The propulsion system of a satellite is influenced by the in-flight environment in space. Consequently, to investigate the leakage of propellant from a monopropellant hydrazine propulsion system, a Low Earth Orbit (LEO) satellite is sampled over its devised life. Details regarding orbit shifting, inclination, solar shining angle, and Local Time of Descending Node (LTDN) are discussed. The cause of leakage is attributed to acceleration in the pitch velocity of the satellite when it has no attitude control. A model is presented using the gaseous equation to estimate the parameters of leakage, including mass and gas leakage rates, disturbing torque, and specific impulse. From validation using satellite telemetry data, such as angular velocity and the temperature and pressure of the propellant tank, the estimation results show that the disturbing torque is periodically linear, with maximum and minimum values of approximately 3.4 μN·m and 0.9 μN·m, respectively. Furthermore, the mass leakage rate of the hydrazine propellant, which varies between 7.4 μg·s-1 and 13.4 μg·s-1, is originally at a high level and then decreases gradually to a relatively stable value of approximately 8.0 μg·s-1. The gas leakage rate varies from 0.56 Pa·L·s-1 to 1.18 Pa·L·s-1, stabilizing at 0.60 Pa·L·s-1, and the specific impulse varies between 121 m·s-1 and 249 m·s-1, finally closing at 200 m·s-1. The temperate of the environment has a relatively stronger influence on the specific impulse and disturbing torque, but not on the mass and gas leakage rates. The specific impulse increases with an increase in the temperature, and vice versa. The leakage is possibly caused by the degradation of the elastomeric seal, mainly due to the ageing of the material, which in turn stems from the varying thermal environment. With a low mass leakage rate, the propulsion system is relatively more reliable and life-sustaining in LEO satellites. It is possible to prolong the dump period of the momentum by avoiding the leakage of the hydrazine propellant, if the environmental temperature is decreased.