1. 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

2. 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

3. Excellent Performance in IGS

4. Source of plot: Cecilia Sciarretta based on weekly ILRS combination
Excellent Performance in ILRS
Source of plot: Cecilia Sciarretta based on weekly ILRS combination

5. NAPEOS can efficiently and accurately handle GNSS LEO data
NAPEOS Facts (2)
NAPEOS has been used extensively for GNSS LEO data
JASON-1/2 complete time frame from
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/ 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

6. Excellent quality of LEO orbits

7. 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

8. Observed – Computed Statistics of SLR observations from GNSS Satellites
Small bias and small RMS for GNSS satellites
Combination of the techniques is feasible
Document title | Author Name | Place | Data doc | Programme | Pag. 8

9. 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

10. 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

11. THANK YOU Tim Springer and Florian Dilssner Tim.Springer@esa.int