CDDIS Bulletin - June 1994
Volume 9 No. 5
In this issue:
About the cover: The map on the cover of this issue of the CDDIS Bulletin shows current and planned space geodesy sites in Russia. This information was provided by Dr. Suriya Tatevian of the Russian Academy of Sciences.
The CDDIS routinely provides on-line access to SLR on-site data as well as normal points generated from full-rate data. Until recently, the full-rate data itself, however, has been relegated to our off-line tape archive. Because of recent magnetic disk acquisitions for the VAX computer system, the CDDIS is now able to provide on-line access to the latest SLR full-rate data releases. The releases are stored by month and by satellite in compressed form, using UNIX compression software. This software compresses the data by approximately a factor of five. The files are stored in yearly directories:
where satname is the satellite name (AJISAI, ERS1, ETALON1, ETALON2, GPS35, GPS36, LAGEOS, LAGEOS2, METEOR3, MSTI2, STARLETTE, STELLA, TOPEX), v is the version of the release (e.g., A, B, etc.), yyyy is the four-digit year, yy is the two-digit year, and mm is the month. These data are stored in the MERIT-II format for full-rate data. Due to disk space constraints, only the latest three or four monthly releases will be available on-line at one time. Auxiliary files are also provided for each monthly release: LETTERv.yymm (the release letter generated by ATSC citing operational, engineering, and permanently withheld passes) and SUMMARYv.yymm (the pass-by-pass summary generated by the CDDIS for each monthly release). Interested users should contact the CDDIS staff for more information on retrieving these data sets. We encourage users of full-rate data to retrieve these files via electronic means to save money and time in the generation and mailing of data tapes.
The Russian METEOR-3 satellite was successfully launched by the Mission Control Center in Moscow on January 25, 1994. In addition to laser retroreflectors, the satellite is also equipped with a PRARE instrument. The first SLR station to successfully range to METEOR-3 was MOBLAS-5 in Yaragadee, Australia, on January 25 at 18:09 UTC. The official international satellite number for METEOR-3 is 940301.
The NAVSTAR 36 satellite (PRN 06), one of the Block IIA GPS spacecraft, is equipped with laser retroreflectors (as is NAVSTAR 35, PRN 04). The satellite was successfully launched on March 10, 1994 at 02:40 UTC. The satellite is referred to as GPS-36; its official international satellite number is 9401601. The approximate orbit of the GPS satellites is 20,000 kilometers. The first station to successfully track the spacecraft after stabilization was Maidenak, Russia on April 21, 1994. The Naval Research Laboratory (NRL) and NASA are conducting a joint experiment, the main purpose of which is to unambiguously differentiate between onboard clock errors and satellite ephemeris errors. It is anticipated that SLR tracking of both the GPS-35 and -36 satellites will ultimately reduce the satellite position uncertainty by over an order of magnitude.
The MSTI-2 satellite was launched on May 9, 1994 at 02:49 UTC; its official international satellite number is 9402801. The final orbit is at an altitude of approximately 425 kilometers. The satellite, built by the Ballistic Missile Defense Organization (BMDO), is carrying a laser retroreflector array designed and built by GSFC, Code 920.1. Because of its orbit characteristics, MSTI-2 is expected to help refine Earth gravity field models.
The CDDIS is providing on-line access to the on-site normal point and engineering data for both the STELLA and GPS-35 satellites. These data can be retrieved from the directories DIS_DATA:[STELLADATA.yyyy] and DIS_DATA:[GPS35DATA.yyyy] respectively, where yyyy is the four-digit year. The CDDIS will also provide on-line access to normal points generated from STELLA and GPS-35 full-rate data as well as providing the full-rate data on normal monthly release tapes.
Data from two 1993 DOSE investigation experiments have been submitted to the CDDIS by JPL. In addition, data from one footprint experiment conducted earlier this year has been delivered to the CDDIS by AlliedSignal Technical Services Corporation (ATSC). The text and table below summarize these data sets. Users interested in obtaining data from any of these GPS experiments should contact the CDDIS staff.
Alaska (Lamont-Doherty): Dr. John Beavan's (Lamont-Doherty) DOSE investigation "Deformation in Alaska: (1) Analysis of GPS Reoccupation of Alaskan VLBI Sites; (2) Subduction, Segmentation, and Earthquake Potential South of the Alaskan Peninsula" was conducted June 29 through July 25, 1993. The GPS data set from this experiment is available from the CDDIS in compressed RINEX format and consists of 360 files totaling 44 Mbytes in size.
Alaska (GSFC): Dr. Jeanne Sauber's (GSFC, Code 926) DOSE investigation "The Subduction Zone Process in Alaska" was conducted June 8 through 25, 1993. The GPS data set from this experiment is available from the CDDIS in compressed RINEX format and consists of 288 files totaling 51 Mbytes in size.
Alaska (USGS): Dr. Jim Savage's (USGS) DOSE investigation "Deformation at Subduction and Collision Zones" was conducted June 1 through 16, 1993. The GPS data set from this experiment is available from the CDDIS in compressed RINEX format and consists of 172 files totaling 37 Mbytes in size.
Arequipa Footprint. A footprint at Arequipa, Peru was conducted by ATSC in February 1994. The data are currently available in both raw Trimble receiver format and RINEX format. The raw data consist of 72 files totaling 0.3 Mbytes in size; data in RINEX format consist of 78 files totaling 11.25 Mbytes in size. Site descriptions and log sheets, in hardcopy format, are also available.
Experiment Name Start Date End Date No. Sites Markers Occupied
Alaska (GSFC) 08-Jun-93 25-Jun-93 34 Kodiak, Cape Yakataga,
Sourdough, Whitehorse, AK
Alaska (Lamont-Doherty) 29-Jun-93 25-Jul-93 47 Kodiak, Sand Point, AK
Alaska (USGS) 01-Jun-93 16-Jun-93 33 None
Arequipa, Peru 18-Feb-94 23-Feb-94 4 Permanent GPS mark
Several institutions have submitted their annual IERS solutions for 1994 to the CDDIS. These data are available on-line via Anonymous FTP.
The NASA/GSFC SLR IERS solution. The solution SL8.5 was obtained using LAGEOS-I and -II normal points and spans the January 1980 through December 1993 time frame. The data are available through Anonymous FTP on the CDDIS (directory ANON_DIR:[SLRGSFC.IERS94]):
TEXT94_SL85.SLRGSFC Description of analysis
EOP94_SL85.SLRGSFC Earth rotation parameters
SP94_SL85.SLRGSFC Station positions and velocities
University of Texas/Center for Space Research IERS solution. The data sets span May 1976 through December 1993 and were derived from LAGEOS SLR full-rate and quick-look data. The data are available through Anonymous FTP on the CDDIS (directory ANON_DIR:[SLRCSR.IERS94]):
README.CSR Readme file
CSR94L01.DESC Description of the CSR94L01 solution
EOP94L01. Earth orientation parameter solution
SSC94L01. Station positions and velocities solution
SSC94L01.ECCEN Station eccentricities used in SSC94L01
SSC94L01.SUM Summary Sheet for the station position solution
The NASA/GSFC VLBI IERS solution. The data from the VLBI solution GLB932 spans the August 1979 through December 1993 time frame. The data are available through Anonymous FTP on the CDDIS (directory ANON_DIR:[VLBIGSFC.IERS94]):
NOTES.94 Solution notes
LIST94.2 List of available files
SUMMARY.94 Solution summary sheet
EOP.932 Earth orientation (EOP) and nutation parameters
EOP_COR.932 Correlations between EOP and nutation parameters
EOP_RATES.932 EOP rates, sigmas, and correlations
SIT_BOTH.932 Station coordinates and velocities together
SITA_VEL.932 Station velocities
SIT_XYZ.932 Station coordinates
SIT_XYZV.932 Station coordinates and velocities with correlations
SRC.932 Radio source coordinates
TEXT94.932 Detailed description of solution GLB932
This section is designed to give brief notices of special events, new data sets, or problems encountered in recent months. The CDDIS staff believes the user community should be informed of these problems in order to ensure that the best results possible are produced from data issued by the archive.
The ATSC Data Services group has recently released all outstanding SLR full-rate passes from 1988 through 1991. The table below summariezes the number of passes replaced or added on these releases. The data are avilable on-line (see article presented earlier in this bulletin) or via tape. Interested users should contact the CDDIS staff to obtain copies of the data.
Release Replacement New Total
Year Ver. Satellite Passes Obs Passes Obs Passes Obs
1988 D AJISAI 132 44,241 96 30,731 228 74,972
LAGEOS 175 78,817 83 19,981 258 98,798
STARLETTE 84 23,810 31 6,659 115 30,469
Totals: 391 146,868 210 57,371 601 204,239
1989 C AJISAI 59 35,400 261 119,957 320 155,357
ETALON-I 99 108,680 171 109,764 270 218,444
ETALON-II 5 936 88 60,714 93 61,650
LAGEOS 150 63,665 95 35,447 245 99,112
STARLETTE 74 25,247 55 14,997 129 40,244
Totals: 387 233,928 670 340,879 1,057 574,807
1990 C* AJISAI 37 23,705 178 83,180 215 106,885
ETALON-I 0 0 88 55,543 88 55,543
ETALON-II 0 0 82 39,019 82 39,019
LAGEOS 9 1,832 163 135,885 172 137,717
STARLETTE 9 1,229 47 11,456 56 12,685
Totals: 55 26,766 558 325,083 613 351,849
1991 C AJISAI 87 31,260 87 31,260
ERS-1 188 44,019 188 44,019
LAGEOS 127 31,723 127 31,723
STARLEETE 52 23,478 52 23,478
Totals: 454 130,480 454 130,480
Dr. Richard Gross has recently submitted his SPACE93 data set. These data are combined Earth orientation data generated from space geodetic observations spanning 1976 through 1993. The techniques used include VLBI, SLR, LLR, and GPS. The data, as well as a textual description of the processing, are available on-line from the CDDIS via ANONYMOUS FTP in the directory ANON_DIR:[JPL]; the name of the file is SPACE93.
Since the April 1994 issue of the Bulletin, the CDDIS has archived data from the following new GPS tracking sites:
Name Site Name Data Source Receiver Type Start Date End Date
MONP Monument Peak, CA SIO Ashtech LM-XII3 01-Apr-94 --
Monument Peak is part of the PGGA operated by the Scripps Institution of Oceanography.
ATSC has found a six mm range difference between the field-generated normal points and the normal points derived from full-rate data for the MTLRS-1 during 1993. Peter Sperber/IfAG reports that a new software package for the generation of MERIT II full-rate data was installed in February 1993; the software contained an error in the calibration processing. Data from April through November 1993 are incorrect by 40 picoseconds; a value of 40 picoseconds can be added to the laser range two-way time of flight to correct the full-rate data. The occupations at Hartebeesthoek (monument number 7501) and Sutherland (monument number 7502), South Africa were affected by this error in the processing software. These data will be resupplied on future releases of the 1993 full-rate data sets. Field generated normal points were not affected by the software problem.
ATSC also reports that LAGEOS full-rate data from the SAO-2 laser system at Arequipa, Peru (station number 7907) are biased short by -7.1 cm from January 1, 1976 through May 25, 1988 and -3.1 cm from May 26, 1988 through June 15, 1988. On May 26, 1988 a new calibration range was used in processing the full-rate data; on June 16, 1988 a new calibration procedure was adopted. All SAO-2 LAGEOS data taken since June 16, 1988 should be bias free.