ATV flight phases
Five Automated Transfer Vehicles (ATV) will be launched to supply the International Space Station on a regular basis.
The flight of ATV Jules Verne, the first ATV launched in 2008, differed from later flights, because it was used to demonstrate a number of special ATV features such as attitude control, ATV Control Centre’s capability to perform orbit manoeuvres and collision avoidance manoeuvres, the latter being a key safety requirement for the International Space Station.
ATV is launched from French Guiana by an Ariane 5 ES rocket and injected into a 51.6 degree orbit - the same as the International Space Station - at an altitude of around 260 km, around 100 km lower than the Station. Approximately 75 minutes after liftoff, when separation is confirmed with the launcher, ATV becomes a fully automatic spaceship.
Next, ATV enters a phasing stage of the mission. A set of orbital manoeuvres executed by the ATV Control Centre bring ATV to a distance of 39 km behind and 5 km below the International Space Station. If needed, ATV can hold a parked position 2000 km from the Station.
When phasing is finished, ATV is ready to dock with the International Space Station. ATV sets up a direct link with the Station, allowing it to start relative and accurate navigation using GPS technology.
At a distance of 249 m, ATV's computers use videometer and telegoniometer data for final approach and docking manoeuvres. ATV's speed relative to Station slows down to 7 cm/s - about the speed of a turtle.
As ATV gets closer to its objective, ATV-CC ground controllers direct the ATV in a step-by-step predefined approach. This approach requires authorisation from the Russian Mission Control Centre in Moscow because ATV docks with the Russian Zvezda segment of Station. Coordination with Mission Control Centre in Houston is also necessary as they are responsible for the entire Space Station. For each of these steps, ATV performs automated manoeuvres.
For the final rendezvous manoeuvres, ATV uses its eye-like sensors, combined with additional parallel measurement systems, which ensure an automatic docking with an incredible 1.5 cm precision while the spacecraft and the ISS are circling the Earth at 28 000 km/h.
If there are any last-minute problems, either the ATV’s computers, the control centre or the Station’s crew can trigger a programmed sequence of anti-collision manoeuvres that is fully independent of the main navigation system.
Extension of the Station
Once docked, ATV remains an intrinsic part of the International Space Station for up to six months, becoming an extension of the orbital outpost.
The 48 m³ pressurised module of ATV delivers up to 6.6 tonnes of equipment, fuel, food, water and air for the crew.
ATV uses up to 4 tonnes of propellant to raise the Space Station's altitude which naturally decreases with due to atmospheric drag.
After six months of being an extension of the Station, ATV is loaded with up to 6.5 tonnes of material no longer required on the International Space Station, and separates with the same safety procedures performed for the docking.
ATV then burns up completely during a guided and controlled reentry high over the Pacific Ocean.
Last update: 9 December 2014