Launched on October 15, 2017 on the top of the Atlas V (421) classified National Reconnaissance Satellite was spotted by observers hours after launch.
Rocket with NROL-52 payload was launched on 07:28 UTC on October 15, 2017, from SLC-41 at Cape Canaveral. After first phase of flight when rocket set its course to south-east it was impossible to track vehicle as ULA finished live broadcast. Also as NRO and ULA did not announce precision time of satellite deployment, it was hard to confirm on which orbit satellite was located. Thanks to space enthusiasts we know much more about NROL-52 now.
As last time Atlas V (421) was used on July 2016, satellite spotters decided to take NROL-61 as a reference for calculations to find NROL-52 orbit. Luckily only four hours after launch Paul Camilliery from Australia found and was tracking Centaur upper stage and deployed satellite. He was even able to track satellite for 83 minutes - it helped in estimating orbit of satellite to roughly 1113 km by 35802 km inclined 18.68 degrees what is close to initial orbit of NROL-61 payload deployed on 1108 km x 35806 km, 18.68°.
Also radio signals emitted by NROL-52 satellite were identical as in case of NROL-61. They were picked up by Canadian satellite tracker who also one year ago detected identical signals after NROL-61 launch. Also they were emitted regularly every 240 seconds just as one year ago.
This two facts seem to confirm that NROL-52 is in fact another SDS (Satellite Data System) satellite serving as data transmission spacecraft collecting signals from other intelligence satellites to send them to ground stations remaining out of their range.