NASA - National Aeronautics and Space Administration

It's a rainy day here in Pasadena, CA today, but the weather looks good on Mars for a landing this Sunday. As of 4 p.m. PDT on Friday, May 23, Mars Phoenix Lander has 2.17 million miles still to travel in its 422-million-mile flight to Mars. It remains in good health. The battery cells were recently balanced (so that they all provide the same power), and our navigation team is having daily meetings to evaluate the trajectory of the spacecraft to determine whether a final trajectory correction maneuver will be required on Saturday night. There will be a press conference tomorrow at noon (Pacific time) to relay the status of the spacecraft and the decision for a final trajectory correction maneuver tomorrow night. I will also post another blog update following the press conference to summarize the information that was provided, for those who are interested but can’t tune in to the press conference. Now on to some more fun facts!

As Phoenix approaches Mars, we do daily checks of the health and status of the spacecraft to make sure all the subsystems (propulsion, guidance, navigation, and control; etc) are in good health and ready for Sunday. A status check is also built into the sequence of events that takes place on Sunday.

Some folks are wondering if there is anything we can do to adjust our landing site if we arrive and decide we don't like it. The way Phoenix is designed, our thrusters can't lift Phoenix off the ground and move us to a new location once we’re landed. They're designed purely for controlling our descent, not to fly us to a new location. Fortunately, the business of selecting a desirable landing site was a process that began before we even launched. Throughout the course of this project engineers and scientists have gathered periodically for "Landing Site Workshops" to select a location that will provide an opportunity to have a safe landing and do some interesting science. Our navigation team has then worked throughout the cruise phase to assure that we’ll land within an ellipse on Mars that is 120 kilometers long by 20 kilometers wide. Wherever we land in this ellipse, we should find plenty of science to do. Once we land, if we find that we're perched in a precarious position on top of some rocks, there is a possibility that we could use our robotic arm to shift the lander slightly into a more stable position.

Speaking of images, one reader asked whether we take any pictures of Earth or Mars during the cruise phase. All the cameras Phoenix carries are sealed away with the lander during the cruise phase. Although we have taken a few test images inside the "cocoon" created by the backshell and heatshield, we don't have the ability to take pictures of Earth or Mars during cruise. Deploying our Surface Stereo Imager, however, is one of the events that will happen during the surface initialization phase that takes place just after landing. While the first images will be of the lander itself, with a little luck we'll have some pictures of the Martian landscape by the time of the press briefing on Sunday evening.

Another interesting topic of discussion has been the speed and position of the spacecraft. This is an interesting question because everything in space is moving, so the answer is different depending on what you're referencing your speed and position to. For instance, Phoenix is currently traveling 75,400 miles per hour with respect to Earth. With respect to the sun, however, Phoenix is traveling 44,300 miles per hour. With respect to Mars, Phoenix is traveling a modest 6,090 miles per hour. During most of cruise, these speeds stay relatively constant. As we get closer to Mars, however, our speed begins to increase dramatically due to the extra pull created by Mars' gravity. As for position, Phoenix is currently 170 million miles from Earth, 154 million miles from the sun, and 164,000 miles from Mars. Our navigation engineers use a combination of software packages and tracking data in order to determine where Phoenix actually is and where it will be.

I will be posting a brief update tomorrow, but in the mean time, check out the new real-time, narrated animation of EDL:
+ Play narrated landing animation

Brent Shockley
Phoenix Configuration and Information Management Engineer

To learn more about the spacecraft and the mission, check out the following sites:
www.nasa.gov/phoenix
http://phoenix.lpl.arizona.edu/
www.jpl.nasa.gov/news/phoenix/

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