Method for gauging the liquid propellant tank of a spacecraft, said propellant tank comprising a thermally-conductive wall, having a known geometry and containing a volume of liquid propellant, and said spacecraft being equipped with means of propulsion capable of exerting, according to a given thrust axis, a high thrust allowing said spacecraft to achieve an acceleration of greater than or equal to 0.05 m/s 2, said method being characterised in that it comprises steps of: - during a phase of high-thrust along said thrust axis exerted by said means of propulsion supplied with liquid propellant from said propellant tank, remotely controlling said spacecraft in which are attached, on the outer surface of said wall of the tank, a heating member and at least one temperature sensor in a known position in proximity to said heating member, said temperature sensor being arranged in a plane perpendicular to said thrust axis, referred to as plane of interest, in which the liquid-gas interface in said tank is likely to be located at some time during a phase of high-thrust exerted by said means of propulsion along said thrust axis, in order to implement steps of: ∘ heating the wall of the tank using the heating member; ∘ and acquiring measurements of the temperature of the wall of the tank using said temperature sensor, at a rate of one measurement every 30 seconds or less; - determining the moment I at which the temperature measured by said temperature sensor changes, which corresponds to the moment at which a break of slope occurs on a digital curve representing the temperature recorded by said temperature sensor as a function of time, such a change indicating the presence in the plane of interest of the liquid-gas interface in the tank; - and determining, from the geometrical data of the tank and the known position of the temperature sensor on the wall of the tank, the volume of liquid propellant present in said tank at the moment I. - during a phase of high-thrust along said thrust axis exerted by said means of propulsion supplied with liquid propellant from said propellant tank, remotely controlling said spacecraft in which are attached, on the outer surface of said wall of the tank, a heating member and at least one temperature sensor in a known position in proximity to said heating member, said temperature sensor being arranged in a plane perpendicular to said thrust axis, referred to as plane of interest, in which the liquid-gas interface in said tank is likely to be located at some time during a phase of high-thrust exerted by said means of propulsion along said thrust axis, in order to implement steps of: ∘ heating the wall of the tank using the heating member; ∘ and acquiring measurements of the temperature of the wall of the tank using said temperature sensor, at a rate of one measurement every 30 seconds or less; ∘ heating the wall of the tank using the heating member; ∘ and acquiring measurements of the temperature of the wall of the tank using said temperature sensor, at a rate of one measurement every 30 seconds or less; - determining the moment I at which the temperature measured by said temperature sensor changes, which corresponds to the moment at which a break of slope occurs on a digital curve representing the temperature recorded by said temperature sensor as a function of time, such a change indicating the presence in the plane of interest of the liquid-gas interface in the tank; - and determining, from the geometrical data of the tank and the known position of the temperature sensor on the wall of the tank, the volume of liquid propellant present in said tank at the moment I.