as could other light boosters. It'd be pretty expensive - a Pegasus costs something like $10 million and that's without the payload. The Pegasus would make a good choice because it's air launched, so you can go after targets in just about any orbital inclination. Imagery satellites are typically in high inclination sun-synchronous orbits (they're actually slightly retrograde), so without air launch capability, the only US launch site would be Vandenberg AFB, CA. I doubt that Sea Launch would be a viable option...

You wouldn't want to try the rendevous and nudge technique on an imagery satellite. First, it takes a fair about of time to perform the rendevous and their space surveillance sensors might detect what's going on. Another problem would be the limited fuel capacity of the interceptor to impart a delta-v on the target. Most imagery satellites are pretty massive and a Pegasus can only put about 800 pounds into a polar orbit. Counting TT&C, structural, electrical, guidance system, thermal control system and other weights, I doubt you'd end up with more than 500-600 pounds of propellant left over to use against the target. That might not be enough to deorbit it.

A better alternative might be to ram the target. If you operated the mission in a similar technique to that air-launched ASAT, the Pegasus wouldn't even have to actually enter orbit. It could perform a sounding-rocket style zoom climb and probably reach targets several hundred miles high. A kinetic kill, perhaps using one of the miniature homing vehicles like used on the NMD interceptors, would be sufficient to do the job.