In order to foster the market share and to ensure the platform permanence, evolutions of the Attitude and Orbit Control System (AOCS) have been identified. After a first step of AOCS evolutions (so called AOCS Mk1.5), focused on the on-station pointing performances improvement with implementation of a Star tracker (STR) on-board and all associated algorithms, the next step is the development of STR-based AOCS (so called AOCS Mk2). This AOCS Mk2 evolution fully takes advantage of the STR features, all along the spacecraft lifetime from transfer phase, EOR (Electric Orbit Raising), Earth Acquisition to on-station mode, including recovery mode. Associated with deployable arm (mechanism to orient electric thrusters), this new AOCS ensures a full electric way to manage the Electric Orbit Raising and the On Station mode.
The challenges of AOCS Mk2 was the development of a new full-STR-based AOCS, with new gyroscope and new wheel configuration, compatible with Electric Orbit Raising and ensuring a full-electric capability for transfer and on-station mode.
This development had also strict schedule constraints to ensure delivery of this new product, qualified in time for integration of first E3000 EOR spacecraft (first launch foreseen in 2017).
The AOCS Mk2 is a full-STR-based AOCS. This product is compatible with different spacecraft configurations: full chemical satellites, hybrid satellites (chemical for transfer and electric for on-station), but also and above all full-electric satellites.
This new AOCS, with new 3-axis gyroscope, new wheel configuration with large capacity and also new mechanism to orient electric thrusters, is a robust, versatile and efficient product to manage all these possible missions.
To ensure efficient management of EOR missions, the spacecraft autonomy has been improved in term of commandability, observability and FDIR. These improvements are also of benefit to on-station mode where mission outage risks and duration are minimized.
Thanks to the ARTES 3-4 AOCS Mk2 Evolution program, the following new functions were designed, developed and qualified for AOCS E3000:
• New 3-axis gyroscope and new 4-wheel configuration
• on-board software for management of deployable arm in EOR and on-station.
• Wheel momentum management using deployable arm
• on-station FDIR based on STR
• New robust STR-based back-up mode
• EOR management with autonomy improvement in term of attitude manoeuvre profile management, FDIR, manoeuvre programming and spacecraft “Good Health” observability.
The project has been carried out with the following milestones:
- KO: December 2012
- PDR: February 2014
- CDR & TRR: July 2015
- TRB & FR: May 2016
The AOCS Mk2 Final Review was held in May 2016.
The AOCS Mk2 product is now qualified, in time to be embarked on the first Eurostar 3000 spacecraft which will use Electric Orbit Raising.
The first 3 AOCS Mk2-based satellites are in AIT with launch foreseen in 2017.