The Best Test of General Relativity (by 2 Misplaced Satellites)
On august, 21., 2014, two satellites were launched by the European Space Agency. They're called Galileo Satellites 5 and 6. 0:28 They were intended to become part of the Global Navigation Satellite System, or GNSS.
This is the European version of the American GPS systems. Now, after successfully blasting off into space, The satellites were launched with the Russian 5-6 rockets; The final stage of the rocket was set to inject the satellites into a circular orbit around 23000 kilometers above the Earth.
But that - - is when something went wrong. there was a thermal breach between a line of cold helium, and a line of propellant. So, the propellant, froze; This caused the failure of the attitude control thrusters. The satellites seemed to have been injected into some random direction.
It was launched but in the wrong direction. This sent the satellites into highly elliptical, and seemingly useless orbits.
At their low point, the satellites didn't really get a full view of the earth.
Earth sensors, which enabled them to orient their navigation antennas - stopped working, because the earth just filled their field of view.
At the other extreme, the satellites went too high, experiencing significant radiation exposure due to the van Allen belts. There was a threat, that they would just shut them off.
Okay, who do we have to talk to, to make sure they keep these satellites alive?
They had an idea, for how to use them to make the best tests of general relativity to date; This was a stroke of luck for us, we had been proposing such missions. When we saw that this accident happened, we were very happy about it, of course.
Now, the satellites did have propellant onboard, intended to allow for periodic course corrections over their planned 10-year lifespan.
And they could use that fuel to attempt to correct their orbits. 2:10 So they used the propellant onboard -