At 08:25 PM 19/05/2008, amstuart wrote: >Hi: > >Maybe someone can explain this discrepancy to >me: I am at OakRidge Observatory, 25.6554°N, >80.3503°W. HeavensAbove reported no visible ISS >pass for Sunday, 5-18-08 using the epoch 08139.5172 TLE: > > Epoch (UTC): 12:24:48 PM, Sunday, May 18, 2008 > >I went to Space Track and the latest Elset is epoch 08140.1373 > >If I plug either TLE (obtained from Heavens >Above or Space Track) into Satellite Tracker or >Software Bisque's TheSky, I had a predicted path >for the ISS for 9:35 PM EST 5-18-08 (01:35 UT >5-19-08) just south of the very bright Moon, at >approximately 26* elevation. Wildfire smoke >prevented me from "seeing" if there was indeed a >pass, but had the sjy been clear which Elset, >program and so forth is controlling? > >Thank you. > >Adam If you use HA to select the ISS from the select a satellite option, and ask for all passes in the 10 day interval that includes sunday may 18 for your location , you will see that their is a pass culminating at 21:35 EDT or may 19, 01:35 UT. Its just that HA reckons its in shadow. The other software programmes you used obviously disagreed. Its hard to calculate a satellite illumination accurately when the trajectory is nearly tangent to the shadow cone. Differences in the effective shadowing radius of the Earth that is assumed can result in differing results from different programmes. I remember doing some observations utilizing Echo 1 (1960 9A) or Echo2 ( 1964 4A ) at the request of Moonwatch HQ to help decide the right number empirically. Tony Beresford ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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