GB1422380A - Dual beam radiometer - Google Patents

Abstract

1422380 Measuring atmospheric temperature radiometrically E F FLINT 16 May 1973 23212/73 Heading G1A A radiometer is used to measure atmospheric temperature as an indication of the presence of clear air turbulence. Radiation from the atmos phere is focused by lens 13, which may be rotated for scanning if desired, on to detector 11 (thermistor bolometer). A two sector chopper disc 30 is rotated to allow the atmospheric radiation to reach detector 11 twice per cycle, the other quarter cycles, radiation from a black body source 25 being reflected on to the detector. Rotated in synchronism with disc 30 is a four sector filter disc 40. This can have two equal adjacent sectors having a 1.0 micron bandwidth peaked at 14.2 microns with the other two having a 0.5 micron bandwidth peaked at 13.8 (spectral bands on the edge of a CO 2 absorption band). In this way a four part signal is derived comprising detection of (a) atmospheric radiation at the first wavelength; (b) black body reference radiation at the first wavelength; (c) atmospheric radiation at the second wavelength; (d) black body radiation at the second wavelength. Alternatively, the two sectors corresponding to passage of black body radiation may be peaked at the same wavelength 13.0 microns which is however different from the two wavelengths for atmospheric radiation. To correct for altitude variation errors, an external probe 80 controls the black body source 25 and maintains a constant relationship with the outside temperature.