Pat Flannery wrote


This probably gives the recon satellites the ability to change their
orbital parameters on-station; both to evade interception and to make
their time of passage over interesting photo targets less predictable.


Both the "KH-11-like" electro-optical and the Lacrosse radar imagers
have been tracked fairly closely for the past 15 years or so by the
amateur community. Neither kind maneuvers much after reaching the
operational orbit -- the Lacrosses hardly at all. The "KH-11s"
typically carry out small orbital maintenance maneuvers at intervals
of months(*) plus a larger orbit raising that seems to separate major
mission phases. Given warning, they could dodge a few times, but
at the expense of mission capability.

The classified LEO satellites that have shown significant propulsive
capability are the Titan-launched NOSS-2-A objects, now known to be
TLDs hosting SLDCOM and COBRA BRASS payloads, and USA 53 and USA 144.
There's a fair chance that USA 53 was a stealthified KH-11, so Bus 1
is a good candidate for its propulsion package. USA 144 is a
considerable puzzle, but may be a successor to USA 53.


(*) The maneuver times are quite predictable, BTW. They occur on an
ascending node when the perigee drops below a certain value and the
argument of perigee precesses through zero.