Orbital Express

Program management and contractors

The Orbital Express program was managed by the DARPA Tactical Technology Office (TTO). Boeing Integrated Defense Systems developed the ASTRO servicing satellite, which included the Orbital Express Demonstration Manipulator System (OEDMS) built by MacDonald, Dettwiler and Associates. Ball Aerospace & Technologies Corp. developed NEXTSat.

NASA's involvement came through the Automated Systems and Automated Rendezvous and Docking Division of the Engineering Directorate at MSFC, which also managed the Advanced Video Guidance System (AVGS) for the project. VACCO Industries designed, developed, and produced the refueling mechanism. Sierra Nevada Corporation (SNC) Space Systems designed, developed, and produced the docking mechanism and the launch adapter.

Goals

The project hoped to demonstrate several satellite servicing operations and technologies, including rendezvous, proximity operations and station keeping, capture, docking, fluid transfer (specifically hydrazine on this mission), and Orbit Replaceable Unit (ORU) transfer. A prime military mission would be to refuel reconnaissance satellites so they can improve coverage, increase surprise, and be more survivable. Fluid and ORU transfers were completed successfully at the lowest levels of spacecraft autonomy. Subsequent transfers over a three-month period were intended to demonstrate greater autonomy.

Robotics: the Orbital Express Demonstration Manipulator System (OEDMS)

The Orbital Express Demonstration Manipulator System (OEDMS), provided by MDA Space, was the mission's integrated robotics solution. It consisted primarily of a 6-DOF rotary joint robotic arm, its flight avionics, the Manipulator Control Unit (MCU) and arm vision system, two On-Orbit Replaceable Units (ORUs) with their spacecraft attachment interfaces, a visual target and grapple fixture installed on NEXTSat, and the Manipulator Ground Segment. Mounted on ASTRO, the OEDMS captured and serviced NEXTSat.

The mission demonstrated autonomous capture of a fully unconstrained free-flying client satellite, autonomous transfer of a functional battery ORU between two spacecraft, and autonomous transfer of a functional computer ORU. All robotic operations were scripted prior to execution and performed autonomously as part of increasingly complex mission scenarios. Early scenarios incorporated Authority to Proceed (ATP) pause points requiring a signal from the ground to authorize the ASTRO Mission Manager to continue.

Later scenarios incorporated fewer ATPs, and the final scenarios were compound autonomous sequences performing rendezvous, capture, ORU transfer, and fluid transfer without any ATPs.

End of mission

The final rendezvous and docking between the two spacecraft occurred on 29 June 2007, followed by the final demonstration of a flight computer changeout aboard ASTRO. NASA's plans for an extended mission from mid-July to September 2007 were abandoned over cost. The two craft demated for a final time, with ASTRO backing out to greater than 400 km in a test of sensor performance, then performing a rendezvous to a standoff where decommissioning took place.

NEXTSat was deactivated on 21 July, when its computers were turned off and solar panels pointed away from the Sun. ASTRO vented its hydrazine propellant and was deactivated on 22 July 2007. ASTRO reentered the atmosphere on 25 October 2013, after only 6.5 years. NEXTSat decayed from orbit on 21 April 2023, almost 16 years after decommissioning.