Despite a small period of time where it was hoped communications and commanding might be established with the stricken Fobos-Grunt spacecraft, it now appears the Russian probe’s future is one which will see it head towards a fiery end, as its orbit continues decay over time. The likely scenario now points to a destructive re-entry sometime in January.
With a mass of 13,500 kilograms, Fobos-Grunt is the largest planetary spacecraft ever built in the former Soviet Union and was to be the first sample return mission to the natural satellite of another planet, and the first such mission to be conducted by Russia.
The spacecraft’s primary mission was to conduct a sample-return effort from Mars’ larger natural satellite, Phobos – which is likely to be the first Martian destination for humans in the 2030s, to be used as a precursor to a mission to Mars itself.
Fobos-Grunt – which was also hosting China’s first Mars probe, Yinghuo-1 as a passenger – enjoyed a nominal launch via a Zenit-2 launch vehicle, which occurred at 02:16 local time on November 8 from the Baikonur Cosmodrome.
All launch events were nominal, until problems were revealed shortly after Fobos-Grunt had been set to perform an orbit-raising manoeuvre two and a half hours after lift-off, prior to a second burn 126 minutes later, which would have taken it into heliocentric orbit to begin its journey to Mars.
Both burns failed to materialize, resulting in the spacecraft’s current predicament of being stuck wandering around in Low Earth Orbit (LEO).
There is now no hope of the spacecraft carrying out its mission to Phobos, despite a late boost when a level of communications were established, thanks to a modified dish on one of the European Space Agency (ESA) assets in Perth, Australia.
This was a great achievement on its own, as challenges associated with communicating with Fobos-Grunt during passes over ground stations included a potential blockage by the yet-to-be-used fuel tank of the low gain antennas.
This tank – located on the aft of the cruise stage – would be expended and released in the event of both burns being completed. It is understood the spacecraft was never designed to be commanded prior to these two burns.
With the European Space Operations Centre (ESOC) in Darmstadt, Germany passing on information gained by the Perth station to NPO Lavochkin, operator of the mission on behalf of the Russian space agency, Roscosmos, the ultimate goal was to gain telemetry from the spacecraft to check its health, prior to a potential route to send operational commands.
With very short windows of opportunity to send communications to Fobos-Grunt as it raced overhead in Low Earth Orbit (LEO), controllers only had a matter of minutes to send commands, which related to switching on the the spacecraft’s transmitter and send back a confirmation signal.
Some telemetry was gained, along it was understood to be incomplete and “garbled”. Russian media also reported that a second dish – at the Baikonur Cosmodrome – had made a level of contact with the spacecraft, although this was believed to be only a short term success.
While it appears clear that no useful commands were successfully received during the short period contact was established, the spacecraft soon went silent again, leading to ESA officially giving up after numerous attempts to talk to Fobos-Grunt without success.
“In consultation and agreement with Phobos-Grunt mission managers, ESA engineers will end tracking support. Efforts to send commands to and receive data from the Russian Mars mission via ESA ground stations have not succeeded; no response has been seen from the satellite,” noted an official ESA release.
“ESA teams remain available to assist the Phobos-Grunt mission if indicated by any change in the situation.”
As such, the spacecraft’s fate now appears certain, as much as challenges remain in knowing when exactly the spacecraft will return to Earth for a destructive re-entry.
This sad event will be of great interest, given the spacecraft’s 13,500 kg of mass, most of which is made up of the highly toxic propellants unsymmetrical dimethylhydrazine (UDMH) and dinitrogen tetroxide (DTO). Its mass is double that of NASA’s defunct Upper Atmospheric Research Satellite (UARS), which re-entered in September of this year.
At the time, NASA went to great lengths to emphasize that even if any surviving elements of UARS’ hardware had reached the ground, the chances of it being a threat to the human population were tiny.
The uncontrolled entry did find its way into the mainstream media despite NASA’s attempts to show it wasn’t a major threat, backed up by a Special Safety Topic review by NASA, which looked into the hazards posed by space hardware fragmentation during re-entry, with the aim to apply further mitigation to any potential risks from hardware breaking up and surviving entry – in turn threatening human life on the ground.
In the end, the satellite – which was originally launched on Shuttle Discovery during STS-48 – re-entered over water.
Notably, no major items of hardware on Fobos-Grunt have been listed as potentially surviving entry, while the aluminium tanks containing the large amount of propellant mass are likely to be some of the initial hardware to succumb to the destructive forces of entry.
The spacecraft’s orbit can be observed via amateur and professional groups, allowing for a level of modelling to be carried out on its decaying orbit, although – providing no control is established – the exact entry location of the probe won’t be predicted until shortly before the event.
It is currently estimated that the entry will occur sometime in January of next year, handing Russia a sad record of all of its 19 missions to the Red Planet since the 1960s resulting in failure.
(Images: Via Roscosmos and ESA)