COOLED BAFFLE SYSTEM FOR SPACEBORNE INFRARED TELESCOPES

We report the design and testing of a compact system of baffles for co oled infrared telescopes. The baffle system consists of a reflecting f orebaffle and a black aftbaffle and provides a high level of rejection of emission from off-axis sources. The firebaffle reflects radiation incident at angles greater than 40 degrees off axis out of the telesco pe, thereby reducing the aperture heat load. The black aftbaffle absor bs radiation scattered or diffracted by the forebaffle, as well as rad iation from sources within 40 degrees off axis. We describe ground-bas ed measurements at lambda = 0.9 mu m of the baffle system at ambient t emperature and rocketborne measurements at far-infrared wavelengths of the baffle system at similar to 3 K. The effective emissivity of the cooled forebaffle was measured to be 7 x 10(-3). The system has been s uccessfully used in rocketborne measurements of the diffuse infrared b ackground and will be used in the Infrared Telescope in Space.