Note: I am posting my old blog entries from elsewhere on the internet. This entry was originally posted on 6/30/08.
Today is the 39th anniversary of our first footprints on the Moon as well as the 32nd anniversary of the U.S.’s first landing on Mars with Viking I . And it is Sol 55 of Mars Phoenix.
We have now not only successfully inserted the TECP into the soil several times, but we’ve also spent several days monitoring thermal and electrical properties of the soil and the near-surface humidity. No announceable results yet, but the team is very happy with the data. (And I’ve been happy because I’ve been the person sending up the commands!) For Sol 55, Phoenix is staying awake for over a full day to allow us to get TECP measurements across the entire day, and at the same time the met station and the imager are doing coordinated atmospheric observations with Mars Reconnaissance Orbiter. We will measure the dust content of the atmosphere by looking up at the same time that MRO takes images looking down. We’ve done this several times already through the mission, but not as many in one day.
We’re still trying to get ice into TEGA. Because of the potential for a short circuit, we have to consider each TEGA oven as if it is the last one. In order to achieve mission success, TEGA has to analyze a sample of ice from one of the trenches. The difficulty has been getting the ice out of the trench and into the scoop. First we tried just scraping the icy surface. Then we tried rasping two little holes and scooping up the shavings. That seemed to work, but when we tried again with more holes to get a larger sample, the robot arm had some problems (it may have slid across the ice) and didn’t get the shavings. This is supposed to be the “easier” trench to sample – the ice in the other one is at an angle, which makes getting at it trickier. We’re continuing to do test runs to work out the best strategy to rasp the ice, get the shavings in the scoop, and deliver it to TEGA, all before 7:30 in the morning. The good thing is that the next set of TEGA oven doors opened correctly, and it doesn’t look like there’s any sign of a short. They are still working through some diagnostics.
Finally, if you have a pair of 3d glasses, you should check out our gallery of stereo images.
Questions from friends on the original post:
Q: Ooh, I’m so excited about the ice sampling! How much longer is the mission anticipated to last? You said it won’t be a success unless the ice is analyzed but that doesn’t mean it’s done as soon as you figure out the scraping, right?
A:Short answer: Our primary mission goes until Sol 90, or August 31, but we will have an extended mission until we freeze due to the CO2 seasonal ice, probably in the November timeframe. I am not sure if I will still be working on PHX after the end of August.
Long answer: When a spacecraft mission is approved, when everything is still on paper, there is essentially a contract between NASA Headquarters and the various groups who are coming together to build and operate the mission. This contract includes what science we are going to do (which then feeds into what the instruments are what what resolution of data we will get), and how long we have to achieve that. We have to hit at least what we’ve specified as the science for “minimum mission success” before the end of this timeframe, or we are not considered to be a successful mission. We only have to do the TEGA ice measurement to hit this milestone, but we have a lot more to do before we get to “full mission success.” Phoenix is a Mars Scout mission, which means it was proposed by a group of scientists and engineers and competed against a number of other proposed missions. In order to be selected, we had to prove that we could do a worthwhile amount of science in a feasible amount of time. For Phoenix, since we are so far north, the amount of sunlight hitting the solar panels – providing our power – was a major constraint on the length of operation, as was the temperature. The engineers made a lot of conservative assumptions about temperature, atmospheric dust loading, and so on, to make a strong case for the reviewers. It turns out that we are doing better than those assumptions, so there’s no reason why we can’t keep going past our 90 day primary mission. Of course, when we get to the end of our primary mission but have a perfectly healthy (or even mostly healthy) spacecraft, it doesn’t make sense to just turn it off. But it costs money to keep a mission staffed and operating, so we have to ask NASA HQ for more money, and given the tiny NASA budget, we have to justify having an “extended mission.” For Phoenix, I think it was somewhat understood that we’d just keep going until we lost contact (due to freezing), and they’ve already told us we are extended. But I know that other Mars missions, like the orbiters, have to submit a proposal for an extended mission each time. They write up a document where each instrument team outlines their new science goals for an extended mission (usually in increments of 1 Mars year, or 2 Earth years), and NASA decides if that justifies the cost.
I believe that the only time that a successful mission was turned off for financial reasons was the Apollo Lunar Surface Experiment in 1977 – because we were planning on going back to install a better set of instruments – but possibly there are others. Usually missions end due to something breaking or fuel running out (Viking Orbiters), human error (Viking Lander II and Mars Global Surveyor), or purposeful destruction for scientific reasons (Galileo was sent into Jupiter to prevent it from crashing into Europa when the fuel ran out and contaminating it biologically; NEAR was crash-landed onto the surface of Eros to get higher resolution images and better gamma ray spectrometer data).
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