A passive ranging system for determining the slant range from a ground station to a drifting radiosonde. In one embodiment, the ground station receives meteorological data ranging and internal temperature signals from the radiosonde. The data signals are read out as ambient conditions of the atmosphere and the range signal is phase-compared to a reference signal at periodic intervals. Changes in frequency due to temperature fluctuations in the radiosonde components are factored into the phase-comparison, and the resultant change in phase represents movement of the radiosonde. In another embodiment the range tone from a remote broadcast station is retransmitted by the radiosonde and received at the ground station simultaneously with the same tone directly from the broadcast station. The phase lag is measured and coupled with measurements of direction from the ground station to the radiosonde, and with the distance between the ground station and the broadcast station for determining the slant range.
A system for wind profiling comprises sondes for being borne through the atmosphere by balloons and transmitting signals enabling identifying the sondes, and received by receivers capable of determining the angle of arrival (AOA) of the signals from the sondes, so that they can be tracked. In the preferred embodiment, the signal transmitted by each sonde is a phase-shift-keyed (PSK) signal. The carrier phase difference as measured at two spaced antennas is measured to provide an accurate but ambiguous measure of the difference in distance of the path length between the sonde and receivers, and the symbol phase difference is employed to remove the ambiguity. The difference in path length is then used to determine AOA. Atmospheric data and the sonde identification are encoded using a psuedo-random sequence (PRS) of the PSK symbols.
A ranging method for measuring the flight distance of a flight object is implemented by means of a simple system construction. The ranging method is also capable of continuing ranging even if an interruption occurs in data transmission. The ranging method comprises the steps of inserting ranging pulses in a telemeter signal transmitted from a transmitting apparatus provided on the flight object, separating and extracting a ranging pulse from a telemeter signal received by a receiving apparatus provided on the ground side, obtaining a time difference between the ranging pulse and a reference clock signal generated in the receiving apparatus on the basis of a time reference equal to that of the transmitting apparatus (clock signal periods t1 and t2 of both time references are equal), and calculating the flight distance. Since there is no need to provide a transponder or the like on the flight object nor to provide a ranging-tracking system on the ground side, it is possible to realize a simple system construction. Since the ranging pulses are transmitted in the state of being contained in the telemeter signal, it is not necessary to independently prepare ranging-signal transmiting means. In addition, since the telemeter signal can be restored at any time on the ground side, it is possible to prevent ranging from being made impossible due to the interruption of transmission of the signal.
