Development of a multichannel thermal infrared radiometer: Performance of the wide field-of-view prototype CLIMAT
Developpement d'un radiometre infrarouge thermique multicanal: Qualification du prototype large champ CLIMAT
Résumé
A multichannel radiometer, which is designed to have up to six channels in the thermal infrared, in particular the atmospheric window centered on 10 µm, has been performed to realize ground measurements of radiance and brightness temperatures, and for aiborne measurements. The detector is a fast thermopile characterized by a very low temperature dependence of its responsivity. The CIMEL company has been in charge of the instrumental realization. The physical analyze and the qualification of the successives steps of the instrument development have been performed by the Laboratoire d Optique Atmosph´erique (LOA). A wide field of view prototype named CLIMAT (Conveyable Low noise Infrared radiometer for Measurements of Atmosphere and surface Targets) has been analyzed in laboratory and in realistic conditions. The essential characteristics of sensitivity, noise, field of view, thermal behavior, temporal stability have been studied with the prototype. The first results of brightness temperature collected in Lille in clear sky conditions, are then presented and compared with brightness temperature computed with a radiative code. The prototype behavior is besides compared with the one of a monochannel Barnes PRT-5 (8-14µm). The instrument has been also qualified for airborne measurements of brightness sea surface temperature off Calais, with the aid of satellite data (AVHRR) of sea temperature.
Un radiometre multicanal comportant jusqu a six canaux dans la fenetre spectrale de l infrarouge thermique a 10 µm, a ete concu pour realiser des mesures, sur le terrain et aeroportees, de luminance et de temp´erature de brillance. Le detecteur est une thermopile rapide dont la reponse est faiblement dependante de la temperature. La realisation instrumentale a ete conduite par la societe CIMEL. L'analyse physique et la qualification des differentes etapes du developpement de l'instrument ont ete effectuees au Laboratoire d'Optique Atmospherique (LOA). Un prototype nomme CLIMAT (Conveyable Low noise Infrared radiometer for Measurements of Atmosphere and surface Targets) dont le champ de visee est de 10 degres a ete qualifie en laboratoire puis en conditions reelles. Les caracteristiques essentielles de sensibilite, bruit, champ, comportement thermique, stabilite temporelles ont ete etudiees sur le prototype. Les premiers resultats de mesures de la temperature de brillance d'un ciel clair, r´ealisees a Lille, sont presentes et compares avec les resultats de simulations obtenus avec un code radiatif. Le comportement du prototype est en outre compar´eavec celui d un radiometre monocanal Barnes PRT-5 (8-14µm). L instrument a enfin ete qualifie lors de mesures a´eroportees de temperature de brillance de la surface marine au large de Calais, a l aide des donnees satellitaires (AVHRR) de temperature de la mer.