|
CDDIS Bulletin - August 1996
Volume 11 No. 6
In this issue:
About the cover: The map on the cover of this issue of the CDDIS Bulletin shows the VLBI stations scheduled to participate in CONT96, an experiment planned for September through November 1996. The VLBA sites will participate during the last six days of the experiment. This experiment will be the longest span (eleven weeks) of high resolution EOP data yet obtained.
The International GPS Service for Geodynamics (IGS) now produces high quality rapid GPS ephemerides. These daily solutions, derived by the IGS Analysis Coordinator from the seven individual analysis center solutions, are available within 24 hours. After and including GPS week 0860, these files are denoted IGRwwww7.typ, where wwww is the GPS week number, and typ is the file type (SP3 for orbit, SUM for summary, and ERP for Earth rotation parameters); prior to week 0860, the products were named IGP. All IGS rapid products can be retrieved from the CDDIS in subdirectories by GPS week of the main directory GPS3:[PRODUCTS].
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 new WWW home page (URL http://cddis.gsfc.nasa.gov/cstg/slr_cstg.html) for the CSTG SLR/LLR Subcommission was announced in the June 1996 issue of the CDDIS Bulletin. Since that time, a few updates have been made. A new section, called SLR/LLR Data Information, has been added which provides links to relevant data format documentation, SLR predicts, known data problems, normal point bin size recommendations, and results from a recent survey of SLR data use. Comments on this home page are welcome, as well as links to home pages of SLR/LLR stations and satellites.
Since the June 1996 issue of the CDDIS Bulletin, the CDDIS has archived data from the following new GPS tracking sites:
Table 1. New GPS Tracking Sites
Mon.
Name |
Site Name |
Data
Source |
Receiver
Type |
Start
Date |
| AZU1 |
Azusa, CA |
JPL |
Rogue SNR-8000 |
26-July-96 |
| BAHR |
Manama, Bahrain |
DMA |
Ashtech Z-XII |
23-Jun-96 |
| CHUR |
Churchill, Manitoba, Canada |
NRCan |
Rogue SNR-8000 |
18-Jun-96 |
| COCO |
Cocos Island, Australia |
AUSLIG |
Rogue SNR-8100 |
13-Jun-96 |
| FLIN |
Flin Flan, Manitoba, Canada |
NRCan |
Rogue SNR-8000 |
08-Jun-96 |
| KRAK |
Mammoth Lakes, CA (Krakatoa site)* |
JPL |
Rogue SNR-8000 |
25-July-96 |
| TID2 |
Tidbinbilla, Australia |
JPL |
Rogue SNR-8000 |
26-July-96 |
| WHIT |
Whitehorse, Yukon Territory, Canada |
NRCan |
Rogue SNR-8000 |
07-Jun-96 |
| XIAN |
Xian, Peoples Republic of China |
JPL |
Rogue SNR-8000 |
10-July-96 |
*Note: The KRAK site is part of Frank Webb's (JPL) Long Valley Caldera Continuous GPS Network investigation.
The Data Services Group at ATSC reports that in July MOBLAS-5 at Yarragadee, Austraila (monument number 7090) started to experience problems with their Cesium clock, e.g., excessive drift rates, which has affected the timetags in data from the system. The data is totally recoverable by applying the epoch corrections given in the table below. In order to correct MOBLAS-5 timetags these epoch corrections must be subtracted from the normal point timetags using the equation:
corrected timetag = normal point timetag - epoch correction
Table 2. MOBLAS-5 Epoch Timetag Corrections
| Date |
Epoch Corrections (microseconds) |
| 18-Jul-96 |
-1.0 |
| 19-Jul-96 |
-1.2 |
| 20-Jul-96 |
-1.3 |
| 21-Jul-96 |
-1.5 |
| 22-Jul-96 |
-1.6 |
| 23-Jul-96 |
-1.8 |
| 24-Jul-96 |
-2.0 |
| 25-Jul-96 |
-2.1 |
| 26-Jul-96 |
-2.3 |
| 27-Jul-96 |
-2.3 |
| 28-Jul-96 |
-2.4 |
| 29-Jul-96 |
-2.4 |
| 30-Jul-96 |
-2.5 |
| 31-Jul-96 |
-2.5 |
| 01-Aug-96 |
-2.5 |
| 02-Aug-96 |
-2.5 (before 21:57 GMT) |
| 02-Aug-96 |
+0.5 (after 21:57 GMT) |
The problem was resolved on August 02, 1996 at 21:57 GMT, when the drift rate returned to nominal levels and the station clock was resychronized to the Cesium.
|
