****************************************************************************** dorisreport 28-Feb-2013 22:59:56 Message No 3258 ****************************************************************************** Author: "Lemoine, Frank G. (GSFC-6980)" Subject: Delivery of Full GSCWD15 Sinex Series (1992-2012) Technical Description of gscwd15 solution: February 2013 -------------------------------------------------------- This series represents a complete reprocessing of all DORIS data from November 1992 to December 2012. It is a step to the production of a completely updated series to be submitted for the next ITRF. (ITRF2013) The initial delivery (February 2013) includes files from November 1992 to December 2012. The delivery includes weekly SINEX files in Normal Equation (NEQ) format. The satellites included in this series, when data are available, include TOPEX/Poseidon, SPOT-2, SPOT-3, SPOT-4, SPOT-5, Envisat, Jason-2 and Cryosat-2. The major updates for this series (gscwd15), with respect to the ITRF2008-submitted series and their operational successors include the following: 1. New Gravity Model (Static) GOCO2S instead EIGEN-GL04S1 2. New Gravity Model (Time-Varying) At GSFC we have developed a 4x4 time series from SLR & DORIS tracking to up to ten satellites. We have done harmonic fits to this time series adjusting coefficients as appropriate (rates, annual, semiannual). This "fit" model now represents a conventional model we can apply in the DORIS processing. The C21/S21 terms are represented according to IERS conventions. The fit appears applied here are the same as in the gscwd13 series, however for C20 we replace the 9.3 year term for C20 with an 18.6 year term for C20. We also apply annual terms to from 5x5 to 20x20 derived from a GSFC GRACE solution provided by Scott Luthcke. These annual terms are determined over the period 2003-2011. As with the previous series, atmospheric gravity in the form of 6-hrly series from ECMWF is systematically applied. 3. Troposphere. -The GMF mapping function is used instead of Niell. -The Saastomoinen troposphere model is used instead of Hopfield. -GPT is used for the apriori met data (no change from gscwd11, gscwd12) -Only the wet troposphere delay scale factor is adjusted. 4. Update of Ocean Tide and Loading Model: GOT4.8 instead of GOT4.7 5. Ocean pole tide is systematically applied. 6. In the previous ITRF2008 series, there was an error in GEODYN that did not apply the atmospheric gravity for the C21, S21 terms. This has been corrected. 7. More rigorous editting is applied at the SINEX formation level. There are three levels of editting: 1. Stations with large adjustments are removed from the NEQ. 2. Stations with fewer than 250 observations/week are removed from the NEQ. 3. The weekly solutions are screened for further stations that perturb the Helmert transformation. A small number of stations are screened out on this basis, on a week-by-week basis. 8. The SPOT5 attitude modelling after January 2008 has been updated to model explicitly the pitch of the solar array (-40 deg). This obviates the necessity to "tune" the SPOT5 Cr after that date, as was done in the previous series. 9. The Envisat DORIS data has been re-imported so we use the new DORIS data for Envisat supplied by the CNES as documented in DORISMAIL 0823 (16-May-2012 17:14:24 from Luca.Cerri@cnes.fr). In addition, since the SPOT-4 data for 1998 have been corrected (May 1998 - January 1999), we now include these data in the solutions. The delivery of these new SPOT-4 data is documented in the following message: DORISMAIL 0701 (22-September-2010 08:44:16 from Pascale.Ferrage@cnes.fr) Finally, the updated Jason-2 & Cryosat-2 DORIS data have also been used. These data correct the a priori beacon frequency for stations GR3B and GAVB in the DORIS 2.2 format, as documented in DORISMAIL 0750 (17-May-2011, Pascale Ferrage). This correction affected Jason-2 cycles 1-102, and Cryosat-2 cycles 1-54. 10. Drag Coefficients are adjusted systematically for all low-altitude satellites at cd/2-hrs with a exponentially decaying time-correlation of 2-hrs. During periods near the solar maximum, including specific weeks identified by Gobinddass et al. (2010, doi:10.1016/j.asr.2010.04.004), cd/1-hr with a time-correlation of 1-hr are adjusted. For the low-altitude satellites, the a priori cd used was determined from annual averages determined from POD runs where the time-correlation was not applied. 11. The station set used for this series was DPOD2008v1.9 12. The ITRF2008 arcs for SPOT-4, SPOT-5, Envisat, SPOT-2 were re-examined for spurious behaviour (aberrant drag values or empirical accerlation values, or high RMS). This led to corrections for some arcs to the arc setups (shortening of arcs to avoid no-data periods, or splitting of arcs into shorter sets, etc.). 13. The GEODYN version used for this series is 1212. At the present time the correction to handle frequency changes/errors in the assumed frequency at the stations is not included in this series. As documented by Soudarin et al. (2010), frequency changes at stations map into spurious vertical jumps in the station coordinate time series for some stations. A correction is to be included in a future version of GEODYN, and once this is validated a new long-term series will be delivered to the IDS. The reference for this series at the present time is the following: Le Bail et al. (2010, updated) Le Bail, K., Lemoine, F.G., and D.S. Chinn (2010), GSFC DORIS Contribution to ITRF2008 Adv. Space Research,45(12), doi:10.1016/j.asr.2010.01.030. The specific Jason-2 processing pertaining to DORIS is described by the following paper. Zelensky, N.P., F.G. Lemoine , M. Ziebart, et al. ( 2010), DORIS/SLR POD modeling improvements for Jason-1 and Jason-2, Adv. Space Res., doi:10.1016/j.asr.2010.05.008. Authors and Contacts for More Information: +++++++++++++++++++++++++++++++++++++++++++ Frank Lemoine (Email. Frank.G.Lemoine@nasa.gov) Douglas Chinn (Email: Douglas.S.Chinn@nasa.gov) Nikita.P.Zelensky (Email: nzelensky@sgt-inc.com) Karine Le Bail (Email: Karine.Lebail@nasa.gov) Cliquez sur l'url suivante https://www.mailcontrol.com/sr/ZtP1quFurYvGX2PQPOmvUuj0JJAQpJ0nFNaGAfqOf9M9brlEZLpz0kpWoLrS7uV5FeBg751CQltqvfHxypKb0g== si ce message est indésirable (pourriel). Please do not reply directly to this message, but send comments and suggestions to IDS.central.bureau@cls.fr