| Date: | 2004-07-07 00:47:00 | |
| Sender: | Julie Horvath/HTSI and Carey Noll/CDDIS <Carey Noll <noll@cddisa.gsfc.nasa.gov>> | |
| Subject: | [SLR-Mail] No. 1232: SLR support of Gravity Probe B (GP-B) | |
| Author: | Julie Horvath | |
| Content: | ******************************************************************************** SLR Electronic Mail 2004-07-07 00:47:00 UTC Message No. 1232 ******************************************************************************** Author: Julie Horvath/HTSI and Carey Noll/CDDIS Subject: SLR support of Gravity Probe B (GP-B) Dear Colleagues, The Gravity Probe B (GP-B) Satellite was launched from Vandenberg Air Force Base on April 20th, 2004. As Mike Pearlman discussed in the SLRMail 1204, the GP-B project has requested that the ILRS begin SLR tracking of the satellite with an initial short test campaign, and then with operational support beginning at the end of July. The ILRS Governing Board has approved the Mission Support request. The mission is scheduled to last for 16 months. The GP-B project has first requested that three SLR sites (MOBLAS-7, MOBLAS-4 and MLRS) begin a test campaign on 7/7/04 and continue through 7/13/04 to verify predictions and to test the retroreflector array. GP-B is a relativity gyroscope experiment developed by NASA and Stanford University to test two extraordinary, unverified predictions of Albert Einstein´s general theory of relativity. The experiment relies on very accurate knowledge of the spacecraft position and orientation. SLR is one of several techniques that will be used to achieve and maintain that accuracy. A explanation of the experiment and some of the major subsystems are given at the GP-B website at: http://einstein.stanford.edu/content/story_of_gpb/gpbsty1.html GP-B will be pointed at all times toward a guide star (IM Pegasus) which is at Right Ascension 343 deg. and Declination 16 deg. The GP-B orbit plane will be exactly aligned with IM Pegasus. The retroreflectors form a ring on the backend of the spacecraft exactly on the center line, pointing exactly in the opposite direction of the star. SLR tracking can only be done for short intervals when the station is on the same side of the Earth as the Pegasus IM. Once tracking begins, stations will be supplied with regular predictions and a viewing schedule that will provide all passes where the retroreflector is available to the station. This viewing schedule will be distributed by the ILRS Prediction Exploder, and will be a standard text format as shown in this sample: Satellite : GP-B Generation Date : 2004-07-02 16:41:34 [UTC] Generated by : GP-B Mission Operations / Stanford University Minimum Elevation : 5 deg -------------------------------------------------------------------- Start Date/Time End Date/Time MaxEl Durtn ID SAT [UTC] [UTC] [deg] [min] ---- ---------- ------------------- ------------------- --- ----- 7105 GP-B 2004-07-07 08:28:56 2004-07-07 08:32:16 41 3.3 7105 GP-B 2004-07-07 21:06:25 2004-07-07 21:08:13 15 1.8 7105 GP-B 2004-07-08 08:53:14 2004-07-08 08:57:20 89 4.1 7105 GP-B 2004-07-08 21:32:05 2004-07-08 21:32:43 7 0.6 7105 GP-B 2004-07-09 09:18:31 2004-07-09 09:21:36 41 3.1 7105 GP-B 2004-07-09 20:18:47 2004-07-09 20:20:01 10 1.2 7105 GP-B 2004-07-10 08:06:10 2004-07-10 08:08:31 31 2.3 7105 GP-B 2004-07-10 20:43:01 2004-07-10 20:44:55 15 1.9 7105 GP-B 2004-07-11 08:29:59 2004-07-11 08:33:59 67 4.0 7105 GP-B 2004-07-11 21:08:19 2004-07-11 21:09:32 11 1.2 7105 GP-B 2004-07-12 08:54:51 2004-07-12 08:58:35 56 3.7 7105 GP-B 2004-07-12 19:55:53 2004-07-12 19:56:33 7 0.7 7105 GP-B 2004-07-13 20:19:48 2004-07-13 20:21:35 14 1.8 The subject of the email containing the viewing schedule with be GP-B GLOBAL PASS LIST STANFORD; the name of the viewing files available at CDDIS and EDC will be of the form gpb_globalpasslist_YYMMDD.stanford where YYMMDD is the date the file was generated. Here is some important information for GP-B: - Launch Date: April 20, 2004 from Vandenberg Air Force Base - Altitude: 650 km - Eccentricity: 0.0 - Inclination: 90 degrees - Mission Duration: 16 months - Purpose of SLR: Establish POD then backup for GPS - Array information: 9 cube open hemisphere - COSPAR ID: 0401401 - SIC #: 8603 - NORAD #: 28230 - NPT Bin Size: 15 seconds During this test, data will appear on the CDDIS and the EDC. We will inform you as soon as possible about the initial start date for ILRS operational support. We hope that you will give this mission your full support, and we thank you in advance for all of your efforts with GP-B. Regards, ILRS Central Bureau +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ Ms. Carey Noll Manager, Crustal Dynamics Data Information System (CDDIS) Secretary, ILRS Central Bureau Code 922 E-mail: Carey.Noll@nasa.gov NASA GSFC Voice: (301) 614-6542 Greenbelt, MD 20771 Fax: (301) 614-6099 USA WWW: http://cddisa.gsfc.nasa.gov/cddis_welcome.html +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ From: Carey Noll ******************************************************************************** |