Marcus wrote: > Considering that STS-112 is docked to the ISS, why H-A gives two times with > a difference of 3 seconds each other? I asked almost the same question a week ago: > Though other comments in this group indicate that Progress M1-9 > has docked with the ISS, HA is saying it is two seconds behind > in orbit. Could HA be still using old elements for it as > presumably new ones will not have been issued since docking? Mike McCants replied with a simple explanation which I guess will also apply here: > The "one hour ago" elements from OIG are: > > ISS (ZARYA) > 1 25544U 98067A 02276.16030093 .00055685 00000-0 65283-3 0 2145 > 2 25544 51.6347 230.8205 0017186 328.6962 81.8736 15.60780477220874 > SOYUZ TM-34 > 1 27416U 02020A 02275.47199074 .00055222 00000-0 64944-3 0 1517 > 2 27416 51.6352 234.2875 0017116 326.2129 174.3876 15.60703815 25005 > PROGRESS M1-9 > 1 27531U 02045A 02275.47199074 .00055222 00000-0 64944-3 0 320 > 2 27531 51.6352 234.2875 0017116 326.2129 174.3876 15.60703815 1063 > > So the Soyuz and Progress do have identical elsets, but they are both > about 12 hours older than the ISS elset. So depending on the accuracy > of the mean motion and drag, a two second discrepancy between elsets > that are 12 hours apart is not unreasonable. ----------------------------------------------------------------- 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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