A system and method for forming a range rate estimate for a target with a laser detection and ranging system including a laser transmitter and an array detector. The method includes: transmitting a plurality of laser pulses at a pulse repetition frequency; forming a one dimensional time series array corresponding to a time record of ladar return photons detected with the array detector; fitting the time series array with a superposition of a sine and a cosine of an initial value of a tentative frequency; iteratively fitting the time series array with a superposition of a sine and a cosine of the tentative frequency, and adjusting the tentative frequency until a completion criterion is satisfied at a final value of the tentative frequency.