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Time to stretch

by Mark Lemmon

March 15, 2008 -
We continued the dry run of the Phoenix mission characterization phase today. With the Sol 1 afternoon downlink, Phoenix completed nearly a full sol on simulated Mars. That includes getting engineering data on the lander’s behavior in the Martian polar environment. Data like that are
crucial, since we will extend what we can do and when we can do things.

The downlink included several images of things on the deck and of the Martian terrain near the lander. Many images of the robotic arm workspace and the rest of our site were taken, but are stored on the lander waiting for the next downlink (morning of sol 2). I jumped the gun yesterday -- we imaged the lidar cover, but the lidar’s first use is part of the sol 2 plan.

An exciting result of the downlink is that communications have performed well enough that we are go to use the high bandwidth communication -- 4x as much data per communications window! That means we can get more of what we have taken, and can plan taking larger data sets. In real life, sol 2 is about as early as this could happen -- it could easily be delayed.
However, we would be able to continue to advance the characterization of the lander with the
lower data rate. We just learn about our site faster with the high rate.

Phoenix includes 3 calibration targets of a new design. They have magnetically protected chips
of various colors and shades of gray. They help us with a couple things. They were designed to allow us to measure sunlight and skylight falling on the Martian surface. That is interesting for our analysis -- sunlight heats the soil, which sublimates ice -- and helps convert what we see on Mars to color a person might perceive. Nearly all Martian airborne dust is magnetic, so we use magnets to shield our targets. The magnets serve as an experiment in their own right, and will help understand how magnetic minerals are distributed in the dust. Anyway … I mention this because we got images of each target, and saw that they got dusty during the landing. But, the magnets did their job and there are still clean areas. We’ll watch the dust accumulate on the magnets over the next 90+ sols, but hope to have clean areas in the middle.

We also started another experiment with a single image. Phoenix has a telltale for measuring wind. A check out image showed it to be in good shape, and ready for use in the next sols. In addition, RAC got most of their check-out images down, too. Interestingly, they show traces of dirt in the scoop. In real flight, that would be bad (a biobarrier leak?). Given our test situation,
it just reflects that there have been many ongoing tests with that scoop.

So far, all the instruments are healthy, as is the lander. We proceeded with the sol 2 plan, despite some minor glitches in our planning tools (ahem, yes, that’s it, minor glitches). The featured activity for the day is the unstow of the robotic arm. This is a complicated operation, with a bunch of imaging documentation (SSI and RAC). There will still be some characterization of the RA to do, but at least after this sol we will have it in a ready position. Lidar gets to do its thing sol 2 (with pictures, of course). And TEGA gets a checkout, on the path to doing an atmospheric composition analysis and then getting ready for a surface sample.

Finally, SSI will continue the initial panorama of the site. We also get to use the camera earlier in the sol (before noon), and hope to be going before 10 AM by sol 3. The lander’s normal “daytime” will be 9 AM to 4 PM, once we understand the thermal environment. We are also continuing a series of images we started sol 1: we image a spot on the lander with a good bit of Mars in the background. We do this repeatedly so that we can see if the lander shifts. There may be settling in the first sols; later, their may be more significant shifting as the RA interacts with the terrain. We need to keep track of how we’re moving around over the trench we’ll soon dig.

So, right now sol 3 is looking like a busy day. That’s a good thing -- if all goes as planned we can advance the RA and TEGA characterization as well as start picking out a site for the first sample, use the lidar and the telltale, and MECA gets to join the fun. If something doesn’t go as planned, we’ll push ahead where we can and repeat what we need to.

The image below shows one of the SSI calibration targets (top center, with several colored circles). Also in the image are a geometric target (far right), communications antenna, and part of TEGA. This image was taken in prelaunch tests -- on sol 1 the image will have Mars in the background.