NROL-47 search elements from radio observations

Radio transmissions from NROL-47 have been received by Scott Tilley
and myself on 6 of the 7 orbits since launch. The satellite transmits
at 2242.51MHz, which is the same frequency at which the four FIA Radar
satellites transmit.

The search elements below fit circular orbits for different
inclinations to 8 Doppler curves obtained over an approximately 11
hour period. The fits prefer an inclination around 105.5 degrees, and
the elements below bracket this range. The fits implicitly assume that
NROL-47 has not manouvered during this time range. All circular orbit
fits indicate that NROL-47 is orbiting at an altitude of 1057 km.

Observers at Northern latitudes (~50 deg) should have visibility early
in the evening, though the satellite will be at low elevations (~20
deg or lower) in the North West.

We will continue the radio monitoring of NROL-47 and will provide
updated search elements.

Happy hunting!
   Cees and Scott

1 70002U          18013.19920400  .00000000  00000-0  50000-4 0    09
2 70002 104.0000 136.1570 0000000   0.0000  46.1473 13.54358399    04
# 20180112.97-20180113.42, 2399 measurements, 1.660 kHz rms
1 70002U          18013.19920400  .00000000  00000-0  50000-4 0    09
2 70002 105.0000 136.3524 0000000   0.0000  46.1710 13.54331881    07
# 20180112.97-20180113.42, 2399 measurements, 1.449 kHz rms
1 70002U          18013.19920400  .00000000  00000-0  50000-4 0    09
2 70002 106.0000 136.4239 0000000   0.0000  46.1576 13.54304339    00
# 20180112.97-20180113.42, 2399 measurements, 1.453 kHz rms
1 70002U          18013.19920400  .00000000  00000-0  50000-4 0    09
2 70002 107.0000 136.3766 0000000   0.0000  46.1046 13.54274171    07
# 20180112.97-20180113.42, 2399 measurements, 1.634 kHz rms
1 70002U          18013.19920400  .00000000  00000-0  50000-4 0    09
2 70002 108.0000 136.2994 0000000   0.0000  46.1141 13.54239425    09
# 20180112.97-20180113.42, 2399 measurements, 1.910 kHz rms
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