A Delta IV rocket launched the classified NROL-47 satellite from Vandenberg in California on January 12, 2018. The satellite is believed to be the 5th member of the Topaz (FIA Radar) project, radar satellites operating in 1100km altitude, 123 degree inclined retrograde orbits. Broadcast warnings for the NROL-47 launch placed the impact areas of the solid rocket motors, the first stage and the de-orbit area of the second stage at markedly different locations than with previous Topaz launches, indicating an orbital inclination around 108 degrees. Hence, it was not clear if NROL-47 is a Topaz satellite.
As the previous Topaz satellites all transmit in channel 9 of the USAF Space Ground Link System (SGLS), at 2242.51MHz, this frequency was monitored after the launch of NROL-47. About 70 minutes after launch, radio signals were detected from the Netherlands, roughly consistent with pre-launch orbital estimates of NROL-47. The Doppler curve confirms that NROL-47 transmits at the same frequency as the previous four Topaz satellites.
Riddles in the Sky 