******************************************************************************** README ******************************************************************************** University of Bern Astronomical Institute (AIUB) Daniel Arnold daniel.arnold@aiub.unibe.ch +41 31 684 3802 or: Adrian Jaeggi adrian.jaeggi@aiub.unibe.ch +41 31 684 8596 Address: Sidlerstrasse 5 3012 Bern, Switzerland Short notice on AIUB GRACE-FO kinematic orbits: |------------------------------------------------------------------------------| | Processing strategy | |-------------------------------------|----------------------------------------| | Software | Bernese GNSS Software v5.3 | | GNSS system | GPS | | Arc length | 1.0 days | | Reference system | | | Time | GPS time (GPST) | | Position | Earth-centered Earth-fixed (see below) | | Polar motion and UT1 | CODE final products | | Pole model | IERS 2010 conventions | | Precession/Nutation | IERS 2010 conventions | | GPS orbits | CODE final products | | GPS clocks | CODE final 5s clocks | | GPS measurements | | | Observations | Ionosphere-free linear combination of | | | phase measurements, pseudo-range used | | | for clock synchronization and wide-lane| | | ambiguity resolution | | Sampling | 10s | | Elevation angle cutoff | 0 deg (RL01) and 10 deg (RL02) | | Antenna offset (w.r.t. CoM) | Time-dependent values | | GPS antenna phase center var. | Determined for each antenna from | | | stacking of carrier phase residuals of | | | reduced-dynamic orbit determination | | Observation weighting | Constant | | Antenna phase-center wind-up | Correction applied | | Relativistic corrections | Applied | | Solution strategy | Daily least-squares solution based on | | | data from 00:00:00 to 23:59:59 | | Estimated parameters | | | Receiver position | Every epoch | | Receiver clock correction | Every epoch | | Carrier phase ambiguities | Fixed (using CODE clock and OSB prod.) | |------------------------------------------------------------------------------| General remarks =============== This product contains kinematic orbit positions of the GRACE-FO satellites given in daily batches per single satellite. File naming convention: GFO_RL_.KIN : C or D (specifying the corresponding GRACE-FO satellite) : Release number (see below) : year (last two digits) : day of year Format description ================== File header: Line 1: description of orbit including release number and orbit generation date and time Line 2: dummy line Line 3: information about geodetic datum and date & time of first epoch (GPS time) Line 4: a posteriori standard deviation of L1 GPS carrier phase res. [m] Line 5: description of columns Line 6: dummy line Data records: After the header each line represents one epoch. The columns contain the following quantities: Column 1: LEO name (GRACE-FO C: GRCC, GRACE-FO D: GRCD) Column 2: modified SVN number (GRACE-FO C: L64, GRACE-FO D: L65) Column 3: GPS antenna used for POD (main antenna: POD1, redundant antenna: POD2) Column 4: GPS week Column 5: GPS second within the given GPS week [s] Column 6: position x-component (Earth-centered Earth-fixed) [m] Column 7: position y-component (Earth-centered Earth-fixed) [m] Column 8: position z-component (Earth-centered Earth-fixed) [m] Column 9: quality flag (possible values are K, X, S and G, see below) Column 10: xx-element of 3x3 epoch-wise cofactor matrix Column 11: yy-element of 3x3 epoch-wise cofactor matrix Column 12: zz-element of 3x3 epoch-wise cofactor matrix Column 13: xy-element of 3x3 epoch-wise cofactor matrix Column 14: xz-element of 3x3 epoch-wise cofactor matrix Column 15: yz-element of 3x3 epoch-wise cofactor matrix Meaning of quality flags: K: kinematic orbit position could be properly determined X: kinematic orbit position could not be determined (less than 4 satellites) S: kinematic orbit position could be determined, but less than 5 satellites were available G: kinematic orbit position has been flagged during internal AIUB orbit screening (if screening applied) Please note: - Users who would like to use all available epochs or do their own orbit screening should use all epochs marked with the flags K or G. - Users who would like to rely on the internal AIUB orbit screening should use only epochs marked with flag K. - It is recommended not to use epochs denoted with the flag S. Note on cofactors: Columns 10-15 contain the epoch-wise 3x3 cofactor matrix. In order to compute the epoch-wise covariance matrix for the positions these cofactors need to be multiplied by the square of the a posteri RMS value found in line 4 of the header. Releases ======== RL01: - Orbits for 30-May-2018 (day 18/150) to 31-Dec-2021 (day 21/365). - Based on RL04 GRACE-FO GPS and attitude data. - GPS data not screened for ionosphere-induced artifacts. - An elevation cutoff of 0 deg was applied. - Carrier phase ambiguities are fixed to their integer values based on undifferenced ambiguity resolution using CODE's final clock and Observation Specific Bias (OSB) product. - Reference frames (defined by GNSS products): - 18/150-20/137: IGS14 - 20/138-21/365: IGb14 - Kinematic orbit positions were not screened for outliers. - Notice that the orbits of GRACE-FO C after day 21/082 and for GRACE-FO D after day 21/201 are not of optimal quality as they are based on PCVs not taking into account the lowered elevation cutoffs. - When using these GRACE-FO kinematic orbits, please cite them using the following reference: Arnold, Daniel; Jäggi, Adrian (2020). AIUB GRACE-FO kinematic orbits, release 01. Published by Astronomical Institute, University of Bern. URL: http://www.aiub.unibe.ch/download/LEO_ORBITS/GRACE-FO; DOI: 10.7892/boris.147231 RL02: - Orbits for 23-May-2018 (day 18/143) to now (regularly updated). - Based on RL04 GRACE-FO GPS and attitude data. - GPS data not screened for ionosphere-induced artifacts. - An elevation cutoff of 10 deg was applied. - GNSS products: CODE repro I20 products (http://ftp.aiub.unibe.ch/REPRO_I20) for days 18/143-18/365, operational CODE final products from day 19/001 onwards. - Carrier phase ambiguities are fixed to their integer values based on undifferenced ambiguity resolution using CODE's clock and Observation Specific Bias (OSB) products. - Reference frames (defined by GNSS products): - 18/143-20/137: IGS14 - 20/138-22/330: IGb14 - 22/331-now : IGS20 - Kinematic orbit positions were not screened for outliers. - When using these GRACE-FO kinematic orbits, please cite them using the following reference: Arnold, Daniel; Jäggi, Adrian (2022). AIUB GRACE-FO kinematic orbits, release 02. Published by Astronomical Institute, University of Bern. URL: http://www.aiub.unibe.ch/download/LEO_ORBITS/GRACE-FO; DOI: 10.48350/169040