Preparation for ITRF2020

[February 2020] IDS Recommendations and suggestions for ITRF 2020 reprocessing 

 pdf file

Orbits and force modeling

• Quaternions (strongly recommended for Jasons, and if possible, for Cryosat-2 and Sentinels if available),
• Introduce precise SPOT-5 solar panel angle values,  
• Use last version of macromodel from IDS documentation (ftp://ftp.ids-doris.org/pub/ids/satellites/DORISSatelliteModels.pdf) or/and own improvements
• Adjust Cr/arc determined from POD with separate arc empirical accelerations on TOPEX, and Jason satellites,
• For sun-synchronous, polar-orbiting satellites: adjust mean. Cr over entire time series (suggestion),
• Apply more complex Earth radiation modeling than Knocke (e.g. from CERES) (suggestion),
• New mean pole model (secular model),
• Up to date TVG (e.g. last EIGEN proposed by Jean Michel Lemoine). Be careful about consistency with new mean pole model,
• Desai & Sibois HF (diurnal-subdiurnal) tidal EOP model recommended by IERS
• Ocean tides model (e.g. FES2014b, be careful to use the version with all recent corrections),
• De-aliasing model must be applied since gravity models were determined using this model. It can be CNES-provided or GFZ-RL06 (provided for GRACE Follow-On project). Air Tides need to be separately applied e.g. as described by Dobslaw et al. (2017), in the case of GFZ RL06.

Data using, editing/weighting

• Do not use validity indicators from Doppler observation files (Doris2.2 format),
• ACs have to do their own preprocessing,
• Use elevation dependent downweighting, no strong recommendations of which applied function to be used by ACs (CNES weighting function suggested),
• Reasonable elevation cut off (7-10 deg),
• One RINEX/Doppler data format per mission,
• Adjust tropospheric gradients if possible.

South Atlantic Anomaly 

              The following mix of strategies is proposed:

• Corrected data for Jason-1 and SPOT-5,
• Data corrective model from A. Belli for Jason-2 can be used, if available (Free decision for ACs),
• Suggestion of removing or downweighting of data from SAA stations (Free decision for ACs)
• Using SAA data from the most affected satellites only for POD (recommendation for satellites and set of stations TBD),
• Linear or quadratic frequency adjustment per pass – ACs can apply if they can demonstrate that it is beneficial.

Others

• Alcatel, STAREC-B/C + associated phase laws

IDS reprocessing schedule

• 2020, March 30 th : AC delivery of 1993.0 2002.3 (Until start of Envisat First DORIS 2G receiver)
• 2020, June 30 th : AC delivery of 2002.3 2011.8 (Until start of HY-2A).
• 2020, Sept. 30 th : AC delivery of 2011.8 2020.0.
• 2021, Feb. 10 th : First delivery of the IDS combined solution to the IERS (1993.0 2020.0).
• 2021, Feb. 14th: AC delivery of 2020.
• 2021, Mar. 15 th : Complete delivery to the IERS of the IDS combined solution (1993.0-2021.0)

SINEX Content

In order to facilitate the preprocessing of your weekly SINEX files by the IDS CC, please:

1. Add the list of missions in the FILE/COMMENT block (ex: SATELLITE LIST : CRYOSAT2,HY2A,SARAL,JASON3,SENTINEL3A,SENTINEL3B).
2. Check the consistency of the station 4 characters, DOMES numbers, site names in your SITE/ID block with either the DORIS SINEX master file (ftp://ftp.ids-doris.org/pub/ids/stations/ids.snx) or the IGN file (ftp://itrf.ign.fr/incoming/codomes_doris.snx).
3. Check the consistency between the SINEX date, the time interval of the first line of the SINEX and the observation periods of all the stations in the SOLUTION/EPOCHS block.
4. If, as GOP, you deliver in your SINEX files different solutions for the SAA stations with a dedicated renaming, define the renaming convention in the FILE/COMMENT block.
5. Use ‘D‘ (DORIS) for the observation code (‘T‘). The letter ‘C‘ is only for a multi-technique solution, which is not our case.

[June 2019] IDS Roadmap for ITRF2020

• IDS Roadmap for ITRF2020 (Analysis Coordination, June 7, 2019)

This document presents the roadmap to be followed by the IDS Analysis Centers and Combination Center for the next ITRF solution (ITRF2020).

They have to work on 4 following essential items:

• Modeling improvement. Attempt to mitigate the non-conservative force model error on satellites (draconitic signals).
• Adopt and evaluate the new models/standards (TVG, HF-EOP model, ocean tides, …).
• SAA compensation.
• Scale (Elevation cut off and data downweighting).

Each topic will be leaded by one IDS member with one of the analysis coordinators.

First, the responsible of each topic will propose and follow the work made by the ACs and CC.

Second, he will present a synthesis at the next IDS AWG planed on 30th September and 1th October @CNES in Paris.

[April 2019] IERS request

• IERS Call for participation

• IERS Roadmap for ITRF2020 (Z. Altamimi, ITRS Center, AWG meeting in Munich, April 4, 2019)

• Schedule & time-line (as of April 4, 2019):