Precise orbit determination for ESA’s Sentinel missions

Precise Orbit Determination (POD) has traditionally been an area of expertise reserved to research institutes and space agencies. The reason for this is the detailed and complex modelling needed to achieve the required accuracies and state-of-the-art tracking techniques involved: mainly Global Navigation Satellite Systems (such as GPS), Satellite Laser Ranging (SLR) and DORIS.

As a rule of thumb, we talk about POD operations when the orbit is known with accuracy well below 1 meter. In the most demanding and challenging cases, this is reduced to few centimetres for a spacecraft spanning several meters, weighing a few tones and moving at more than 20000 km/h hundreds of kilometres above our heads!

Thus, very few companies have developed proper skills in this rather scientific field. However, GMV has been involved in POD activities since the early 90’s. The first steps were performed with the support to the POD operations of the ERS missions at ESA’s European Space Operations Centre (ESOC) in Darmstadt, Germany.

Since then GMV has provided uninterruptedly expert support to ESA in this field for other missions. For instance, this includes the estimation and propagation of the precise orbits and clocks of the GPS and GLONASS constellations at the Navigation Facility of ESOC, where one of the most accurate solutions in the world is obtained with SW systems developed and operated by GMV. Other examples are the ENVISAT or GIOVE-A/B satellites.

Furthermore, GMV has developed the operational POD system for EUMETSAT’s Metop satellites, ESA’s SWARM mission and the Spanish PAZ Earth observation satellite.

On the strength of its acquired experience, GMV has recently been chosen by ESA to lead an even more far-reaching consortium to provide POD solutions for the COPERNICUS (previously known as GMES) Sentinel-1, -2 & -3 missions as an operational service. This service will be developed by GMV and is expected to be operated routinely and continuously on a 7x24 basis at GMV premises in Tres Cantos, Spain, for a global community of users.

GMV’s POD service will be capable of processing all relevant tracking techniques and provide precise orbits with several timing and accuracy levels , ranging from near-real time to most accurate off-line solutions. For example, orbits with centimetre accuracy will be provided for both Sentinel-1 and Sentinel-3.