Objective of the project is the development and the qualification of the Eurostar Antenna Tracking System (ATS) functional chain. This includes the architecture design, the system analysis, the control loop design, the FDIR strategy, the software implementation and validation.
The following design and development activities were achieved:
- Antenna Tracking System architecture,
- Eurostar accommodation of the RFS hardware (mechanical, thermal, electrical),
- Control loop design and performance demonstration,
- Equipment management and control loop on-board software development,
- Antenna Tracking System performances validation on the numerical test bench,
- Hardware/Software integration and validation,
- Development and validation of the FDIR mechanisms and the system functions dedicated to the mission and operations management,
- RF sensing chain validation using EQMs of the RFS units to check electrical interface compatibility.
The Antenna Tracking System allows improving the antenna pointing performance down to 0.05°, thus being compatible with multimedia missions and a global capacity of more than 70 Gigabits per second.
The EUROSTAR satellites with Antenna Tracking System enable to offer end-users high speed internet connections to corporate and consumer users comparable to ADSL2 equipped with small diameters (typically 60-80 cm).
The Antenna Tracking System functional chain is based on the following assemblies:
- Ground beacons (RF transmitters and fixed antennas) located on 4 different beams,
- Antennas: 4 reflectors and in each feed cluster a RFS (RF Sensing) function implemented,
- An RF sensing chain in charge of antenna pointing measurement which generates digital data representative of antenna pointing,
- An ATS control loop software (part of the mission on-board software),
- Data handling resources (SCU, MPIU, 1553 data bus) to provide command / monitoring capabilities and support for the software application,
- Antenna Deployment Trimming Mechanisms (ADTM) to control the antenna reflector orientation (one per antenna).
The RF sensing system uses the RF signal transmitted from a ground beacon to measure the angular pointing error of the antennas. These angular pointing errors are then transferred to the on-board data handling subsystem that processes these data and controls the antenna pointing mechanism to minimize the pointing error.
The system beam pointing error is then reduced down to 0.05° including station keeping manoeuvre phase.
This system therefore allows cancelling of:
- Spacecraft and payload thermo-elastic distortions,
- Constant biases due to on-ground characterization and integration errors,
- Attitude errors during the in-orbit correction manoeuvres.
The project has been carried out within a timeframe of 40 months with the following milestones:
|Kick Off||December 2006|
|Baseline Design Review||June 2007|
|Mid-Term Review||December 2008|
|Test Readiness Review||May 2009|
|Test Review Board||March 2010|
|Final Review||March 2010|
Final Review held with ESA on the 30th of March 2010.