Russian Space Program Prepares for Phobos-Grunt Re-Entry

by David Warmflash on December 13, 2011

Configuration of the Phobos-Grunt spacecraft. Credit: NPO Lavochkin

Editor’s note: Dr. David Warmflash, principal science lead for the US team from the LIFE experiment on board the Phobos-Grunt spacecraft, provides an update on the mission for Universe Today.

As last-ditch efforts to recover control of the unpiloted Phobos-Grunt spacecraft continue, officials, engineers, and scientists at the Russian Federal Space Agency (Roscosmos) have shifted their focus to the issue of reentry. Launched November 9 by a Zenit-2 rocket on a mission to return a sample from Phobos, the larger of Mars’ two small moons, the spacecraft reached low Earth orbit. However, since the engine of the upper stage that was to propel it on a trajectory to Mars failed to ignite, the spacecraft continues to orbit Earth in a low orbit. Despite some limited success in communicating with Phobos-Grunt by way of tracking stations that the European Space Agency (ESA) operates in Perth, Australia, and Masplalomas, Canary Islands, the spacecraft remains stranded in an orbit whose decay will take the craft into the atmosphere sometime in early January.

Beginning on Tuesday, December 13th, Phobos-Grunt’s course around Earth will expose it to sunlight, constantly for about thirty hours. Since difficulties in communication may be influenced by the amount of time that Grunt’s battery remains charged, constant sunlight may increase the chance that spacecraft will respond to commands to boost its orbit. Thus, Roscosmos has asked ESA to renew efforts to hail the spacecraft during the sunlight period.

In a letter sent to the international team of scientific collaborators participating in the mission, Lev Zelenyi, Director of Russia’s Space Research Institute, wrote that the analysis of the coming reentry will include calculations of the probability of where and which fragments may hit the ground (if any). Zeleny also noted how non-Russian organizations, such as ESA, NASA, NORAD-STRATCOM, and numerous amateur observers, have been helping in tracking the spacecraft to understand its orbital and attitude parameters and to establish communication.

The Planetary Society’s Living Interplanetary Flight Experiment (LIFE) capsule, on board the Phobos-Grunt spacecraft. Credit:The Planetary Society

Although it is more likely that spacecraft fragments will come down over water, should the return capsule come down on land it is possible that useful engineering and scientific data could be recovered. Designed to carry a sample of regolith (surface material consisting of crushed rocks and dust) from Phobos, the Grunt return capsule is about the size of a basketball and also carries the Planetary Society’s Living Interplanetary Flight Experiment (LIFE).

In traveling to Phobos and back over a period of 34 months, LIFE was to provide insight as to the question of whether life on Earth could have originated on Mars and survived transit billions of years ago. Though it will have traveled only in low Earth orbit for just over two months, the return of the LIFE biomodule from space would have some value in terms of astrobiology, while also confirming that the engineering of both the biomodule and the return capsule is sound. Designed to withstand a force 4,000 Gs, the LIFE biomodule is suitable for a variety of space missions.

While concerns have been raised that the many tons of hydrazine and nitrogen tetroxide in Phobos-Grunt’s fuel tanks may pose a danger, the fuel is expected to burn up high in the atmosphere. One of the probe’s instruments, a Mössbauer spectrometer, contains Cobalt-57, a radioactive isotope, but the quantity is so small that no problems are anticipated.

While efforts to hail Phobos-Grunt will continue until the craft actually begins a fiery descent in January, Roscosmos is moving forward on several unpiloted missions to explore Earth’s own Moon, beginning within the next 2-3 years.

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