Characterization of NEON Imaging Spectrometer (NIS) and its Radiometric Stability Analysis

Abstract:

The NIS (NEON Imaging Spectrometer) is an airborne pushbroom hyperspectral imaging instrument developed by NASA JPL based on the Next Generation Airborne Visible/Infrared Imaging Spectrometer (AVIRISng) and its requirements for high performance airborne remote sensing. A NIS is included in all three AOP (Airborne Observation Platform) payloads operated by NEON (National Ecological Observatory Network). In addition to the NIS, AOP payloads include a discrete and full-waveform lidar and a high resolution RGB camera. NEON has recently completed the construction phase and is in the initial operational phase, which represents annual activities that will be repeated for the remaining 30-year lifetime of the project. The AOP began data collection in 2013 and provides 28 data products, which are publicly available and can be freely accessed from NEON data portal: https://data.neonscience.org/home.

The NIS optical design consists of a two-mirror anastigmat telescope, an all-reflective Offner-type spectrometer, and a single focal panel array (FPA). It measures radiant energy both in VNIR (Visible-Near Infrared) and SWIR (Shortwave Infrared) spectral region (380-2510 nm) with ~5 nm sampling and 1 mRad instantaneous field of view (IFOV) (Kuester et al. 2010). This 1 mRad IFOV leads to a ground resolution of 1 m at a typical flight altitude of ~1000m. In order to ensure the accuracy of the measurements, the NIS requires stable and consistent calibrations (Leisso et al. 2014). Each NIS instrument is calibrated annually before the flight season in the NEON sensor calibration facility located in Boulder, CO. In addition, the lab calibration is validated independently with vicarious calibration, and the instrument performance is monitored throughout the flight season using its on-board calibration (OBC) data. Experience and assessment of NIS calibration and OBC data through the construction period has revealed anomalies. Such anomalies include dark pedestal shift, electronic panel ghost, and grating ghost. This presentation will discuss characterization and techniques implemented to correct such anomalies. In addition, we will also provide details on the NIS stability analysis, where we have observed ~99% stability, except in the water absorption bands.