DEOS Phase A

In the context of the Phase A study performed by SpaceTech GmbH, the user needs were defined in the Functional Specification, a concept for the implementation was traded, elaborated and detailed into a technical baseline design, and, last not least, a realistic mission scenario for the experimental program was worked out. Using advanced simulation tools, the feasibility of the DEOS mission was demonstrated, as well.

The DEOS space segment consists of a Servicer and a Client spacecraft. The Client spacecraft simulates the multitude of characteristics of a spacecraft in need of service. The Servicer tasks comprise constellation flight, rendezvous and fly-around, docking, berthing and in-orbit servicing.The ground segment consists of a primary ground station and the Mission Control Centre. During critical mission phases (LEOP, proximity experiments) the primary ground station is temporarily amended by an adequate supplementary ground station network. Each spacecraft maintains a direct link to ground. Furthermore the Servicer is able to receive the Client telemetry data for board-autonomous mission supervision purposes. Additional communication via geostationary relay satellites and their operating ground stations may be utilized depending on the availability of such system.

The following experiments will be performed where in general the complexity of the experiment execution is required to be stepwise increased over the mission period:

• Far formation flight between Servicer and Client including the identification of the dynamic parameters of the individual spacecraft

• Rendezvous maneuvers consisting of approach maneuvers of the Servicer to the non-co­operative Client, departing maneuvers of the Servicer from the non-cooperative Client and fly-around and inspection of the non-cooperative Client by the Servicer

• Berthing of the non-cooperative Client by the Servicer’s manipulator system (see Figure 2) under different environmental and operational conditions as well as different attitude states of the Client (three axes stabilized, spinning and tumbling), as well as experiments in a dynamically coupled configuration controlled by the manipulator system under different operational conditions

• Docking of the Servicer at the cooperative Client under different operational environments

• Flight maneuvers in a rigidly coupled configuration including the identification of the dynamic parameters of the rigidly coupled configuration and attitude and orbit maneuvers

• On-orbit servicing tasks such as refueling and mounting of mechanical / electrical devices in the rigidly coupled configuration, using a coupling device other than the manipulator

• De-orbiting of the configuration rigidly coupled by the manipulator arm, executed as a purposive re-entry within a given re-entry corridor

Both spacecraft are to be injected together into the initial low Earth near polar orbit on the same launcher. The initial orbit altitude will be stepwise decreased during the planned one year orbit lifetime in order to increase the operational complexity caused by reduced contact time to the communication network. The near polar inclination of the orbit offers variable illumination conditions for the experiments over the life time.

The phase A of DEOS has been performed on behalf of the Agency of the German Aerospace Center funded by the Federal Ministry of Economy and Technology, funding code 50 RA 0802.