| Date: | 2002-03-14 20:30:00 | |
| Sender: | Ch. Reigber, R. Koenig, R. Schmidt, GFZ Potsdam <Roland Schmidt <rschmidt@gfz-potsdam.de>> | |
| Subject: | [SLR-Mail] No. 909: GRACE launch March, 16th 2002, 09:23 UTC | |
| Author: | Ch. Reigber, R. Koenig, R. Schmidt, GFZ Potsdam | |
| Content: | ******************************************************************************** SLR Electronic Mail 2002-03-14 20:30:00 UTC Message No. 909 ******************************************************************************** Author: Ch. Reigber, R. Koenig, R. Schmidt, GFZ Potsdam Subject: GRACE launch March, 16th 2002, 09:23 UTC Subject: GRACE-A NPs from Dear colleagues, the launch rehearsal of the GRACE satellites today, March 14th 2002 has been successfull and the launch has been confirmed for March, 16th 2002, 09:23 UTC at launch site Plesetzk, Russia. As already announced in SLRMAIL No. 0903 an updated version of the preliminary prediction sets based on the nominal separation information has been distributed via standard communication channels to ILRS stations and data centers, today. As specified in the ILRS tracking request form, the two GRACE satellites expect to have highest tracking priority at the ILRS tracking stations during the initial orbit phase. Tracking should commence after separation of the two satellites from the rocket at 10:49 UTC (note: all orbit prediction products, i.e. IRVS & Co. have been artificially extended backwards to 00:00 UTC of launch day). At separation the Breeze stage is pitched down at 30 degrees. Both satellites are released simultaneously. GRACE-A is pushed by springs down and back while GRACE-B is pushed up and forward. Breeze is speeding along at about 7 km/s. Due to orbital mechanics GRACE-A soon overtakes and passes under GRACE-B. The drift rate of the two satellites is at about 77 km/day. On days 4 and 5 after launch thrusting manoeuvres are made by GRACE-B to stop the drift and stabilize the separation at about 220 km. The satellites will automatically move to coarse nadir pointing mode short time after separation. No tracking priority between GRACE-A and GRACE-B is defined, however the following alternating tracking procedure is given as a recommendation: Tracking of only one satellite at a particular SLR station per pass. If tracking has been successful, the station should switch to the other GRACE satellite in the next pass and so on. Of course, stations capable of tracking the two satellites in one pass are encouraged to do so. Those SLR stations providing CHAMP normal points directly to GFZ via email are kindly asked to do so for GRACE, too. The email address (which is the same for CHAMP) and mail subject to be used are: Address: ppr@gfz-potsdam.de Subject: GRACE-A NPs from GRACE-B NPs from After launch GFZ will try to update prediction sets as soon as and as often as valuable observational data is available. Best regards, Chris Reigber, GRACE mission Co-PI Rolf Koenig, Laser Tracking System Manager Roland Schmidt From: Roland Schmidt ******************************************************************************** |