Europe has launched the new automatic transfer vehicle (ATV), which weighs 20.7 tons at takeoff and delivers a payload of up to 9 tons (four times that of a Progress). ATV is the largest European satellite in history. It measures 10.3 m in length, 4.5 m in diameter, and has a wingspan of over 22 m with its solar panels deployed. ATV carried 7 tons of ergols on board, including 3 tons for the mission and 4 tons to boost the station. Airbus Defence Space is the ATV's prime contractor and was also responsible for and integrator of the vehicle's complete electrical system. GTD , on behalf of Airbus, produced a large part of the ATV's software, including the most critical sequences such as " RENDEZ VOUS " and " DOCKING ." The unit had five redundant computers, including three main ones for mission control and two reserved solely for safety aspects. The ATV software is the most complex ever developed in Europe. It is ten times larger than that of Ariane-5 in terms of memory size. In total, around 100 people worked on this software. The avionics system consisted of more than 50 onboard devices, weighing over 400 kg, plus another 400 kg of batteries and 200 kg of cabling (there were 18,000 connection points). Airbus Defence Space provided the gyroscopic and accelerometric control unit, the acquisition and telemetry box, the TM/TC module, and the solar acquisition sensor. The ATV docking operation with the station was entirely automatic and controlled by the vehicle's own processors, which communicated continuously with the station's processors and the ground control segments (Toulouse and Houston). The module was initially assembled on the ISS in just three days, but the final docking operations lasted up to five days. The orientation system included a gyroscope, various accelerometers, and a star sensor. The long-range approach system (for the first phase of the approach, ranging from 30 km to 6 km) used GPS receivers. There is a checkpoint 3,500 m from the ISS, and if everything was in order, the ATV would proceed with the remainder of the approach maneuver. At 250 m, for the final phase, the ATV used a "videometer" as its approach sensor. This innovative device, manufactured by Sodern, is derived from the SED-16 star sensor. It operates in the infrared for shape recognition and uses a series of retroreflectors installed on the ISS. There is also another system for the final approach phase based on a telegoniometer-type sensor (manufactured by Iena-Optronic) that uses a scanning laser. The ATV was equipped with an anti-collision system (which does not exist on either the American Shuttle or the Soyuz or Progress). In the event of a problem during the approach phase, the approach could be halted or, as a last resort, the vehicle could initiate a full abort maneuver. The unit was capable of performing up to ten docking attempts. The ATV was able to dock with the ISS only via the Russian segment (Zvezda module). Credits to ESA
