GPS Precise Orbit Determination

The Product

GPS based Precise Orbit Determination uses high-quality carrier and code measurements of a dual-frequency GPS receiver on-board of a satellite to achieve a position measurement accuracy of this satellite of a few centimetres in an on-ground post-processing run.

Based on extensive GPS experience and flight heritage of RUAG Space GmbH (RSA) the dual-frequency GPS Precise Orbit Determination (POD) receiver provides high integration of the RF- and digital circuits as key innovations, thus resulting in low mass and low power.

The GPS POD Instrument down-converts and digitizes the GPS L1 and L2 signals by means of dedicated RF- and mixed-signal ASICs. The AGGA-2 chips and a LEON processor form the heart of the digital signal processing.

This product has been developed together with RUAG Space in Sweden consolidating the expertise and capabilities of both sites.



  • Low mass and power consumption
  • Antenna with improved multipath suppression
  • Sensitive RF-filter and low-noise amplifier for improved performance figures
  • Force model-based orbit propagator automatically adapts to changing satellite altitudes
  • Advanced code-phase and carrier-phase processing by means of curve-fitting algorithms
  • Autonomous start-mode determination for minimized time-to-first-fix
  • Flexible acquisition and tracking concept providing:
    - C/A, P/Y (codeless) and L2C dual-frequency signal processing of up to 8 satellites
    - Sliding search window determination for minimized acquisition times
    - Doppler-based loop aiding
    - Highly configurable due to numerous parameters like tracking loop filter order and bandwidth, integration time, discriminator type
  • Flexible AGC loop
  • Flexible sample rate concept allows to set the data rate per measurement type
  • Modern design developed for the powerful SPARC V8 architecture (LEON-FT)
  • Modular SW concept with clearly separated functional blocks and database for common parameters, signal &channel properties, navigation data
  • Powerful parameter interface supports changes in standby and operational mode
  • Additional data products provide excellent visibility of receiver internals
  • Periodic dump feature allows flexible monitoring of PPS related data
  • Raw data dump supports mission specific loop optimisation

Data Products:

  • Navigation solution based on the GPS constellation resulting in the best GDOP
  • Generation of the PPS signal
  • Carrier phase measurements (L1 & L2) for each tracked GPS satellite
  • C/A and either P/Y (codeless) or L2C code phase measurements for each tracked GPS satellite
  • Support data:
    - tracking state
    - GDOP
    - carrier to noise (C/N) measurement of each tracked GPS satellite
    - amplitude measurement of each tracked satellite
    - noise measurements of each channel
    - satellites in view status
    - satellite navigation message


  • UART (RS-422) TC/TM interface or
  • MIL-STD-1553B TC/TM interface
  • 1 PPS output (RS-422)
  • Primary power interface 28 V unregulated
  • ON/OFF high level command interface
  • Thermistor interfaces
  • Test interface

On-board Navigation Solution Accuracy:

  • Position: 1,9 m  3D rms
  • Velocity: 3 mm/s  3D rms
  • time offset 1PPS (1σ): < 50 ns (typ. 25ns rms)

Instrument data outputs:

  • L1 carrier phase error <   5mm rms
  • L2 carrier phase error < 10mm rms
  • L1 C/A code measurement error < 0.7 m rms
  • L1&L2 P code measurement error < 1m rms
  • L2C code measurement error < 1m rms

Time to first fix:

  • Warm Start < 120 s
  • Cold start < 30 min

Physical / Environment

Electronic box (with UART I/F):

  • Size: 300x240x104 mm3
  • Weight: 2.8 kg
  • Operating temperature: -20º C to +50º C
  • Minimum switch-on temperature: -30° C
  • Radiation: Cumulative dose >60 kRad (Si)
  • Latch-up threshold > 70 MeV mg-1 cm2
  • Power Consumption: 9 W av.

Patch Excited Cup antenna
with optimized multi-path performance:

  • Size: Ø 200 mm, h: 87 mm
  • Weight: < 735 g

Smaller size available upon request


RUAG has delivered the GPS Precise Orbit Determination Receiver flight models for the Swarm earth-observation mission of ESA, which is based on three satellites flying in formation with a common launch in 2013. We have received further orders for these receivers for the Sentinel series of satellites of ESA and the European Commission (6 satellites) as well as for the ESA/JAXA mission Earthcare. All together this means a total number of 20 flights units are now in production respectively delivered from this product generation. All recent European missions requiring GPS POD Receivers are relying on our novel product line.

RUAG is also providing the GPS Precise Orbit Determination Receivers for NASAs mission ICESat-2.

In the field of on-board GPS receivers RSA has been responsible for the signal-processing core of the GPS Occultation Instrument GRAS on the METOP satellite and of the GPSOS instrument on NPOESS. RSA has also been involved in the ESA development of the AGGA chip in its different versions.