GPS-AODS Demonstrator

Status date

Demonstration of an integrated AODS based on the MosaicGNSS receiver with the AGGA-2 and complemented by star sensors and optional gyros for multimedia applications.

Higher level signal processing functions and software algorithms (GPS receiver, star sensor and gyro) are centralized on a single DSP.

The common hardware platform for these components is the GPS/AODS Demonstrator Hardware.

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Integration of an AODS (Attitude and Orbit Determination System) demonstrator, being a sensor system that provides full state information and having a large degree of autonomy. The system comprises the following components:

  • MosaicGNSS receiver that provides position, velocity, time and attitude,

  • 3-axis star sensor, inertial 3-axis attitude information can be provided with spacecraft rates up to typically 2 deg/sec,

  • Optional gyroscopes for inertial rate measurements.

  • Compact integrated AODS, stand-alone unit and slide-in module,

  • Portability, Modularity and Flexibility,

  • GPS Rx and Star Sensor and Gyro SW share MosaicAODS board:

    1. Reduction of mass, volume, power consumption costs,

    2. Easy to implement module interconnections,

    3. Improvement in robustness,

  • Radiation tolerant (up to 100 krad),

  • Short initial acquisition,

  • Fit for LEO / MEO / GEO missions,

  • Relative navigation.

The GPS/AODS demonstrator will consist of three boards:

  • MosaicGNSS Receiver Base Board, comprising the DSP with program memory and data memory, a GPS ASIC developed by Astrium for signal preprocessing, board and boot control (BBC) and communication interfaces(UART/HDLC, SpaceWire, MIL-STD-1553), a boot PROM containing the primary boot loader, an EEPROM bank containing the application software. The base board has all the hardware required for a software correlator based GPS signal reception.

  • AGGA-2 Extension Board, comprising one AGGA-2. The AGGA-2 is connected to the DSP using the data bus extension of the base board. Four RF front-ends, one RF multiplexer (MUX) and three RF power splitter (PS) will be used to route the RF signals as required for the different modes.

  • Power Converter Board with the required DC/DC converters.

Since the GPS receiver as well as the star sensor require significant processor load, the key is the implementation of all functions on a single DSP. This is made even more difficult by the limitation of the DSP clock frequency (20 MHz) due to radiation requirements.

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The MosaicAODS system is composed of the following components:

  • A GPS receiver that provides full PVT information. The use of GPS receivers in low Earth orbits is common practice. Also, commercial applications in geostationary orbit and eccentric orbits are envisaged,

  • A 3-axis star sensor. Inertial 3-axis attitude information,

  • Optional gyroscope

Project start was the 1st of January 2003. The Baseline Design Review is planned 4 months after the project start. A Mid Term Review (MTR) is planed 11 months after the project start. The Final Review (FR) is planned for December 2005. 

Milestones in this activity are: 

Project StartT0January 2003
BDR:Baseline Design ReviewApril 2003
MTR:Mid Term Review December 2003
FP/FR:Final Review December 2005


Current status

  • Start date of the project was 01.01.2003,

  • Successful BDR at ESA/ESTEC in Noordwijk, 28.04.03,

  • Successful MTR at ESA/ESTEC in Noordwijk, 08.12.03,

  • The system architecture of the GPS/AODS Demonstrator has been revised and a MIL-STD-1553 Bus interface has been added to the system architecture,

  • Adaptations of parts of the GPS attitude determination software have been performed,

  • The AGGA-2 breadboard has been used for differential phase measurement in full parallel attitude mode and in hybrid-multiplexed mode,

  • Adaptations of O/S and Interface SW using the AGGA-2 breadboard have been done,

  • GPS/AODS DC/DC converter manufactured,

  • RF Multiplexer PCB manufactured,

  • AGGA-2 extension board manufactured,

  • Successful board level tests and first functional tests,

  • Successful environmental and functional tests.