In-flight aircraft weather radar calibration
OwnerJohn P. Chisholminventor
Life of this patent
Estimating the term…
Abstract
A weather radar calibration system, wherein one or more radar reflectors are located at a known position adjacent to an airport runway. Each of the reflectors are shaped to direct reflective patterns of known radar cross-section in response to radar signals transmitted from an aircraft following a known guidance path to the airport. The aircraft radar detects the radar return signals from the reflectors. Circuitry is responsive thereto for utilizing the radar returns for calibrating the weather radar for precipitation measurement and display purposes. The design of the reflectors is such as to minimize multipath reflections off the ground and prevent them from disturbing the reflective properties for aircraft following the guidance path.
Claims13
An in-flight calibration system for calibrating an aircraft weather radar while the aircraft is approaching touchdown on a runway along a fixed glideslope path, the system including the combination of:
- (a) approach guidance means cooperatively located in the aircraft and on the ground for guiding the approach of the aircraft toward touchdown along said fixed glideslope path;
- (b) encoded radar reflector means mounted on the ground substantially at touchdown and directed upwardly along said glideslope path, the reflector means having a fixed and predetermined equivalent radar cross-section as viewed along said path and having a reflective pattern aimed upwardly along the path and with a cutoff approaching but above the plane of the runway;
- (c) the aircraft weather radar having an antenna and a transmitter and a receiver and means to adjust the radar sensitivity;
- (d) a decoder coupled to said receiver and operative to deliver signals responsive to decoded reflections from said coded reflector means;
- (e) range measuring means for determining the range from the aircraft to the encoded reflector means, and operative to deliver an enabling signal when the range reaches a predetermined value;
- and
- (f) calibrator means enabled by signals from said decoder and said range measuring means and operative to compare the intensity level of the output from the receiver representing reflections from the coded reflector means with a reference level, whereby to correct the sensitivity of the receiver to make the output level equal the reference level.
The method of calibrating a weather radar in an in-flight aircraft while approaching touchdown on a runway having at least one uniquely identifiable reflector of known equivalent radar cross-section, the aircraft having range measuring means, the method comprising:
- (a) flying the aircraft along a fixed glideslope path approaching touchdown while illuminating the reflectors with the weather radar output and receiving reflections therefrom, and while measuring range thereto;
- (b) sampling the intensities of reflections from the reflectors;
- (c) determining when the aircraft is at a predetermined range along the glidepath from the reflectors;
- (d) when the predetermined range is reached, comparing the sampled intensities with a reference signal intensity to determine the difference therebetween;
- and
- (e) correcting the sensitivity of the radar to eliminate the difference determined in step (d).
Dependencies are inferred from the claim text.