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ATV flight phases
Jules Verne was the first of seven ATVs planned to be launched from 2008 throughout the following ten years.
The flight of Jules Verne differed from the later ones, because it was used to demonstrate a number of special ATV features - attitude control, ATV Control Centre’s capability to perform orbit navigation with its own GPS, its ability to execute orbital and collision avoidance manoeuvres, the latter being a key safety feature for the ISS.
The flight of the ATV will follow this plan, after being validated with Jules Verne and demonstrated with Johannes Kepler.
Launch
The ATV is launched from French Guiana (ATV-2 was be launched on 16 February, at 21:50 GMT, 18:50 local time in Kourou) by an Ariane 5 ES rocket and injected into a 51.6 degree orbit - the same as the ISS - at an altitude of around 260 km, whilst the Station's altitude is around 340. Approximately 75 minutes after lift-off, when separation is confirmed with the launcher, the ATV becomes a fully automatic spaceship.
Phasing
Next, ATV enters a phasing stage of the mission. A set of orbital manoeuvres prepared by the ATV Control Centre are executed to bring ATV to a distance of 39 km behind and 5 km below the ISS. If needed, the ATV can hold a parked position 2000 km from the ISS.
Rendezvous and docking
After successful completion of the phasing, the ATV is ready to dock with the ISS (Thursday, 24 February, for ATV-2). The ATV sets up a direct link with the Station, allowing the ATV to start relative and accurate navigation to the ISS using GPS technology.
At a distance of 249 m, the ATV computers use videometer and telegoniometer data for final approach and docking manoeuvres. The approach of the ATV to the ISS slows down to 7 cm/s - approximate 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 Rus-sian Mission Control Centre in Moscow (MCC-M) because the ATV docks on the Russian Zvezda segment of ISS. Overall coordination with Mission Control Centre in Houston (MCC-H) is also required as they are responsible for the entire ISS. For each of these steps, the ATV performs automated manoeuvres.
Eye-like sensors
For the final rendezvous manoeuvres, the 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 pre-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 ISS for up to six months, becoming an extension of the Station.
The 48 m³ pressurised module of the 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 ISS altitude which naturally de-creases with the residual atmospheric drag.
Destructive re-entry
After six months of being an extension of the Station, ATV is loaded with up to 6.5 tonnes of material no longer required by the ISS, and separates with the same safety procedures performed for the docking.
The ATV then burns up completely during a guided and controlled re-entry high over the Pacific Ocean.
Fluid and dry cargo
The ATV is designed to re-supply the ISS with up to 6600 kg of cargo. Depending on the needs on board the ISS, the ATV is able to accommodate very different combinations of supplies, carrying up to:
- 855 kg of drinking water
- 102 kg of gas (air or oxygen or nitrogen)
- 860 kg of refuelling propellant for the Station's own propulsion system
- 4000 kg of propellant for re-boost
- 3200 kg of dry supplies like bags, drawers and fresh food
Last update: 2 March 2011
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