Current technology: [1,2]. There is an interesting note in [3], about how one of these satellites is being stalked by a Russian satellite, which is trying to learn more about the US satellite.

[1] https://en.wikipedia.org/wiki/KH-11_Kennen

[3] https://en.wikipedia.org/wiki/National_Reconnaissance_Office...

[4] https://en.wikipedia.org/wiki/USA-245

---- Edit:

Wikipedia has an image from one of the above

https://en.wikipedia.org/wiki/USA-224#/media/File:2019-08-29...

Estimated resolution is 10cm or better (the 10cm/pixel image is a photo of a printout, not the original). Distance is estimated to be 382km.