Assessing the utility of high spectral resolution lidar for measuring particulate backscatter in the ocean and evaluating satellite ocean color retrievals
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Brian Collister↗
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The Focal Plane Crystal Spectrometer for the HEAO-B satellite
The very low flux from even the brightest (non-solar) X-ray source has discouraged the use of instruments with high spectral resolution because of their inevitably low sensitivity. Mission B of the High Energy Astronomy Observatory will provide the first opportunity for moderate and high resolution spectral studies of celestial X-ray sources with high sensitivity. The Focal Plane Crystal Spectrometer (FPCS) described here is the instrument with the highest spectral resolution. It is designed to allow detailed spectral studies of both point and extended celestial sources in the energy range 0.2-3.3 keV with resolutions of 50 to 1000.
Donaghy, J. F.↗
ORIGIN: Metal Creation and Evolution from the Cosmic Dawn
ORIGIN is a proposal for the M3 mission call of ESA aimed at the study of metal creation from the epoch of cosmic dawn. Using high-spectral resolution in the soft X-ray band, ORIGIN will be able to identify the physical conditions of all abundant elements between C and Ni to red-shifts of z=10, and beyond. The mission will answer questions such as: When were the first metals created? How does the cosmic metal content evolve? Where do most of the metals reside in the Universe? What is the role of metals in structure formation and evolution? To reach out to the early Universe ORIGIN will use Gamma-Ray Bursts (GRBs) to study their local environments in their host galaxies. This requires the capability to slew the satellite in less than a minute to the GRB location. By studying the chemical composition and properties of clusters of galaxies we can extend the range of exploration to lower redshifts (z approx. 0.2). For this task we need a high-resolution spectral imaging instrument with a large field of view. Using the same instrument, we can also study the so far only partially detected baryons in the Warm-Hot Intergalactic Medium (WHIM). The less dense part of the WHIM will be studied using absorption lines at low redshift in the spectra for GRBs. The ORIGIN mission includes a Transient Event Detector (coded mask with a sensitivity of 0.4 photon/sq cm/s in 10 s in the 5-150 keV band) to identify and localize 2000 GRBs over a five year mission, of which approx.65 GRBs have a redshift >7. The Cryogenic Imaging Spectrometer, with a spectral resolution of 2.5 eV, a field of view of 30 arcmin and large effective area below 1 keV has the sensitivity to study clusters up to a significant fraction of the virial radius and to map the denser parts of the WHIM (factor 30 higher than achievable with current instruments). The payload is complemented by a Burst InfraRed Telescope to enable onboard red-shift determination of GRBs (hence securing proper follow up of high-z bursts) and also probes the mildly ionized state of the gas. Fast repointing is achieved by a dedicated Controlled Momentum Gyro and a low background is achieved by the selected low Earth orbit.
Kouveliotou, C.↗
Impact of Measurement System Characteristics on Advanced Sounder Information Content
Advanced satellite sensors are tasked with improving global observations of the Earth's atmosphere, clouds, and surface to enable enhancements in weather prediction, climate monitoring capability, and environmental change detection. Achieving such an improvement in geophysical information inferred from these observations requires optimal usage of data from current systems as well as instrument system enhancements for future sensors. This presentation addresses results of tradeoff studies evaluating the impact of spectral resolution, spectral coverage, instrument noise, and a priori knowledge on remote sensing system information content, with a specific emphasis on thermodynamic state and trace species information obtainable from advanced atmospheric sounders. Particular attention will be devoted toward information achievable from the Atmospheric InfraRed Sounder (AIRS) on the NASA EOS Aqua satellite in orbit since 2002, the Infrared Atmospheric Sounding Interferometer (IASI) aboard MetOp-A since 2006, and the Cross-track Infrared Sounder (CrIS) instrument to fly aboard the NPP and JPSS series of satellites expected to begin in late 2011. While all of these systems cover nearly the same infrared spectral extent, they have very different number of channels, instrument line shapes, coverage continuity, and instrument noise. AIRS is a grating spectrometer having 2378 discrete spectral channels ranging from about 0.4 to 2.2/cm resolution; IASI is a Michelson interferometer with 8461 uniformly-spaced spectral channels of 0.5/cm (apodized) resolution; and CrIS is a Michelson interferometer having 1305 spectral channels of 0.625, 1.250, and 2.50/cm (unapodized) spectral resolution, respectively, over its three continuous but non-overlapping bands. Results of tradeoff studies showing information content sensitivity to assumed measurement system characteristics will be presented.
Larar, Allen M.↗
The LPSP instrument on OSO 8. II - In-flight performance and preliminary results
The paper describes the in-flight performance for the first 18 months of operation of the LPSP (Laboratoire de Physique Stellaire et Planetaire) instrument incorporated in the OSO 8 launched June 1975. By means of the instrument, an absolute pointing accuracy of nearly one second was achieved in orbit during real-time operations. The instrument uses a Cassegrain telescope and a spectrometer simultaneously observing six wavelengths. In-flight performance is discussed with attention to angular resolution, spectral resolution, dispersion and grating mechanism (spectral scanner) stability, scattered light background and dark current, photometric standardization, and absolute calibration. Real-time operation and problems are considered with reference to pointing system problems, target acquisition, and L-alpha modulation. Preliminary results involving the observational program, quiet sun and chromospheric studies, quiet chromospheric oscillation and transients, sunspots and active regions, prominences, and aeronomy investigations are reported.
Bonnet, R. M.↗
Simulating Exoplanet Transit and Eclipse Observations with JWST
The James Webb Space Telescope (JWST) will be a nearly ideal machine for acquiring the transmission and emission spectra of transiting exoplanets over its large wavelength range 0.7 - 28 microns. The NIRSpec, NIRCam, nTFI, and MIRI instruments will have spectroscopic capabilities that span spectral resolutions from 20 - 3000 and can cover up to 2 - 3 octaves in wavelength simultaneously. This will allow observing multiple molecular features at once, facilitating the separation of atmospheric temperature and abundance effects on spectra. Many transiting planets will also be able to be observed with both transmission and eclipse spectroscopy, providing further insights and constraints on planetary thermal structures and energy transport. Simulated JWST spectra of planets ranging from mini-Neptunes to gas giants will be presented. These simulations include planets ranging from mini-Neptunes to gas giants will be presented. These simulations include current best estimates of actual instrument throughput, resolution, spectral range, systematic noise, and random noise terms. They show that JWST will be able to determine the atmospheric parameters of a wide variety of planets, often when observing only one or a few transit or eclipse event sequences. The thermal emissions of rocky super-Earths will also be quickly detectable via mid-IR eclipse observations if such planets are found around nearby M star hosts beforehand.
Greene, Tom↗
Geophysical Information from Advanced Sounder Infrared Spectral Radiance
Advanced satellite sensors are tasked with improving global observations of the Earth's atmosphere, clouds, and surface to enable enhancements in weather prediction, climate monitoring capability, and environmental change detection. Satisfying this type of improvement for inferred geophysical information from these observations requires optimal usage of data from current systems as well as enhancements to future sensors. This presentation addresses the information content present in infrared spectral radiance from advanced atmospheric sounders with an emphasis on knowledge of thermodynamic state and trace species. Results of trade-off studies conducted to evaluate the impact of spectral resolution, spectral coverage, instrument noise, and a priori knowledge on remote sensing system information content will be discussed. A focus is placed on information achievable from the Atmospheric InfraRed Sounder (AIRS) on the NASA EOS Aqua satellite in orbit since 2002, the Infrared Atmospheric Sounding Interferometer (IASI) aboard MetOp-A since 2006, and the Cross-track Infrared Sounder (CrIS) instrument aboard the NPP and JPSS series of satellites which began 28 October 2011.
Larar, Allen M.↗
Infrared measurements of atmospheric constituents
The objective of this program is to obtain data concerning the concentration versus altitude of various constituents of interest in the photochemistry of the stratospheric ozone layer. Data pertinent to this objective are obtained using balloon-borne instruments to measure the atmospheric transmission and emission in the mid infrared. In addition to obtaining constituent profile information, the spectral data obtained are also used to identify absorption or emission features which may interfere with the retrieval of constituent data from satellite instruments using lower spectral resolution. The spectral resolution obtained with the solar spectral system is 0.0025 cm(exp -1) and represents about a factor of 5 greater resolution than any solar spectra previously obtained in this spectral region. As a result of the increase in spectral resolution, a large number of features are observed in these spectra which were not observed in previous studies. Identification and analysis of these features is in progress. The results of this analysis to date shows a number of HNO3 features which have not been observed before, and these occur where they will interfere with the retrieval of other constituents. An example of the interference is the occurrence of features in the 780.2 cm(exp -1) region which overlap the ClONO2 feature which will be used for retrieval of ClONO2 by the CLAES instrument on UARS. A number of features due to COF2 were also identified in the 1250 cm(exp -1) region which may interfere with retrieval of N2O5.
Murcray, David G.↗
Pan-sharpening for microscopy
Techniques for generating full-spatial resolution, full spectral resolution image(s) from a 3D spectral-data cube for any spectral value within a given spectral range are provided without requiring the acquisition of all full-spatial resolution, full spectral resolution data by an instrument. The 3D spectral-data cube is generated from a limited number of full-spatial resolution, sparse spectral resolution data and a sparse-spatial resolution, full-spectral resolution data of the same area of the sample. The use of the 3D spectral-data cube reduces the data acquisition time.
Ovchinnikova, Olga S.↗
Improvements in Virtual Sensors: Using Spatial Information to Estimate Remote Sensing Spectra
Various instruments are used to create images of the Earth and other objects in the universe in a diverse set of wavelength bands with the aim of understanding natural phenomena. Sometimes these instruments are built in a phased approach, with additional measurement capabilities added in later phases. In other cases, technology may mature to the point that the instrument offers new measurement capabilities that were not planned in the original design of the instrument. In still other cases, high resolution spectral measurements may be too costly to perform on a large sample and therefore lower resolution spectral instruments are used to take the majority of measurements. Many applied science questions that are relevant to the earth science remote sensing community require analysis of enormous amounts of data that were generated by instruments with disparate measurement capabilities. In past work [1], we addressed this problem using Virtual Sensors: a method that uses models trained on spectrally rich (high spectral resolution) data to "fill in" unmeasured spectral channels in spectrally poor (low spectral resolution) data. We demonstrated this method by using models trained on the high spectral resolution Terra MODIS instrument to estimate what the equivalent of the MODIS 1.6 micron channel would be for the NOAA AVHRR2 instrument. The scientific motivation for the simulation of the 1.6 micron channel is to improve the ability of the AVHRR2 sensor to detect clouds over snow and ice. This work contains preliminary experiments demonstrating that the use of spatial information can improve our ability to estimate these spectra.
Oza, Nikunj C.↗
Self-Heterodyne Laser-Spectrum Analyzer
Apparatus measures spectral widths of light emitted by GaAs or other narrow-linewidth diode lasers at wavelengths between 800 and 900 nm. Operating on quasi-homodyne of self-heterodyne principle, apparatus provides relatively high spectral resolution: measures spectral widths of order of 100 kHz. Fine spectral resolution of apparatus provides data relevant to use of AlGaAs diode lasers in such applications as coherent optical communication through free space and injection seeding of solid-state lasers. Also used to explore connections between lifetimes and spectral widths of diode lasers.
Saif, Babak↗
FISM 2.0: Improved Spectral Range, Resolution, and Accuracy
The Flare Irradiance Spectral Model (FISM) was first released in 2005 to provide accurate estimates of the solar VUV (0.1-190 nm) irradiance to the Space Weather community. This model was based on TIMED SEE as well as UARS and SORCE SOLSTICE measurements, and was the first model to include a 60 second temporal variation to estimate the variations due to solar flares. Along with flares, FISM also estimates the tradition solar cycle and solar rotational variations over months and decades back to 1947. This model has been highly successful in providing driving inputs to study the affect of solar irradiance variations on the Earth's ionosphere and thermosphere, lunar dust charging, as well as the Martian ionosphere. The second version of FISM, FISM2, is currently being updated to be based on the more accurate SDO/EVE data, which will provide much more accurate estimations in the 0.1-105 nm range, as well as extending the 'daily' model variation up to 300 nm based on the SOLSTICE measurements. with the spectral resolution of SDO/EVE along with SOLSTICE and the TIMED and SORCE XPS 'model' products, the entire range from 0.1-300 nm will also be available at 0.1 nm, allowing FISM2 to be improved a similar 0.1nm spectral bins. FISM also will have a TSI component that will estimate the total radiated energy during flares based on the few TSI flares observed to date. Presented here will be initial results of the FISM2 modeling efforts, as well as some challenges that will need to be overcome in order for FISM2 to accurately model the solar variations on time scales of seconds to decades.
Chamberlin, Phillip C.↗
On cloud altitude determinations from High Resolution Interferometer Sounder (HIS) observations
High Spectral Resolution Interferometer Spectrometer (HIS) data are used with simultaneous airborne lidar data to investigate the accuracy of cloud height determinations using the 'COz slicing method'. It is shown that the accuracy of cirrus cloud heights are greatly improved as the spectral resolution and coverage is increased. Since next generation infrared temperature and moisture sounders will yield high spectral resolution with quasicontinuous spectral coverage, improved cloud height accuracies achieved from these sensors will improve soundings in clouded areas and will also improve our global cloud climatology.
Smith, William L.↗
Large Observatory for X-ray Timing (LOFT-P): A Probe-Class Mission Concept Study
LOFT-P is a mission concept for a NASA Astrophysics Probe-Class (less than $1B) X-ray timing mission, based on the LOFT M-class concept originally proposed to ESA's M3 and M4 calls. LOFT-P requires very large collecting area, high time resolution, good spectral resolution, broadband spectral coverage (2-30 keV), highly flexible scheduling, and an ability to detect and respond promptly to time-critical targets of opportunity. Many of LOFTP's targets are bright, rapidly varying sources, so these measurements are synergistic to imaging and high-resolution spectroscopy instruments, addressing much smaller distance scales than are possible without very long baseline X-ray interferometry, and using complementary techniques to address the geometry and dynamics of emission regions. LOFT-P was presented as an example mission to the head of NASA's Astrophysics Division, to demonstrate the strong community support for creation of a probe-class, for missions costing between $500M and $1B. We submitted a white paper4 in response to NASA PhysPAG's call for white papers: Probe-class Mission Concepts, describing LOFT-P science and a simple extrapolation from the ESA study costs. The next step for probe-class missions will be input into the NASA Astrophysics Decadal Survey to encourage the creation of a probe-class opportunity. We report on a 2016 study by MSFC's Advanced Concepts Office of LOFT-P, a US-led probe-class LOFT concept.
x-ray↗
Position Paper: Workshop on Geologic Applications of Remote Sensing to the Study of Sedimentary Basins
The utility of LANDSAT Multispectral Scanner (MSS) and Thematic Mapper (TM) data for providing regional coverage has been demonstrated. Information derived from LANDSAT spectral data is varied, but has primarily been used for distinguishing materials in a scene. Because of the limited number and width of the MSS and TM bands, LANDSAT data has only limited utility for actual identification of materials. The new advanced sensors (currently airborne, but eventually shuttle-based) have more limited areal extent than LANDSAT, but greater spatial and spectral resolution. The Airborne Imaging Spectrometer (AIS) has spectral resolution of about .01 microns and, typically, has 10m/pixel spatial resolution. This improved spectral resolution means that diagnostic spectral features may now be identified, which in turn means that actual identification of mineral phases present can be addressed (of either monominerallic or composite materials). Another new sensor, the Thermal Infrared Multispectral Scanners (TMS), obtains data in the 8 to 12 micron range. The information from the various sensors (e.g., LANDSAT, AIS, and TIMS) is complementary, covering different wavelength regions and consequently sensitive to different materials or physical properties of materials. In addition, the new sensors also produce a higher volume of data, which must be cleverly and efficiently handled.
Blake, P. L.↗
Electrographic instrumentation for ultraviolet imaging and spectrography
The latest results in the NRL program of far-UV electrographic camera development, and application of these cameras to astrophysical and upper-atmospheric investigations, are presented. A new large electrographic Schmidt camera, of 15 cm aperture and f/2 focal ratio, has been successfully used in two sounding rocket flights, one for direct imagery in the 1230-2000 A wavelength range and the second for objective spectrography in the 950-2000 A range, of stars and nebulae in the Cygnus region of the sky. The camera has an 11 deg field of view and better than 30 arcsec resolution (2 A spectral resolution with 600 line/mm objective grating). A nebular spectrograph, based on a microchannel-intensified electrographic Schmidt camera, is the payload of a May 1979 rocket flight. It will reach emission line features as faint as 5 Rayleighs in 100 second exposures in the 1050-2000 A range, with 5 A spectral resolution.
Carruthers, G. R.↗
Multiplex Fabry-Perot interferometer
Attention is given to a Fabry-Perot interferometer (FPI) technique in which one of the etalon plates is moved over a large optical distance while the other remains fixed, thus exploiting the multiplex advantage of the instrument. This technique involves the application of Fourier-transform spectrometer to the multiple harmonics passing through the FPI etalon. It is shown that the multiplex FPI acts as several Michelson interferometers working at the same time, over the same spectral interval, and at different spectral resolutions. A high spectral resolution has been obtained over a large wavenumber interval, while the advantage of a reasonable scan length has been retained.
Hays, Paul B.↗
The Objective Double Crystal Spectrometer
The solar corona, supernova remnants, the hot diffuse interstellar gas in the Galaxy, galactic halos, and the hot intracluster gas in rich clusters of galaxies, are examples of extended astrophysical plasmas which emit line-rich spectra in the X-ray spectral range from 1.5 to 25 A. These phenomena represent a significant fraction of the baryonic matter in the universe. The study of the composition, structure and dynamics of these astrophysical plasmas requires observations with both high spectral and spatial resolution simultaneously. The Objective Double Crystal Spectrometer, coupled with a grazing incidence X-ray telescope, represents a stigmatic instrument which is highly efficient for the study of such sources. We describe the configuration and performance (spatial resolution, spectral resolution and efficiency) of the Objective Double Crystal spectrometer.
Walker, Arthur B. C., Jr.↗