NROL-82 made its first pass over Europe. Ted Molczan's 78701 orbit estimate would've been visible, as would objects in that orbital plane at higher altitudes. None were seen, ruling out the satellite being at orbital altitudes from 600 to 1100 km between ~22:02 to ~22:10UTC. S-band signals at the expected frequency for KH-11 satellites were picked up, and had a TCA (time of closest approach) 4 minutes late compared to the 78701 orbit estimate. Fitting the Doppler curve with the 78701 TLE and allowing for changes in argument of perigee and mean anomaly allow for a reasonable fit, but would've placed NROL-82 at 700 km altitude when passing through the camera field-of-view and hence it should have been visible. These observations may suggest that the orbit is quite different from the estimates by Ted and Marco, possibly a low circular orbit like USA 290 [43941/19004A] (400x417 km) may be a possibility. The single Doppler curve does allow for such an orbit, but is not able to constrain it. Scott Tilley is currently tracking the S-band signal of NROL-82 which may allow for additional constraints. Regards, Cees _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-lReceived on Mon Apr 26 2021 - 17:28:56 UTC
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