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NASA NTRSDate not supplied

Evaluation of Spectral Band Adjustment Factors for Cross-Calibration of Visible Imagers

The CERES EBAF dataset provides TOA SW and LW fluxes for long-term monitoring of the Earth’s energy balance and to validate climate models. The EBAF products, based on the Terra and Aqua CERES instrument observed radiances, rely on coincident measurements from the onboard MODIS imagers to determine cloud properties that are used in the angular distribution model scene selection required to convert the CERES observed radiances into flux values. Once the Terra and Aqua orbits start drifting outside of their 15-minute window, the CERES project will rely solely on the NOAA-20 CERES observations. A seamless transition of fluxes and clouds can only occur if the analogous MODIS and VIIRS channels are properly inter-calibrated. The visible band (0.65 µm) in MODIS (band 1) and VIIRS (M5 or I1) is critical for retrieving the cloud mask and optical depth. The spectral response functions (SRF) of these bands differ noticeably and will require scene dependent spectral band adjustment factors (SBAF) for proper radiometric scaling between them. Fortunately, the VIIRS I1 and M5 bands are calibrated using the same solar diffuser as a reference, which implies that band reflectance differences must be due to the spectral disparity. The coincident I1 and M5 TOA reflectance measurements provide the optimal opportunity to validate SBAFs over many surface and cloud conditions. The CERES project maintains SCIAMACHY, GOME-2, Hyperion, and radiative transfer model-based scene-stratified hyper-spectral reflectance measurements that can be convolved with sensor pair SRFs to compute the corresponding SBAF. This study will evaluate the SCIAMACHY, GOME-2, Hyperion, and RTM based SBAFs over tropical ocean targets used in SNO inter-calibration of MODIS and VIIRS, including clear-sky ocean, deep convective clouds (DCC), and liquid cloud targets in terms of their applicability to absolute intercomparison of visible imagers. The large SCIAMACHY and GOME-2 footprints and the lack of Hyperion cloudy scenes will impact the resulting SBAFs and necessitates the need for future CLARREO hyper-spectral reflectances to decrease SBAF uncertainties Preliminary results indicate that the SCIAMACHY and GOME-2 based SBAFs for the VIIRS I1 and M5 band pairs may differ by 1.5% for some ATO scene types. Because most of the modern GEOs visible band SRFs encompass the VIIRS I1 band SRF, these evaluations are critical to ensure that the MODIS, VIIRS, and GEO clouds and fluxes are consistent. SBAFs for Libya-4, Dome-C and other Earth invariant target will also be evaluated.

D. R. Doelling↗
NASA NTRS1973

Monitoring coastal water properties and circulation from ERTS-1

The author has identified the following significant results. Imagery and digital tapes from nine successful ERTS-1 passes over Delaware Bay during different portions of the tidal cycle have been analyzed with special emphasis on turbidity, current circulation, waste disposal plumes, and convergent boundaries between different water masses. ERTS-1 image radiance correlated well with Secchi depth and suspended sediment concentration. MSS band 5 seemed to give the best representation of sediment load in the upper one meter of the water column. Circulation patterns observed by ERTS-1 during different parts of the tidal cycle, agreed well with predicted and measured currents throughout Delaware Bay. During flood tide the suspended sediment as visible from ERTS-1 also correlated well with the depth profile. Convergent shear boundaries between different water masses were observed from ERTS-1, with foam lines containing high concentrations of lead, mercury, and other toxic substances. Several fronts have been seen. Those near the mouth of the bay are associated with the tidal intrusion of shelf water. Fronts in the interior of the bay on the Delaware side appear to be associated with velocity shears induced by differences in bottom topography. Waste disposal plumes have benn detected 36 miles offshore.

Klemas, V.↗
NASA NTRS2005

High-Power Radar Sounders for the Investigation of Jupiter Icy Moons

The high power and high data rate capability made available by a Prometheus class spacecraft could significantly enhance our ability to probe the subsurface of the planets/moons and asteroid/comets. The main technology development driver for our radar is the proposed Jupiter Icy Moon Orbiter (or JIMO) mission due to its harsh radiation environment. We plan to develop a dual-band radar at 5 and 50 MHz in response to the two major science requirements identified by the JIMO Science Definition Team: studying the near subsurface (less than 2 km) at high resolution and detection of the ice/ocean interface for Europa (depth up to 30 km). The 50-MHz band is necessary to provide high spatial resolution (footprint and depth) as required by the JIMO mission science requirements as currently defined. Our preliminary assessment indicates that the 50-MHz system is not required to be as high-power as the 5-MHz system since it will be more limited by the surface clutter than the Jupiter or galactic background noise. The low frequency band (e.g. 5 MHz), which is the focus of this effort, would be necessary to mitigate the performance risks posed by the unknown subsurface structure both in terms of unknown attenuation due to volumetric scattering and also the detection of the interface through the attenuative transition region at the ice/ocean interface. Additionally, the 5-MHz band is less affected by the surface roughness that can cause loss of coherence and clutter noise. However, since the Signal-to-Noise-Ratio (SNR) of the 5-MHz radar band is reduced due to Jupiter noise when operating in the Jupiter side of the moon, it is necessary to increase the radiated power. Our challenge is to design a high-power HF radar that can hnction in Jupiter's high radiation environment, yet be able to fit into spacecraft resource constraints such as mass and thermal limits. Our effort to develop the JIMO radar sounder will rely on our team's experience with planetary radar sounder design gained during our participation in the MARSIS radar sounder implementation.

Safaeinili, A.↗
NASA NTRS2011

Imaging Asteroid 4 Vesta Using the Framing Camera

The Framing Camera (FC) onboard the Dawn spacecraft serves a dual purpose. Next to its central role as a prime science instrument it is also used for the complex navigation of the ion drive spacecraft. The CCD detector with 1024 by 1024 pixels provides the stability for a multiyear mission and its high requirements of photometric accuracy over the wavelength band from 400 to 1000 nm covered by 7 band-pass filters. Vesta will be observed from 3 orbit stages with image scales of 227, 63, and 17 m/px, respectively. The mapping of Vesta s surface with medium resolution will be only completed during the exit phase when the north pole will be illuminated. A detailed pointing strategy will cover the surface at least twice at similar phase angles to provide stereo views for reconstruction of the topography. During approach the phase function of Vesta was determined over a range of angles not accessible from earth. This is the first step in deriving the photometric function of the surface. Combining the topography based on stereo tie points with the photometry in an iterative procedure will disclose details of the surface morphology at considerably smaller scales than the pixel scale. The 7 color filters are well positioned to provide information on the spectral slope in the visible, the depth of the strong pyroxene absorption band, and their variability over the surface. Cross calibration with the VIR spectrometer that extends into the near IR will provide detailed maps of Vesta s surface mineralogy and physical properties. Georeferencing all these observation will result in a coherent and unique data set. During Dawn s approach and capture FC has already demonstrated its performance. The strong variation observed by the Hubble Space Telescope can now be correlated with surface units and features. We will report on results obtained from images taken during survey mode covering the whole illuminated surface. Vesta is a planet-like differentiated body, but its surface gravity and escape velocity are comparable to those of other asteroids and hence much smaller than those of the inner planets or

Keller, H. Uwe↗
NASA NTRS1972

Dynamics of playa lakes in the Texas High Plains

The author has identified the following significant results. Three small playa lake basins on the southern High Plains, Texas, have been examined by geologists, pedologists, hydrologists, and botanists to establish ground truth for correlation with ERTS-1 imagery. Although the sites are recognizable, details of the three playa basins are too small, at present resolution, to be accurately determined by the available MSS imagery. However, a fourth study site, consisting of a dual playa complex approximately 5 miles long in a basin of 9 square miles, does resolve available imagery allowing accurate measurement of water fluctuations and water depth. Of the available MSS imagery, Band 5 is the most usable. Definition of Band 4 is less due to reduced tonal contrast. The greatest tonal contrast appears on Band 6 and Band 7 between dry land and water areas. Band 6 is particularly good for defining large water areas, Band 7 being best for small lake basins, and Band 5 for growing fields.

Reeves, C. C., Jr.↗
NASA NTRS1979

Sulfur dioxide in the Venus atmosphere - Distribution and implications

The Pioneer Venus Orbiter ultraviolet spectrometer sees variable disk brightness features similar to the well-known 'UV markings' seen at longer wavelengths. The bright features are consistent with a homogeneous cloud of H2SO4 aerosols. The darker features show the presence of a broad-band absorber, which is at some depth in the cloud layer. Additional contrast arises from SO2 absorption. The observed strength of the SO2 absorption as a function of wavelength rules out a uniform mixing ratio for the SO2. The data are well fitted by an inhomogeneous light scattering model in which the SO2 scale height is one-fifth of the CO2 scale height, and the mixing ratio of SO2 at 40 mb is 10 to the -7th. A model of the oxidation of sulfur dioxide in the upper cloud reproduces the observed vertical distribution of SO2 and indicates that SO2 alone is sufficient to produce the observed amount of H2SO4 in this region.

Esposito, L. W.↗
NASA NTRS1984

ESA activities in the use of microwaves for the remote sensing of the Earth

The program of activities under way in the European Space Agency (ESA) directed towards Remote Sensing of the oceans and troposphere is discussed. The initial project is the launch of a satellite named ERS-1 with a primary payload of microwave values in theee C- and Ku-bands. This payload is discussed in depth. The secondary payload includes precision location experiments and an instrument to measure sea surface temperature, which are described. The important topic of calibration is extensively discussed, and a review of activities directed towards improvements to the instruments for future satellites is presented. Some discussion of the impact of the instrument payload on the spacecraft design follows and the commitment of ESA to the provision of a service of value to the ultimate user is emphasized.

Maccoll, D.↗
NASA NTRS1984

Surface of Miranda - Identification of water ice

Near-infrared spectrophotometry at 5-percent resolution shows Miranda to have a water-ice surface. Estimates of Miranda's albedo made from the depth of its 2.0-micron absorption band suggest that its visual geometric albedo is likely to be between 10 and 70 percent which when combined with the satellite's visual magnitude, yields a diameter of 500 + or 225 km. There is some evidence that suggests the visual geometric albedo of Miranda may be greater than or equal to 0.3, which implies that its diameter may lie near the lower end of the estimated range. With these results all the Uranian satellites are now known to have water-ice surfaces.

Brown, R. H.↗
NASA NTRS1986

The removal of atmospheric effects from remotely sensed near-infrared spectral data

A technique has been developed for removing atmospheric effects from high-resolution remotely sensed 0.7-2.5-micron spectral data. This calibration technique relies solely on the raw spectra data for calibration information. Results are presented for a set of reflectance spectra for rock samples obtained at a distance of about 0.5 km using an InSb spectrophotometer. The calibration technique uses the depths of water-vapor absorption bands in the remotely obtained spectral data to estimate the degree to which atmospheric attenuation has affected these data.

Blake, P. L.↗
NASA NTRS1994

The morphology of faint galaxies in Medium Deep Survey images using WFPC2

First results from Hubble Space Telescope (HST) Medium Deep Survey images taken with Wide Field/Planetary Camera-2 (WFPC2) demonstrate that galaxy classifications can be reliably performed to magnitudes I814 approximately less than 22.0 in the F815W band. Published spectroscopic surveys to this depth indicate a mean redshift of bar-z approximately 0.5. We have classified over 200 galaxies in nine WFPC2 fields according to a basic morphological scheme. The majority of these faint galaxies appear to be similar to regular Hubble-sequence examples observed at low redshift. To the precision of our classification scheme, the relative proportion of spheroidal and disk systems of normal appearance is as expected from nearby samples, indicating that the bulk of the local galaxy population was in place at half the Hubble time. However, the most intriguing result is the relatively high proportion (approximately 40%) of objects which are in some way anomalous, and which may be of relevance in understanding the origin of the familiar excess population of faint galaxies established by others. These diverse objects include apparently interacting pairs whose multiple structure is only revealed with HST's angular resolution, galaxies with superluminous star-forming regions, diffuse low surface brightness galaxies of various forms, and compact galaxies. These anomalous galaxies contribute a substantial fraction of the excess counts at our limiting magnitude, and may provide insights into the 'faint blue galaxy' problem.

Griffiths, R. E.↗
NASA NTRS2013

SEDS: The Spitzer Extended Deep Survey. Survey Design, Photometry, and Deep IRAC Source Counts

The Spitzer Extended Deep Survey (SEDS) is a very deep infrared survey within five well-known extragalactic science fields: the UKIDSS Ultra-Deep Survey, the Extended Chandra Deep Field South, COSMOS, the Hubble Deep Field North, and the Extended Groth Strip. SEDS covers a total area of 1.46 deg(exp 2) to a depth of 26 AB mag (3sigma) in both of the warm Infrared Array Camera (IRAC) bands at 3.6 and 4.5 micron. Because of its uniform depth of coverage in so many widely-separated fields, SEDS is subject to roughly 25% smaller errors due to cosmic variance than a single-field survey of the same size. SEDS was designed to detect and characterize galaxies from intermediate to high redshifts (z = 2-7) with a built-in means of assessing the impact of cosmic variance on the individual fields. Because the full SEDS depth was accumulated in at least three separate visits to each field, typically with six-month intervals between visits, SEDS also furnishes an opportunity to assess the infrared variability of faint objects. This paper describes the SEDS survey design, processing, and publicly-available data products. Deep IRAC counts for the more than 300,000 galaxies detected by SEDS are consistent with models based on known galaxy populations. Discrete IRAC sources contribute 5.6 +/- 1.0 and 4.4 +/- 0.8 nW / square m/sr at 3.6 and 4.5 micron to the diffuse cosmic infrared background (CIB). IRAC sources cannot contribute more than half of the total CIB flux estimated from DIRBE data. Barring an unexpected error in the DIRBE flux estimates, half the CIB flux must therefore come from a diffuse component.

Spitzer↗
NASA NTRSDate not supplied

Constraints on the surface materials of Ryugu from spectral and water analysis of experimentally-heated CI carbonaceous chondrite

We performed heating experiments of the Orgueil CI chondrite in vacuum conditions at fO2 around I/W to evaluate systematic changes in mineralogy, water contents, and visible to infrared spectral features. Our goal is to interpret the spectra of Ryugu, the target C asteroid of the Hayabusa2 mission, because Ryugu shows spectral features similar to partially dehydrated carbonaceous chondrites. However heated carbonaceous chondrites can be easily contaminated by terrestrial water, which makes it almost impossible for laboratory data to be compared with spectra of asteroids directly. Therefore, our heated samples were analyzed without exposure to the air after experimental heating to minimize the effects of terrestrial water. The depth of the 2.7-µm absorption band and the water content of the heated Orgueil form a positive correlation trend which follows the results of experimental heating of CM and Tagish Lake meteorites using our experimental procedures. It is found that 500-°C heated Orgueil sample shows the best spectral match with Ryugu in terms of the low reflectance (~2%) at visible wavelengths and a weak absorption (~10%) at around 2.72 µm owing to survival of Mg-rich phyllosilicates. We suggest that Ryugu might have experienced heating and dehydration at a temperature around 500 °C, after aqueous alteration, and presently contains a small quantity of hydrated minerals equivalent to 1-2 wt.% of water at the surface.

K. Amano↗
NASA NTRS1982

Surface composition and radius of Hyperion

New spectrophotometric data for Hyperion in the region 1.5-2.6 microns obtained in 1981 confirm the presence of water ice bands reported by Cruikshank (1980). The bands are now shown with sufficient clarity to permit improved comparisons with other ice-bearing satellites of Jupiter and Saturn and with laboratory samples. Comparisons with Ganymede and Rhea are shown, and Hyperion is found to differ from both satellites in terms of depth and width of the water ice bands. The sense of the difference is the same as noted earlier from broadband infrared photometry, but the physical cause is not fully understood. The effective radius of Hyperion (considered circular in cross section) derived from a 20-micron flux measurement and a revised value of V(1,0) = 4.62 is r = 140 + or - 19 km. This result is in better accord with both preliminary and refined values of the radius derived from Voyager images; the Voyager result supersedes that deduced from infrared observations.

Cruikshank, D. P.↗
NASA NTRS1991

Detection of metal stress in boreal forest species using the 0.67-micron chlorophyll absorption band

Several recent studies have shown that a shift of the red-edge inflection near 0.70 micron in vegetation reflectance spectra is an indicator of metal stress, partially attributable to changes in chlorophyll concentration. This 'red-edge shift', however, is difficult to detect and has been reported both toward longer (red) and shorter (blue) wavelengths. Our work demonstrates that direct measurement of the depth and width of the chlorophyll absorption band at 0.67 micron using digital feature extraction and absorption band characterization procedures developed for the analysis of mineral spectra is a more consistent indicator of metal stress. Additionally, the magnitude of these parameters is generally greater than that of the red edge shift and thus should be more amenable to detection and mapping using field and aircraft spectrometers.

Singhroy, Vernon H.↗
NASA NTRS1981

Synergistic relationships among remote-sensing and geophysical media: Geological and hydrological applications

Skylab photographs, side-looking radar imagery, published soil maps, topographic maps, conventional aerial photography as well as LANDSAT imagery under wet and dry changes for several years were analyzed over selected areas in Minnesota to test their usefulness in detecting near-surface ground water. Results show that optical density read from LANDSAT data is not a reliable discriminator of depth to shallow ground water when one band of one scene is used alone, and is little improved when several bands of several scenes are used synergistically. The method is enhanced if information from soil maps is included in the analysis, especially for discriminating boggy ground from better drained areas. It appears, however, that in areas where soil maps and good topographic maps already exist, the depth to ground water can be predicted from those media as well as (if not better than) it can be predicted from remote imagery. The LANDSAT method used demonstrated no capability for recognizing deeper categories of ground water.

Southwick, D. L.↗
NASA NTRSDate not supplied

Observation of Deep Convective Cloud-Top Height and Vertical Temperature Structure of Hurricane Using Hyperspectral Infrared Sounder and its Single-Field-View Retrieval Products

Hurricanes, severe tropical cyclones (TC), or typhoons are significant natural disasters that often result in substantial loss of life and property damage. Numerous studies have indicated that changes in TC intensity are closely linked to deep convective clouds (DCC), with stronger TCs typically exhibiting higher cloud top heights (CTH) compared to weaker TCs. The CTH can help determine if a tropical depression is at the onset of rapid intensification based on case studies. Therefore, accurate determination of TC CTH will be greatly helpful for monitoring TC development and studying TC dynamics. One traditional and most common method to derive CHT from satellite observations is using the thermal brightness temperature in atmospheric channels to match the sounding temperature profile. However, it was found that thermally derived CTH has a lower bias of approximately 1 km, and this bias tends to worsen for the tallest clouds. A new method using the hyperspectral infrared sounder will be presented. From the measurements of Cross-track Infrared Sounder (CrIS) on S-NPP and J-1, along with radiative transfer simulations, we identified the inverted-V spectral feature in the ozone (O3) band (near 9.6 μm) corresponding to high clouds. The depth of the inverted-V can be used to estimate the CTH. Since the depth is computed using the peak absorption O3 channel and the nearby most transparent O3 channel in this O3 band, the uncertainties associated with cloud emissivity and scattering by cloud particles in the traditional method can be ignored. From several hurricane case studies, we found that the CHT derived using this method can accurately capture the structure of the cloud tops in the eyewall, spiral rainbands, and surrounding regions. For example, Hurricane Dorian on September 2, 2019, showed a nicely outward-sloping and circular shape eye cloud in the early morning, but the circular shape of the eyewall cloud became distorted in the afternoon. For various hurricanes we examined, the distribution of CHT for the eyewall clouds differed significantly. To better study the thermodynamic structure of hurricane clouds, this research will analyze the vertical temperature profiles from a new single Field of View (SFOV) Sounder Atmospheric Products (SiFSAP), derived using CrIS and the Advanced Technology Microwave Sounder (ATMS) onboard SNPP and JPSS-1. SiFSAP has a spatial resolution of 15 km at nadir, which surpasses most global weather and climate models and other current operational sounding products. The combined use of ATMS and CrIS allows for retrievals near hurricane eyewalls and spiral rainbands. Wind fields from NASA’s Modern-Era Retrospective Analysis for Research and Applications Version-2 (MERRA-2) and ERA5 will be used to characterize transport, and comparisons between the model temperature and water vapor profiles with the corresponding SiFSAP products will also be provided.

SiFSAP↗
NASA NTRS1977

Microwave absorption characteristics of the clouds of Venus from Mariner 10 radio occultation

Measurements of received signal strength at S-band (13 cm) and X-band (4.8 cm) wavelengths during the radio occultation of Mariner 10 by Venus on February 5, 1974, are examined in order to study the structure and composition of the absorbing medium. The frequency excursions of the signals are determined and used to obtain the structure of the refractive index in the lower atmosphere. Profiles of excess signal attenuation due to atmospheric scattering and absorption are presented which indicate that the X-band signal experienced much more absorption and was extinguished at about 50 km, while the S-band signal penetrated to about 42 km. The optical-depth data are inverted by means of a discrete inversion method to obtain the absorption coefficient for each band as a function of height, and the resulting absorption-coefficient profiles are compared with the attenuation at vertical incidence modeled from planetary radar and passive microwave observations of Venus. The absorption coefficients at the two wavelengths are employed to estimate the liquid content and composition of the microwave-absorbing cloud particles.

Kliore, A. J.↗
NASA NTRS1994

Retrieval of sizes and total masses of particles in volcanic clouds using AVHRR bands 4 and 5

The advanced very high resolution radiometer (AVHRR) sensor on polar orbiting NOAA satellites can discriminate between volcanic clouds and meteorological clouds using two-band data in the thermal infrared. This paper is aimed at developing a retrieval of the particle sizes, optical depth, and total masses of particles from AVHRR two-band data of volcanic clouds. Radiative transfer calculations are used with a semi-transparent cloud model that is based on assumptions of spherical particle shape, a homogeneous underlying surface, and a simple thin cloud parallel to the surface. The model is applied to observed AVHRR data from a 13-hour old drifting cloud from the August 19, 1992, eruption of Crater Peak/Spurr Volcano, Alaska. The AVHRR data fit in the range of results calculated by the model, which supports its credibility. According to the model results, the average of effective particle radius in the test frame of this cloud is in the range of 2 to 2.5 micrometer, the optical depth at 12 micrometer is about 0.60 - 0.65. The total estimated mass of ash in the air amounts to 0.24 - 0.31 x 10(exp 6) tons, which is about 0.7-0.9% of the mass measured in the ashfall blanket. Sensitivity tests show that the mass estimate is more sensitive to the assumed ash size distribution than it is to the ash composition.

Wen, Shiming↗