PARIS — A European tracking antenna in Australia failed to pick up any signals from Russia’s Phobos-Grunt spacecraft the night of Nov. 24-25 after two consecutive evenings of success, a setback raising concerns the window of opportunity for sending the stranded spacecraft towards Mars appears to be closing.
Manfred Warhaut, head of operations at the European Space Agency (ESA)’s European Space Operations Centre (ESOC) in Darmstadt, Germany, which controls the antenna near Perth, Australia, that has been trying to contact Phobos-Grunt, said the favorable relative positions of the Earth to Mars now mean that the mission must be recovered immediately, or not at all.
“We are not sure why we were unable to communicate last night,” Warhaut said in a Nov. 25 interview. “It could have been that Phobos-Grunt was only just coming out of eclipse and had not sufficiently charged its batteries to permit communications. It could be because one of the spacecraft’s low-gain antennas is not working. We will now give our teams a rest and, in consultations with our Russian colleagues, renew attempts on [Nov. 28].”
The Russian space agency, Roscosmos, has not said whether the information picked up by the ESA antenna in the previous two days has been of any value in understanding why Phobos-Grunt’s engines did not function, leaving the spacecraft and its small Chinese Mars orbiter stuck in an orbit that, if not corrected, will see it re-enter the Earth’s atmosphere sometime in February, according to the latest estimates. The spacecraft was designed to land on Mars’ larger moon, Phobos, and return samples of it to Earth.
In a Nov. 24 statement, Roscosmos said the data received through the ESA antenna had been passed on to the Phobos-Grunt prime contractor, NPO Lavochkin. The agency had said earlier that the spacecraft must be sent into an Earth-escape trajectory by December or it would lose its chance to reach Mars orbit.
The inability of Phobos-Grunt to power itself beyond low Earth orbit into a Mars trajectory is the latest in a series of attempts every 26 months by one or another space power to take advantage of the Earth-Mars proximity. This year was the first time China took part in the biennial endeavor.
The next big test will be the NASA Mars Science Laboratory Curiosity rover, which must launch by Dec. 18 or wait another two years. At press time, launch was scheduled for Nov. 26.
While ESA officials may have been unable to save Phobos-Grunt, the agency apparently has succeeded in overcoming a solid-state-memory failure on Europe’s Mars Express satellite, which has been in Mars orbit since December 2003.
The memory module on Mars Express — designed to last two years in Mars orbit and now completing its eighth year — appears definitively out of service for most operations, ESA announced Nov. 24. But ESOC ground teams have developed a workaround that will enable science operations, which were stopped in October, to continue with one instrument at a time for now.
Michel Denis, Mars Express spacecraft operations manager at ESOC, said in a statement that the satellite should regain the ability to perform combined operations of its payload by January, returning to near-100 percent operability.
To give it a better chance of finding Phobos-Grunt — whose orbit was known but not with sufficient precision to permit a pencil-thin beam to connect to it — ESA had modified its 15-meter-diameter Perth antenna with a small “horn” that would widen its transmit aperture from 2 degrees to 20 degrees.
Further complicating the task was that Phobos-Grunt’s extremely low orbit takes it into solar eclipse so often that its batteries are apparently unable to sustain a charge. The Perth antenna’s ability to communicate with Phobos-Grunt, when Russian tracking stations had not, was attributed to the fact that the spacecraft was in sunlight and receiving power during its passage over the Perth station.
For the four-man ESOC team, this meant all-night duty cycles.
The link that was first established the night of Nov. 22-23 was done with a 7-bit-per-second link that took some 80 seconds to transmit. To be certain it was properly received, it had to be sent three times during the 6 to 8 minutes during which Phobos-Grunt was within range of the Perth antenna.
Warhaut said data collected by the U.S. Space Surveillance network of ground radars in recent days show that Phobos-Grunt is in a stable orbit. As of Nov. 25, Phobos-Grunt was in an orbit with a perigee of 211 kilometers and an apogee of 315 kilometers, according to U.S. Strategic Command’s Space-Track website. This compares with an orbit of 208 kilometers by 333 kilometers registered by the U.S. network on Nov. 14.
Klaus-Juergen Schulz, ESOC’s head of ground station systems, said devices similar to the horn attached to Perth antenna could be added to ESA’s Maspalomas site in Spain’s Canary Islands if needed. The agency’s third equatorial tracking station is at the Guiana Space Center spaceport.
Schulz said ESA is acting merely as a communications node to Phobos-Grunt and does not know the nature of the commands sent to the satellite, nor the telemetry received from it. Russia’s Phobos-Grunt mission control center sent the commands to ESOC, which then sent them through the Australian antenna.
ESA’s Perth station will soon need to devote itself to preparing for down-range tracking of the second flight of a Russian Soyuz rocket from Europe’s Guiana Space Center spaceport in French Guiana. That launch will carry a French civil-military optical Earth observation satellite, four French military radar-reconnaissance satellites and a Chilean Earth observation satellite.
Warhaut said ESA could make some of the Perth assets available for the Phobos-Grunt operation, especially if the Russian teams want assistance in placing the satellite into a higher orbit or preparing it for atmospheric re-entry.
“The fact is that engineers, we also want to know what went wrong with Phobos-Grunt,” Warhaut said. “It is of paramount importance. We [at ESA] also want to show that we are a very good partner in our hoped-for cooperation with Russia on ExoMars.”
ESA is trying to extend its collaboration with NASA on a Euro-American Mars rover for launch in 2018 to include Russia as a way of compensating for NASA budget constraints that have caused the U.S. agency to back off an agreement to launch an ESA Mars telecommunications orbiter and small lander in 2016.