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Multifrequency remote sensing of soil moisture
Multifrequency sensor data collected at Guymon, Oklahoma and Dalhart, Texas using NASA's C-130 aircraft were used to determine which of the all-weather microwave sensors demonstrated the highest correlation to surface soil moisture over optimal bare soil conditions, and to develop and test techniques which use visible/infrared sensors to compensate for the vegetation effect in this sensor's response to soil moisture. The L-band passive microwave radiometer was found to be the most suitable single sensor system to estimate soil moisture over bare fields. In comparison to other active and passive microwave sensors the L-band radiometer (1) was influenced least by ranges in surface roughness; (2) demonstrated the most sensitivity to soil moisture differences in terms of the range of return from the full range of soil moisture; and (3) was less sensitive to errors in measurement in relation to the range of sensor response. L-band emissivity related more strongly to soil moisture when moisture was expressed as percent of field capacity. The perpendicular vegetation index as determined from the visible/infrared sensors was useful as a measure of the vegetation effect on the L-band radiometer response to soil moisture.
Microwave remote sensing of soil moisture, volume 1
Multifrequency sensor data from NASA's C-130 aircraft were used to determine which of the all weather microwave sensors demonstrated the highest correlation to surface soil moisture over optimal bare soil conditions, and to develop and test techniques which use visible/infrared sensors to compensate for the vegetation effect in this sensor's response to soil moisture. The L-band passive microwave radiometer was found to be the most suitable single sensor system to estimate soil moisture over bare fields. The perpendicular vegetation index (PVI) as determined from the visible/infrared sensors was useful as a measure of the vegetation effect on the L-band radiometer response to soil moisture. A linear equation was developed to estimate percent field capacity as a function of L-band emissivity and the vegetation index. The prediction algorithm improves the estimation of moisture significantly over predictions from L-band emissivity alone.
Spaceborne SAR sensor architecture
Spaceborne imaging radars for the decade of the '90s will be called upon to provide increased illumination parameter flexibility, polar orbital coverage, and to operate from the same platform with other advanced sensors such as multilinear arrays. The potential information content in accurately merged microwave infrared, or microwave visible images is enormous by comparison to either radar images alone or visible/infrared images alone, since microwave images are principally responsive to surface geometry whereas visible/infrared images are highly sensitive to surface chemistry. A strawman system concept in which a SAR and multilinear array (MLA) are flown on a polar orbiting free flyer at 800 km altitude is discussed. Data would be relayed to ground via the TDRSS (or equivalent).
Detection of lowland flooding using active microwave systems
The development of radar systems with longer wavelenths (greater than 3 cm) has provided new possibilities regarding the utilization of radar. Thus, it has been found that the interpretation of data from radar images can be a valuable classification aid for applications related to water resources. In the case of an interpreter accustomed to photographic or visible/infrared images, an evaluation of radar images presents some problems, because the radar is sensing a set of surface characteristics which have little influence on visible/infrared systems. Detectable features in radar images caused by differences in dielectric properties are usually associated with the water content of either soils or vegetation. The present paper is concerned with studies which were initiated in 1976. The studies had the objective to define the magnitude of the effects on radar data caused by flood waters under vegetation. The obtained results indicate the feasibility to detect flood conditions beneath a forest canopy, and to obtain an improved definition of the land-water boundary.
Imaging spectroscopy II; Proceedings of the Meeting, San Diego, CA, Aug. 20, 21, 1987
The conference presents papers on airborne imaging spectrometers, imaging spectrometry analysis, and spaceborne imaging spectrometers. Consideration is given to an imaging spectrometer for ocean and land remote sensing, an advanced solid-state array spectroradiometer, airborne visible/infrared imaging spectrometer design and performance, and a signal chain for the airborne visible/infrared imaging spectrometer. Other topics include imaging spectrometry as a tool for botanical mapping, the estimation of forest canopy characteristics and nitrogen cycling using lasing spectrometry, and a continuous readout photon counting imaging detector.
VIIRS ZEMAX and FORTRAN Polarization Models
The Visible/Infrared Imager/Radiometer Suite (VIIRS) collects visible/infrared imagery and radiometric data. The radiometric requirements are such that the instrument's polarization sensitivity must be very well understood. This paper presents the ZEMAX and FORTRAN polarization ray trace models of the instrument's visible light path. This will include the measured optical surface reflectance data, the bandpass shapes and a comparison of the results of the two models.
Assessment of AVIRIS Laboratory and In-Flight Uniformity
An assessment of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) laboratory and in-flight uniformity is presented in this Slide presentation. The ideal uniform system is described, being a system where every spectrum is intercomparable to every other spectrum. Two types of failures to achieve this uniformity are described. Graphs showing measured spectral upwelling radiance, the expanded spectral convolution, the radiometric error from spectral error, the results from the hyperion Arizaro calibration experiment and a AVIRIS cross-track uniformity are among those presented. The reasons why uniformity matters are presented.
Design of a Pushbroom Imaging Spectrometer that Exceeds AVIRIS Performance
This slide presentation reviews the design of a Pushbroom Imaging Spectrometer, that will exceed the performance of Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). The approach for the AVIRIS-II instrument is reviewed as are the specifications for the new spectrometer. Even though the pushbroom spectrometer is inherently non-uniform, the design of the AVIRIS-II provides for uniformity. Spot diagrams at the slit and at the detector inside the 27micron box are presented. A few of the challenges in the mechanical design and the making of the slit are discussed. The specifications of the 6604A detector array are reviewed. Slides showing the expected Signal to Noise Ratio performance are presented.
Radiometric Performance Model for AVIRIS
This slide presentation reviews the radiometric performance model for Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). This model allows for an estimation of the signal throughput and noise properties of AVIRIS for the components. This understanding can point to areas for improvements of the components.. The signal to noise ratio properties may be estimated. An accurate radiometric performance model is essential for the use of existing instruments and the design of new instruments. Included in the presentation is a design view and a picture of the AVIRIS instrument. There is discussion of the signal, the signal area solid angle product, aspects of area solid angle time, the idealized radiometer photon calculation and noise both instrument read and photon counting noise. Graphs of signal throughput efficiency, input radiance, photons at the detector, signal e-, noise e- and the signal to noise ratio are presented.
Proceedings of the 11th JPL Airborne Earth Science Workshop
This publication contains the proceedings of the JPL Airborne Earth Science Workshop forum held to report science research and applications results with spectral images measured by the NASA Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). These papers were presented at the Jet Propulsion Laboratory from March 5-8, 2001. Electronic versions of these papers may be found at the A VIRIS Web http://popo.jpl.nasa.gov/pub/docs/workshops/aviris.proceedings.html
AVIRIS User's Guide
This paper serves as a brief overview of the AVIRIS instrument (Airborne Visible/Infrared Imaging Spectrometer) and its role in the field of imaging spectrometry. Mission planning and flight operations are discussed, and recommendations are given regarding the deployment of ground truth experiments.
Inflight Validation of AVIRIS Calibration in 1996 and 1997
The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) measures spectral radiance in the solar reflected spectrum from 400 to 2500 nm.
Mapping Chaparral in the Santa Monica Mountains Using Multiple Endmember Spectral Mixture Models
A new technique, called multiple endmember spectral mixture analysis (MESM) was developed and tested in the Santa Monica Mountains, using Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data acqired in the fall of 1994 to map California chaparral.
MODIS Aerosol and Low‐Cloud Retrievals: Orographic Effects in the Wake of Macquarie Island
Abstract Visible/infrared imagery from passive satellites is commonly relied upon to study low cloud microphysics over oceanic regions, including for the Southern Ocean (SO), but relatively little validation has been undertaken for the SO. In this article, we compare low‐cloud effective radius ( r e ), cloud droplet number concentration ( N d ) and cloud liquid water path (LWP) retrievals from the NASA Moderate Imaging Spectroradiometer (MODIS) with surface measurements collected during the Macquarie Island Cloud and Radiation Experiment (MICRE). MODIS 3.7‐μm band retrievals show little bias and moderately good correlation relative to MICRE retrievals for liquid‐phase low clouds when restricted to Solar Zenith Angles <65° on spatial scales of 50–100 km. However, the low overall bias in 3.7‐μm band effective radius ( r e 3.7 ) retrievals partly results from cancellation of errors: r e 3.7 is overestimated for non‐to‐lightly precipitating clouds, and underestimated for heavier drizzling clouds by ∼1–1.5 μm. 1.6‐μm and 2.1‐μm band r e retrievals are biased high. N d may likewise be slightly under‐ or overestimated depending on the concentration, but there is insufficient data to provide confidence in this result. Interestingly, a composite of MODIS retrievals from 2002 to 2020 show a distinct region of enhanced cloud cover and N d (and lower r e ) in the wake of Macquarie Island associated with orographic cloud formation. MODIS retrievals of aerosol optical depth (AOD) and Angstrom Exponent (AE) upwind and downwind of the island do not differ significantly. Comparison with MICRE measurements suggests that MODIS Collection 6 AOD retrievals are reasonable, while AE is problematically large.
Airborne imaging spectroscopy surveys of Arctic and boreal Alaska and northwestern Canada 2017–2023
Since 2015, NASA’s Arctic Boreal Vulnerability Experiment (ABoVE) has investigated how climate change impacts the vulnerability and/or resilience of the permafrost-affected ecosystems of Alaska and northwestern Canada. ABoVE conducted extensive surveys with the Next Generation Airborne Visible/Infrared Imaging Spectrometer (AVIRIS-NG) during 2017, 2018, 2019, and 2022 and with AVIRIS-3 in 2023 to characterize tundra, taiga, peatlands, and wetlands in unprecedented detail. The ABoVE AVIRIS dataset comprises ~1700 individual flight lines covering ~120,000 km 2 with nominal 5 m × 5 m spatial resolution. Data include individual transects to capture important gradients like the tundra-taiga ecotone and maps of up to 10,000 km 2 for key study areas like the Mackenzie Delta. The ABoVE AVIRIS surveys enable diverse ecosystem science, provide crucial benchmark data for validating retrievals from the PACE, PRISMA, and EnMAP satellite sensors and help prepare for the SBG and CHIME missions. This paper guides interested researchers to fully explore the ABoVE AVIRIS spectral imagery and complements our guide to the ABoVE airborne synthetic aperture radar surveys.
Seasat-A - A product of user interests
The paper describes how user requirements were integrated into the development of the Seasat-A program and shows how user requirements influenced sensor selection, mission planning, satellite systems design, and the end-to-end data system. User requirements included the measurement of ocean topography, surface winds, gravity waves, surface temperature, sea ice, salinity, and surface pressure. Particular attention is paid to the selection of sensors: compressed pulse radar altimeter, synthetic aperture imaging radar, microwave wind scatterometer, visible/infrared radiometer, and multispectral microwave radiometer.
Seasat-A oceanographic data system and users
The Seasat-A system is reviewed with emphasis on data retrieval, processing and dissemination plans. Attention is paid to the sensors of the Seasat satellite including the compressed pulse radar altimeter, the coherent synthetic aperture imaging radar, the microwave wind scatterometer, and the scanning visible/infrared radiometer. Particular emphasis is placed on a particular set of experiments: the Navy's Fleet Numerical Weather Control will receive Seasat data in real time and process the data into products that will be used in weather and sea condition forecasts.