Atmospheric sondes and method for tracking

• US 6,421,010 B1
• Filed: 02/16/2001
• Issued: 07/16/2002
• Est. Priority Date: 02/16/2001
• Status: Expired due to Term

• Current Assignee: United States Department of Commerce As Represented By The Secretary of Commerce
• Original Assignee: THE GOVERNMENT OF THE UNITED STATES OF AMERICA, AS REPRESENTED BY THE SECRETARY OF COMMERCE
• Inventors: MacDonald, Alexander E., Chadwick, Russell B.
• Primary Examiner(s): PHAN, DAO LINDA
• Application Number:
  US09/784,206
• Time in Patent Office: 515 Days
• Field of Search: 342/442, 342/450, 342/462, 342/463, 342/465
• US Class Current: 342/465
• CPC Class Codes: G01S 3/48 the waves arriving at the antennas being continuous or intermittent and the phase difference of signals derived therefrom being measured
• CPC Class Codes: G01S 5/04 Position of source determined by a plurality of spaced direction-finders
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence

Abstract

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.

Claims

1. A method for determining wind profile information, comprising the steps of:

providing a plurality of sondes, each comprising a transmitter capable of transmitting a signal modulated according to a predetermined pattern that (1) allows signals received from different ones of said sondes to be differentiated from one another and (2) allows precise measurement of the difference in path length between the sonde and three or more antennas spaced from one another at one or more receiving locations;

releasing said sondes into the atmosphere, for movement with the wind;

operating said sondes to transmit said signals;

receiving said signals at said three or more antennas;

demodulating the signals transmitted thereby at one or more receiving locations to separate the atmospheric data from the modulation pattern;

analyzing the modulation pattern to determine the difference in path length between each sonde and the three or more antennas;

employing said difference in path length to determine an angle of arrival (AOA) of said signal at said receiving location;

determining the location of each said sonde as a function of said AOA, and tracking the positions of said sondes over time to determine the wind profile.

2. The method of claim 1, wherein said transmitted signal comprises atmospheric data including pressure data ambient to the sonde location.

3. The method of claim 2, wherein said ambient pressure data is referenced to a pressure plane established using other measurements to yield a value for the actual altitude of said sonde.

4. The method of claim 1, comprising the step of measuring a carrier phase difference between the signal as received at the spaced antennas, to derive a precise but ambiguous measure of the difference in path length between each sonde and the three or more antennas, and the step of analyzing symbol information in the modulated signal to remove the ambiguity.

5. The method of claim 1, wherein said modulation pattern provides a signal comprising a phase shift keyed, pseudo random sequence of chips of precise length, wherein 1) the pseudo random sequence can be compared to stored sequences to identify the transmitting sonde, and 2) the phase difference between the signal as received at the spaced antennas is used to derive a precise but ambiguous measure of the difference in pathlength.

6. A method for locating a sonde in space at a given instant comprising the steps of:

providing said sonde with a transmitter to send a modulated data signal, including in situ pressure measurements, having a pseudo random sequence of phase-shift-keyed pulses;

receiving said signal at a site comprising at least three closely spaced antennas;

demodulating said received signals to separate data from the modulation pattern;

analyzing the modulation pattern to determine the difference in path length between each sonde and the three or more antennas;

employing said difference in path length to determine an angle of arrival (AOA) of said signal at said receiving location;

determining the altitude of the sonde from the in situ pressure measurement transmitted in the data signal; and

combining the AOA with the pressure-height altitude to locate the sonde in space at a given instant.

7. A method for tracking the trajectory of a sonde by performing the method of claim 6 repeatedly over time.

8. A method for locating a sonde in space at a given instant comprising the steps of:

providing said sonde with a transmitter to send a modulated data signal having a pseudo random sequence of phase-shift-keyed pulses;

receiving said signal at two or more sites each comprising at least two closely spaced antennas, and each time synchronized with the others;

demodulating said received signals to separate data from the modulation pattern;

analyzing the modulation pattern to determine the difference in path length between each sonde and the two or more antennas at each site;

employing said difference in path length to determine an elevation angle of arrival (AOA) of said signal at each site;

analyzing the modulation pattern to determine the difference in time of arrival (TOA) between each sonde and the two or more sites; and

combining the AOAs with the TOAs to locate the sonde in space at a given instant.

9. The method of claim 8, wherein plural measurements are made with respect to each site, and consensus averaging is performed with respect to said plural measurements in order to identify the correct sonde location.

10. A sonde signal receiving site apparatus comprising two sonde receiving antennas located to align the phase centers thereof along a vertical axis a known distance apart, said antennas having identical gain patterns independent of azimuth, a GPS antenna collocated therewith to provide timing information, and a support structure for supporting said antennas and for housing associated electronic processing components.

11. A method for tracking the movement of sondes released from a high altitude balloon, comprising the steps of:

providing each sonde with a transmitter capable of transmitting a signal modulated according to a predetermined pattern that (1) allows signals received from different ones of said sondes to be differentiated from one another and (2) allows precise measurement of the difference in path length between the sonde and three or more antennas spaced from one another at one or more receiving locations;

releasing said sondes into the atmosphere, for movement with the wind;

operating said sondes to transmit said signals;

receiving said signals at said three or more antennas;

demodulating the signals transmitted thereby at one or more receiving locations to separate the atmospheric data from the modulation pattern;

analyzing the modulation pattern to determine the difference in path length between each sonde and the three or more antennas;

employing said difference in path length to determine an angle of arrival (AOA) of said signal at said receiving location;

determining the location of each said sonde as a function of said AOA, and tracking the positions of said sondes over time to determine the wind profile.

12. The method of claim 11 wherein at least one of said receiving stations is affixed to said balloon, and said balloon is further provided with precise positioning capability.

13. The method of claim 12 wherein said receiving station affixed to said balloon receives the signal from said sonde, processes said signal to determine the AOA of the sonde with respect to the balloon, and transmits a signal responsive thereto to a ground station.

14. The method of claim 11 wherein said sondes additionally comprise ambient pressure measurement capability, and said transmitters comprised by said sondes additionally transmit said pressure information.