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UARS, ROSAT and now Phobos-Grunt returning to earth?

End of September the American satellite UARS made it’s way back to earth, followed by the German Röntgensatellite ROSAT one month later.

Right now, it seems a next satellite is about to come down. Since the launch the engineers have not been able to communicate with the malfunctioning satellite. Being unable to steer Phobos-Grunt, the satellite might well fall back to earth soon. It is being mentioned as “the most toxic falling satellite ever”.


Picture: DLR.de

What went wrong with Phobos-Grunt?

On the 8th of November 2 other satellites were launched, Fobos-Grunt or Phobos-Grunt (the Russian name has to be translated as “Phobos-soil” though) and Yinghuo-1. They were both supposed to go to Mars. The Chinese mini satellite should circle around Mars and the Russian Phobos Grunt should land on Mars’ moon Phobos, take samples and then fly back to earth.

Unfortunately; for yet unclear reasons the satellite never got into the orbit they were supposed to be. A booster should be ignited once they were circling around earth to “slingshot” the satellites to earth using gravity, however the ignition apparently never took place. The satellites seem to hang in a relative steady circle around the earth, not able to break lose from the gravity.

At least, that is what the experts could retrieve from the few data that was sent back from the satellite. Since then, the satellite is quiet and does not send back any confirmation it has received the information and commands that were send from earth.

Lost in space

During the launch with the Zenit-2SB rocket everything seemed to be fine. Communications with the satellite should arrive once it has gotten out of the top capsule of the rocket, somewhere out in space. It however stayed quiet after launch, there was no acquisition of signal.

The satellite also was not there where it was expected to be. With the help of amateur astronomers the satellites’ position could be roughly found and data and commands (telemetry) was send towards that position.

Normally the satellite sends back an answer it has received the information and then sends back the confirmation it has done the required tasks. The engineers had a rough indication where Phobos Grunt would be and sent data in it’s course via the ground stations where the big dishes were set in it’s direction to listen and to send telemetry.


Credit: Tony Craddock Science Photo Library

It stayed quiet. Not a sound came back.

Toxic fuel

As a satellite exists of many instruments, some boosters to steer it; a few huge tanks with fuel for the propulsion (Mars is far, far away and it needed to return too), some computers (hardware) to steer the instruments and boosters as well as the software to run it; the cause could be in any of these. A real puzzle for the engineers on earth trying to send telemetry to it and try to work around the standard commands and programs.

With the help of the same amateur astronomers it was found out that the satellite does seem to reflect a steady light. This might mean that the satellite has got a stable flight and doesn’t flip over. That might mean some of the instruments might have worked and that it is locating it’s course based upon the position of the sun and stars.


Credit: Roskosmos

Phobos Grunt had set itself into an orbit around the earth instead, slowly dropping height. There is not much time left before it will hit the atmosphere and crash somewhere on our planet.

From various sources on the internet (see below) rumors were started that Phobos Grunt is told to drop it’s fuel. That would mean that the mission to Mars for both satellites is aborted and that preparations are made for a safe(r) return into the atmosphere. With the huge amount of toxic fuel on board it might be safer to release propellant while it’s out in space. Due to the cold up there the fuel might freeze up and could cause problems once turning back to earth. When the satellite would come back is not clear yet. Dates have been mentioned from end of November till somewhere in January 2012. Noone really knows, as there is no contact and precise course known from the satellite.

One of the more certain things is that it will come down between 51 degrees north and 51 degrees south – basically covering North- and South America; Mid- and South Europe, Africa, China, Australia, Japan etc. On one of my favorite sat tracking sites, n2yo.com, they have a rough prediction of Phobos-Grunt orbit as well as where it is (estimated to be) right now.

Time will tell how this mission will end, but so far it does not look good.

Sources:
* Twitter (what else?)

* The Russian Spaceweb (by Anatoly Zak)

* NASA NSSDC Spacecraft information

* Wikipedia

* The Planetary Society Blog (by Emily Lakdawalla)

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