Trio of Mars orbiters to monitor Phoenix probe's landing

日期:2019-02-26 02:16:10 作者:屈突怒氟 阅读:

By David Shiga NASA and the European Space Agency (ESA) are now moving three Mars-orbiting spacecraft into position to watch over the landing of NASA’s Phoenix probe in May. Phoenix launched in August 2007 and will arrive at Mars on 25 May, landing at the southern edge of the planet’s ice-rich northern polar cap. It will dig up samples of the ice and soil there, looking for complex organic molecules and investigating whether conditions there might once have been favourable to life. A record three Mars orbiters will watch over Phoenix’s upcoming landing and help it communicate with Earth. Prior to Phoenix’s entry into the atmosphere, ESA’s Mars Express spacecraft, which has been orbiting the Red Planet since 2003, will use its spectrometers to measure the density of the Martian atmosphere, which can affect the trajectory of an incoming probe. It may also try to observe the heating of the Martian atmosphere due to the probe’s passage. Mission managers have already been testing out Mars Express’s ability to act as a communication link between Earth and Phoenix. “Last year, we practised relaying commands from NASA to Mars Express and then down to the surface, using NASA’s Mars rovers as stand-in for Phoenix,” says Mars Express spacecraft operations manager Michel Denis of ESA. “It worked fine.” The Mars Express team has been making small adjustments to the spacecraft’s orbit since November 2007 so that it will be in the right place at the right time to watch over the landing. NASA’s Mars Odyssey spacecraft, in orbit since 2001, will keep one antenna trained on Phoenix as it descends towards the surface, relaying the lander’s communications back to Earth using a second antenna pointed our way. “We have been precisely managing the trajectory to position Odyssey overhead when Phoenix arrives, to ensure we are ready for communications,” says Bob Mase, Mars Odyssey mission manager at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, US. “Without those adjustments, we would be almost exactly on the opposite side of the planet when Phoenix arrives.” NASA’s most recent arrival, the Mars Reconnaissance Orbiter (MRO), which reached Mars in 2006, fired its thrusters on 6 February to adjust its orbit for the Phoenix landing. Another burn is planned for April. In case Odyssey is not able to relay everything on its own, MRO, like Mars Express, will stand by to record Phoenix’s communications during the landing. MRO has also been taking images of candidate landing sites to help Phoenix mission managers choose a precise location for the lander to touch down. MRO images will also be needed to help scientists understand the characteristics of the location where Phoenix comes to rest, since the lander’s own descent camera will be limited to taking just one picture during landing,