There have been recent descriptions on Seesat of various methods of generating elements for objects that may be many minutes off prediction due to lack of observations over several weeks or months. For example Ted wrote: >Adjusting for Earth's rotation is not difficult, but it can be tedious. >An easy method is to adjust the epoch by the desired time increment. For >example, to compute the path of an object if it arrives 2 min early, >subtract 2/1440 from the epoch. The above epoch would become >02115.12912960 - 2/1440 = 02115.12774071 . Here is the method that I use, with the example of 94-17B elements amended to give a set of search tracks. USA 102 1.0 0.0 0.0 6.9 v 1 70001U 02115.12912960 .00010500 00000-0 67123-3 0 08 2 70001 105.0290 67.4212 0021000 276.6353 83.3646 15.08406176 02 I change the value of the mean anomaly at epoch (in this case, 83.3646) Usually this is altered in steps of 40 degrees, which will approximate to steps of ten minutes. (360 degs in 90 minutes equals 40 degs in 10 minutes) I also alter the "catalog no." so that each sets is identified uniquely. The resulting set would then look like this: USA 102 1.0 0.0 0.0 6.9 v 1 69999U 02115.12912960 .00010500 00000-0 67123-3 0 08 2 69999 105.0290 67.4212 0021000 276.6353 163.3646 15.08406176 02 USA 102 1.0 0.0 0.0 6.9 v 1 70000U 02115.12912960 .00010500 00000-0 67123-3 0 08 2 70000 105.0290 67.4212 0021000 276.6353 123.3646 15.08406176 02 USA 102 1.0 0.0 0.0 6.9 v 1 70001U 02115.12912960 .00010500 00000-0 67123-3 0 08 2 70001 105.0290 67.4212 0021000 276.6353 83.3646 15.08406176 02 USA 102 1.0 0.0 0.0 6.9 v 1 70002U 02115.12912960 .00010500 00000-0 67123-3 0 08 2 70002 105.0290 67.4212 0021000 276.6353 43.3646 15.08406176 02 USA 102 1.0 0.0 0.0 6.9 v 1 70003U 02115.12912960 .00010500 00000-0 67123-3 0 08 2 70003 105.0290 67.4212 0021000 276.6353 3.3646 15.08406176 02 This set can then be used with your favourite prediction programme, and will cover the period about 20 minutes each side of the central time. The set is very quickly generated, provided you can mentally add/subtract 40 to the value of the mean anomaly. If the uncertainty is greater than 40 minutes, you can use 9 sets that will give 360 degrees range. Good hunting. Best wishes, Russell Eberst 55.9486N, 3.1383W, 150 feet = 46 metres above MSL ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www.satellite.eu.org/seesat/seesatindex.html
This archive was generated by hypermail 2b29 : Fri Aug 16 2002 - 04:48:12 EDT