| Date: | 1998-10-16 01:00:00 | |
| Sender: | John J. Degnan <[Mailed John Degnan <jjd@ltpmail.gsfc.nasa.gov>]> | |
| Subject: | [SLR-Mail] No. 166: GEOS-3 Campaign Reminder | |
| Author: | John J. Degnan | |
| Content: | ******************************************************************************** SLR Electronic Mail 1998-10-16 01:00:00 UTC Message No. 166 ******************************************************************************** Author: John J. Degnan Subject: GEOS-3 Campaign Reminder I apologize for this late reminder concerning the GEOS-3 campaign which was scheduled to start today for a minimum period of three months with a possible extension to six months in support of gravity modelling. I received several questions for which I did not have answers and it took me a while to collect them. I am grateful to Frank Lemoine of GSFC, Scott Wetzell of ATSC, and Mike Pearlman who provided the following information. As you may recall, this campaign was approved at the CSTG SLR/LLR Subcommission General Assembly in Nice, France, last April based on a presentation by Dr. frank Lemoine of NASA/GSFC. Predicts for the GEOS-3 campaign are now available from ATSC. ATSC will be providing the acquisition data via our normal channels and the tracking data tracked should be sent via your normal channels. PI: Frank G. Lemoine, Space Geodesy Branch, NASA GSFC, Code 926 Purpose of campaign: * Earth Gravity field modelling improvement. (GEOS-3 data was included in many previous Goddard gravity models. These data ranged from 1975-1980, when the SLR network was in its infancy. Since that time great strides have been made in instrument and data quality. The ”old” GEOS-3 data were still valuable in the latest solution (EGM96). We seek ”new” and ”modern” SLR data to include in our future gravity solutions. (GEOS-3 was last tracked in 1980-1981, when the SLR network was in its infancy. Tracking the s/c with the high precision instruments of the international satellite laser ranging network will give us valuable data for gravity field determination, by virtue of the relatively low altitude and unique inclination). Geos-3 is gravity gradient stabilized. It should be visible everywhere within +/- 65 degrees in both hemispheres. It certainly was when it was launched in 1975. BASIC FACTS ABOUT GEOS-3 Owner: NASA Launched 4/9/75 COSPAR #: 7502701 NORAD #: 7734 4-digit NASA num. used: 1127 Normal Point Period: 30 sec Period: 101.6 Inclination: 115.0 Apogee: 845 km Perigee: 824 km Payload: radar altimeter; SLR retroreflector; TRANET Doppler beacon. Radar altimeter and doppler beacon no longer operational; We have had very successful recent tracking from several Northern Hemisphere stations including Moblas-7, Moblas-4, RGO and some of the Russian stations. As far a we can tell, this satellite is in an orbit that we have had no problem providing predictions for. NASA stations report very strong returns similar to Ajisai. Please initiate tracking of GEOS-3 as soon as possible. John J. Degnan Chairperson, ILRS Governing Board [Mailed From: John Degnan ******************************************************************************** |