| Date: | 2008-12-17 16:15:00 | |
| Sender: | Remko Scharroo <Remko Scharroo <remko@altimetrics.com>> | |
| Subject: | [SLR-Mail] No. 1738: GFO decomissioned | |
| Author: | Remko Scharroo | |
| Content: | ******************************************************************************** SLR Electronic Mail 2008-12-17 16:15:00 UTC Message No. 1738 ******************************************************************************** Author: Remko Scharroo Subject: GFO decomissioned Dear RADS users, This is to remind you that GFO has been decommissioned. You will have noticed that over the last year the coverage has been quite spotty. This was because of the degradation of the batteries. Only while the satellite was in sunlight it could offer enough power to run the altimeter, and not even the radiometer. Relatively new international regulations require that satellites should be taken out of the orbit in an attempt to curb the ever growing amount of space debris. Between 7 and 25 November GFO executed a series of de-orbit burns, totalling 65 minutes, thus exhausting all remaining propellant. Instead of bringing the near-circular orbit down to a lower near- circular orbit, the fuel is actually used more efficiently by bringing only the perigee (the lowest point in the orbit) down. So the apogee (the highest point in the orbit) actually stayed at 783 km, while the perigee is now at 456 km. From now on, the increased drag around the perigee will make the satellite lose more and more velocity at that point, thus lowering the apogee and finally making the orbit circular again at about that altitude (of 456 km). From then onward the orbit will continue to decay in its entirety. Re-entry into the earth´s atmosphere is expected in about 15 to 25 year. On behalf of all RADS users, and on behalf of NOAA, the producer of the GFO scientific data products, I want to express our enormous gratitude to the International Laser Ranging Service (ILRS) and all contributing laser ranging stations for their commitment to tracking the GFO satellite during its approximately 10 year mission. Without that relentless support, the GFO satellite would have been without high-precision tracking data that are essential to the precise orbit determination and the quality of the sea surface height information. Cheers, Remko From: Remko Scharroo From: slrmail@dgfi3.dgfi.badw-muenchen.de From: Remko Scharroo ******************************************************************************** |