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This paper summarizes the anticipated performance of the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Visible Infrared Imaging Radiometer Suite (VIIRS) sensor. Predictions are generated from models and demonstration hardware based on the design described in a companion paper [1]. VIIRS risk-reduction will continue as the Engineering Development Unit (EDU) is assembled and tested over the next year facilitating performance verification and lowering flight unit development risk.

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The Earth Radiation Budget Experiment (ERBE) instruments, developed by NASA's Langley Researctt Center and TRW, were first launched on the Earth Radiation Balance Satellite (ERBS) on October 5, 1984 and launched subsequentlyon NOAA-9 and NOAA-10. The radiometric calibration of ERBE instruments was performed at TRW in a cryogenic vacuum chamber developed specifically for that purpose. During calibration each instrument was mounted on a carousel located at the center of the chamber. Broadband calibration sources covering the wavelength range from 0.3 um to >50 um were located around the chamber perimeter. The required absolute radiometric error bounds for the ERBE scanner instruments were +1-3.5% in the shortwave (0.3 urn to 3.5 urn), +1-2.0% in the longwave (5 urn to >50 urn), and +1-1.7% in the total (0.3 urn to >50 urn) bands.1The performance of this facility is being enhanced significantly in preparation for calibration of the Clouds and the Earth's RadiantEnergy System (CERES) instruments. Absolute radiometericcalibrationerror boundsfor the CERES instrument are +1-1% in the shortwave band and +1-. 0.5% longwave and total bands. Enhancements include a new blackbody source, a complete re-design of the shortwave reference source, and a new cryogenic active cavity radiometer (ACR) developed by Cambridge Research and Instrumentation, Inc. The ACR will be used to transfer calibration from the longwave blackbody source to the shortwave reference source. In addition, the master reference blackbody used as the radiometric standard for calibrating ERBE and space simulation equipment including LN2 cooled space references and two albedo plates for Earth simulation are being upgraded. and monitor the environmental conditions within the vacuum chamber. The overall layout of the Radiometric Calibration Facility is shown in figure 2. 0-8194-0602-3/91/$4.O0