The National Ecological Observatory Network (NEON) is a planned facility of the National Science Foundation with the
mission to enable understanding and forecasting of the impacts of climate change, land use change and invasive species
on continental-scale ecology Airborne remote sensing plays a critical role by providing measurements at the scale of
individual shrubs and larger plants over hundreds of square kilometers The NEON Airborne Observation Platform is
designed to bridge scales from organism and stand scales, as captured by plot and tower observations, to the scale of
satellite based remote sensing Fused airborne spectroscopy and waveform LiDAR is used to quantify vegetation
composition and structure Panchromatic photography at better than 30 cm resolution will retrieve fine-scale information
on land use, roads, impervious surfaces, and built structures NEON will build three airborne systems to allow for
regular coverage of NEON sites and the capacity to respond to investigator requests for specific projects The system
design achieves a balance between performance and development cost and risk, taking full advantage of existing
commercial airborne LiDAR and camera components To reduce risk during NEON construction, an imaging
spectrometer design verification unit is being developed at the Jet Propulsion Laboratory to demonstrate that operational
and performance requirements can be met As part of this effort, NEON is also focusing on science algorithm
development, computing hardware prototyping and early airborne test flights with similar technologies This paper
presents an overview of the development status of the NEON airborne instrumentation in the context of the NEON
mission

Progress in the development of airborne remote sensing instrumentation for the National Ecological Observatory Network

The Visible Infrared Imaging Radiometer Suite (VIIRS) is the new US operational environmental imaging spectroradiometer in polar orbit. The first VIIRS flight unit onboard Suomi NPP has been providing high-quality visible/infrared Earth observations since 2011. VIIRS provides an unprecedented combination of higher spatial resolution data across a wider area and more complete spectral coverage with onboard calibration than legacy instruments including AVHRR developed in the 1970s for NOAA, OLS developed in the 1970s for US DoD, MODIS developed in the 1990s for the NASA Terra and Aqua satellites and SeaWiFS developed for the commercial SeaStar system in the 1990s. A highly sensitive low light level day/night band (DNB) in VIIRS is improving weather forecasting around the world and providing new ways to observe the Earth from space. VIIRS replaces four legacy sensors with a single instrument enabled by innovations that were driven by requirements defined by NPOESS in the late 1990s. This paper highlights innovations developed by the VIIRS design team in response to challenging driving NPOESS requirements that resulted in remarkable improvements in operational remote sensing.

System engineering of the visible infrared imaging radiometer suite (VIIRS): improvements in imaging radiometry enabled by innovation driven by requirements

A new variant to the standard on-orbit calibration of the reflective solar bands (RSBs) using a solar diffuser (SD) is formulated. Instead of direct solar exposure through the SD port in the front of the instrument as originally designed, the variant method uses light reflecting off Earth's surface coming through the nadir port as the light source to illuminate the built-in onboard SD. The methodology is applied to the Visible Infrared Imaging Radiometer Suite on board the Suomi National Polar-orbiting Partnership satellite, and is shown to be viable and useful. This approach effectively preserves the standard calibration pipeline other than using a different set of illumination data, corresponding to a different illumination source, for computing the radiance emanating from the SD. It has the added advantages of not dealing with operational needs for the standard calibration activities and completely bypassing the characterization of the transmission function of the attenuation screen in the front of the SD port. The RSB calibration coefficients are computed from the data of scattered light from the SD sector per each orbit, and a 16-day average is taken. The variant calibration coefficients are shown to well match the standard solar-based RSB calibration coefficients for Bands M5 to M8, but diverging results emerge for Bands M1 to M4, highlighting the known non-ideal behavior in the degradation of SD that contributes to the worsening error in RSB calibration. The result also shows a consistent 2% variation mission-long for all RSBs, showing the overall consistency of this first analysis of the new method but also the level of the uncertainty. The result and the implications of this study are discussed.

Visible Infrared Imaging Radiometer Suite reflective solar bands on-orbit calibration using solar diffuser illuminated by scattered light through the nadir port.

The NIST role in supporting our Nation’s climate research is described. The assembly of climate data records over decadal time scales requires assimilating readings from a large number of optical sensors deployed in space and on the Earth by various nations. NIST, in partnership with NASA and NOAA, develops and disseminates the calibration tools and standards to ensure that the measurements from these sensors are accurate, comparable, and tied to international standards based on the SI system of units. This effort helps to provide confidence that the small decadal changes in environmental variables attributed to climate change are not an artifact of the measurement system. Additionally, it ensures that the measurements are physics based and thus comparable to climate models.

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Remote Sensing System Engineering III

The Visible/Infrared Imager Radiometer Suite (VIIRS) is the next-generation imaging spectroradiometer for the future operational polar-orbiting environmental satellite system. A successful Flight Unit 1 has been delivered and integrated onto the NPP spacecraft. The flexible VIIRS architecture can be adapted and enhanced to respond to a wide range of requirements and to incorporate new technology as it becomes available. This paper reports on recent design studies to evaluate building a MW-VLWIR dispersive hyperspectral module with active cooling into the existing VIIRS architecture. Performance of a two-grating VIIRS hyperspectral module was studied across a broad trade space defined primarily by spatial sampling, spectral range, spectral sampling interval, along-track field of view and integration time. The hyperspectral module studied here provides contiguous coverage across 3.9 - 15.5 μm with a spectral sampling interval of 10 nm or better, thereby extending VIIRS spectral range to the shortwave side of the 15.5 μm CO 2 band and encompassing the 6.7 μm H 2 O band. Spatial sampling occurs at VIIRS I-band (~0.4 km at nadir) spatial resolution with aggregation to M-band (~0.8 km) and larger pixel sizes to improve sensitivity. Radiometric sensitivity (NEdT) at a spatial resolution of ~4 km is ~0.1 K or better for a 250 K scene across a wavelength range of 4.5 μm to 15.5 μm. The large number of high spectral and spatial resolution FOVs in this instrument improves chances for retrievals of information on the physical state and composition of the atmosphere all the way to the surface in cloudy regions relative to current systems. Spectral aggregation of spatial resolution measurements to MODIS and VIIRS multispectral bands would continue legacy measurements with better sensitivity in nearly all bands. Additional work is needed to optimize spatial sampling, spectral range and spectral sampling approaches for the hyperspectral module and to further refine this powerful imager concept.

Eugene Kim

Papers

Future VIIRS enhancements for the integrated polar-orbiting environmental satellite system