Hydrogen Depletion Sensor (HDS) is mainly used to detect the predetermined depletion level of Liquid Hydrogen in the tank during the flight. The purpose of this sensor is to sense the depletion level and to ensure that there is defined quantity of Liquid Hydrogen left inside the tank before the depletion of LOX during the flight, to avoid a possible disaster. When the dielectric medium between the two conducting plates changes the capacitance of the sensor also changes. This principle is utilized in the function of depletion sensor. The sensor works with the signal conditioning electronics. The Depletion sensors are mounted inside the bottom part of the tank. During the end of the flight the level of the propellant depleted from the predetermined level is detected and signal is sent for Engine shut off (for monitoring) before depleting the LH2. Thus the Depletion sensor plays a major role in shutting off the Cryo engine at the end of the flight. The sensor worked successfully during filling and depletion in GSLV D5, D6, F05, F09, Mk3 X & D1 missions.