Robot digger set to land Sunday at Martian pole (Phoenix Mars lander & "seven minutes of terror")

LOS ANGELES - Like a miner prospecting for gold, NASA hopes its latest robot to Mars hits pay dirt when it lands Sunday near the red planet's north pole to conduct a 90-day digging mission. The three-legged Phoenix Mars lander fitted with a backhoe arm is zeroing in on the unexplored arctic region where a reservoir of ice is believed to lie beneath the Martian surface.

Phoenix lacks the tools to detect signs of alien life — either now or in the past. However, it will study whether the ice ever melted and look for traces of organic compounds in the permafrost to determine if life could have emerged at the site.

Before this robotic geologist can excavate the soil, it must first survive a nail-biting plunge through the Martian atmosphere. Despite the rousing success of NASA's twin Mars rovers, which landed in 2004, more than half of the world's attempts to land on the planet have failed.

"It's kind of like first-day jitters," said Ed Sedivy, program manager at Lockheed Martin Corp., which built Phoenix. "There's a lot of excitement, but there's also some nervousness."

Launched last summer from Cape Canaveral, Fla., Phoenix has traveled 422 million miles for Sunday's touchdown.

The spacecraft's main tool is an 8-foot aluminum-and-titanium robotic arm capable of digging trenches 2 feet deep. Once ice is exposed — believed to be anywhere from a few inches to a foot deep — the lander will use a powered drill bit at the end of the arm to break it up.

"It'll be a construction zone," said mission co-leader Ray Arvidson of Washington University in St. Louis. He predicts the ice will be "as hard as a sidewalk."

The excavated soil and ice bits will then be brought aboard Phoenix's science lab. It will be baked in miniature ovens and the vapors analyzed for organic compounds, the chemical building blocks of life.

The last time NASA did tests for organics it was on a hunt for extraterrestrial life in 1976 with the twin Viking spacecraft. No conclusive signs of life were found.

On this mission, Phoenix will also probe whether the underground ice ever melted during a time when Mars was warmer and wetter. If Phoenix finds salt or sand deposits, it might be evidence of past flowing water.

Phoenix's landing target — a broad shallow valley in the high northern latitudes comparable to Greenland or northern Alaska on Earth — was chosen because if organic compounds existed, they're more likely to have been preserved in ice. Researchers do not expect to find water in its liquid form at the site because it's too cold.

"The polar region is a great preserver," said principal scientist Peter Smith of the University of Arizona, Tucson. "Just as in your kitchen you preserve your food in the freezer, so the planet preserves organic materials and the history of life ... inside of the ice."

On Sunday, Phoenix will punch through the Martian atmosphere at more than 12,000 mph. Over the next seven minutes, it will use the atmosphere's friction and a parachute to slow to 5 mph. Seconds before touchdown, Phoenix will fire its thrusters for what scientists hope will be a soft landing. If all goes well, ground controllers expect to hear a signal at 7:53 p.m. EDT.

"Try holding your breath for seven minutes," he said. "It's plenty of time to get very nervous."

The last time NASA tried a soft landing on Mars, it ended in disaster. In 1999, the Mars Polar Lander was angling for the south pole when it prematurely shut off its engine and tumbled to its death.

The loss, coupled with the earlier failure of the Mars Climate Orbiter during NASA's "faster, better, cheaper" era, forced the space agency to scrap another lander and restructure its Mars exploration program.

Phoenix, named after the mythological bird that rose from its own ashes, was cobbled together from the mothballed lander mission in the wake of the back-to-back failures.

Barry Goldstein, project manager at NASA's Jet Propulsion Laboratory in Pasadena, said engineers extensively tested Phoenix's systems and instruments to minimize risk of failure.

"Since we inherited a lot of hardware, we spent a lot of effort in testing this vehicle and understanding how it works," Goldstein said.

If successful, Phoenix would join the twin rovers Spirit and Opportunity on the Martian surface. Together, the rovers have traveled more than 10 miles in their four years exploring opposite sides of the equator. They have uncovered geologic evidence that water once flowed at or near the surface of ancient Mars.

Unlike the six-wheeled rovers, Phoenix will stay in one spot. The cost of the mission is $420 million, excluding the $100 million NASA sunk into the canceled predecessor. Phoenix will communicate with Earth through the two NASA orbiters circling the planet.

Once on the ground, the 772-pound Phoenix will wait 15 minutes for the dust to settle before unfurling its solar panels. Then it will hoist its weather mast and beam back the first images of its surroundings. Over the next several sols, as days are known on Mars, it will check its instruments and stretch its robotic arm to scoop up the first soil sample. A Martian day is about 40 minutes longer than a day on Earth.

By around sol 10, Phoenix will dive into the digging phase that is expected to dominate the rest of the mission, excavating about two hours a day.

While scientists say there's a chance Phoenix could live a month or so beyond its 90-day mission to see late summer or fall, it won't survive as long as the rovers. That's because its solar panels won't produce enough power to keep it alive during the Martian winter.

Said Arvidson: "Its feet will be embedded with dry ice and the sun will be below the horizon."

Phoenix Landing Events Schedule
May 21-26, 2008

http://www.nasa.gov/mission_pages/phoenix/news/landingevents.html

Unless otherwise noted, the location for news briefings and commentary are NASA’s Jet Propulsion Laboratory, Pasadena, Calif.
Times are Pacific Daylight and some are subject to change.

Thursday, May 22
— News briefing, 11:30 a.m. to 12:30 p.m.

Saturday, May 24
— News briefing, noon
— Trajectory correction maneuver opportunity (TCM6), 7:46 p.m.

Sunday, May 25
NOTE: The times below for the Phoenix spacecraft events on May 25 are for a nominal scenario. Remaining navigational adjustments before May 25 could shift the times by up to about half a minute. In addition, the times for some events relative to others could vary by several seconds due to variations in the Martian atmosphere and other factors. For some events, a “give or take” range of times is given, covering 99 percent of possible scenarios from the atmospheric entry time. For events at Mars, times are listed in “Earth-receive time” (ERT) rather than “spacecraft event time” (SCET). This means the listed time incorporates the interval necessary for radio signals traveling at the speed of light to reach Earth from Mars. On landing day, May 25, the two planets are 275 million kilometers apart (171 million miles), which means it takes the signal 15 minutes and 20 seconds to reach Earth. For some spacecraft events, engineers will not receive immediate radio confirmation.

— Trajectory correction maneuver opportunity (TCM6X), 8:46 a.m.
— News briefing, noon
— Begin non-commentary live television feed from JPL control room, 3 p.m.
— Begin commentated live television feed from JPL control room, 3:30 p.m.
— Propulsion system pressurization, 4:16 p.m.
— Begin “bent-pipe” relay relay (continuous transmission of Phoenix data as it is received) through NASA’s Mars Odyssey spacecraft to Goldstone, Calif., Deep Space Network station, 4:38 p.m.
— Green Bank, W. Va., radio telescope listening for direct UHF from Phoenix, 4:38 p.m.
— Cruise stage separates, 4:39 p.m.
— Spacecraft turns to attitude for atmospheric entry, 4:40 p.m.
— Spacecraft enters atmosphere, 4:46:33 p.m.
— Likely blackout period as hot plasma surrounds spacecraft, 4:47 through 4:49 p.m.
— Parachute deploys, 4:50:15 p.m., plus or minus about 13 seconds.
— Heat shield jettisoned, 4:50:30 p.m., plus or minus about 13 seconds.
— Legs deploy, 4:50:40 p.m., plus or minus about 13 seconds. -
- Radar activated, 4:51:30 p.m.
— Lander separates from backshell, 4:53:09 p.m., plus or minus about 46 seconds.
— Transmission gap during switch to helix antenna 4:53:08 to 4:53:14 p.m.
— Descent thrusters throttle up, 4:53:12 p.m.
— Constant-velocity phase starts, 4:53:34 p.m., plus or minus about 46 seconds.
— Touchdown, 4:53:52 p.m., plus or minus about 46 seconds.
— Lander radio off 4:54:52 p.m., plus or minus about 46 seconds.
— Begin opening solar arrays (during radio silence) 5:13 p.m.
— Begin NASA’s Mars Reconnaissance Orbiter playback of Phoenix transmissions recorded during entry, descent and landing, 5:28 p.m. However, data for analysis will not be ready until several hours later.
— Begin Europe’s Mars Express spacecraft playback of Phoenix transmissions recorded during entry, descent and landing, 5:30 p.m. However, data for analysis will not be ready until several hours later.
— Post-landing poll of subsystem teams about spacecraft status, 5:30 p.m.
— Mars Odyssey “bent-pipe” relay of transmission from Phoenix, with engineering data and possibly including first images, 6:43 to 7:02 p.m. Data could take up to about 30 additional minutes in pipeline before being accessible. If all goes well, live television feed from control room may show first images as they are received. The first images to be taken after landing will be of solar arrays, to check deployment status.
— News briefing, 9 p.m.

Monday, May 26
— News briefing, 11 a.m.

Tuesday, May 27, through Friday, May 30
Daily news briefings at 11 a.m.

Anticipated pace of Mars surface operations
— If operations proceed relatively smoothly, the first eight to 10 days after landing will be a “characterization phase” of checking out and understanding the performance of the spacecraft’s power and thermal systems, as well as the robotic arm and other instruments.
— At the end of the characterization phase (date tba), the first sample of surface soil will be delivered to the Thermal and Evolved-Gas Analyzer onboard Phoenix.
— Analysis of soil from the surface in both the Thermal and Evolved-Gas Analyzer and in the Microscopy, Electrochemistry and Conductivity Analyzer will likely take 10 to 15 days if all processes go well. After that, each additional sampling cycle will reach a deeper subsurface level, in increments of about two to three centimeters. At each different layer, collecting and analyzing samples is expected to take 10 to 15 days, barring operational difficulties.
— How soon the digging reaches the expected icy layer will depend on how far below the surface that layer lies. Estimates in advance of landing range from two to five centimeters. If the ice is at the deeper end of that range, the first analysis of an icy sample could be in July or later.

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