The navigation support office (OPS-GN) at the European Space Operations Centre (ESOC) of the European Space Agency (ESA) is active in all three international satellite geodesy services: the IDS, IGS, and ILRS. A unique feature of the ESOC participation in these three services is that its contributions to all three techniques are based on the same software, called NAPEOS. And we are well advanced in adding the VLBI processing capability to NAPEOS.
ESOC has been a full analysis centre of the IGS since its beginning in 1991. In 2008 ESOC undertook a significant effort to become a full analysis centre also in the IDS and ILRS. As AC in the three techniques it also participated in the reprocessing efforts for the ITRF2008 and the ITRF2014 and is now also participating in the reprocessing for the ITRF2020 in all three services.
The participation in all three techniques is considered as a “first step”. Our ultimate goal is to do a fully combined analysis of the data of all three techniques, and in the future even 4 techniques when adding VLBI. In such a combined analysis the strength of each technique may be used to overcome the weaknesses in the other techniques. In this combination of techniques SLR plays a crucial role as it is the only technique that provides (more or less) unbiased range measurements. Furthermore, SLR is the only technique that provides direct access to the orientation and the scale of the terrestrial reference frame. In addition SLR is extremely important in validating the orbits of both the IGS and the IDS or more general in validating the GNSS and LEO orbits as long as they are equipped with SLR reflecting arrays.
Weekly and Daily Processing
The ESA/ESOC ILRS Analysis Centre contributes to all analysis centre products. The are the routinely generated weekly (or final) and daily (or rapid) solutions. The daily and weekly solutions are very similar, the main difference is in the delay with which to become available. Both solutions make use of a 7-day arc and use all the SLR data from the ILRS tracking network to the four satellites currently used for the ILRS service: LAGEOS-1, LAGEOS-2, ETALON-1 and ETALONG-2. The ILRS is planning to add LARES to this list in the near future.
As AC we also try to participate in all the pilot projects performed within the ILRS analysis working group.
The daily solution are made available every day within 17 hours after the end of the last observation day. The weekly solutions are made available 10 days after the end of the last observation day, i.e. on Tuesday for the week ending on the Saturday before that.
Our products are publicly available to the scientific community, being published at several data servers, such as navigation-office.esa.int , and the CDDIS at NASA’s Goddard Space Flight Center, and the EUROLAS Data Centre (EDC) hosted at the DGFI in Münich, Germany.
Besides as analysis centre we also contribute to the ILRS as prediction center for the Galileo satellites and other ESA missions where needed.
Recent Progress and Analysis Center Improvements
Besides the weekly and daily processing in the ILRS there are several different pilot projects to which we contribute.
The space debris office of ESOC makes use of several of the other SLR cannonball targets as they use them as “calibration” targets. Since we start our processing with a 3 week pre-processing solution we decided to include these targets in this pre-processing step. The satellites we included are: LARES (to be included in the ILRS soon anyway), Ajisai, Stella, Starlette, and Larets.
For more information about the ILRS in general see: https://ilrs.gsfc.nasa.gov/
For more information about the ILRS analysis center products: https://ilrs.gsfc.nasa.gov/science/analysisProducts/index.html
Download our products: navigation-office.esa.int