ESA Makes Contact with Russia’s Stranded Phobos-Grunt Spacecraft

by

PARIS — A European Space Agency (ESA) tracking antenna in Australia on Nov. 22 established communications with Russia’s Phobos-Grunt spacecraft, which has been stuck in low Earth orbit since its launch Nov. 8 following an unexplained engine failure, ESA and the Russian space agency, Roscosmos, announced Nov. 23.

A fresh attempt to load commands to the spacecraft will be made late Nov. 23 as Phobos-Grunt again becomes visible, for a period of no more than six or eight minutes, to the Australian station. An ESA official said Nov. 23 that the agency is weighing whether to add its antenna in Spain’s Canary Islands to the task.

It remained unclear whether the communications link between Phobos-Grunt and a specially modified 15-meter-diameter antenna in Perth, Australia, will be sufficient to command the spacecraft to switch on its engines to take it on its intended trajectory toward Mars or, barring that, prevent an uncontrolled re-entry into the Earth’s atmosphere.

Roscosmos officials had said the window of opportunity to salvage Phobos-Grunt would close in early December, after which it would declare the mission a loss. In addition to a lander designed to return to Earth samples from the surface of Phobos, the spacecraft is carrying a small Chinese satellite intended to orbit Mars.

Roscosmos officials say Phobos-Grunt, which until the ESA made contact had not sent signals to ground teams, is in a stable “safe mode” orbit, oriented toward the sun to charge its batteries. The U.S. Space Surveillance Network of ground-based radars said Phobos-Grunt as of Nov. 22 was in an orbit with a perigee of 212 kilometers and an apogee of 318 kilometers. This compares to an orbit of 208 kilometers by 333 kilometers registered by the U.S. network on Nov. 14.

Klaus-Juergen Schulz, head of ground station systems at ESA’s Esoc space operations center in Darmstadt, Germany, said the agency attached a small “horn” to the 15-meter antenna in Perth to provide the widest possible aperture to its transmit signal to establish a link with Phobos-Grunt, whose exact orbital parameters are not known with sufficient precision to use a smaller-aperture antenna.

In an interview, Schulz said the Perth station is particularly well suited to the task because Phobos-Grunt is illuminated by the sun, enabling its batteries to charge, when it is within view of the ESA tracking station. Schulz said ESA and Roscosmos are evaluating whether to add ESA’s tracking antenna in Maspalomas, in Spain’s Canary Islands, to the Phobos-Grunt campaign because its location also permits it to see Phobos-Grunt while the spacecraft is illuminated by the sun.

Even if Phobos-Grunt is in safe mode, its orbit takes it so often into solar eclipse that its batteries likely drain, meaning communications links may need to be limited to when the spacecraft is receiving solar power, Schulz said.

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. Russia’s Phobos-Grunt mission control center sent the commands to Esoc, which then sent them through the Australian antenna.

Schulz said it was too early to determine whether the fact that the spacecraft responded to the commands from the Australian tracking antenna by sending a signal of its own means the mission can be revived. The Russian agency has said that if the Phobos-Grunt engines cannot be activated, the spacecraft’s orbit would decay with atmospheric drag, with the spacecraft returning to Earth sometime in January.