1B-CPR measures the backscattered power as a function of distance from the radar. The backscattered power is sampled every ~240 m; there are 125 range bins, for a total window of 30 km. The raw, Level 0 data is converted to calibrated Level 1B data using pre-launch and in-flight calibration measurements.
Tanelli, S.; Durden, S.L.; Im, E.; Pak, K.S.; Reinke, D.G.; Partain, P.; Haynes, J.M.; Marchand, R.T., CloudSat's Cloud Profiling Radar After Two Years in Orbit: Performance, Calibration, and Processing, Geoscience and Remote Sensing, IEEE Transactions on, vol.46, no.11, pp.3560,3573, Nov. 2008 doi: 10.1109/TGRS.2008.2002030