| Date: | 1999-07-19 15:50:00 | |
| Sender: | Christoph Reigber <prd@dfd.dlr.de (PRD)> | |
| Subject: | [SLR-Mail] No. 376: GFZ-1 EOL-Message | |
| Author: | Christoph Reigber | |
| Content: | ******************************************************************************** SLR Electronic Mail 1999-07-19 15:50:00 UTC Message No. 376 ******************************************************************************** Author: Christoph Reigber Subject: GFZ-1 EOL-Message for id OAA18506; Mon, 19 Jul 1999 14:56:36 +0200 id OAA15909; Mon, 19 Jul 1999 14:56:34 +0200 GFZ-1 EOL-Message ----------------- On June 23rd, 1999, 01:00 UT GFZ-1 has completed its mission as a shooting star. The satellite burned up in upper atmosphere. Since its spectacular ”start” (i.e. GFZ-1 was jettonised into orbit from the MIR space station) on April 19th, 1995, 19:12 UT GFZ-1 has cycled nearly 24,000 times around earth in order to sense the gravity field. During four years and 64 days in space GFZ-1 has gathered some remarkable statistics. 605 predictions sets (including 31 sets based on Fence data) have been provided by GFZ (together with 1,389 time bias functions) to the tracking community. All in all 5,402 passes have been observed by 33 sites of the global SLR network (the first one in USA by Greenbelt in orbit no. 4, the last one by Yarragadee in Australia at an altitude of 230 km in orbit no. 23,718). At this point we would like to ex- press our deepest appreciation to all network participants for their strong and continuous tracking support. Truely, we can be proud of this campaign. With an orbit decaying from an initial altitude of 400 km, GFZ-1 has been the geodynamic satellite with lowest orbit flown ever since. Thus the gathered observations represent a yet unique data set for the determination of the gravity field. Unfortunately, towards the end of its mission being the most interesting phase with respect to its sensitivity due the gravity field, the low orbit of GFZ-1 turned out to be a hard to meet challenge for the SLR tracking technique. Due to the lack of SLR data the last months were a period of almost zero tracking, inducing the necessity to derive orbits from less accurate radar observations ( NORAD provided twoline elements, Fence orbits have been provided by NASA ). In that way GFZ-1 has demonstrated the possibilities and difficulties tracking such low targets using the standard procedures and state-of-the-art techniques. There is no doubt that there is a need of improving the current situation which is, of course, a great challenge for future applications and contributions of SLR, especially with upcoming missions like CHAMP and GRACE in mind. In view of first results showing the unique contribution of GFZ-1 data in the gravity field determination from satellite observations, together with a great deal of invaluable experiences gathered throughout this mission, we think of it as a big success which was worth all efforts. Thanks again for your great support and thanks also to the GFZ personal, which has taken care of our first satellite with such great enthusiasm: the technical manager Rolf Koenig, the orbit prediction and POD crew F.H. Massmann, Gerald Baustert, Zongping Chen, Jean-Claude Raimondo, Craig Roberts and Roland Schmidt. Best regards Ch. Reigber From: prd@dfd.dlr.de (PRD) ******************************************************************************** |