Clementine Near-Infrared CCD Camera (NIR)

Description

The Clementine Near-Infrared camera (NIR) was designed to study the surfaces of the Moon and the near-Earth asteroid 1620 Geographos at six different wavelengths in the near-infrared spectrum. This experiment yielded information on the petrology of the surface material on the Moon. The rendezvous with Geographos was cancelled due to equipment malfunction.

The camera consisted of a catadioptric lens which focused on a mechanically-cooled (to a temperature of 70 K) Amber InSb CCD focal-plane array with a bandpass of 1100--2800 nm and a six-position filter wheel. The filter center wavelengths (and bandpass widths (FWHM)) were: 1100 nm (60 nm), 1250 nm (60 nm), 1500 nm (60 nm), 2000 nm (60 nm), 2600 nm (60 nm), and 2780 nm (120 nm). The aperture was 29 mm with a focal length of 96 mm. The field of view was 5.6 x 5.6 degrees, giving a cross-track width of about 40 km at a nominal 400 km lunar altitude. The Moon had complete mapping coverage during the two month lunar phase of the mission. The image array is 256 x 256 pixels, and pixel resolution varied from 150--500 m during a single orbit mapping run at the Moon. (At Geographos the pixel resolution would have been 40 m at closest approach, giving an image size about 10 x 10 Km.) The camera took twelve images in each 1.3 s image burst, which occured 75 times over the 80 minute mapping span during each five hour lunar orbit. The dynamic range was 15,000. The signal-to-noise ratio varied from 11--97 depending on the surface albedo and phase angle, with a relative calibration of 1% and an absolute calibration of 30%. The gain varied from 0.5 to 36x.