Subject: [SLR-Mail] No. 57: TiPS SLR Tracking From: Bill Purdy, NRL TiPS Program Manager ******************************************************************************** SLR Electronic Mail 1997-05-03 00:00:00 UTC Message No. 57 ******************************************************************************** Author:Bill Purdy, NRL TiPS Program Manager Subject: TiPS SLR Tracking Author:Bill Purdy, NRL TiPS Program Manager To the TiPS Tracking Community: As we end April, the Naval Research Lab would like to express our appreciation to the SLR community for their diligence and initiative in tracking the TiPS tethered satellite. Your efforts are greatly appreciated especially in light of the difficulty in tracking this system. Due to the great volume of data in the last month, we have been able to obtain a proper estimate of the satelliteÕs drag properties. Gratefully, this has enabled us to generate our first orbit predict with a stable time bias. Previously, the tether dynamics and shortage of data had complicated the orbit determination problem enough to induce in our predicts an unstable drift which made tracking problematic even with terminator assist. The gaps in our observation data made calibration of our drag model very difficult. The tether motion increased the complexity of the problem because it caused the tether´s effective surface area to vary. By combining an outstanding period of SLR tracking with a generous supply of radar data from the Kwajalein Atoll, we now have a very good estimate for the drag. As a result, NASA´s MOB-4 and MOB-7 have been able to demonstrate on several occasions over the past three days (4/25-4/27) that TiPS can be tracked in the blind. In producing this solution we would especially like to thank the European sites in Herstmonceux, Potsdam, Riga, Metsahovi, Wettzell, and Borowiec, the NASA sites in Greenbelt and Monument Peak and the ALTAIR radar crew in the Marshall Islands. Working with you on this project has been a pleasure. Furthermore, your support of this experiment has made our successes possible and we are duly thankful. We recognize that we have asked a great deal of you in the past and have no right to make any further requests. Having said that, to the extent that you have resources available over the next week, we would be very interested to learn if any of you have success in obtaining blind passes using our latest ephemeris prediction. Sincerely, Bill Purdy, Program Manager Shannon Coffey, Flight Operations Lead Jim Barnds, Dynamics Analyst Naval Research Laboratory 4555 Overlook Ave SW Washington, DC 20375 United States (202) 767-4001 (Voice) (202) 404-7785 (Fax) From: DSGJEH@cdslr3.atsc.allied.com ********************************************************************************