NAPEOS: The ESA/ESOC Tool for Space Geodesy

Tim Springer, Florian Dilssner, Diego Escobar, Drazen Svehla, Claudia Flohrer, Rene Zandbergen EGU 2011, Vienna, Austria 07/04/2011

NAPEOS Facts (1)

– ESOC Navigation Support Office does all its operational work with NAPEOS – ESOC uses NAPEOS operational for three space geodetic techniques – GNSS, DORIS, SLR – ESOC is a full analysis centre in the three technique services – IDS, ILRS, and IGS – Performance is excellent in all three services – ESOC contributed significantly to the ITRF2008 by participating in the reprocessing of all three techniques

NAPEOS is very well suited for analysing the data from all three space geodetic techniques

Excellent Performance in IGS

Excellent Performance in ILRS

Source of plot: Cecilia Sciarretta based on weekly ILRS combination

NAPEOS Facts (2)

– – – NAPEOS has been used extensively for GNSS LEO data – JASON-1/2 complete time frame from 2001-2011 High accuracy LEO orbits – Using ESOC IGS reprocessing with 30 second clocks – PPP-like solution for JASON-1 and JASON-2 – Reference: Paper by Claudia Flohrer et al. in “Advances in Space Research” GNSS PCVs for LEO processing based on combined GNSS solution – – JASON-1/2 + 100 IGS stations as “normal” IGS solution No external reference frame needed to derive z-PCOs!

– – Reference: Poster by Florian Dilssner at EGU 2011 Resulting PCV product: ideal for LEO GNSS processing

NAPEOS can efficiently and accurately handle GNSS LEO data

Excellent quality of LEO orbits

NAPEOS Facts (3)

– NAPEOS is used in the “Combination at the Observation Level” project of the IERS – Provided 3 different solutions: – GNSS + SLR (IGS-like + SLR of the GNSS sats.) – – – – DORIS + SLR (IDS-like + SLR of the DORIS sats.) SLR only solution (LAGEOS 1/2, ETALON 1/2) Description: ftp://dgn6.esoc.esa.int/cool/000readme.cool

– Reference: COL-WG poster here at the EGU 2011 Next steps: – Adding JASON GNSS data to “GNSS + SLR” solution – Combination of the 3 solutions on NEQ level

NAPEOS is capable of combining the observations from all three space geodetic techniques on the observation level

Observed – Computed Statistics of SLR observations from GNSS Satellites

50 40 -10 -20 -30 30 20 10 0 GPS-35 GPS-36 GLO-729 GLO-723 GLO-716 GLO-714

Mean RMS #Obs Small bias and small RMS for GNSS satellites Combination of the techniques is feasible

5000 4000 3000 2000 1000 GLO-713 0 -1000 -2000

Main Goals with NAPEOS at ESOC

– Connect the three space geodetic techniques on the observation level which has as advantages (compared to ITRF 2008 realization): – It makes full use of the common parameters – E.g. GNSS and JASON orbit parameters – – We can introduce JASON-1 and JASON-2 for SLR and GPS solutions (for ITRF only IDS made use of this satellites) Connect the techniques in space (“space-ties”) using the local ties between the on-board instruments (but also using the local site-ties on the ground) – Main differences compared to ITRF 2008 realization: – Includes SLR observations from the GNSS targets – – Includes GNSS and SLR observations from JASON-1 and -2 Uses “space-ties” and local ties but will lack VLBI data

Summary and Conclusions

– Combination of GNSS, SLR and DORIS will allow – Determination of “unified” reference frame – Absolute estimation of GNSS satellite antenna offsets – Already possible with just GNSS when including a LEO like JASON – – Absolute estimation of SLR station biases (where needed) – Definitely needed for some sites. Combination also makes it easier to detect the biases Determine the orbits of all satellites in the unified reference frame – NAPEOS is the unique tool that is capable of doing this

THANK YOU

Tim Springer and Florian Dilssner [email protected]

[email protected]