NROL-82 first pass

From: C. Bassa via Seesat-l <seesat-l_at_satobs.org>
Date: Tue, 27 Apr 2021 00:27:37 +0200
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
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Received on Mon Apr 26 2021 - 17:28:56 UTC

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