| Date: | 2004-06-25 23:51:00 | |
| Sender: | R. Schmidt, R. Koenig, GeoForschungsZentrum Potsdam <Roland Schmidt <rschmidt@gfz-potsdam.de>> | |
| Subject: | [SLR-Mail] No. 1229: Status CHAMP SLR-Tracking | |
| Author: | R. Schmidt, R. Koenig, GeoForschungsZentrum Potsdam | |
| Content: | ******************************************************************************** SLR Electronic Mail 2004-06-25 23:51:00 UTC Message No. 1229 ******************************************************************************** Author: R. Schmidt, R. Koenig, GeoForschungsZentrum Potsdam Subject: Status CHAMP SLR-Tracking Dear colleagues, for a few weeks now we observe discrepancies in the weekly/monthly tracking statistics for CHAMP and for the GRACE satellites. In comparison to the GRACE satellites the amount of passes obtained for CHAMP is significantly smaller, sometimes a factor of 2 can be seen. Closer inspection of e.g. the weekly statistics shows that a certain set of stations still tracks a comparable amount of passes for CHAMP and for GRACE during one week, whereas many others do not obtain passes for CHAMP but only for GRACE in the same period. Changing wheather conditions at stations could be attributed for part of the imbalance, but surely do not explain the currently observed decrease in tracking for CHAMP. We suspect that the ever-decreasing low altitude of CHAMP, currently ~ 380 km, might be responsible for increasing difficulties in finding and tracking CHAMP. Due to an accelerated aging of the predicts it might be indicated to increase the prediction update rate at GFZ from currently 3 predicts/day to e.g. 5 predicts/day. There is no principle problem in doing this since we have orbit-wise actual GPS tracking data available.On the other hand, some SLR stations still seem to live well with 3 updates/day and it might be that only these stations really use all available updates. Also it might be that some stations face already technical problems with this fast moving object. At this point we would like to ask for feedback from the ILRS stations before changing our operations for CHAMP. It would be helpful if stations could send a reply to the following questions: - Do you make use of the sub-daily updates of CHAMP orbit predictions? - Are you in general satisfied with the quality of the CHAMP orbit predictions? - Are there any technical problems coming up in tracking CHAMP? - Do you have further suggestions/comments for CHAMP orbit prediction operations? Please send your reply to rschmidt@gfz-potsdam.de. Looking forward hearing from you, Roland Schmidt Rolf Koenig From: Roland Schmidt ******************************************************************************** |