NAPEOS: The ESA/ESOC Tool for Space Geodesy

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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

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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
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Excellent Performance in IGS
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Excellent Performance in ILRS
Source of plot Cecilia Sciarretta based on
weekly ILRS combination
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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
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Excellent quality of LEO orbits
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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/000readm
  e.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
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Observed Computed Statistics ofSLR
observations from GNSS Satellites
Small bias and small RMS for GNSS
satellites Combination of the techniques is
feasible
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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

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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

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THANK YOU

• Tim Springer and Florian Dilssner
• Tim.Springer_at_esa.int
• Florian.Dilssner_at_esa.int