I've been looking around and saw on What is the highest inclination orbit ever attained from a Cape Canaveral launch? a question about launching into retrograde orbit. Of course, due to range safety requirements you can't launch into a retrograde orbit from Canaveral, but in one of the comments, Matt Large stated that NROL-25 was launched into a retrograde orbit from Vandenberg.
Simply, why would you want a retrograde orbit? For a reconnaissance satellite, especially, I would think that a polar orbit would be the obvious choice. A retrograde orbit means that you're moving over the surface quite fast, which would probably induce some motion blur in photos and reduce the window of time for which the satellite is over a given target. A polar orbit, while it has significant surface speed, allows you to surveil any point on the planet. Realistically, however, the reconnaissance folks are unlikely to be checking out the penguins' nuclear missile testing (you heard nothing and if you did the penguins will get you!) and could thus be put in an orbit that excludes the poles and allows for more frequent visitation of points of interest.
A retrograde satellite still doesn't make much sense. If the concern is range safety, launch from the East coast instead into a prograde orbit. Prograde orbit also allows for a small reduction in delta-V required to get to orbit, thus saving money on the launch.
For scientific or communications satellites, retrograde still doesn't seem to make sense. Communications satellites are usually in geostationary orbits, and scientific satellites are put in whatever orbit is needed for their particular experiments.
In addition, retrograde orbits vastly increase the potential for space debris - any possible collision now occurs at much higher velocities with larger spreads of debris.
So, I have two questions:
1) Why was NROL-25 launched into a retrograde orbit?
2) What are some uses for a retrograde orbit?