The main technologies currently used for Space Domain Awareness (SDA) are radar, optical telescope, and reflected laser tracking. These technologies alone cannot provide the comprehensive and persistent SDA that is becoming increasingly vital due to the increase in space traffic and the resulting higher probability of collisions. Passive Radio Frequency (RF) sensing is a promising technology to support the SDA mission, particularly due to its ability to operate 24/7 in all weather conditions. By observing the Doppler shift and angle of arrival of signals transmitted by satellites, their orbit can be determined. This paper describes an algorithm for Doppler estimation and demonstrates its efficacy for Low Earth Orbit (LEO) satellites. The algorithm can effectively estimate Doppler for both continuous and intermittent satellite transmissions.