[X] My Assistant

[Guest_Oersted_*]

OK, premature, premature, but still... After a succesful landing and thouroughly having dug holes and trenches in the original working volume of the arm: how about moving about a tiny bit? - I was wondering if the rocket engines could possibly be used to shift position just a few decimeters at a time. Small blips, which should be so weak that they wouldn´t overturn the lander.

It could also come in handy when the snows come in later in the year and threaten to bury the lander.

A few things would be necessary: no post-landing venting of possible excess fuel (who knows about that?). No permanent disabling of the rockets after EDL. A possibility to stow and unstow the solar panels (ok, that is probably a show-stopper, but just humour me here...). The last would only be an issue if it was thought that small blips of the rockets would raise sufficient dust to degrade the solar panels´efficiency.

Just thinking out of the box here... - And I know it very probably won´t ever happen. But if!

- Well, let us just get this baby down in one piece for now.

[edstrick]

Actually, I expect there would be some value in Phoenix being able to move... particularly as the once concieved Viking 3 lander <with mini-crawler treads instead of footpads>

The landing site is homogenous on a large scale, 100 meters or so, but heterogeneous on a scale of 10 meters or so. It also has topography on that scale.

The lander might land, for example, with a polygon-trench just out of reach of the arm... it would be of value to be able to move 5 meters and trench across the polygon, even if all onboard sample analysis ability was exhausted.

It would be of value to be able to move 8 meters to the south side of a nearby boulder and do a week's multispectral petrologic study of the boulder, both with mast camera and the arm camera.

Viking 2 saw well defined small drifts in the shallow troughs at it's site. It would be of value to be able to move to where it could trench across one if they are present at the Phoenix site and examine internal structure of the soil... deriving info on recent climate / meteorology history.

And it would be nice to be able to crawl so one foot is in a trough and the others are on the north side, tilting the solar panels to the south to get another month of autumn meteorology.

I thought Mars Surveyor Lander 2001 should have had such ability, I think Phoenix would benefit from it, but it wasn't in the budget or weight margins and it's not onboard.

Some landers, netlander type landers, really don't benefit from the added complexity of limited roving, but a landed "station" like Vikings or other rocket-and-landing-legs landers would.

[djellison]

It would be of value to be able to move 8 meters to the south side of a nearby boulder and do a week's multispectral petrologic study of the boulder, both with mast camera and the arm camera.

It would, indeed, be of value. But that's not Phoenix's job. It's got a very specific very unique job to do and one that mobility is not required for.

As I have said - would a rover been nice in the polar plains? Yes. Does Phoenix need mobility to do its job? No. Would Phoenix even have the time to use Mobility to great effect? At the time of selection, they had a full 90 day digging schedule with one massive trench. The analysis that suggests it is soil then concrete-like-ice will change that perhaps, but Phoenix wouldn't have had time to do the science it's sent for AND be mobile. Let me repeat this so people don't missinterpret me here. Mobility is good. Mobility is great. Mobility is sexy and very very usefull if you're trundling around doing geology on rocks somewhere like Meridiani or Gusev , and indeed a long lived rover up near the pole would be very cool. But - would mobility make Phoenix 10x more scientifically productive?

If Phoenix were mobile, it would not be 4 days from Mars. It would be on PPT's on hard drives on Earth as it wouldn't have gone under the scout budget, and MARVEL would be 4 days out from MOI.

The argument is moot anyway. Phoenix is Phoenix. It's got a job to do, it's going to do it. A fossilized martian 5 cm outside the arm range doesn't change the fact that for the job that Phoenix is going to do, mobility is not required.

The question ' Wouldn't it be nice if Phoenix could move ' is essentially ' Wouldn't it be nice if Phoenix never got selected '. Because that what mobility would have meant to Phoenix during the scout process.

Doug