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The pre-launch characterization and calibration of remote sensing instruments should be planned and carried out in conjunction with their design and development to meet the mission requirements. The onboard calibrators such as blackbodies and the sensors such as spectral radiometers should be characterized and calibrated using SI traceable standards. In the case of earth remote sensing, this allows inter-comparison and intercalibration of different sensors in space to create global time series of climate records of high accuracy where some inevitable data gaps can be easily bridged. The recommended best practice guidelines for this pre-launch effort is presented based on experience gained at National Institute of Standards and Technology (NIST), National Aeronautics and Space Administration (NASA) and National Oceanic and Atmospheric Administration (NOAA) programs over the past two decades. The currently available radiometric standards and calibration facilities at NIST serving the remote sensing community are described. Examples of best practice calibrations and intercomparisons to build SI (international System of Units) traceable uncertainty budget in the instrumentation used for preflight satellite sensor calibration and validation are presented.

The Visible Infrared Imaging Radiometer Suite (VIIRS) is a key sensor carried on the NPOESS (National Polar-orbiting Operational Environmental Satellite System) Preparatory Project (NPP) mission [1] (http://jointmission.gsfc.nasa.gov/viirs.html), and is scheduled to launch in October 2011. VIIRS sensor design draws on heritage instruments including AVHRR, OLS, MODIS, and SeaWiFS. It has on-board calibration components including a solar diffuser (SD) and a solar diffuser stability monitor (SDSM) for the reflective solar bands (RSB), a V-groove blackbody for the thermal emissive bands (TEB), and a space view (SV) port for background subtraction. These on-board calibrators are located at fixed scan angles. The VIIRS response versus scan angle (RVS) was characterized prelaunch in lab ambient conditions and will be used on-orbit to characterize the response for all scan angles relative to the calibrator scan angle (SD for RSB and blackbody for TEB). Since the RVS is vitally important to the quality of calibrated radiance products, several independent studies were performed and their results were compared and validated. This document provides RVS results from three groups: the NPP Instrument Calibration Support Team (NICST), Raytheon, and the Aerospace Corporation. A comparison of the RVS results obtained using a 2 nd order polynomial fit to measurement data is conducted for each band, detector, and half angle mirror (HAM) side. The associated RVS fitting residuals are examined and compared with the relative differences in RVS found between independent studies. Results show that the agreement is within 0.1% and comparable with fitting residuals for all bands except for RSB band M9, where a difference of 0.2% was observed. Band M9 is highly sensitive to the atmospheric water vapor variations during the sensor ambient testing at Raytheon, and its correction Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/17/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx might be a contributor to the observed RVS uncertainty differences. In general, NICST results have shown slightly larger RSB RVS uncertainties but still well within the 0.3% total uncertainty allowed for the RVS characterization defined in the Performance Verification Plan.

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MODIS is a scanning radiometer that uses a two-sided scan mirror, making the Earth view (EV) observations over an angular range of ±55° relative to instrument nadir. The 16 thermal emissive bands (TEB) are calibrated on a scan-byscan basis using a quadratic algorithm that includes corrections for the sensor response versus scan angle (RVS). Currently, there are two MODIS instruments operated on-orbit. For Terra MODIS (launched in December 1999), the TEB RVS was characterized on-orbit using deep space observations made during spacecraft maneuvers. For Aqua MODIS (launched in May 2002), the TEB RVS was measured pre-launch. In this paper, we describe an approach used to monitor the on-orbit stability of MODIS TEB RVS using observations made during its data sector rotation (SR). The SR is implemented via flight software commands, during which the EV data collection is purposely shifted such that the EV data is taken when the sensor actually views the instrument scan cavity. We will show that this approach can accurately determine the TEB RVS differences between the mirror sides and track the TEB RVS changes on-orbit.

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