Time for farewells!! The Dragon spacecraft left the International Space Station earlier this week and today ESA’s ATV spaceship with the catchy name Georges Lemaître detached from the Station and will plunge after several orbits into Earth’s atmosphere. Due to the enormous heat from friction caused by its deceleration through the upper layers of air layers the spacecraft will turn into a huge fireball – a fitting end to the spacecraft that is named after one of the founding fathers of the Big Bang theory!
Unfortunately, this will be the last ATV – after five very successful missions, the project is now complete. At the Columbus Control Center (Col-CC) we provided for each flight the ground infrastructure and supplied our colleagues at ATV Control Centre in Toulouse, France, with data, video and voice connections to the International Space Station network.
After ESA astronaut Samantha Cristoforetti and cosmonaut Alexander Samokutyaev closed the hatches of ATV yesterday, the Space Station was prepared for the last hours of undocking of ATVs. We turned off our little amateur radio station [http://www.ariss.org/] in Columbus as well as the external Rapidscat experiment [http://www.jpl.nasa.gov/missions/iss-rapidscat/], any radio interference with ATV’s navigation from the International Space Station should be avoided.
Slowly the Space Station turned to an appropriate orientation for undocking. When the moment arrived the Space Station’s active position control was turned off completely: Georges Lemaître needs to push away from the Space Station without the mothership trying to compensate for this force.
Afterwards all that remained was for the astronauts to wave good-bye …
ATVs are part of a large space fleet that supplies the International Space Station. When the American Space Shuttle withdrew from service the Russian Soyuz spacecraft became the only way to get people to the Space Station and back on Earth. Three astronauts share a small space – and so there is little room for other supplies.
Despite this there is enough transport capacity to supply the International Space Station with vital cargo: The Russian unmanned Progress cargo has been flying for years as well as the Japanese HTV and the European ATV. Relatively new in the family of cargo ferries are two unmanned American commercial vehicles: SpaceX’s Dragon and Orbital Science’s Cygnus.
While the ATV and Progress ships fly to the International Space Station and dock on their own accord, the others need assistance from the Station’s robotic arm. They approach the Station and fly in formation together – not so easy with complex orbital mechanics to calculate – before being gently captured by the robotic arm and moved securely to a docking port. Only then can the astronauts enter and start unloading cargo.
It is much more complicated to bring something from the International Space Station back to Earth. The ATV, HTV, Progress and Cygnus spacecraft have no heat shield or other systems that are needed to survive a reentry into Earth’s atmosphere: they are designed to burn up in the upper layers of the atmosphere of Earth. Because of this the astronauts load them full of trash from the International Space Station and they serve as cosmic garbage disposal.
Aside from the manned Soyuz only the Dragon is designed to withstand the tremendous energy from decelerating at speeds of 23 faster than the speed of sound. Paradoxically it is more difficult to get things from the Space Station to Earth than vice versa.
Columbus Flight Director at the DLR center in Oberpfaffenhofen/Germany
Cover image by ESA astronaut Samantha Cristoforetti: https://www.flickr.com/photos/astrosamantha/16546104212/ .