Art Glick requested assistance in predicting precise ephemerides for his post-undocking STS/ISS pass on 2002 Apr 17 UTC: http://satobs.org/seesat/Apr-2002/0197.html Here is how I approach this problem: First find out the undocking time. The flight plan is available at both CBS News and Spaceflight Now. Here is the latter: http://www.spaceflightnow.com/station/sts110/fdf/110plan.html Undocking is scheduled for 2002 April 17 at 2:39 PM EDT = 18:39 UTC. I am going to go to a NASA page that provides planned 2-line elements several days in advance, so I need to convert the above date and time to the 2-line epoch format: yyddd.dddddddd Where yy is the last two digits of the year = 02 ddd. is the day of the year; 2002 Apr 17 = day 107 .ddddddddd is the fraction of the day; 18:39 UTC = (18 X 60 + 39) / 1440 = .777083 Putting it all together, the undocking epoch is 02107.777083 Now, let's go to NASA's shuttle elements page and find the element set that is later than the undocking and closest in time prior to Art's pass, which he told us is 6h 14m after undocking: http://spaceflight.nasa.gov/realdata/sightings/SSapplications/Post/JavaS SOP/orbit/SHUTTLE/SVPOST.html I found this set: 1 27413U 02018A 02107.88243482 .00071000 00000-0 10050-3 0 9028 2 27413 51.6362 355.8852 0009700 343.6021 16.4819 15.58484112 1439 Now, I need to check the flight plan for any reboosts prior to undocking, so back to Spaceflight Now: http://www.spaceflightnow.com/station/sts110/fdf/110plan.html I see that a reboost is planned for 2002 Apr 17 at 7:19 AM EDT = 11:19 UTC. I covert this to 2-line epoch format = 02107.4715278, and go to NASA's ISS elements page, in search of an elset after the reboost that is closet to the time of Art's pass: http://spaceflight.nasa.gov/realdata/sightings/SSapplications/Post/JavaS SOP/orbit/ISS/SVPOST.html Here it is: 1 25544U 98067A 02108.45973608 .00070138 00000-0 83646-3 0 9026 2 25544 51.6373 352.9945 0007995 352.1898 7.9131 15.58003683 4756 My ephemeris generator reports that Art's post-undocking shuttle pass on 2002 Apr 17 will culminate at 86 deg elevation, azimuth 221 deg, at 20:48:21 EDT, followed about 5.5 s later by ISS. At that point, their angular velocity will be 1.09 deg/s, so they will appear about 6.0 deg apart. Of course, they will appear closer together at all other points during the pass. I caution that the elements on the above NASA pages may revised (in fact they were revised as I typed this message, changing the STS-ISS separation at culmination from 3.8 deg to 6.0 deg!), so for precision work, it is necessary to review before the pass. Now I have to get back to work. Clear skies! Ted Molczan ----------------------------------------------------------------- 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
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