This is a fairly old unit. It might have a hard time with a rocket.
Remember that to accurately measure speed with dopler radar, you must
be as close as possible to directly behind or in front of the target.
There isn't a lot of difference up to about 8 degrees, but after that
the measured speed will be significantly LESS than actual. At 90
degrees to the target, the measured speed will be zero, because there
is no change in distance from the target to the radar as the target
moves. The target will also need to be relective. A 29 mm RMS might be
big enoungh for a modern police radar, but they are very small from
behind. An Applewhite saucer would be a good target, especially if the
rear surface was reflective foil or mylar.