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Planetary News: Phoenix (2008)Phoenix Soars on Final "Wing" of Flight to MarsBy A.J.S. Rayl PASADENA -- Right on schedule and 168 million miles from Earth, Phoenix is soaring toward Mars on its final flight before touch down Sunday, May 25, scheduled to happen not long after the annual Indy 500 has run its last lap at the Indianapolis Motor Speedway.
If everything goes as planned, Phoenix will race into the Martian atmosphere at almost 21,000 kilometers (12,750 miles) per hour just before 5 pm Pacific Daylight Time [just before 8 pm EDT] and triumph during the seven scariest minutes on the whole mission. In order to land, Phoenix has to make a harrowing seven-minute dive to the surface. It must first endure temperatures of 2,600-degrees Fahrenheit as it begins to initiate and complete a challenging sequence of events to slow itself from 21,000 kilometer per hour to about 8 kilometers (5 miles), then stretch out its three legs and reach for the ground. Phoenix is to touch down somewhere in the middle of a landing ellipse that measures 20 kilometers by 80 kilometers (49.7 miles by 12.4 miles) in the northern arctic plains of the planet, at 68 degrees north right near the polar cap. It should be a talon-numbing -50 degrees F when it sets down Phoenix is a lander, not a rover like Spirit and Opportunity, and its three-month mission -- though more tightly-focused on the target of water-ice that will lie just beneath it and all around it -- is just as important to furthering NASA objectives. From its solitary position in the polar arctic, it will be the first spacecraft to dig into the ice-rich permafrost beneath the surface and spend three months studying the history of the water in the polar ice, investigating whether the subsurface environment in the far-northern plains of Mars has ever been favorable for sustaining microbial life and assess the biological potential of the ice-soil boundary, as well as monitoring weather of the region. But first, this bird's got to go from 13,000 mph to 5 mph, from scorching to way below freezing, in 7:00 minutes and everything's got to work. All 26 little "pyros" have to fire, to release the parachute and initiate all the other systems for landing. There is no margin for error when it comes to landing on Mars. Confirmation of the landing could come as early as 4:53 pm Sunday Pacific Daylight Time (PDT).
"So far, so good," smiled Peter Smith, Phoenix principal investigator, of the University of Arizona. He had just settled into a chair with his sandwich and bag of chips, taking a break and a late lunch amidst yesterday's activities at the Jet Propulsion Laboratory. He arrived Wednesday and he looked relaxed in the way the veteran Mars explorers all do, and gratefully acknowledged the many good wishes and "Godspeeds" he's been getting. By now, of course, he's been asked so many times, 'How's it going?' "It reminds me of the old joke about the window washer," he said. Window washer? The window washer who's had it, given up on life given up on life and decides to jump. On the way down, someone inside sees him, opens the window and asks, 'How's it going?' The window washer looks down, then back at him and says, 'So far, so good.' You have to laugh. But that's a taste of just how scary the entry, descent, and landing --better known simply as E-D-L -- is for these planetary pioneers. Phoenix, of course, with parachute and retro rockets, has a superhuman capability of lighting down. Nevertheless, "this will be a very nail-biting time for us," as Fuk Li, director for JPL's Mars Exploration Directorate, put it earlier during the daily press conference. "The E-D-L process is what I call reverse rocket science." Where rocket science puts a spacecraft up and into flight, reverse rocket science in this context take it from cruising thousands of miles per hour to landing. "Rocket science is hard, but I submit to you that reverse rocket science is even harder," Li said.
Even Smith admits he's sporting a Phoenix tattoo for good luck. Still, as Martian weather predictions -- from the Mars Reconnaissance Orbiter's (MRO's) Mars Color Imager (MARCI) -- go, Sunday looks to be as good a sol as any to land. In fact, Mars is looking particularly welcoming and all the other spacecraft there -- Mars Odyssey, its main communication relay, MRO, the European Space Agency's Mars Express and on ground Spirit and Opportunity -- are ready to assist in whatever ways they can. In fact, MRO will be trying to take a picture of the event for history's sake. "The weather looks good," Smith announced at the press conference. A small dust storm in the northeast is downwind from the landing poses no threat and there is no overbearing amount of dust in the atmosphere, he told the assembled throng of journalists and others at JPL Thursday. "The spacecraft has been behaving so well, we've actually skipped one of the final trajectory correction maneuvers," added Barry Goldstein, Phoenix project manager, of JPL. "The latest calculation from our navigation team shows the center of the area where we're currently headed lies less than eight miles from the center of our target area and we may decide Saturday that we don't need to use our final opportunity for fine tuning the trajectory Phoenix is on. "All systems are nominal and stable," expounded Ed Sedivy, Phoenix spacecraft program manager for Lockheed Martin Space Systems, Denver, which built the spacecraft. "We have plenty of propellant, the temperatures look good and the batteries are fully charged."
The $520 million Phoenix will land farther north than any other spacecraft has on the Red Planet, the first mission to Martian arctic plains and the first to experience the up to -100 degrees F temperatures there. Viking 1 and Viking 2, Pathfinder/Sojourner, Spirit and Opportunity all landed near the equatorial zone of the planet. When it lands, Phoenix will be delivering a special message from Earth to the surface, a silica glass mini-DVD, provided by The Planetary Society, that contains more than 250,000,000 names and a collection of Mars-related literature, art, and audio called Visions of Mars. The disk, designed to last hundreds of years, is sent with the hope that future explorers may one day find the message. In its arctic locale on Mars' northern icy plains, equivalent to the Northwest territories of Canada on the Earth way up near the Arctic Sea, Phoenix –- which sports a 7.7-foot robotic arm -- will be the first to reach out and touch water-ice in Mars' north polar region, scooping into and digging under the protective top soil layer to the layers below. It will then bring both soil and water-ice samples back to the lander platform for sophisticated scientific analysis with laboratory instruments onboard. "There are a lot of things that we're learning about Earth in the Arctic regions," Smith noted at the press conference. "One is that climate change on our planet is written into the ices in the Arctic regions and this is where the history of life is preserved in its purest form, in other words, organic molecules, cellular bacteria and microbes are preserved in this ice. We're wondering if this is true on Mars.
Phoenix is part of larger NASA program to look for life on Mars. As the first mission to return data from either polar region, Phoenix will provide an important contribution to the agency's "Follow the Water" science strategy and will be instrumental in achieving the four science goals of NASA's long-term Mars Exploration Program: 1) determine whether life ever arose on Mars; 2) characterize the climate of Mars; 3) characterize the geology of Mars; and 4) prepare for human exploration. Although liquid water does not currently exist on the surface of Mars, evidence from Mars Global Surveyor, Odyssey and Mars Exploration Rover (MER) missions suggest that water once flowed in canyons and persisted in shallow lakes billions of years ago. Phoenix will probe the history of liquid water that may have existed in the arctic in the past, as recently as 100,000 years ago. By analyzing the chemistry and mineralogy of the soil and ice using robust instruments, scientists will better understand the history of the Martian arctic and determine whether or not it is habitable. "There are three parts to looking for life on Mars," Smith told reporters yesterday. "The first is to follow the water -- that's what Odyssey has done and that's what Phoenix is all about to understand the discovery Odyssey made. We're landing on ice. The second -- is there a habitable zone associated with the water areas on Mars and that is the business of the Phoenix mission. Third and for future missions, and not Phoenix, is this habitable zone" inhabited. "We will not be able to do this. We don't have the instruments."
Although Phoenix may not have the instruments to detect microscopic life and it is not assigned to look for life -- something Smith frequently must say these days -- it is equipped with cameras and should there be, by any bizarre chance, any actual visible "bugs" its cameras could pick up, they would certainly image them. All images from the mission are to be released to the public as they come through the Deep Space Network (DSN) pipeline. Phoenix also boasts a Canadian-supplied weather station and will be studying the Mars' arctic region. Coordinated observations are planned with the orbiters above to get a top-down analysis of the polar atmosphere. Beyond being the world's first Martian arctic explorer, Phoenix is the first of its kind mission in another way. It is being led by The University of Arizona for NASA. This is the first time in space agency history that mission operations are being turned over to a public university Phoenix is the first in the NASA Scout program, missions designed to be highly innovative and relatively low-cost complements to major missions being planned as part of the agency's Mars Exploration Program. Once Phoenix has landed and stretch out it solar array "wings" and tested its 7.7-foot long robotic arm the operations command center will shift to Tucson and the University of Arizona's Phoenix Science Operations Center. That shift is expected to occur on Wednesday, May 28, once the spacecraft is on the ground and its arm has been checked out. The Phoenix Science Team gathered at University of Arizona Monday in Tucson and began to shift to Mars time. Some of the various teams are holding training the rest of the week. "I'd say the mood is relaxed," reported Sara Hammond, public affairs manager for the mission, from the UA. "People are anxious to get on the surface and start their science experiments and investigations. Of course there are concerns about the landing. It's hard to land on another planet. But we're confident the spacecraft team will deliver us safely to Green Valley."
Meanwhile, the university is "sprucing up" the space operations center and making "last-minute improvements" to host 400+ lucky people Sunday for a friends and family event. Wherever they are, Tucson or Pasadena, after five years of intense work, this Sunday will be a Memorial Day weekend the Phoenix team will remember forever. At the moment, all eyes are on JPL and getting down to the surface is the order of the next two days. The excitement and angst and exhilaration and suspense is building and coalescing into a familiar kind of electricity that always seems to crackle around JPL during these events arrival events The usual amount of hand-wringing worries have been drifting west from headquarters. In the end, as every Mars-bound explorer knows, you can do everything you can do and then it's up the equipment and it's up to Mars. But for those who think the effort, the mindstates, and other intangibles can be meaningful, Smith and this team believe in their bird. "The team is committed and dedicated," assured one of Smith's Martian scientist-colleagues, more than many and in ways most are not. That's in part because this team knows the agony of defeat, when the bonding goes deepest. In fact, it is fitting testament to exploration in general that Phoenix will be landing in the midst of Memorial Day weekend. Formerly known as Decoration Day, Memorial Day is an American holiday that commemorates men and women who have died in military service to their country. With every bit of respect to and in honor of those American heroes, this arrival at Mars will also commemorate planetary exploration's fallen, a couple in paticular. Mars Polar Lander entered the Martian atmosphere in December 1999 – and something went terribly wrong. Its engines prematurely shut down and it presumably crashed onto the surface, never to utter a sound again. Its follow-on, Mars Surveyor 2001 Lander was subsequently canceled and the spacecraft, which was nearly completed, was mothballed. Smith and the team developed a plan to bring the Surveyor spacecraft out of storage, thoroughly analyze and test it, resolve all known problems, and add upgrades so it could pursue a new set of science goals.
NASA liked the idea and in 2003, gave Smith and team the green light, allowing Phoenix to rise from the ashes. In fact, it is fitting testament to exploration in general that Phoenix will be landing in the midst of Memorial Day weekend. Formerly known as Decoration Day, Memorial Day is an American holiday that commemorates men and women who have died in military service to their country. With every bit of respect to and in honor of those American heroes, this arrival at Mars will also commemorate planetary exploration's fallen. Phoenix's heritage's from the "faster, better, cheaper" era of NASA, brought with it opportunities, as well as challenges. "One consequence of having so much of the hardware in place from the start was that we could focus our resources into testing and analysis," said Goldstein. We evaluated the robustness of the vehicle to perform the mission we designed, most notably the entry, descent and landing." Extensive testing and analysis also identified concerns that could have affected the lander, solar array deployment, and its science instruments after arrival on the Martian surface. Soon, it was ready for its flight to Mars. The mission has significant international participation: the Canadian Space Agency being is a formal partner, companies in Canada, Denmark, Finland, Germany and Switzerland contributed hardware, and the European Space Agency is playing an improtant role, offering up Mars Express as a witness Phoenix's entry, descent, and landing. Together, the Phoenix team put their bird together and made it happen. On August 4, 2007, the bird, perched atop a Delta II rocket, took off from Cape Canaveral Air Force Base disappearing into the predawn sky, above Florida's Atlantic coast at 5:26 a.m. Eastern Daylight Time (EDT) and spent a pleasantly uneventful 10 months cruising to the Red Planet.
"It's been a very clean flight to Mars," said Sedivy. "Yesterday, we took our EDL sequence that had been loaded in non-volatile memory since launch and unpacked that, if you will, and loaded that and began executing the EDL sequence. So we are live in our EDL sequence, and our spacecraft is completely nominal and we're all really happy. We're ready go. This is the easy part. We're getting to the hard part now." During entry, descent and landing, data from the Phoenix spacecraft will be relayed to Earth through Odyssey. At the same time, however, MRO and Mars Express orbiter will also be monitoring the EDL and collecting data, which will be played back later to Earth. In fact, MRO's High Resolution Imaging Science Experiment (HiRISE) experiment will be attempting to catch a picture of Phoenix as it fireballs into the atmosphere and later as it deploys its parachute. Wishes of "Godspeed Phoenix" and "Good Luck" are everywhere wafting through the ether and in every form, from audio to visual to vibes, the Internet, television news, in the hallways, via cell phones and person to person. The Mars exploration community is small and tight-knit. There's a lot of camaraderie and caring that may seem highly unusual to the outside world, but the support is as solid as it is heartfelt. "Phoenix has an absolutely crucial event coming up, noted Steve Squyres, principal investigator for Mars Exploration Rovers (MER) science, in an interview Wednesday. About 4.5 years ago, he was in the throes of landing anxiety himself with the rovers. While Spirit and Opportunity are keepin' on with their tasks, "to a very great extent right now our thoughts are really with the Phoenix team," offered Squyres. "To the extent that we can help and make things easier by giving them relay assets when they need them -- and giving them people when they need them -- Ray Arvidson has basically left MER and has been with Phoenix for a while -- we're doing everything we can to help our friend on the north end of the planet have a successful mission. We've really got our finger crossed and are rooting for them." Arvidson, the chair of the department of Earth and planetary sciences at Washington University, St Louis, is, indeed, a gift. He's been working Mars missions since Viking, when he was a student at Brown University, under the tutelage of the renowned and revered Tim Mutch, and probably has more experience getting spacecraft down on the ground than any other Mars scientists currently working. Even with all that experience and even though NASA's last three Mars-bound spacecraft made it (despite dark clouds of skepticism hanging all over Spirit and Opportunity), and the European Space Agency's Mars Express dropped beautifully into its orbit, bettering the overall global "batting" average for getting spacecraft to Mars -- landing on that Red Planet is never easy. Phoenix won't be bouncing down onto the surface like the Mars Exploration Rovers did. Rather, it will be using 12 descent rocket engines, retro rockets to power down to the surface. The last spacecraft to successfully land on Mars using retrorockets like Phoenix was the second Viking lander 32 years ago in 1976 and so what is old seems – and is – new again.
"We're confidant," said Goldstein. "We're confidant in that we've done everything we can do. We've retired all the risks." When asked during the Q&A session after the press conference if there is anything comparable in the degree of difficultly of EDL, Goldstein, suggested, tongue somewhat in cheek: "Teenage daughters?" On the last "wing" of its final flight in, at 125 kilometers (78 miles) above the surface, Phoenix will enter the thin Martian atmosphere, slowing itself down by using friction. A heat shield will protect the lander from the extreme, 2,600-degree F temperatures generated during entry. Antennas located on the back of the shell that encases the lander will be used to communicate with one of three spacecraft currently orbiting Mars, Odyssey -- through which most communications will be relayed -- MRO and ESA's Mars Express. These orbiters will then relay signals and landing info to Earth. After Phoenix has decelerated to Mach 1.7 (1.7 times the speed of sound), a tiny little "pyro" or explosive device will fire and the parachute will deploy. Shortly after that, it will jettison the heat shield and activate the landing radar, and then it will extend its legs. Phoenix will continue to descend through the Martian atmosphere until it comes within 1 km (.6 miles) of the Martian surface. At this point, the lander separates itself from the parachute, then throttles up its landing thrusters, and decelerates. When the spacecraft is either at an altitude of 12 meters (39 feet) or traveling at 2.4 meters per second (7.9 feet per second), it will be traveling at a constant or terminal velocity, and then will land while still moving at approximately 5 miles per hour. The spacecraft will be taking data throughout its descent and its recorders will stay on for a minute after landing. When sensors on the footpads of the lander detect touchdown, Phoenix will turn off its landing engines. At the same time, the flight operations team at JPL will also be listening for the confirmation signal from Phoenix using the 100-meter radio telescope at Green Bank, West Virginia. For more information, log back on as coverage of Phoenix flight continues, and be sure to check out Emily Lakdawalla's Planetary Society Planetary Weblog. General Timeline for Phoenix Mission OperationsEvent times are given in Spacecraft Event Time
(SCET), which is the time according to the spacecraft's clock, and also
Earth Received Time (ERT), which accounts for the 15 minutes and 20 seconds
it takes radio signals to traverse the 275 million kilometers (171 million
miles) separating Earth and Mars on landing day. ERT is given both in Universal
Time (UTC) and Pacific Daylight Time (PDT).
The first week following landing will be a "characterization phase," during which the instruments and systems will be ckecked out and tested. Approximately one week after landing, the digging phase will begin, and the first sample of surface soil will be delivered to the Thermal and Evolved-Gas Analyzer (TEGA) instrument. The first analyses will take 10 to 15 days. At the same time as the instruments are being checked out, a parallel effort will be undertaken to determine exactly where Phoenix landed. An approximate location will be known within hours of landing, and two Mars Reconnaissance Orbiter HiRISE images will be taken. However, the knowledge of the location of Phoenix may not be good enough to steer the targeting of HiRISE on the first day. Another imaging attempt planned for the fifth day is more likely to be successful. Digging will proceed in several cycles lasting 8 to 15 days apiece. After each two to three centimeters of digging, new samples will be delivered to TEGA and to the Microscopy, Electrochemistry, and Conductivity Analyzer (MECA). The nominal mission plan accounts for a total of seven cycles of digging and analysis. It is unknown how far Phoenix will have to dig to reach ice, but it is epected to be about two to five centimeters. If the ice is found at the deeper end of the range, the first ice samples may not be analyzed until July or later. The digging phase is expected to last until the beginning of September, 90 sols after landing. Once the digging phase is over, Phoenix will continue to operate essentially as a polar weather station. The mission will end when the Sun travels low enough in the sky that Phoenix no longer receives sufficient power. The spacecraft will conserve power as long as possible. The cameras will search for the first carbon dioxide frost deposits while the Meteorological Station (MET) instrument monitors the weather conditions. The northern autumnal equinox will arrive on Mars on December 26, 2008, bringing winter darkness to the north pole. Phoenix will not survive past this date. In fact, it may not survive beyond November. Emily Lakdawalla put together and contributed this Timeline to this report. For the Phoenix Mars Mission home page, go to: http://phoenix.lpl.arizona.edu/ NASA TV will cover the Phoenix landing events. For information on how to connect: http://www.nasa.gov/multimedia/nasatv/index.html
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