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 tri-agency Integrated Program Office (IPO) is managing the development of the National Polar-orbiting Operational Environmental Satellite System (NPOESS). Later this decade, the IPO, through its prime contractor, Northrop Grumman Space Technology (NGST), will launch NPOESS spacecraft into three orbital planes (1330, 1730, and 2130 equatorial ascending nodal crossing times) to provide global coverage with a data refresh rate of approximately four hours. A globally distributed ground system will deliver 95 percent of the data within 26 minutes from the time of on-orbit collection. With the development of NPOESS, we are evolving the existing "weather" satellites into integrated environmental observing systems. To meet user-validated requirements, NPOESS will deliver global data for 55 Environmental Data Records (EDRs). Performance characteristics and attributes have been defined for each of the 55 parameters, including: horizontal/vertical resolution; mapping accuracy; measurement range; measurement precision and uncertainty; refresh rate; data latency; and geographic coverage. Long-term stability requirements have been defined for key parameters to ensure temporal consistency and continuity of data over the operational life of NPOESS. The actual EDR performances will be a result of the sensor and algorithm performances. In order for NPOESS program to determine estimates of EDR performance based on current design data and to assess potential sensor design changes or algorithm modifications, NGST developed an Integrated Weather Products Test Bed (IWPTB). This system can generate simulated radiances from mission/orbit variable, sensor variables, atmospheric and background conditions, and radiative transfer models. These simulated radiances at aperture are used with sensor models and spacecraft factors to generate simulated radiometric temperatures which are processed by science retrieval code to generate EDRs. This paper presents an assessment of the impact of the VIIRS sensor design modification to correct Modulated Instrument Background in the sensor's optical train. This assessment, which focuses on the Sea Surface Temperature EDR in particular, was generated by the IWPTB end-to-end performance assessment capability.

Abstract-This paper will examine the initial results of performance verification testing of the first VIIRS sensor, the Engineering Development Unit (EDU).The EDU was completed and began the initial stages of integration testing in late 2004. As the EDU progresses through ambient and thermal vacuum testing, test data are collected, analyzed, and evaluated. Raytheon SBRS evaluates the data for compliance with sensor specifications. Northrop Grumman evaluates the data to ensure the 21 NPOESS System EDRs to which the VIIRS sensor contributes are satisfied. Initial performance estimates that have been derived from sensor models and updated based on subassembly testing are then measured against test data, at each stage of the test plan.