ELEVATION-TIME DOPPLER METHOD OF DETERMINATION OF SPACECRAFT IN DISTRESS COORDINATES Russian patent published in 2008 - IPC B64G1/10 H04B7/185 

FIELD: space engineering.

SUBSTANCE: proposed method consists in that, on receiving the spacecraft in distress alarm signal, the Doppler frequency of the signal above is measured by an interrogatorless method to locate the spacecraft at the moment when the said frequency equals zero. At this very moment, the angle between the spacecraft receiving antenna axis and that of the horizon pickup is measured to calculate the coordinates of the point below the satellite. The aforesaid measurements are made two times and the coordinates of the points below the satellites along the measured angles allow determining the coordinates of the spacecraft in distress on the Earth surface. To measure the Doppler frequency, two signal processing channels are used wherein the received signal frequency is converted using the onboard master oscillator. In the first processing channel, the oscillator voltage is phase-shifted by 90°, the frequency difference voltages are isolated, amplified and amplitude limited to be converted into rectangular clipped voltages. The first channel voltages of this type are converted into a series of short positive pulses with their time position corresponding to the moments of the voltage passing through the zero level with a positive derivative. Adjacent clipped positive voltages of the second channel are inverted in phase by 180° and quantised by the said short positive pulses of the first channel. The quantised pulses digital form allows determining the Doppler frequency. Given its zero value, corresponding to the spacecraft passing through the beam point, the control pulse is generated to allow the further processing of the received signal.

EFFECT: higher accuracy of measuring minor values of the Doppler frequency and fixation of its zero value.

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