[X] My Assistant

[RNeuhaus]

This topic is for posts concerning to any preparation of Phoenix Lander Mission to Mars programmed to launch on August 2007 (less than 2 years... but the time will fly)

http://marsprogram.jpl.nasa.gov/missions/future/phoenix.html

Overview

The Phoenix mission is the first chosen for NASA's Scout program, an initiative for smaller, lower-cost, competed spacecraft. Named for the resilient mythological bird, Phoenix uses a lander that was intended for use by 2001's Mars Surveyor lander prior to its cancellation. It also carries a complex suite of instruments that are improved variations of those that flew on the lost Mars Polar Lander.

Canada Will Land Instrument On Mars To Study Weather

http://www.spacedaily.com/news/mars-future-05t.html

Rodolfo

[Guest_BruceMoomaw_*]

Pardon my newbie question, but are there any issues with "temperature contamination" from the lander? If we are trying to study pristine permafrost conditions, what affect would hot thrusters and the attendant gasses have? Would there be any delicate CO2 frost or ice melt that might change the local conditions? Or will the low temperature and pressure of Mars' atmosphere sufficiently dissipate any excess heat quickly enough?

I haven't heard anything about there being any problem with the temperature. Presumably the arm has a long enough reach to get beyond any places on the surface that might have been temperature-modified. (Nor did I ever hear anything about any such problem with Mars Polar Lander, which had similar engines and a similar arm.)

[Bob Shaw]

I haven't heard anything about there being any problem with the temperature...

Bruce:

It's OK, for safety reasons they'll cut the engines at 30m above the surface.

Bob Shaw

[Guest_BruceMoomaw_*]

Ho ho, yuk yuk, har de har har. While going through the report of MEPAG's "Mars Human Precursor Group" on the necessary safety measurements for Mars' atmosphere (more on that soon, down in the "MTO Cancelled" thread), I found the following little note: "Phoenix landing thruster system may erode 0.3 cubic meters of soil, which is a cloud containing a few hundred kg of loose soil and dust." Gaaack. However, they never made a fuss about this for Mars Polar Lander -- which had the same system using touchdown sensors on the foot pads themselves to shut down the engines.

[djellison]

So on one hand we've got reports of a terrain so hard they'll struggle to dig through it, and on the other reports that the engines will blow away 1/3rd of a ton of the stuff.

Doug

[lyford]

Upside down creme brulee?

um, i mean the hard permafrost UNDER the dust....

[centsworth_II]

If the "blow zone" is four meters in diameter, the average amount of surface dust removed by the landing blast would be a couple centimeters. This is still a surprising amount to me.

[Guest_BruceMoomaw_*]

What they're apprehensive about blowing away is the 5 cm or so of loose soil on top of that hard permafrost -- and what they're apprehensive about contaminating with hydrazine is both the soil and the surface of that permafrost. (As I said last night, however, Deborah Bass' August 27 blog entry suggests that they're not all that worried about it.)

[helvick]

(As I said last night, however, Deborah Bass' August 27 blog entry suggests that they're not all that worried about it.)

It bears repeating that Deborah Bass' Blog contain's lots of excellent material and Suzanne Young's has a load of relevant info on the risks (or not) of Hydrazine contamination

[climber]

Hydrazine contamination

Is this still a problem when you know exactely the contaminant and the quantity of it ? I mean, not talking about soil/ice disturbance, can we "remove" Hydrazine from the analysis ?

[chris]

Is this still a problem when you know exactely the contaminant and the quantity of it ? I mean, not talking about soil/ice disturbance, can we "remove" Hydrazine from the analysis ?

In order to be able to remove it from the analysis, you would need to be able to know what
it had reacted with. Since part of the reason for going is to find out what the geochemistry is,
I guess the answer is at very best "perhaps", and more likely "no".

From reading Suzanne Youg's blog, it seems that the engines are very efficient, so hydrazine
isn't a big worry. The ammonia produced by the breakdon of hydrazine may still be an issue though,
as approaching 80% of the exhaust gas is ammonia.

Chris

[climber]

Since part of the reason for going is to find out what the geochemistry is,

Oh Yes! Exploration is. I kind of forget the reason we're doing this, didn't I ?

[Joffan]

Given our struggles to get the power required for Spirit from solar panels, with the sun at about 50degrees up (midwinter midsol at Gusev), how well are the Phoenix panels going to manage? Is there any plan to tilt the panels and catch a few more rays? Or does Phoenix have another power source that I don't know about? (in which case why are the panels there??)

[djellison]

Phoenix is just arrays, they will be almost parallel to the ground - but it will get 24 hr sunlight early in the mission (check the website for an animation that shows this) so a tilt would be a bad idea as you would get from one side only what you would drop on the other.

Phoenix is going to be a short lived mission, the very long, very cold polar night will kill it.

Doug

[helvick]

Given our struggles to get the power required for Spirit from solar panels, with the sun at about 50degrees up (midwinter midsol at Gusev), how well are the Phoenix panels going to manage? Is there any plan to tilt the panels and catch a few more rays? Or does Phoenix have another power source that I don't know about? (in which case why are the panels there??)

Phoenix has a very well defined mission and there will be more than enough energy available for it during it's 3 month primary mission as it will occur during the late NH spring-summer season when insolation at high latitudes is high (higher than at the equator in fact because the sun will never set at all at the height of summer) and it may have enough energy to continue to do some science for up to 190 sols. Extending Phoenix's mission may be only of marginal value though since it has very specific objectives and extending the mission will only really make sense if scheduling difficulties mean that it can't complete it's planned tasks in the first three months or if some of the secondary instruments yield something really dramatic.

I've attached my estimate of the power that would be available from a 1M^2 panel, 26% efficiency cells with an 80% power subsystem efficiency for the Phoenix landing site (70degN) starting on the exected landing date of 10 May 2008. I've put in fairly aggressive dust loss parameters (0.2% per sol) and modelled Tau using the 1997 dust storm model from Viking (which was a medium scale global storm) which is fairly conservative. As you can see there's lots of power for 120 Sols or so but then it rapidly tails off as winter arrives and since it is above the martian arctic circle it will eventually get to a stage (around Sol 320) when it is dark 24.65979 hours of the Sol.

I've no idea what the actual solar panel area for Phoenix is or what the cell types are but 1m^2 seemed reasonable from the pictures I've seen online and 26% efficiency should be about right if they are using recent Triple Junction GaInP cells.

[Joffan]

Thanks helvick, very attractive graphs.

I'm surprised at the idea that you can get more power near the poles than the equator even in summer, since you'll need many hours of 5º sun to equate to an hour of 90º sun. However the trig is too hard for me to do without some serious thought and lots of envelopes with plenty of space on the back, so I'll take your word for it (for now)!

And I guess the other thing is the limited mission, as you say. Once the analysis reagents are used, the most interesting part of the mission is done and the quiet slipping away of the Phoenix will be easier to bear.