Orbital Express
The Orbital Express Project was an experiment DARPA to develop safe and cost-effective techniques for autonomous satellite servicing in orbit (English: On- orbit servicing ).
Orbital Express consists of two satellites:
- ASTRO (Autonomous Space Transport Robotic Operations ) is the active satellite, which serves as a prototype of a supply and maintenance satellites. ASTRO was built by Boeing Integrated Defense Systems and has a mass of about 700 kg. ASTRO has a docking port and a gripper arm as well as tanks and equipment to transfer the fuel.
- NextSat (Next Generation Serviceable Satellite ) simulates a serviceable satellite. The 224 kg satellite was built by Ball Aerospace. NextSat is equipped with a coupling adapter and the tank for receiving the transferred fuel.
The following technologies will be tested with the two satellites:
- Automatic rendezvous operations
- Automatic docking
- Transfer of liquids ( hydrazine )
- Replacement of satellites in orbit components ( Orbital Replacement Unit)
Mission
Orbital Express was launched on 9 March 2007 along with six other satellite on an Atlas V rocket from Kennedy Space Center.
On 17 April, the satellite performed the first autonomous transfer of fluids and components.
The first autonomous free-flight and docking maneuver took place on May 10. In another docking experiment, there was a malfunction of the onboard computer of ASTRO, which meant that the satellite drifted apart accidentally. After ASTRO was supplied by the ground station with data for a trajectory to return in the near NextSat, ASTRO was able to dock on its own without further intervention. A complex approximation, inspection and docking maneuvers, which can serve as a basis for future service missions, was carried out on June 22.
The last rendezvous and docking maneuver took place on 29 June 2007. Then the last component replacement took place with the change of flight computer on ASTRO. Plans for further use of the satellite by NASA were not translated into reality. Finally, the satellite separated for the last time and maneuvered to a distance of over 300 km to the sensor perform testing. After a final maneuver to increase the distance the satellites were decommissioned by the remaining fuel supplies were drained and the satellites were shut down on July 22, 2007. Is NextSat after 3 to 5 years and ASTRO enter and burn up after about 15 years in the earth's atmosphere.
NextSat in free flight. Recorded by ASTRO
NextSat shortly before docking at ASTRO