Apparatus and method for performing open loop tracking of a signal
AssigneeSaab Ericsson Space AB
InventorsJacob Christensen, Manfred Sust, Magnus Bonnedal, Anders Carlström
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Abstract
A radio occultation instrumentation system includes a first satellite arranged with a transmitter for transmitting a signal with a carrier frequency and a second satellite arranged with a receiver for receiving the signal. The receiver receives information I(x,v) regarding the position and velocity of the first and second satellite and provides a prediction of the Doppler shift displacement of the carrier frequency of the signal for use in tracking the signal. The predicted Doppler shift displacement is also used to determine atmospheric conditions.
Claims8
Apparatus for performing tracking of a signal in a radio occultation instrumentation system, wherein the signal is transmitted by a first satellite to a second satellite, the apparatus comprising:
- means for receiving the signal;
- and
- means for providing a prediction of Doppler shift displacement of the received signal based on the geometry of the first and second satellites and earth and on the velocity of the first and second satellites to allow for open loop tracking of the received signal.
Apparatus for performing open loop tracking of a signal in a radio occultation instrumentation system, wherein the signal is transmitted by a first satellite to a second satellite, the apparatus comprising:
- means for receiving the signal;
- and
- means for providing a prediction of Doppler shift displacement of the received signal based on the geometry of the first and second satellites and earth and on the velocity of the first and second satellites, and
- wherein the means for providing provides a parametric value (Q(x,v,α(x))), which corresponds to the predicted Doppler Shift displacement, for use in tracking of the received signal, and
- wherein the signal has a ray path from the first satellite to the second satellite, wherein the ray path descends into and ascends from the atmosphere and wherein (a) the parametric value (Q(x,v,α(x))) asymptotically converges towards a first function (F(x,v)) dependent on the satellite positions and velocities and independent of atmosphere conditions when the ray path leaves the atmosphere;
- and (b) the parametric value (Q(x,v,α(x))) asymptotically converge towards a second function (G(x,v,r)) dependent of the local earth radius and independent of atmosphere conditions when the ray path approaches the surface of the earth.
A method for determining atmospheric conditions from information of Doppler shift displacement in a radio occultation instrumentation system, the method comprising the steps of:
- receiving information at ground from a satellite, which collects the information by performing open loop tracking of a transmitted signal from another satellite by predicting Doppler displacement of the transmitted signal;
- and
- determining atmospheric conditions from the received information.
Dependencies are inferred from the claim text.