Phoenix Lands on Mars today

Mars Phoenix - Entry into atmosphere
Mars Phoenix: Entry (NASA/JPL-Caltech/University of Arizona)

Phoenix mission lands today — in less than 6 hours. The mission homepage has a countdown clock.

Arizona Republic has the background story. (AZ news sources are good to check; the science part of the mission is being run out of University of Arizona)

Today on NASA TV: Noon Pacific/3pm Eastern press briefing. Live coverage at 3pm Pacific/6pm Eastern.

Emily Lakdawalla of the Planetary Society will be liveblogging from JPL.

I’ll be at the Planetary Society Planetfest Event at the Pasadena Hilton today. I’ll liveblog if there’s wifi. But if not, go read Emily’s blog. Here’s some background.

Mars Phoenix - Descent and deceleration
Mars Phoenix: Descent (NASA/JPL-Caltech/University of Arizona)

The most critical time in the landing is the final 7 minutes — that’s when the spacecraft enters the atmosphere, decelerates (involving heat shields and high temperatures), jettisons coverings at the right time, gets a radar lock on the ground, and fires retro rockets to slow the spacecraft to a 5mph landing. It’s all done on auto-pilot, all the programming and engineering are done, and all anyone can do is wait and monitor the signals. When we receive signal, it’s 15+ minutes after the events have transpired–that’s how long it takes for the radio signal to travel from Mars to Earth.

When they launched the mission, one of the engineers described landing as “we’re not landing on the planet, we’re landing on a model” — a mental and statistical model of what the surface of the planet is like, constructed from all the info we have gathered in past missions and with the orbiting spacecraft. Those 7 minutes are the crubicle where mental model meets reality, combined with health of the spacecraft. Are all systems functioning successfully?

Those seven minutes are the moment of supreme tension: willitwork? willitwork? comeonbaby–Land! ohpleaseplease don’tletMY partofthemission bethethingthatBreaks. The stakes for this mission are higher, of course. Last decade, the first Mars Polar lander, the elder twin of this spacecraft, disappeared without a trace. In an effort to cut costs, that mission had no telemetry for EDL (entry, descent and landing). What happened? How did things go wrong? We don’t know for sure.

Telemetry is the sending of spacecraft health signals and information about instrumentation that are in operation all the way down to the surface. Since that time, JPL has placed two or three spacecraft into orbit around the planet. (One of those spacecraft has stopped functioning). Those satellites pick up signals from the landers and transmit back to earth. The radio transmitters on the spacecraft don’t need to “shout” as loud and far as if there were no satellites. So between the Mars Polar Lander failure and the ability to capture signals more easily, telemetry during EDL is now essential.

Mars Phoenix - Landing
Mars Phoenix: Landing (NASA/JPL-Caltech/University of Arizona)

Doc M (who works at JPL in the radar section, and has been working on the radar systems for the next Mars mission, MSL) described the underlying mood on Friday. Two people converse– they’ve worked on the radar for Phoenix.

A: Are you in mission control?

B: No. I’m watching from the auditorium (location where Phoenix staff who aren’t at mission control –and families–will watch). You?

A: No, I’m going to go to a quiet place and wait it out.

There are many, many nervous JPL, NASA, UofA and Lockheed employees today.

Coming up: Jargonwatch. All the terms they’ll throw around during NASA TV coverage that will help you understand what they’re saying.