ESA’s 5-ATV (Automated Transfer Vehicle 5) “Georges Lemaître” was used in a manner different from the usual. The cargo spacecraft is docked to the International Space Station since August 12 2014 and yesterday its thrusters were used to lower the Station about a kilometer. The purpose is to allow spaceships that reach it to carry a greater cargo.
The ATV-5 cargo spacecraft was launched on July 29, 2014 and is the last of the ATVs. It’s really big and has relatively powerful thrusters. The ATVs have always remained docked to the International Space Station for several months instead of only a few weeks as generally happens for these spaceships.
When are docked to the Station, the ATVs are used among other things to lift a bit its orbit. Even at those heights there’s always a slight friction caused by the tenuous atmosphere and it brings down the Station so sometimes this type of maneuver is needed. Yesterday, the opposite happened.
To allow cargo ships to reach the International Space Station especially rockets must use a certain amount of fuel. Greatly simplifying the problem, the higher you send the cargo the more fuel it takes. The various space agencies carefully study the spaceships’ routes and consumption to find better solutions in terms of consumption and transportable cargo.
Following one of these studies, ESA was asked to use the ATV-5 to slightly brake the International Space Station. The consequence of its speed decrease was the loss of altitude of about one kilometer. To allow this maneuver, the Station was turned 180° due to the location of the ATV-5.
It’s not the first time that an ATV was used to lower the International Space Station instead of boosting it. In 2008, the ATV-1 “Jules Verne” conducted a similar maneuver. In that case, however, the aim was to move the Station out of the way of potentially dangerous space debris. In that case, the Station was lifted again at the end of the maneuver, this time it will remain in the new orbit at least for a while.