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Initial Ideas and Suggestions for a New IGS Orbit Format

This document provides a brief history of the IGS orbit format and lists new features and interesting ideas for improvement. Examples of the new format are also included.

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Initial Ideas and Suggestions for a New IGS Orbit Format

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  1. Initial Ideas and Suggestions for a New IGS Orbit Format Steve Hilla National Geodetic Survey, NOAA IGS Analysis Center Workshop 2-6 June 2008, Miami Beach, Florida, USA

  2. Outline • Brief History • List of New Features • Other Interesting Ideas • Some Examples • Summary and Future Plans

  3. A Brief History • SP3-a: developed by Ben Remondi in 1991 and used by the IGS from 1994 to 2004. • SP3-b: modifications by Gurtner/Rothacher in 1998 to provide a way to mix GPS and GLONASS satellites. • SP3-c: additions made in 2002 to provide time dependent accuracies, XYZt correlations, and event flags. The IGS switched from SP3-a/b to SP3-c in 2004.

  4. An example SP3-c file, the GPS final orbit for May 7, 2008 #cP2008 5 7 0 0 0.00000000 96 ORBIT IGS05 HLM IGS ## 1478 259200.00000000 900.00000000 54593 0.0000000000000 + 31 G02G03G04G05G06G07G08G09G10G11G12G13G14G15G16G17G18 + G19G20G21G22G23G24G25G26G27G28G29G30G31G32 0 0 0 + 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 + 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 + 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ++ 2 2 3 2 2 2 2 3 2 2 3 3 3 3 3 3 3 ++ 3 3 3 3 3 3 3 2 3 3 3 2 3 3 0 0 0 ++ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ++ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ++ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 %c G cc GPS ccc cccc cccc cccc cccc ccccc ccccc ccccc ccccc %c cc cc ccc ccc cccc cccc cccc cccc ccccc ccccc ccccc ccccc %f 1.2500000 1.025000000 0.00000000000 0.000000000000000 %f 0.0000000 0.000000000 0.00000000000 0.000000000000000 %i 0 0 0 0 0 0 0 0 0 %i 0 0 0 0 0 0 0 0 0 /* FINAL ORBIT COMBINATION FROM WEIGHTED AVERAGE OF: /* cod emr esa gfz grg jpl mit ngs sio /* REFERENCED TO IGS TIME (IGST) AND TO WEIGHTED MEAN POLE: /* PCV:IGS05_1473 OL/AL:FES2004 NONE Y ORB:CMB CLK:CMB * 2008 5 7 0 0 0.00000000 PG02 -8809.661438 13800.152093 20688.250986 200.145019 11 8 10 152 PG03 8783.028077 -23775.730485 -7563.365732 224.532353 12 10 10 135

  5. Main list of new features • Unlimited number of satellites • Unlimited number of comments • Irregularly spaced epochs for LEOs • Variable number of SVs at each epoch • A more flexible, SINEX-like header • 0.1 mm precision (for GRACE, LEO veloc.) • Attitude information (quaternions)

  6. Other interesting ideas (1 of 2) • Use white space delimited fields (any precision) • Put time tag on each line to easily extract one SV: • ( POS G02 2008 05 22 23 45 30.12345678 X Y Z t ) • Instead of quaternions, use ITRF body-x unit vector • Have attitude information in a separate section after the position/clock data • Make the format usable for real-time data

  7. Other interesting ideas (2 of 2) • Future mixed GNSS files should be in UTC or TAI • Allow the use of the format for inertial orbits • Include EOP information in the header • Include Maneuver information in the header • Allow additional records for acceleration • Provide User Range Accuracy (URA) values • Supply satellite DCBs in the header

  8. %=ORBEX 1.00 140 IGSACC 2008 05 20 12 0 0 * :START HEADER ================================================================== +FILE/DESCRIPTION DESCRIPTION IGS FINAL GNSS ORBIT COMBINATION CREATED BY IGS Analysis Center Coordinator CREATION DATE 2008 5 20 12 0 0 INPUT DATA Weighted Average of: cod emr esa gfz grz jpl mit ngs sio CONTACT Jim.Ray@noaa.gov SOFTWARE Orbit Combination Software Version 2.03 START TIME 2008 05 07 0 0 0.000000000000000 END TIME 2008 05 07 23 45 0.000000000000000 EPOCH INTERVAL 900.0 SECONDS COORD SYS IGS05 TIME SYS GPS ORBIT TYPE HLM DATA USED ORBIT NUMBER OF SVS 47 NUM OF SV TYPES 2 LIST OF SV TYPES G R NUM OF REC TYPES 1 LIST OF REC TYPES POS OCEAN LOADING FES2004 (Center-Of-Mass correction included: Yes) ATMOS LOADING NONE (Center-Of-Mass correction included: N/A) CMC FOR ORBIT CMB (CoN=CenterOfNetwork,CoM=CenterOfMass,CMB=Combination) CMC FOR CLOCKS CMB (CoN=CenterOfNetwork,CoM=CenterOfMass,CMB=Combination) GPS WEEK/SECWK 1478 259200.000000000000000 (start time) -FILE/DESCRIPTION *------------------------------------------------------------------------------- +SATELLITE/NAMES_AND_STD_DEVS *SV_ COSPAR#__ SV_TYPE______ SVN_ STDP(mm) STDCLK(psec) #EPOCHS CHAN# G02 2004-045A BLOCK_IIR-B G061 31.0 42.7 96 N/A G03 1996-019A BLOCK_IIA G033 16.0 28.0 96 N/A G04 1993-068A BLOCK_IIA G034 33.0 68.2 96 N/A . . . R19 2007-052C GLONASS-M R720 28.0 58.2 96 3 R20 2007-052B GLONASS-M R719 34.0 57.1 96 2 R23 2005-050A GLONASS-M R714 38.0 73.5 96 3 R24 2005-050B GLONASS-M R713 42.0 71.8 96 2 -SATELLITE/NAMES_AND_STD_DEVS :END HEADER ==================================================================== * Example ORBEX Header

  9. Example ORBEX Data Epoch :END HEADER ==================================================================== * ## 2008 5 7 0 0 0.000000000000000 47 *REC SV_ ______X_(km)__ ______Y_(km)__ ______Z_(km)__ __SVCLK_(usec) __STD_X __STD_Y __STD_Z ____STD_CLK * (mm) (mm) (mm) (psec) POS G02 -8809.6614480 13800.1521030 20688.2509810 200.1561940 11.6 5.9 9.3 42.7 POS G03 8783.0280890 -23775.7304950 -7563.3657510 224.5436290 14.6 9.3 9.3 28.0 POS G04 -20366.9183010 7751.4287030 15329.9240560 -61.6745610 9.3 11.6 14.6 68.2 M . . . POS R19 -15108.0638680 20059.3830880 4484.7639460 -58.1237860 11.8 5.9 9.3 58.1 E POS R20 -2774.8011210 16607.6942980 19201.9866650 -57.2753910 12.7 5.8 7.2 43.2 POS R23 14982.6131490 -20030.9220740 -4887.6747570 -164.5623570 13.6 8.9 10.4 43.3 POS R24 1343.5390390 -15564.1095240 -20114.5221140 -177.3452340 14.2 7.9 9.6 73.4 * ## 2008 5 7 0 15 0.000000000000000 47 POS G02 -11140.7631150 13404.3243040 19780.8448450 200.1606680 11.6 4.8 9.3 41.6 . . . :EOF

  10. %=ORB 4.01 XYZ 08:122:60854 IGS 08:021:00000 08:024:00000 P 00060 0 XTVCA *------------------------------------------------------------------------------ +FILE/REFERENCE *INFO_TYPE_________ INFO_______________________________________________________ DESCRIPTION My agency/institute OUTPUT One-session solution generated by RNX2SNX BPE CONTACT My e-mail address SOFTWARE Bernese GPS Software Version 5.1 HARDWARE My computer INPUT IGS/IGLOS GNSS tracking data TIME SYSTEM GPS ORBIT TYPE FIT -FILE/REFERENCE *------------------------------------------------------------------------------ +INPUT/ACKNOWLEDGMENTS *AGY DESCRIPTION_______________________________________________________________ XYZ My agency/institute and its address IGS International GPS Service -INPUT/ACKNOWLEDGMENTS *------------------------------------------------------------------------------ *Orbits generated at Center for Orbit Determination in Europe (CODE) *GNSS: Middle day of a 3/day arc GPS/GLONASS solution * Gravity field JGM3 12x12 *------------------------------------------------------------------------------ +SATELLITE/ID *CODE PRN SVN_ COSPAR___ TYP NAME________________ COMMENT______________________ G01 001 32 1992-079A GPS G02 002 61 1992-079A G03 003 32 1992-079A L06 2000-039B LEO CHAMP -SATELLITE/ID *------------------------------------------------------------------------------ +ANTENNA/OFFSET *CODE ANTENNA_____________ FRQ X_OFFSET Y_OFFSET Z_OFFSET ANTEX________________ G01 BLOCK IIA L1 279.00 0.00 2201.00 IGS05_1480.ATX G01 BLOCK IIA L2 279.00 0.00 2201.00 IGS05_1480.ATX G02 BLOCK IIR-B L1 0.00 0.00 614.00 IGS05_1480.ATX G02 BLOCK IIR-B L2 0.00 0.00 614.00 IGS05_1480.ATX G03 BLOCK IIA L1 279.00 0.00 2201.00 IGS05_1480.ATX G03 BLOCK IIA L2 279.00 0.00 2201.00 IGS05_1480.ATX L06 SPENCER/CR L1 0.60 -0.50 56.30 L06 SPENCER/CR L2 -0.10 -0.60 91.90 -ANTENNA/OFFSET *------------------------------------------------------------------------------ Example ORBEX File (1 of 2) (Courtesy of Urs Hugentobler)

  11. +ACCURACY/CODE *CODE AC Accuracy Ecl Unh G01 2 3.8 - - G02 5 31.2 E U G03 3 7.1 - - -ACCURACY/CODE *------------------------------------------------------------------------------ +CENTER/DEFINITION *DATA__ CENTER_______________ ORBITS CENTER OF NETWORK CLOCKS CENTER OF NETWORK -CENTER/DEFINITION *------------------------------------------------------------------------------ +CENTER_OF_MASS/INFO *CORRECTION ON MODEL_______________ OTL Y FES2004 ATL N -CENTER_OF_MASS/INFO *------------------------------------------------------------------------------ +ORBIT/INFO *CODE PLANE SLOT G01 A 1 G02 B 2 G03 C 3 L06 -ORBIT/INFO *------------------------------------------------------------------------------ +MANEUVER/INFO *CODE MANV_START__ MANV_END____ DV_RADIA DV_ALONG DV_CROSS G01 08:020:45367 08:020:45389 1.23 324.50 -10.234 -ORBIT/INFO *------------------------------------------------------------------------------ +EPHEMERIS/DATA > 2008 01 06 00 00 0.0000000 10 POS G01 -14784237.0620 -3230043.6852 -21615673.5353 VEL G01 1234.0000 123.0000 1.0000 CLK G01 176.303984 COV G01 ... ATT G01 ... POS G02 22264336.8400 -10011598.2350 -10248988.2470 VEL G02 1234.0000 123.0000 1.0000 POS G03 22264336.8400 -10011598.2350 -10248988.2470 VEL G03 1234.0000 123.0000 1.0000 POS L06 13273.1421 14323.3948 323421.3423 Example ORBEX File (2 of 2) (Courtesy of Urs Hugentobler)

  12. Summary and Future Plans • There are several valid reasons to move to a new format. • These changes will benefit both LEO and GNSS users. • Next step: with the ACs, create a draft format document. • Solicit comments via IGS Mail. • Work with the other services (ILRS, IDS, etc.). • After final acceptance, the IGS will need to support both SP3-c and ORBEX (for one year, or maybe longer). • Tools will be needed later to convert ORBEX to SP3-c . Steve.Hilla@noaa.gov

  13. Thank You. Questions? Comments?

  14. Acknowledgements The author would like to thank the following individuals who offered their initial ideas and suggestions about what might be needed in a future IGS orbit format: Willy Bertiger, Yehuda Bock, Henno Boomkamp, Oscar Columbo, Rolf Dach, Mark Davis, Gerd Gendt, Clyde Goad, Jake Griffiths, Heinz Habrich, Urs Hugentobler, Jan Kouba, Gerry Mader, Michael Meindl, Oliver Montenbruck, Erricos Pavlis, Jim Ray, Benjamin Remondi, Ignacio Romero, Eun Hwan Shin, Mark Schenewerk, Tim Springer, and Robert Weber.

  15. http://www.gsfc.nasa.gov/sp3c_satlist.html

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