Phoenix sol 58 update: rasping and scraping in Wonderland
Posted by Emily Lakdawalla
24-07-2008 16:00 CDT
Today I caught up with Leslie Tamppari, Phoenix project scientist, to get the latest from Mars' north pole. What I was most concerned about was trying to understand the chronology and rationale of all the work they've been doing at their trench site at Wonderland, and where they think they are headed with TEGA. So here's the recent timeline in a nutshell, some of which overlaps with what I talked about from my previous conversation with Ray Arvidson.
- On sol 47, having finished up some work with the TECP, they commanded the arm to move and accidentally ran it into the rock named Alice. This wasn't a big problem, it just caused a one-sol hiatus in arm operations, because they had to figure out what the situation of the arm was on sol 48; the rest of sol 48 was filled out with remote sensing stuff. More on that below.
- Sol 50 was their first successful rasping, consisting of two holes, as I discussed previously. However, Leslie told me that the placement of the rasp wound up being farther back in the trench than they had desired, and as a result they weren't confident that they'd actually rasped into hard material.
- Then, on sol 51, while trying to scrape clean the trench, the arm ran in to some kind of little obstruction at the bottom of the trench, so it met more resistance than expected. After three attempts to scrape it quit trying and waited for further instructions, and they spent sol 52 figuring out what went on.
- So on sol 53 they tested out the rasping procedure again, doing four holes. Again, though, it was a little farther back in the trench than they really wanted and they weren't completely sure they got into the hard, icy layer. They also got the TEGA oven 0 doors open.
- On sol 54 they did a test placement of the rasp on the bottom of the trench, but then they had to pause their rasping work to get ready for an overnight campaign with the soil temperature and conductivity probe, TECP. On sol 54 they also took the ground photos for that cool "midnight sun" montage.
- Sol 55 was spent on this lengthy campaign with TECP and also atmospheric observations coordinated with Mars Reconnaissance Orbiter. Every two hours, as the orbiter crossed Phoenix' latitude, Phoenix gathered measurements on its sky as the orbiter did too. Particularly involved was Mars Climate Sounder, which was able to point over in the direction of Phoenix to make measurements from the sky down as Phoenix was pointing from the ground up; they did this for more than a full sol.
- On sol 56 they tried a third test of the rasping procedure. This time they followed the rasping by using the scoop over the rasped area to try to scoop up any raspings that may have fallen to the bottom of the trench, maximizing their sample volume. The team was pleased enough with how this test went that they decided to proceed toward the real sample acquisition for TEGA.
- On sol 57 they scraped the heck out of Snow White to get it ready.
- A last test on sol 58 was to do a few scrapings and then take pictures over the course of the sol to see what changes unfolded; Leslie says they're still analyzing those images but think they see both sublimation (icy material going away) and frost formation (ice from the air condensing on the ground).
- They're now planning sol 59. They're moving toward the TEGA acquisition but Leslie had to run away from the phone to get back to her planning meeting so it wasn't clear to me whether the sample acqusition could actually happen on sol 59. I think not; I think they'll do last preparations of the trench on 59, and, if everything looks good, acquire and deliver the sample in the very early morning hours of sol 60.
- Finally, Leslie cleared up something I've apparently been confused about for a while. The reason they're pressing toward getting an ice-rich sample for TEGA is because of concern about a possible short. This short is a "high-side" short that could affect the whole instrument. It is not the same as the short that affected oven 4; that one is "cleared," it can't possibly affect the operation of TEGA in the future.
- Also, she mentioned one further detail about the problem with the TEGA doors: apparently the manufacturing problem is with "the rail at the bottom," and that it wasn't manufactured to a precise enough tolerance, so in some places it seems to bind the motion of the doors and in some places it does not.
The Phoenix team simulates all these moves with software and often using a full-scale mockup of the lander, but there are always slight differences between the real world on Mars and the test world on Earth, and in this case some difference between the two resulted in the arm on Mars attempting to move the scoop through a space that included the ground and the rock they named Alice. This wasn't a big deal -- the lander could tell when the arm contacted the ground, and it quit executing its sequence, and waited for further instructions from Earth. The circumstances were just like any number of aborted drives that have happened with the rovers. And in the end it got me a neat picture of the arm buried in the soil. They took sol 48 to look at where the arm was, and then moved on with their work.Hopefully, next week's update will cover triumphant news of a successful sample delivery to TEGA oven 0!
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