Subject: [SIR-Mail] No.680: igs08_1745.atx: Update including GPS satellite antenna PCV extension From: Laura Sanchez ******************************************************************************** SIR Electronic Mail 2013-06-24 07:37:45 UTC Message No. 680 ******************************************************************************** The absolute IGS antenna correction file (igs08_wwww.atx) has been updated. The new release is called ´igs08_1745.atx´. According to an IGS 2012 Workshop recommendation, the satellite antenna phase center variations (PCVs) of the following GPS block types were extended with correction values [mm] for nadir angles between 15 and 17 degrees derived from the analysis of low Earth orbiter (LEO) data performed by CODE: |-------------------|--------|--------|--------|--------| | Nadir angle | | | | | | [degrees] | 14 | 15 | 16 | 17 | | | | | | | | Block | | | | | |-------------------|--------|--------|--------|--------| | I | -0.30 | -- | -- | -- | |-------------------|--------|--------|--------|--------| | II/IIA | -0.90 | -0.90 | -0.90 | -0.90 | |-------------------|--------|--------|--------|--------| | IIR-A | -1.40 | -0.80 | +2.00 | +6.40 | |-------------------|--------|--------|--------|--------| | IIR-B/M | +12.10 | +22.00 | +30.40 | +40.60 | |-------------------|--------|--------|--------|--------| | IIF | +5.70 | +12.40 | +18.20 | +23.50 | |-------------------|--------|--------|--------|--------| The results are based on ionosphere-free GPS data of the LEO missions Jason-2, GRACE-A, GRACE-B, GOCE, and MetOp-A from 2009. In addition, Jason-2 data from the second half of 2011 were analyzed to derive extended PCV estimates for Block IIF. Block I satellites were only active before the first launch of a GPS-based LEO mission. Therefore, Block I PCVs remain unchanged. The PCVs of Block IIA satellites were extended with constant values beyond 14 degrees and constrained when estimating PCV values for the remaining satellite block types (IIR-A, IIR-B/M, IIF). Such a constraint for one of the satellite blocks is necessary, as PCVs for the transmitter and the receiver antennas on board the LEOs have to be estimated simultaneously. In fact, the analysis is only sensitive to PCV differences between different satellite blocks. More details can be found in the following IGS 2012 Workshop presentation: Jäggi A, Dilssner F, Schmid R, Dach R, Springer T, Bock H, Steigenberger P, Lutz S: Extension of the GPS satellite antenna patterns to nadir angles beyond 14°. http://www.igs.org/assets/pdf/Poland%202012%20-%20P09%20Dach%20PR14.pdf The PCV extension is mainly relevant for the analysis of LEO data. Solutions using terrestrial data will be hardly affected. If any, there might be a tiny benefit for terrestrial observations at very low elevations that slightly exceed a nadir angle of 14 degrees. LEO users should be aware that an update of the LEO antenna PCVs might be necessary when implementing the PCV extension for the transmitter antennas. Many thanks to Adrian Jäggi and the CODE group for providing the final PCV estimates as well as to Florian Dilssner and the ESOC group who supported this effort by independent PCV solutions for the purpose of comparison. The updated antenna correction model is available at ftp://igs.org/pub/station/general/igs08_1745.atx or ftp://igs.org/pub/station/general/igs08.atx Those users who don´t want to implement the new model including the PCV extension immediately are referred to ftp://igs.org/pub/station/general/igs08_1745_woPCVextension.atx that is identical with the previous release (igs08_1740.atx). In order to allow a smooth transition, parallel model updates with and without the PCV extension will be released until about end of July 2013. With best regards, Ralf Schmid and Robert Khachikyan on behalf of the IGS Antenna Working Group ********************************************************************************