A doomed Russian Mars probe that's been stuck in Earth orbit for two months may finally come crashing down on Sunday January 15 over the Indian Ocean, Russian space officials say.
The 14.5-tonne Phobos-Grunt spacecraft should fall back to Earth sometime between Saturday and Monday, Russia's Federal Space Agency, known as Roscosmos, announced in a statement.
If Phobos-Grunt comes down at the "central point" in that window — 8:18pm AEDT (0918 GMT) on Sunday — it will fall over a stretch of empty ocean west of the Indonesian island of Java, according to a re-entry projection map Roscosmos published with the update.
But these projections are far from set in stone. The predicted time and place of re-entry may change as engineers continue to track the spacecraft's decaying orbit, officials said. All that's known for sure is that Phobos-Grunt will come down somewhere between 51 degrees north latitude and 51 degrees south latitude.
Falling back to Earth
Phobos-Grunt launched November 8th on a mission to collect soil samples from the Mars moon Phobos and return them to Earth ("grunt" means "soil" in Russian). However, the probe's main engines failed to fire as planned to send it toward Mars, and the craft got stuck orbiting Earth.
Russian officials still aren't sure what caused the failure. They recently raised the possibility that some form of sabotage may have crippled Phobos-Grunt and doomed its $165 million mission.
The spacecraft has been spiraling lower and lower for months, on an inevitable collision course with Earth's atmosphere. The minimum altitude of Phobos-Grunt's orbit as of today is about 171 kilometres, according to Roscosmos.
The huge probe is carrying about 7.5 tonnes of toxic hydrazine fuel, prompting some observers to worry about potential environmental impacts of the probe's looming re-entry. Russian space officials have repeatedly dismissed those concerns, however, saying that the fuel — which is encased in an aluminium tank — should burn up high in Earth's atmosphere.
Most of Phobos-Grunt should meet that same fate. Experts predict that just 20 to 30 pieces, weighing a maximum of 200 kilograms in total, will actually hit the Earth.
Phobos-Grunt's demise comes close on the heels of two other uncontrolled satellite falls recently. NASA's 6.5-tonne UARS climate satellite re-entered over the Pacific Ocean in September, and Germany's 2.7-tonne ROSAT satellite crashed over the Indian Ocean a month later.
Both the UARS and ROSAT re-entries were expected, however, and the two satellites had long since completed their primary science missions. No one on the ground was hurt in either instance.
A series of Russian space failures
Phobos-Grunt's failure was just one of a series of embarrassing setbacks for the Russian space program in 2011.
On Febuary 1st, for example, a Rockot launch vehicle failed to place an Earth-observing satellite in the proper orbit. On August 18th, a Proton rocket similarly underperformed, delivering a $300 million communications satellite to the wrong orbit.
Less than a week later, on Aug. 24, the unmanned Progress 44 supply ship crashed while hauling cargo to the International Space Station. Progress 44 was done in by a problem with its Soyuz rocket. Russia uses a similar version of the Soyuz to launch astronauts to the space station, so manned flights were put on hold until the problem with the rocket could be identified and fixed.
Finally, a Soyuz-2 rocket crashed just after liftoff on December 23rd, destroying a Russian military communications satellite.