Phobos-Grunt’s mission ends

The Russian probe that was to have brought samples back from one of Mars’ two moons became locked in Earth orbit after its launch. It finally re-entered the atmosphere on 15 January and its debris ended up in the Pacific Ocean.

 

Phobos-Grunt re-enters the atmosphere (illustration). Credit: NASA/Lavochkin/Enjoy Space

Phobos-Grunt was to have marked Russia’s come back to the interplanetary mission scene. In fact, since the failure of Mars 96 15 years ago, Roscosmos, the Russian Space Agency, saw this new probe as a symbol of the revival of their solar system exploration programme.

Rescue attempts
On 9 November 2011, at 00:16 local Moscow time, Phobos-Grunt blasted off from Baikonur atop a Ukrainian rocket which sent it into orbit as planned. Then, the propulsion system, designed and built like the probe by the Russian company Lavochkin, was to have positioned the probe on course to Mars. The ultimate aim was to land on Phobos, the bigger of the Red Planet’s two moons, in order to bring a sample back to Earth. Unfortunately, the booster stage did not fire and Phobos-Grunt stayed locked in Earth orbit.

Diagram of Phobos-Grunt. 1: propulsion system (the one that did not fire - with its aluminium tanks containing toxic fuel). 2: Chinese passenger satellite Yinghuo-1. 3: lander intended to land on Phobos. 4: part of the lander due to return to Earth with a sample from Phobos taken by means of a small robotic arm. Crédit: Lavochkin/Enjoy Space

With help, notably, from an antenna network belonging to the ESA (European Space Agency), Russian mission managers attempted to get data from their spacecraft and even to send it new instructions. Despite all efforts, the probe could not be brought back into line and a permanent failure became more and more inevitable, triggering the anger of Russian President Dmitry Medvedev who promised to “punish those responsible”.

Re-entry over the Pacific
Roscosmos recently estimated that the probe would re-enter the atmosphere around mid January. The Agency tried to be reassuring by reiterating that our planet is 75% composed of seas and oceans, reducing the risks of impact on populations, and that the 7 tonnes and more of toxic fuel in the main stage would be burnt in the upper layers of the atmosphere, as their aluminium tank would not be able to stand up to the heat of the re-entry. It was initially announced that the debris would come down over the Atlantic Ocean.

This map drawn up by Roscosmos, the Russian Space Agency, shows an initial estimation of Phobos-Grunt’s re-entry zone situated in the Atlantic Ocean (red square indicated by the black arrow). But officials have referred to a re-entry, 1,250 km off the coast of Chile (orange dot that we added to the original map), which is at the beginning of the estimated range. Russian ballistics experts do not, however, exclude the possibility that debris could have reached the continent according to the Russian press agency RIA-Novosti. Credit: Roscosmos/Enjoy Space

However, the Ministry of Defence stated that Phobos-Grunt re-entered the atmosphere on Sunday 15 January above the Pacific Ocean at 17:45 Universal Time, 1,250 km west of Wellington Island (situated off the Chilean coast). About 200 kg of debris could have reached our planet’s surface and sunk into the ocean. Russian officials have stressed the lack of danger that such debris represented, highlighting the fact that the 10 micrograms of radioactive cobalt-57 contained in one of the instruments posed very little risk of contamination due to the minute quantities involved. But the destruction of Phobos-Grunt does not just affect Russian scientists because the mission was part of an international co-operation agreement. French participations have therefore been lost as well as the Chinese Yinghuo-1 satellite which was to have been placed in orbit around Mars.
An investigating committee is to determine the reasons for this failure in what is a tense climate in the Russian space industry which was marked by more than one disappointment in 2011.

Published on 16 January 2012