Long Trace Profiler (LTP)
Crystal Scientific has a Long Trace Profiler (LTP). This is set up on the same air beam as the NOM which allows comparative LTP and NOM measurements to be made along the length of a mirror up to 1.4 m without having to adjust any of the optics.
The LTP is a scanning interferometer that is able to precisely measure sub-microradian slope errors from point-to-point along the whole mirror length.