We report a multiple imaging capability of replicated binary Fresnel phase-encoded lenses written on programmable spatial light modulators (SLMs). These lenses produce a large number (up to 9 x 9) of equally intense replica images from either an external object or from a pattern which is encoded onto the SLM along with the phase-encoded lens. Theoretical details and experimental results using the magnetooptic spatial light modulator are presented.

The CERES instrument has three radiometers which operate in the short-wave (0,3 μm to 5 μm), the long-wave (8 μm to 12 μm) and total broadband (0,3 μm to >200 μm) spectral regions. The long-wave calibration plan for CERES provides for absolute radiometric calibration of the two CERES sensors operating in the long-wave portion of the spectrum. Ground calibration is carried out in the TRW Radiometric Calibration Facility (RCF), a cryogenic vacuum chamber with the capability to simulate radiometrically both cold space and Earth viewing conditions. Absolute calibration is made using a temperature-based radiometric scale created by a black-body radiance standard controlled at temperatures from 200 K to 320 K. In May 1992, the CERES radiometric test model (RTM), a developmental but functionally flight-like instrument, was calibrated at TRW in the RCF. This was the first end-to-end long-wave calibration of a CERES sensor and provided a test and initial validation of the long-wave calibration plan and procedures. The gain, offset, out-of-field response and spectral response were determined for each sensor. The end-to-end long-wave calibration plan is described and the RTM calibration and validation results are presented.

The Clouds and the Earth's Radiant Energy System (CERES) instruments for the NASA Earth Observing System each contain three broadband scanning radiometers operating in bands at wavelengths from 0.3 to 5 pm, 8 to 12 pm, and 0.3 to >150 pm. The primary radiance standard for CERES ground calibration is an absolute blackbody. This standard provides radiance calibration in the long wave spectral region over a blackbody temperature range of 200 K to 320 K. A cryogenic active cavity radiometer operating at liquid helium temperature is used to transfer the radiance scale of the blackbody to a secondary, shortwave calibration source. The longwave to shortwave calibration transfer makes use of the spectrally flat absorptance of the ACR across the entire spectral region. The thermal properties of the copper receiver cavity at 4 K permit a noise equivalent power performance adequate for calibration of the shortwave reference source in a series of narrow (10 % wide) spectral bands which span the shortwave spectral region. The narrow spectral regions greatly reduce the errors in the relative spectral response knowledge of the shortwave source. Results are presented for a transfer that was made during validation tests of the ground calibration system in preparation for the CERES Functional Test Model instrument calibration.

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