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Emily LakdawallaJuly 23, 2008

How are we coming on Phoenix mission success?

So we're approaching the two-thirds mark on the mission, and some of you readers out there are getting a little antsy about what Phoenix has accomplished to date. The issues with TEGA have certainly slowed down the plans to examine soil samples. But TEGA's not the only instrument on the mission, and things are really going very well. Let's look at the Phoenix mission success criteria and see how the mission is doing. You can read the mission success criteria and other pre-landing plans for the mission in the thrilling document "Mission Design Overview for the Phoenix Mars Scout Mission" (thanks to James Canvin for the link).

Firstly, let's consider the minimum mission success criteria. Phoenix has successfully completed all of these.

Note that even if TEGA hadn't worked at all, Phoenix would still have achieved minimum mission success. But this is a pretty limited list, and I don't think anyone would have been pleased if Phoenix had quit here. So let's now consider the full mission success criteria, which Phoenix is not done with yet. I've put the not-yet-completed items in bold text and commented on them in regular text.So far, so good on this one; the only reason it's not complete is that Phoenix isn't dead yet. If Phoenix continues to take temperature and pressure measurements at the current rate until the mission is over, it can tick this one off.Surface soil samples are complete. Another sample from one spot beneath the surface has been delivered to MECA (the Optical Microscope). So this one is half done. We need two more samples to TEGA, and one more to MECA. There's no concern about getting that last MECA sample -- it's TEGA that's the hangup. By now, they could certainly have delivered two soil samples to TEGA -- they have two more sets of open doors and plenty of soil -- but they really want that ice sample, so the last MECA and last two TEGA analyses for mission success are on hold until that all-important ice-rich soil delivery to TEGA.This one is also half done, or less than half, depending on how you count. TEGA has analyzed one soil sample and one atmospheric sample, and there are two soil samples to go. But since "create a profile" is also part of this criterion, and you need at least two points to make a profile, I'd say there's still a ways to go on this one.This one is almost done, and really there's no reason it couldn't be done now except that they've been devoting all their attention to TEGA. There have been two wet chemistry sample analyses, and at least three Optical Microscope observations (I'm not sure of the actual count). Note that the mission success criteria don't state anything about whether any Atomic Force Microscope measurements must be made successfully. Once the robotic arm is free to get a sample for MECA, they'll be able to be done with this one.There have been six samples to date, and they have all been thoroughly imaged. So completing this one rests only on getting on to those other samples.

I'd venture a guess, though, that although NASA would be able to call Phoenix a success if that's all it completed, the scientists wouldn't be satisfied. I'm sure that in their hearts, the science team wants more: four wet chemistry lab analyses, eight TEGA samples, successful operation of the Atomic Force Microscope, and a life a lot longer than 90 sols, just to name a few. The mission success criteria also don't take into account the extensive campaign of coordinated observations they're doing with Mars Reconnaissance Orbiter. Nor do they even mention the TECP probe on the robotic arm. Nor do they include the ongoing observations of atmospheric properties and high-resolution targeted shots of various spots in the landscape with the mast-mounted camera, which are very effectively making use of lander resources that are not being taken up by the laborious process of acquiring an ice-rich soil sample for TEGA. So Phoenix has already done a lot more than its "mission success" criteria include -- yet it's also done less, where TEGA and MECA are concerned.

I do still plan to have a more detailed sol-by-sol update on Phoenix, but probably won't have it ready until at least tomorrow, so stay tuned.

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Emily Lakdawalla

Solar System Specialist for The Planetary Society
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