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Planetary News: Phoenix (2008)Phoenix Ready to Snatch First Sample for AnalysisBy A.J.S. Rayl
TUCSON -- After completing two practice rounds of digging and dumping the clumpy soil at the Martian arctic site this week, engineers and scientists at the University of Arizona uplinked commands to Phoenix last night directing it to take the mission’s first samples, then deliver them to the lander for analysis. But Phoenix never got its daily agenda. Although Phoenix has been going through its motions exceptionally well – so far maintaining its pre-arrival reputation for being “one of the most well-behaved spacecraft ever,” as a number of JPL engineers put it on landing day – its ground team learned this afternoon that Mars Odyssey, which it has been using to relay data to and from Earth, had entered a "safe mode." During safe mode, the orbiter turns off non-essential operations and waits for instructions from Earth. That means the instructions uplinked last night never got to the lander. So, Phoenix flew to its fallback plan, completing a sequence of commands preprogrammed into its flight software just in case of incidents such as this communication delay. The sequence includes instructions for the lander to continue taking the hundreds of pictures required to assemble its first full-color 360-degree high-resolution panorama. The hope now is that Phoenix will collect those much-anticipated samples at the next available opportunity, perhaps as early as tomorrow, Thursday, June 5. Whether it’s tomorrow or the next day, the targets have been chosen. Phoenix will swoop down with its arm and snatch the first three samples from a chosen area right next to the trench dug by the two practice scoops. The team has christened the first three samples Baby Bear, Momma Bear, and Papa Bear, in line with their theme fairy tales. The first of the samples, science team members have decided, will be Baby Bear. After Phoenix grabs the sample, it will take pictures of the scoopful to document the collection, then send them down to the team. Once confirmation is made, Baby Bear will be ready for delivery to the lander's Thermal and Evolved-Gas Analyzer (TEGA) oven that will bake and “sniff” its composition. Until Odyssey’s engineers determine what happened and restore their spacecraft, the Phoenix team will turn back to the Mars Reconnaissance Orbiter (MRO) to uplink commands and receive downlinks.
The Phoenix team was initially uplinking commands to the lander through MRO’s Electra UHF radio, but when it unexpectedly powered off during a relay pass on Sol 2, May 27, 2008, they switched to Odyssey. During the past week, however, the big orbiter’s Electra radio has been repeatedly “exercised” and appears to be operating well. Odyssey has gone into a safe mode before and has always emerged in fine form. As per protocol, the orbiter’s mission managers immediately began troubleshooting and conducting a thorough checkout of the oldest spacecraft at Mars to figure out what happened. Phoenix – the first mission to dig into Mars with a robotic arm since the twin Viking landers in the mid-1970s – settled into a region of permafrost on Mars's northern plains called Green Valley, a polar area somewhat similar to areas in northern Canada. Its mission objectives are to study the history of water in the Martian arctic, search for evidence of a habitable zone, and assess the biological potential of the ice-soil boundary. Another science goal is to determine whether the ice beneath the surface of this Martian polar region ever thaws during long-term climate cycles. During the last several sols, Phoenix twice successfully reached out its 7.7-foot robotic arm and dug into the arctic soil, emptying its cache onto a designated dump area on the ground once the robotic arm camera photographed the soil inside the scoop. Those two practice digs have already enticed scientists about some bright material in the soil just beneath the surface. "Two scoops into the soil we see there's a white layer becoming visible in the wall of the trench," pointed out Phoenix science team member Carol Stoker, of NASA Ames Research Center, during a morning press conference at the University of Arizona in Tucson. With those two scoopes, the lander dug out an obvious trench the team nicknamed Dodo.
“The science team has been having an impassioned discussion about whether that white material may be salts or ice or some other material even more exotic,” offered Peter Smith Phoenix principal investigator, of the University of Arizona, which is leading the mission for NASA. Whatever the stuff is, it’s likely only good news for the mission, even if it’s some kind of salt, such as magnesium sufate, because concentrations of salts can be indicators of formerly wet conditions, as anyone following the paths blazed by the Mars Exploration Rovers Spirit and Opportunity knows well. Throughout its first nine sols or Martian days, Phoenix’s 7.7-foot robotic arm "has been performing flawlessly," reported Ashitey Trebi-Ollennu of the Jet Propulsion Laboratory (JPL), senior robotics engineer on the mission’s robotic arm team. The arm made daring, Tai Chi or Yoga-like moves to position the robotic arm camera to take pictures underneath the lander and carried out its two test digs "magnificently," he added. "We have only dug to a depth of an inch or two, so we know there are challenges ahead," Trebi-Ollennu added. "But we are confident that we'll get a good amount of material to deliver to TEGA. In addition to the bright material seen where the arm collected test samples, the robotic arm camera also homed in on a layer of hard, light-toned substrate underneath the lander. That light-toned layer, science team members believe, extends around the area of the lander.
"We think the lander is sitting on a layer of this white material that possibly extends beyond, out into our work area," said Uwe Keller, robotic arm camera lead scientist from the Max Planck Institute for Solar System Research in Katlenburg-Lindau, Germany. Phoenix's telltale, which is part of the Canadian Space Agency's meteorological package -- and the highest part of the lander -- has proved to be very sensitive to Martian winds, said Haraldur Gunnlaugsson of the University of Aarhus, Denmark, which provided the device. “It’s also sensitive to the air-conditioning in here,” he said, noting how it moved as he held it up at the press conference. "A storm on Mars” is, for the instrument, Gunnlaugsson said, “a gentle hand movement on Earth." Surface Stereo Imager images of the telltale reveal a diurnal pattern to Martian winds. Winds come from the south in the morning, blow in from the north by mid-day, from the west in the afternoon, and again from the south by the end of the day. Knowledge of wind direction and speed is important to prevent possible contamination of samples during digging. “These are the 10 sols that have shaken my world,” said Smith, reflecting during the press conference on the mission’s first week and half on Mars. “It’s been a marvelous experience. We’ve been improving our imaging at the landing site and it’s an absolutely incredibly rich science location. We’ve looked under at the thruster pits that have done some digging for us and excavated the soil and we see what looks like a hard surface that may be ice may be salt or may be partially rock. We just don’t know yet, but it’s certainly the place where we thought we’d find ice in this location. This is so exciting for us.”
All of the instruments on Phoenix have now been checked out and are all functioning to “the full ability of meeting the requirements,” Smith continued. “This is our characterization and calibration phase and we’re expecting great results from every one of them -- and they’re ready to receive samples. In fact, last night we started receiving, though have not yet processed, images from the optical microscope of soil that was thrown into the air by the thrusters then landed in the microscope station and then been pulled back in.” Those pictures, he added, will be available very soon. Amidst all the testing and checkouts, Phoenix continued to monitor the weather. “Every sol we’re getting a weather report,” Smith said. “We’re watching the dust as it moves overhead on the lander and we’re starting to prepare to do nighttime observations, which will tells us how the weather changes overnight. It could be potentially very interesting as it gets quite cold or, perhaps, there will be frost or something else that forms at night. We haven’t been able to check yet.” The first interactions between the robotic arm and the surface is providing some of the most thrilling drama for the team. “This is where things are getting really interesting,” Smith assessed. “This is what the mission is all about and this is as good a place as we could imagine landing.” For more information:
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