The surveillance of large areas with high resolution is limited by the CCD technology, the readout electronics, and the data storage rate. An imaging concept that includes an optical camera and a survey strategy is proposed for remote landing-site certification. A 1-m-diam telescope performs diffraction-limited imaging over its field of view, imaging an area of 0.25 x 0.25 m of the (Martian) surface on a 7 x 7-μm pixel. With the sensor at 350 km above the 10 x 10-km site, this pushbroom imaging configuration incorporates only five sensor passes over the site. The mission time is decreased by nearly 50% from the previously proposed concept for the site certification imaging.
Far-field diffraction resulting from elliptical apertures of different sizes is measured. Both normal and oblique angles of incidence on the apertures are investigated. Diffraction patterns from apertures with dimensions much greater than the wavelength agree with the existing theory. However, new diffraction patterns have been found when using an aperture of wavelength dimension.
A modified Twyman-Green interferometer is in use that makes possible wavefront testing of optical filters at any wavelength from 200 to 1100 nm. The use of mirrors for collimation and pupil imaging makes the instrument achromatic, and therefore the focus is fixed over the entire bandwidth. The beamsplitter and compensator plates are made of
fused silica, and the detector is a UV-enhanced CCD TV camera. A tunable monochrometer with a broadband light source permits selection of any wavelength. Fringe distortion, even when the collimating mirror is spherical, is small enough to keep measurement errors within 0.1 wave peak-to-valley over the 2- x 2-in, aperture.
A modified Twyman-Green interferometer is in use that makes possible wavefront testing of optical filters at any wavelength from 200 to 1100 nanometers. The use of mirrors for collimation and pupil imaging makes the instrument achromatic, and therefore the focus is fixed over the entire bandwidth. The beamsplitter and compensator plates are made of fused silica, and the detector is a UV enhanced CCD tv camera. A tunable monochrometer with a broadband light source permits selection of any wavelength. Fringe distortion, even when the collimating mirror is spherical, is small enough to keep measurement errors within 0.1 wave peak to valley over the 2 by 2 inch aperture.
A "time dilation" push-broom imaging charge-coupled device (CCD) sensor is being considered for certification of landing and roving sites for the exploration of Mars. It will be used to certify several 10 x 10 km candidate sites and to identify rocks and holes of 1 m or larger at those sites, using an optical sensor with 0.25 m resolution. This will require a high-resolution large-aperture camera and a camera-pointing system designed for high accuracy and stability. To reduce the data rate and increase the exposure time, the imaging time will be stretched out by a factor of eight over the time required to fly directly over the imaged site. Six parallel data storage strings will be used to reduce the data acquisition rate, allowing each string to process a manageable 25 Mb/s.
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