd Rationale :
==> It is really just a matter of having the SSI working as long as possible : even gaining one or two more weeks of activity at the end of the mission... Who knows : Mars is always full of surprises for us...
==> the RAC would be, thus, positioned close to the surface to monitor at hi-resolution the frost build-up ;
==> And just think about the impact on the general Public of the release of a SSI pan showing a "snow"-covered Martian landscape !

[brianc]

Apologies if not correct Forum as I'm normally a lurker !

Thinking out of the box - would there be any benefit in stacking large pile of soil in the 'dump' zone ( a Martian sand castle) to image on a regular basis for signs of wind erosion / movement due to lander vibration / tectonics / freeze-thaw etc etc

Might show differential buildup of frost toward winter

[MahFL]

That sounds like a good idea.

[alan]

It Phoenix was able to use its arm to change its tilt it would have to lift one of the legs off the ground.
If you look at this image you can see that two of the three legs are on the north side of Phoenix.
http://www.space.com/php/multimedia/imaged...it%3A+NASA+Ames
If it was possible to tilt the lander it would be tilted mainly to the east or west, most likely west considering the position of the arm.
I doubt tilting it this way would increase the power available.


With regard to frost buildup, after equinox there should be some areas near the north side of Phoenix that are always in shadow.
Perhaps we will see some frost buildup there.

[vikingmars]

Thinking out of the box - would there be any benefit in stacking large pile of soil in the 'dump' zone ( a Martian sand castle) to image on a regular basis for signs of wind erosion / movement due to lander vibration / tectonics / freeze-thaw etc etc. Might show differential buildup of frost toward winter

A very interesting idea indeed ! The Viking team had the same idea, except that they had only a smaller capability to build a big "sand castle" ("conical pile" in scientific terms) than Phoenix' RA, because Viking's shovel was much smaller.
Thanks to Phoenix and its big shovel, we will be able to build even bigger conical piles and see how they evolve from time to time.
Herebelow are 2 pics showing a comparison of such a Conical Pile (here CP #4) built by Viking Lander 1 : left at sol 0921, right at sol 1765, just after having "survived" the dust storm of sols 1728-1742. A change on CP4 (which collapsed) is visible as well as on the surface dust.

[Stu]

Guys, guys... if we're going to do this, let's do it properly...

[phase4]

Guys, guys... if we're going to do this, let's do it properly...

Brilliant joke on a brilliant idea.

[hendric]

Well, we do have lights on the end of the RAC now, so we can take pictures just after sunset and just before sunrise to catch any minute frost that would disappear with the rising sun. I think a sandcastle built with the RAC would be an excellent E/PO opportunity! The RAC could even flatten the sides, and plant a rock on the top!

[fredk]

Plant a rock on top? Hmmm... Remember this is an arctic mission. If the arm controllers are feeling particularly agile, perhaps they could construct an inukshuk:

[Ken McLean]

(Long time lurker, first time poster. Hi)

Just going back a bit to the discussion on solar panel power generation, do the solar panels have any heating conduits in them? I ask because wouldn't CO2 frost on the solar panels cause an aggravated decline in power by diffusing/reflecting light until the panels warm up enough for the frost to sublimate and allow power generation to resume? Presumably it would take slightly longer every day to melt the ice cap on the panels.

And with this in mind, would tilting the lander to point towards the sun (by the hypothetical angle proposed before) make a much larger difference to Phoenix's lifespan than previously shown in helvick's graphs by reducing the angle of incidence and allowing the frost to sublime faster?

I'm just thinking that if the panels could be kept ice free for longer then the mission life would effectively be extended. If there are thermoregulators in the lander (and I imagine there would be for at least some of the componentry - I'm pretty sure MER have them), at what temperature are they designed to keep the vitals above?

Ken

[helvick]

Interesting questions Ken.

The panels don't have heating elements - I'm almost certain of that. They are a very lightweight design that delivers approx 105W/kg at 1 AU (vs about 50W/kg for the MER type rigid panel), total mass of each wing is under 10kg.

The minimum night time surface temperatures will drop towards the CO2 frost point [-123 C] sometime between LS 180 and 210 , that's approximately Sols 205 - 260. Modelling either the effect of frost on the panels or the rate at which it would burn off is well beyond me I'm afraid but it seems probable that a southerly tilt would favourably change the micro climate on the panels\deck so as to add a couple of Sols of extra working time. Once the frost begins to fall in earnest though it's going to be lights out very rapidly I think, whatever gymnastics are tried.

As far as frost\CO2 deposition is concerned I've managed to extract the following from the Mars Climate Database. The basic data seems to only be available as averages across blocks of 30 Ls so I've only got a fairly crude values so far but what is there is interesting. At Phoenix's latitude a thin uniform layer ( <1mm) of frost will have begun to form by LS 210. After that the build up of CO2 proceeds at a rate of around 1cm for every 5 LS or thereabouts and it maxes out at 25cm of solid CO2. If that actually does build up on Phoenix itself there will be about 1.6 tons of CO2 ice on the solar panels (== detached solar panels) and about a ton of CO2 ice on the deck by the end of NH winter. I wouldn't be holding out much hope for a revival after that.

LS..MinTemp.MaxTemp..CO2Ice...PanelIce
Deg...Deg.C...Deg.C......cm......Kg
0......-124....-123......22....1470
30.....-120....-102......08.....529
60......-86.....-23......00.......0
90......-80.....-18......00.......0
120.....-91.....-23......00.......0
150....-108.....-49......00.......0
180....-123....-101......00.......3
210....-123....-123......02.....159
240....-123....-123......08.....508
270....-123....-123......14.....932
300....-123....-123......20....1365
330....-123....-123......25....1646

[tasp]

Surprising amount of interest has been shown here for imaging 'snow' drifts in the Martian boreal realm.

Perhaps a future mission someday might be designed with an extra battery that would be fully charged during Martian summer and then electrically isolated from the rest of the craft, and then with a low power timer circuit, perhaps the battery could be connected to the spacecraft power bus for 1 hour every 30 days or so to take a single image and uplink it to earth or an appropriate Mars orbiter. One might size the battery to the projected winter duration, and time the photos for when the sun is at it's highest point on the days selected. Seems like a white 'snow' field might be photographable with the sun several degrees below the horizon with the high sensitivity cameras we have now. The winter battery might be further justifiable as part of a secondary back up power system for a more robust craft in any regard.

Having a craft with a 'caretaker' mode for winter conditions on Mars might be a pretty good PR tool that would generate scientifically interesting data too.

[Ken McLean]

After that the build up of CO2 proceeds at a rate of around 1cm for every 5 LS or thereabouts and it maxes out at 25cm of solid CO2. If that actually does build up on Phoenix itself there will be about 1.6 tons of CO2 ice on the solar panels (== detached solar panels) and about a ton of CO2 ice on the deck by the end of NH winter. I wouldn't be holding out much hope for a revival after that.

Is that 1.6 tons of CO2 at 1g or 0.4g (in which case it would be about 600 grams)? Due to the lower gravity the solar panels (and indeed the pancam) might be able to withstand a bit of a frost coating before collapsing. But really all this is conjecture because the lander will be well and truly power deprived before the weight of the ice causes any vitals to snap off. Lets just hope it puts up a fight long enough to see some white stuff on the ground. I'm also looking forward to HiRISE images of the site once the sun comes back up in spring.

Ken