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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Mapping hydrothermally altered rocks in the Northern Grapevine Mountains, Nevada and California with the airborne imaging spectrometer

Seven flightlines of Airborne Imaging Spectrometer (AIS) data were analyzed for an area of hydrothermally altered rocks. The data were reduced to reflectance relative to an average spectrum, and an automated procedure was used to produce a color coded image displaying absorption band information. Individual spectra were extracted from the AIS images to determine the detailed mineralogy. Two alteration types were mapped based upon mineralogy identified using the AIS data. The primary alteration type is quartz sericite pyrite alteration which occurs in northwest-trending zones in quartz monzonite porphyry. The AIS data allow identification of sericite (muscovite) based upon a strong absorption feature near 2.21 micron and weaker absorption features near 2.35 and 2.45 micron. The second alteration type occurs as a zone of argillic alteration associated with a granitic intrusion. Montmorillonite was identified based on a weak to moderate absorption feature near 2.2 micron and the absence of the two absorption features at longer wavelengths characteristic of sericite. Montmorillonite could be identified only where concentrations of sericite did not mask the montmorillonite spectrum.

Kruse, Fred A.↗
NASA NTRS1992

Remote sensing of cloud, aerosol and water vapor properties from the Moderate Resolution Imaging Spectrometer (MODIS)

The Moderate Resolution Imaging Spectrometer (MODIS) is an Earth-viewing sensor being developed as a facility instrument for the Earth Observing System (EOS) to be launched in the late 1990s. MODIS consists of two separate instruments that scan a swath width sufficient to provide nearly complete global coverage every two days from a polar-orbiting, Sun-synchronous, platform at an altitude of 705 km. Of primary interest for studies of atmospheric physics is the MODIS-N (nadir) instrument which will provide images in 36 spectral bands between 0.415 and 14.235 micrometers with spatial resoulutions of 250 m (2 bands), 500 m (5 bands) and 1000 m (29 bands). These bands have been carefully selected to enable advanced studies of land, ocean and atmosperhic processes. The intent of this lecture is to describe the current status of MODIS-N and its companion instrument MODIS-T (tilt), a tiltable cross-track scanning radiometer with 32 uniformly spaced channels between 0.410 and 0.875 micrometers, and to describe the physical principles behind the development of MODIS for the remote sensing of atmospheric properties. Primary emphasis will be placed on the main atmospheric applications of determining the optical, microphysical and physical properties of clouds and aerosol particles form spectral-reflection and thermal-emission measurements. In addition to cloud and aerosol properties, MODIS-N will be utilized for the determination of the total precipitable water vapor over land and atmospheric stability. The physical principles behind the determination of each of these atmospheric products will be described herein.

King, M. D.↗
NASA NTRS1988

HIRIS - The High Resolution Imaging Spectrometer

The High-Resolution Imaging Spectrometer (HIRIS) is a JPL facility instrument designed for NASA's Earth Observing System (Eos).It will have 10-nm wide spectral bands from 0.4-2.5 microns at 30 m spatial resolution over a 30 km swath. The spectral resolution allows identification of many minerals in rocks and soils, important algal pigments in oceans and inland waters, spectral changes associated with plant canopy biochemistry, composition of atmospheric aerosols, and grain size of snow and its contamination by absorbing impurities. The bands wil have 12-bit quantization over a dynamic range suitable for bright targets, such as snow. For targets of low brightness, such as water bodies, image-motion compensation will allow gains up to a factor of eight to increase signal-to-noise ratios. In the 824-km orbit altitude proposed for Eos, the crosstrack pointing capability will allow 4-5 views during a 16-day revisit cycle.

Dozier, Jeff↗
NASA NTRS1987

Visible and infrared linear detector arrays for the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS)

The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) instrument uses four separate focal plane assemblies consisting of line array detectors that are multiplexed to a common J-FET preamp using a FET switch multiplexing (MUX) technique. A 32-element silicon line array covers the spectral range from 0.41 to 0.70 microns. Three additional 64-element indium antimonide (InSb) line arrays cover the spectral range from 0.68 to 2.45 microns. The spectral sampling interval per detector element is nominally 9.8 nm, giving a total of 224 spectral channels. All focal planes operate at liquid nitrogen temperature and are housed in separate dewars. Electrical performance characteristics include a read noise of less than 1000 e(-) in all channels, response and dark nonuniformity of 5 percent peak to peak, and quantum efficiency of greater than 60 percent.

Bailey, Gary C.↗
NASA NTRS1988

Visible and infrared linear detector arrays for the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS)

The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) instrument uses four separate focal plane assemblies consisting of line array detectors that are multiplexed to a common J-FET preamp using a FET switch multiplexing (MUX) technique. A 32-element silicon line array covers the spectral range from 0.41 to 0.70 microns. Three additional 64-element indium antimonide (InSb) line arrays cover the spectral range from 0.68 to 2.45 microns. The spectral sampling interval per detector element is nominally 9.8 nm, giving a total of 224 spectral channels. All focal planes operate at liquid nitrogen temperature and are housed in separate dewars. Electrical performance characteristics include a read noise of less than 1000 e(-) in all channels, response and dark nonuniformity of 5 percent peak to peak, and quantum efficiency of greater than 60 percent.

Bailey, Gary C.↗
NASA NTRS1990

The Moderate Resolution Imaging Spectrometer (MODIS)

The Moderate Resolution Imaging Spectrometer (MODIS) observing facility on the Earth Observing System (EOS) is composed of two instruments, MODIS-Nadir (N) and MODIS-Tilt (T). MODIS-N has 36 spectral bands between 0.4 and 14.2 micrometers with spatial resolution between 214 and 856 meters. MODIS-T has 32 bands with 10-15 nanometer bandwidths between 0.4 and 0.9 micrometers. MODIS-T scans fore and aft + or - 50 degrees. Both instruments scan cross-track so as to provide daily (MODIS-N) or once every 2 days (MODIS-T) coverage at 705 kilometers altitude. Both instruments are entering into the execution phases of their development in 1990.

Salomonson, Vincent V.↗
NASA NTRS1993

Imaging Spectrometer Using a Liquid Crystal Tunable Filter

A demonstration imaging spectrometer using a liquid crystal tunable filter (LCTF) was built and tested on a hot air balloon platform. The LCTF is a tunable polarization interference or Lyot filter. The LCTF enables a small, light weight, low power, band sequential imaging spectrometer design.

Imaging↗
NASA NTRS1992

Seasonal and spatial variations in phytoplanktonic chlorophyll in eutrophic Mono Lake, California, measured with the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS)

The principal problem with application of airborne imaging spectrometers to lakes is the weak upwelling signal, especially when narrow spectral bands with high spatial resolution are sought. Furthermore, atmospheric path radiance dominates the signal received from dark targets such as lakes. Once atmospheric effects have been removed from the radiance received at the sensor, semi-empirical relationships can be developed to extract information about phytoplankton pigment concentrations for different underwater optical conditions. In lakes where concentrations of dissolved organics and suspended detritus may not co-vary with phytoplankton pigments, the many spectral channels of an imaging spectrometer such as AVIRIS are likely to be required to distinguish the various aquasols. The objectives of our study are to: (1) estimate the chlorophyll content of a lake with hundred-fold seasonal ranges in chlorophyll concentration using atmospherically corrected upwelling radiances derived from AVIRIS imagery, and (2) to examine spatial patterns in chlorophyll after reduction of the coherent noise in the imagery by filtering techniques.

Melack, John M.↗
NASA NTRS2017

Snow and Water Imaging Spectrometer (SWIS): First alignment and characterization results

The Snow and Water Imaging Spectrometer (SWIS) is a fast, high-uniformity, low-polarization sensitivity imaging spectrometer and telescope system designed for integration on a 6U CubeSat platform. Operating in the 350-1700 nm spectral region with 5.7 nm sampling, SWIS is capable of simultaneously addressing the demanding needs of coastal ocean science and snow and ice monitoring. New key technologies that facilitate the development of this instrument include a linear variable anti-reflection (LVAR) detector coating for stray light management, and a single drive on-board calibration mechanism utilizing a transmissive diffuser for solar calibration. We provide an overview of the SWIS instrument design and potential science applications and describe the instrument assembly and alignment, supported by laboratory measurements.

Van Gorp, Byron E.↗
NASA NTRS1990

Mapping alteration in the Goldfield Mining District, Nevada, with the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS)

Analysis of the data acquired by the Airborne Visible/IR Imaging Spectrometer over the Goldfield Mining District, Nevada, demonstrates the unique capabilities of high resolution imaging spectrometers for alteration mapping and identification of mineralogy. The study focuses on the 2-2.45 micron window, as alteration minerals of interest have their distinctive spectral reflectance features in this region. An attempt was made to map the spatial distribution of the individual minerals and produce a mixture maps showing their relative abundance on a pixel-by-pixel basis, focussing on selected subareas. Software and SNR performances limited success in detailed mapping.

Carrere, Veronique↗
NASA NTRS1989

Column atmospheric water vapor retrievals from airborne imaging spectrometer data

High-spatial-resolution column atmospheric water vapor amounts were derived from spectral data collected by the Airborne Visible Infrared Imaging Spectrometer (AVIRIS). The quantitative derivation is made by curve fitting observed spectra with calculated spectra in the 1.14- and 0.94-micron water-vapor band absorption regions with a nonlinear least-squares technique. The precision of the retrieved column water vapor is approximately 5 percent. The derived column water vapor amounts are independent of the absolute surface reflectance. Curve fitting of spectra near 1 micron from areas covered with vegetation indicates that both the amount of atmospheric water vapor and the moisture content of vegetation can be retrieved simultaneously. It should be possible to measure column water vapor over land areas from satellite altitude with the proposed high-resolution imaging spectrometer or even the moderate-resolution imaging spectrometer.

Gao, Bo-Cai↗
NASA NTRS1982

Imaging spectrometer technologies for advanced Earth remote sensing

A major requirement of multispectral imaging systems for advanced Earth remote sensing is the provision for greater spectral resolution and more versatile spectral band selection. The imaging spectrometer instrument concept provides this versatility by the combination of pushbroom imaging and spectrally dispersing optics using area array detectors in the focal plane. The shuttle imaging spectrometer concept achieves 10- and 20-meter ground instantaneous fields of view with 20-nanometer spectral resolution from Earth Orbit. Onboard processing allows the selection of spectral bands during flight; this, in turn, permits the sensor parameters to be tailored to the experiment objectives. Advances in optical design, infrared detector arrays, and focal plane cooling indicate the feasibility of the instrument concept and support the practicability of a validation flight experiment for the shuttle in the late 1980s.

Wellman, J. B.↗
NASA NTRS1982

Imaging spectrometer technologies for advanced earth remote sensing

A major requirement of multispectral imaging systems for advanced earth remote sensing is the provision for greater spectral resolution and more versatile spectral band selection. The imaging spectrometer instrument concept provides this versatility by the combination of pushbroom imaging and spectrally dispersing optics using area array detectors in the focal plane. The shuttle imaging spectrometer concept achieves 10- and 20-meter ground instantaneous fields of view with 20-nanometer spectral resolution from earth orbit. Onboard processing allows the selection of spectral bands during flight; this, in turn, permits the sensor parameters to be tailored to the experiment objectives. Advances in optical design, infrared detector arrays, and focal plane cooling indicate the feasibility of the instrument concept and support the practicability of a validation flight experiment for the shuttle in the late 1980s. Previously announced in STAR as N83-28542

Wellman, J. B.↗
NASA NTRS1986

Development of the Imaging Spectrometer for Shuttle and space platform applications

The concept of the Imaging Spectrometer is becoming established as a major new thrust in remote sensing of the earth. A future step will be the Shuttle Imaging Spectrometer (SISEX) currently planned for a 1990 flight. This paper describes the current state of development of SISEX, including the development of a modular concept which will allow major elements of SISEX to be used on NASA's Space platform, the Earth Observing System. This modular approach is expected to result in a substantial overall cost saving.

Herring, Mark↗
NASA NTRS1996

Development of a Compact Imaging Spectrometer Using Liquid Crystal Tunable Filter Technology

Liquid crystal tunable filters are useful in building compact multi-spectral instruments. The system is portable and adaptable for use in a variety of fields of study in the visible and near-infrared regions of the spectrum.We will present data from calibration targets and some applications, results of the spectral calibration of a spectrometer system, and results of environmental (vibration, radiation, shock, and thermal) testing. Data acquisition and system design are also discussed.

spectrometers imaging↗
NASA NTRS1984

Imaging spectrometer concepts for next-generation planetary missions

In recent years there has been an increasing interest in the imaging spectrometer concept, in which imaging is accomplished in multiple, contiguous spectral bands at typical intervals of 5 to 20 nm. There are two implementations of this concept under consideration for upcoming planetary missions. One is the scanning, or 'whisk-broom' approach, in which each picture element (pixel) of the scene is spectrally dispersed onto a linear array of detectors; the spatial information is provided by a scan mirror in combination with the vehicle motion. The second approach is the 'push-broom' imager, in which a line of pixels from the scene is spectrally dispersed onto a two-dimensional (area-array) detector. In this approach, the scan mirror is eliminated, but the optics and focal plane are more complex. This paper discusses the application of these emerging instrument concepts to the planetary program. Key issues are the trade-off between the two types of imaging spectrometer, the available data rate from a typical planetary mission, and the focal-plane cooling requirements. Specific straw-man conceptual designs for the Mars Geoscience/Climatology Orbiter (MGCO) and the Mariner Mark II Comet Rendezvous/Asteroid Flyby (CRAF) missions are discussed.

Herring, M.↗