Europe’s Mars Express orbiter picked up the signal that Phoenix was transmitting as it descended to Mars’ surface on May 25. The data from the Mars Express Lander Communication system (MELACOM) tracked Phoenix and the signal was received on Earth soon after the Phoenix landing. The Mars Express Flight Control Team has now processed the signals, and the sounds of Phoenix descending are audible, loud and clear. ESA says the signal was tracked successfully, even during the expected transmission blackout window of the descent, until the lander was out of Mars Expressâ€™s view. The transmission blackout window is caused because of ionization around the probe, which builds up as the lander descends through the atmosphere and only very weak signals come through.
The closest Mars Express got to Phoenix was 1550 km. Then, as Mars Express flew away, the lander deployed its parachute, separated from it and landed. Then the signal from the lander was cut off.
Listening to the recording, you’ll notice the Doppler effect, which is very similar to what we hear when listening to the whistle of a passing train, of Phoenix and Mars Express getting closer and then farther away from each other.
Link to the sound recording.
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The rest of the recording, the start and the end, contains background noise generated by Mars Express itself.
During the descent, all of the capabilities of Mars Express were focussed on tracking Phoenix with MELACOM. Unfortunately, the science observations carried out during the descent did not lead to the anticipated results.
Over the next few days, Mars Express will monitor Phoenix using MELACOM 15 more times; at least one of these will be used to demonstrate and confirm that the ESA spacecraft can be used as a data relay station for NASA, receiving data from the surface and transmitting test commands to the lander, which may be important if any issues remain with the communication troubles between Phoenix and the Mars Reconnaissance Orbiter.