| Date: | 2000-03-20 09:06:00 | |
| Sender: | Roger Wood <slr@slrb.rgo.ac.uk (SLR Herstmonceux)> | |
| Subject: | [SLR-Mail] No. 571: URGENT ATTENTION ALL OBSERVERS | |
| Author: | Roger Wood | |
| Content: | ******************************************************************************** SLR Electronic Mail 2000-03-20 09:06:00 UTC Message No. 571 ******************************************************************************** Author: Roger Wood Subject: URGENT ATTENTION ALL OBSERVERS URGENT ATTENTION ALL OBSERVING STATIONS Sudden orbit changes: Ajisai, Starlette, Stella(?) at MJD 51622.10 When I checked the time bias functions this afternoon I found that those for Ajisai, Starlette and Stella had all turned very sharply upwards at very nearly the same time, MJD 51622.10. The same behaviour is seen for all IRV sets, ATSC and RGO. For Ajisai and Starlette the upturn is very obvious since there are normal point data for more than one pass after the discontinuity; for Stella there is only one pass, but the strong hint is that it too is turning up in the same way. At present I have no NP data for other satellites after this time and cannot say it they are doing the same. Clearly some event, probably solar, has caused these satellites to see more drag than was implicit in the predictions. I have not had time to search for solar activity reports to confirm any increases. This mail is simply to alert observers. I have recomputed the standard TBFs for Ajisai, Starlette and Stella and will send an additional TBF message after this. For all other low satellites observers should expect to find large positive time biases. Note that the slopes of the TBFs for Ajisai and Starlette are of order 300ms per day. Good hunting! Regards Roger Wood From: slr@slrb.rgo.ac.uk (SLR Herstmonceux) ******************************************************************************** |