Algorithms of 3D radio-wave imaging in airborne Doppler radar

Abstract The navigation correction method proposed in Testud et al. (referred to as the THL method) systematically identifies uncertainties in the aircraft Inertial Navigation System and errors in the radar-pointing angles by analyzing the radar returns from a flat and stationary earth surface. This paper extends the THL study to address 1) error characteristics on the radar display, 2) sensitivity of the dual-Doppler analyses to navigation errors, 3) fine-tuning the navigation corrections for individual flight legs, and 4) identifying navigation corrections over a flat and nonstationary earth surface (e.g., ocean). The results show that the errors in each of the parameters affect the dual-Doppler wind analyses and the first-order derivatives in different manners. The tilt error is the most difficult parameter to determine and has the greatest impact on the dual-Doppler analysis. The extended THL method can further reduce the drift, ground speed, and tilt errors in all flight legs over land by analyzing the residual velocities of the earth surface using the corrections obtained in the calibration legs. When reliable dual-Doppler winds can be deduced at flight level, the Bosart–Lee–Wakimoto method presented here can identify all eight errors by satisfying three criteria: 1) the flight-level dual-Doppler winds near the aircraft are statistically consistent with the in situ winds, 2) the flight-level dual-Doppler winds are continuous across the flight track, and 3) the surface velocities of the left (right) fore radar have the same magnitude but opposite sign as their counterparts of right (left) aft radar. This procedure is able to correct airborne Doppler radar data over the ocean and has been evaluated using datasets collected during past experiments. Consistent calibration factors are obtained in multiple legs. The dual-Doppler analyses using the corrected data are statistically superior to those using uncorrected data.

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A New Airborne Doppler Radar

Journal of Navigation ◽

10.1017/s0373463300020336 ◽

1962 ◽

Vol 15 (4) ◽

pp. 439-442

Author(s):

Minoru Okada ◽

Jun Tamiya

Keyword(s):

Angular Velocity ◽

Doppler Radar ◽

Vertical Axis ◽

Radar System ◽

Low Speed ◽

Single Beam ◽

Depression Angle ◽

New Type ◽

Airborne Doppler Radar

Many airborne doppler radars in use at present work with several beams in fixed directions and a pair of beams switched in sequence. In this paper, which was presented at the convention held in Dusseldorf in May 1961 (Journal, 14, 480), a new type of doppler radar is described in which a single beam is rotated around the vertical axis with a uniform angular velocity, keeping the depression angle constant. With this type of radar, combined with certain circuits in the transmitter-receiver, the frequency tracker and the data stabilizer, it is possible to measure the velocity of positive as well as negative values (including zero); it also allows easier functioning of data-stabilization. Further, a small and lightweight radar system may be constructed in this manner. This type of doppler radar is considered to be of particular use for small, low-speed aircraft.

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