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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
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NASA NTRS1991

Crustal heterogeneity of the moon viewed from the Galileo SSI camera: Lunar sample calibrations and compositional implications

Summaries are given of the spectral calibration, compositional parameters, nearside color, and limb and farside color of the Moon. The farside of the Moon, a large area of lunar crust, is dominated by heavily cratered terrain and basin deposits that represent the products of the first half billion years of crustal evolution. Continuing analysis of the returned lunar samples suggest a magma ocean and/or serial magmatism model for evolution of the primordial lunar crust. However, testing either hypothesis requires compositional information about the crustal stratigraphy and lateral heterogeneity. Resolution of this important planetary science issue is dependent on additional data. New Galileo multispectral images indicate previously unknown local and regional compositional diversity of the farside crust. Future analysis will focus on individual features and a more detailed assessment of crustal stratigraphy and heterogeneity.

Pieters, Carle M.↗
NASA NTRS1991

Probable age of Autolycus and calibration of lunar stratigraphy

Ar-39 - Ar-40 analyses of three petrographically distinct, shocked Apollo 15 KREEP (i.e., high K, rare earth element, P, and other trace element contents) basalt samples demonstrate that a major impact event affected all three samples at about 2.1 Ga. The Copernican System craters Aristillus and Autolycus are to the north. Autolycus, the older of the two, is in a particularly appropriate terrain and is the most likely source of the 2.1 Ga heating and delivery event. With this calibration point, and if Autolycus really is a Copernican crater, the Copernican System lasted twice as long as has previously been suggested. Furthermore, the moon was not subjected to a constant cratering rate over the past 3 billion years; the average rate in the preceding Eratosthenian must have been twice that in the Copernican.

Ryder, G.↗
NASA NTRS2004

Inter-Comparison of Terra and Aqua MODIS

Nearly identical copies of the Moderate Resolution Imaging Spectroradiometer (MODIS) have been operating on-board the NASA's Earth Observing System (EOS) Terra and Aqua satellites since their launches in December 1999 and May 2002, respectively. Each MODIS has 20 reflective solar bands (RSB) with center wavelengths ranging from 0.41 to 2.1 micrometers and 16 thermal emissive bands (TEB) from 3.7 to 14.4 micrometers. The absolute radiometric accuracy requirements (1 sigma) at the typical spectral radiance levels are plus or minus 2% for the RSB for the RSB reflectance factors and plus or minus 5% for the RSB radiance products. With few exceptions, the TEB requirements are plus or minus 1%. The sensor's on-orbit radiometric calibration is performed by the on-board calibrators, including a solar diffuser (SD) and a solar diffuser stability monitor (SDSM) system for the RSB and a V-groove flat panel blackbody (BB) for the TEB. In addition, the Moon has been extensively used by both Terra and Aqua MODIS to support their on-orbit calibration and characterization. This paper presents MODIS lunar calibration methodology and inter-comparison of Terra and Aqua MODIS in the VIS/NIR spectral regions. Current results from lunar observations show that the calibration difference between the two sensors is less than plus or minus 1%. Also discussed in this paper are the approaches and results of inter-comparison of Terra and Aqua MODIS in the TEB using closely matched thermal infrared (TIR) channels on the Advanced Very High Resolution Radiometer (AVHRR) at 11 and 12 micrometers.

Xiong, X.↗
NASA NTRSDate not supplied

PACE OCI Straylight and Crosstalk Evaluation using Moon

The Ocean Color Instrument (OCI) onboard NASA’s Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission has performed three monthly lunar calibrations. The moon is an extended source over a large dark background, making it an ideal target for evaluating OCI’s straylight and crosstalk performance. The lunar data analysis showed the straylight and crosstalk to be lower than the prelaunch measurements, especially in the along-track direction, where very little straylight is detected. Based on lunar data, the prelaunch measured crosstalk coefficients were reduced, and a crosstalk correction was tested on both lunar and solar calibration data. Applying the revised crosstalk correction, the crosstalk contaminations are significantly reduced to under 0.1% at 2-3 pixels away from the lunar boundary for bands above 350 nm. Below 350 nm, the crosstalk correction residuals gradually increase due to a lack of high-quality prelaunch measurements. Lastly, applying the crosstalk correction changes the calibrated radiance for all science data. This is due to the different spectral shapes between the solar diffuser and the observed scenes. For the moon, the crosstalk correction has an impact of ~0.4% on the overall calibrated radiance for the 400 – 600 nm bands and up to 20% impact on the UV bands.

Shihyan Lee↗
NASA NTRS2011

Nocturnal Aerosol Optical Depth Measurements with a Small-Aperture Automated Photometer Using the Moon as a Light Source

A method is described that enables the use of lunar irradiance to obtain nighttime aerosol optical depth (AOD) measurements using a small-aperture photometer. In this approach, the U.S. Geological Survey lunar calibration system was utilized to provide high-precision lunar exoatmospheric spectral irradiance predictions for a ground-based sensor location, and when combined with ground measurement viewing geometry, provided the column optical transmittance for retrievals of AOD. Automated multiwavelength lunar measurements were obtained using an unmodified Cimel-318 sunphotometer sensor to assess existing capabilities and enhancements needed for day/night operation in NASA s Aerosol Robotic Network (AERONET). Results show that even existing photometers can provide the ability for retrievals of aerosol optical depths at night near full moon. With an additional photodetector signal-to-noise improvement of 10-100, routine use over the bright half of the lunar phase and a much wider range of wavelengths and conditions can be achieved. Although the lunar cycle is expected to limit the frequency of observations to 30%-40% compared to solar measurements, nevertheless this is an attractive extension of AERONET capabilities.

Berkoff, Timothy A.↗
NASA NTRS2015

Radiation Budget Instrument (RBI) for JPSS-2

Radiation Budget Instrument (RBI) will be one of five instruments flying aboard the JPSS-2 spacecraft, a polar-orbiting sun-synchronous satellite in Low Earth Orbit. RBI is a passive remote sensing instrument that will follow the successful legacy of the Clouds and Earth's Radiant Energy System (CERES) instruments to make measurement of Earth's short and longwave radiation budget. The goal of RBI is to provide an independent measurement of the broadband reflected solar radiance and Earth's emitted thermal radiance by using three spectral bands (Shortwave, Longwave, and Total) that will have the same overlapped point spread function (PSF) footprint on Earth. To ensure precise NIST-traceable calibration in space the RBI sensor is designed to use a visible calibration target (VCT), a solar calibration target (SCT), and an infrared calibration target (ICT) containing phase change cells (PCC) to enable on-board temperature calibration. The VCT is a thermally controlled integrating sphere with space grade Spectralon covering the inner surface. Two sides of the sphere will have fiber-coupled laser diodes in the UV to IR wavelength region. An electrical substitution radiometer on the integrating sphere will monitor the long term stability of the sources and the possible degradation of the Spectralon in space. In addition the radiometric calibration operations will use the Spectralon diffusers of the SCT to provide accurate measurements of Solar degradation. All those stable on-orbit references will ensure that calibration stability is maintained over the RBI sensor lifetime. For the preflight calibration the RBI will view five calibration sources - two integrating spheres and three CrIS (Cross-track Infrared Sounder ) -like blackbodies whose outputs will be validated with NIST calibration approach. Thermopile are the selected detectors for the RBI. The sensor has a requirement to perform lunar calibration in addition to solar calibration in space in a way similar to CERES instruments approach. To monitor climate change and to get stable and traceable results, it is critical to assure stable calibration over instrument lifetime.

Georgieva, Elena↗
NASA NTRS2002

Earth Observing-1 Advanced Land Imager: Imaging Performance On-Orbit

This report analyzes the on-orbit imaging performance of the Advanced Land Imager (ALI) on the Earth Observing-1 satellite. The pre-flight calibrations are first summarized. The methods used to reconstruct and geometrically correct the image data from this push-broom sensor are described. The method used here does not refer to the position and attitude telemetry from the spacecraft. Rather, it is assumed that the image of the scene moves across the focal plane with a constant velocity, which can be ascertained from the image data itself. Next, an assortment of the images so reconstructed is presented. Color images sharpened with the 10-m panchromatic band data are shown, and the algorithm for producing them from the 30-m multispectral data is described. The approach taken for assessing spatial resolution is to compare the sharpness of features in the on-orbit image data with profiles predicted on the basis of the pre-flight calibrations. A large assortment of bridge profiles is analyzed, and very good fits to the predicted shapes are obtained. Lunar calibration scans are analyzed to examine the sharpness of the edge-spread function at the limb of the moon. The darkness of the space beyond the limb is better for this purpose than anything that could be simulated on the ground. From these scans, we find clear evidence of scattering in the optical system, as well as some weak ghost images. Scans of planets and stars are also analyzed. Stars are useful point sources of light at all wavelengths, and delineate the point-spread functions of the system. From a quarter-speed scan over the Pleiades, we find that the ALI can detect 6th magnitude stars. The quality of the reconstructed images verifies the capability of the ALI to produce Landsat-type multi spectral data. The signal-to-noise and panchromatic spatial resolution are considerably superior to those of the existing Landsat sensors. The spatial resolution is confirmed to be as good as it was designed to be.

ALI (ADVANCED LAND IMAGER)↗
NASA NTRS2021

Nonlinear Detector Response of Aqua MODIS Land Imaging Bands

The detectors in Aqua MODIS reflective solar bands (RSB) are calibrated assuming a linear relationship between the observed top-of-atmosphere radiance and the instrument output response. Any non-linear behavior in the system response can contribute to errors in NASA’s Level 1B MODIS reflectance and radiance products, which are used in a wide variety of Earth science applications. While most RSB detectors continue to have very linear behavior even after more than 18 years of operation, we present evidence that the detectors in Aqua MODIS bands 1 (645 nm) and 2 (858 nm) have deviations from gain linearity that change over the mission by up to 3%. We show a clear divergence between gain measurements made with the on-board solar diffuser (SD) at two different radiance levels, achieved by collecting data both with and without an attenuation screen. Radiance trends from lunar calibrations and typical desert and ocean scenes are also compared. We present a simple method to characterize the response non-linearity using a quadratic function by combining the results of the two sets of SD calibrations. Applying this quadratic calibration algorithm to the desert and lunar data results in improved agreement in their long-term radiance trends. A clear understanding of the magnitude of the gain non-linearity could be useful to help improve the quality of numerous MODIS science products, including the land imaging applications that rely heavily on these bands.

MODIS↗
NASA NTRS2011

A Wavelength-Dependent Visible and Infrared Spectrophotometric Function for the Moon based on ROLO Data

The USGS's Robotic Lunar Observatory (ROLO) dedicated ground-based lunar calibration project obtained photometric observations of the Moon over the spectral range attainable from Earth (0.347-2.39 microns) and over solar phase angles of 1.55 deg -97 deg . From these observations, we derived empirical lunar surface solar phase functions for both the highlands and maria that can be used for a wide range of applications. The functions can be used to correct for the effects of viewing geometry to produce lunar mosaics, spectra, and quick-look products for future lunar missions and ground-based observations. Our methodology can be used for a wide range of objects for which multiply scattered radiation is not significant, including all but the very brightest asteroids and moons.

Planetary Sciences↗
NASA NTRS2014

Satellite Ocean Color Sensor Design Concepts and Performance Requirements

In late 1978, the National Aeronautics and Space Administration (NASA) launched the Nimbus-7 satellite with the Coastal Zone Color Scanner (CZCS) and several other sensors, all of which provided major advances in Earth remote sensing. The inspiration for the CZCS is usually attributed to an article in Science by Clarke et al. who demonstrated that large changes in open ocean spectral reflectance are correlated to chlorophyll-a concentrations. Chlorophyll-a is the primary photosynthetic pigment in green plants (marine and terrestrial) and is used in estimating primary production, i.e., the amount of carbon fixed into organic matter during photosynthesis. Thus, accurate estimates of global and regional primary production are key to studies of the earth's carbon cycle. Because the investigators used an airborne radiometer, they were able to demonstrate the increased radiance contribution of the atmosphere with altitude that would be a major issue for spaceborne measurements. Since 1978, there has been much progress in satellite ocean color remote sensing such that the technique is well established and is used for climate change science and routine operational environmental monitoring. Also, the science objectives and accompanying methodologies have expanded and evolved through a succession of global missions, e.g., the Ocean Color and Temperature Sensor (OCTS), the Seaviewing Wide Field-of-view Sensor (SeaWiFS), the Moderate Resolution Imaging Spectroradiometer (MODIS), the Medium Resolution Imaging Spectrometer (MERIS), and the Global Imager (GLI). With each advance in science objectives, new and more stringent requirements for sensor capabilities (e.g., spectral coverage) and performance (e.g., signal-to-noise ratio, SNR) are established. The CZCS had four bands for chlorophyll and aerosol corrections. The Ocean Color Imager (OCI) recommended for the NASA Pre-Aerosol, Cloud, and Ocean Ecosystems (PACE) mission includes 5 nanometers hyperspectral coverage from 350 to 800 nanometers with three additional discrete near infrared (NIR) and shortwave infrared (SWIR) ocean aerosol correction bands. Also, to avoid drift in sensor sensitivity from being interpreted as environmental change, climate change research requires rigorous monitoring of sensor stability. For SeaWiFS, monthly lunar imaging accurately tracked stability at an accuracy of approximately 0.1% that allowed the data to be used for climate studies [2]. It is now acknowledged by the international community that future missions and sensor designs need to accommodate lunar calibrations. An overview of ocean color remote sensing and a review of the progress made in ocean color remote sensing and the variety of research applications derived from global satellite ocean color data are provided. The purpose of this chapter is to discuss the design options for ocean color satellite radiometers, performance and testing criteria, and sensor components (optics, detectors, electronics, etc.) that must be integrated into an instrument concept. These ultimately dictate the quality and quantity of data that can be delivered as a trade against mission cost. Historically, science and sensor technology have advanced in a "leap-frog" manner in that sensor design requirements for a mission are defined many years before a sensor is launched and by the end of the mission, perhaps 15-20 years later, science applications and requirements are well beyond the capabilities of the sensor. Section 3 provides a summary of historical mission science objectives and sensor requirements. This progression is expected to continue in the future as long as sensor costs can be constrained to affordable levels and still allow the incorporation of new technologies without incurring unacceptable risk to mission success. The IOCCG Report Number 13 discusses future ocean biology mission Level-1 requirements in depth.

Ocean Color↗
NASA NTRS2020

Analysis of the on-orbit Response-Versus-Scan-angle for the MODIS SWIR Bands Derived from Lunar Observations

The Moderate Resolution Imaging Spectroradiometer (MODIS) on board the Terra and Aqua platforms is a multi-spectral, whiskbroom scanning radiometer with 36 spectral bands covering wavelengths from 0:4 - 14:2 μm. Among these bands, the 20 reflective solar bands (RSB, 0:4 - 2:1 μm) use an on-board solar difuser (SD) and SD stability monitor (SDSM) to track the detector gain changes on orbit. In addition to this, lunar and Earth-view (EV) observations are used in order to characterize the scan-mirror response versus scan angle (RVS), which improves the Earth-view retrieval over the full width of each scan. For the short-wave infrared bands (SWIR, 1:2 - 2:1 μm), the prelaunch RVS has been used for both Aqua and Terra MODIS throughout each mission. While these bands are not expected to have a significant change in the RVS on-orbit, issues such as electronic crosstalk and an out-of-band optical leak have prevented the use of the Moon for deriving the on-orbit RVS for validation. However, recent improvements to the MODIS lunar calibration for the SWIR bands allow us to mitigate the electronic crosstalk impact and derive the RVS for the SWIR bands. In this work, we will assess the impact of this newly derived RVS on the EV data compared to MODIS Collection 6.1. By comparing to EV data obtained from pseudo-invariant calibration sites at different angles-of-incidence on the scan mirror, we can assess the effectiveness of the newly derived RVS from the Moon. We find that while the change in the RVS on-orbit for the SWIR bands is relatively small, applying a correction to the RVS based on the Moon and SD data can provide an improvement for some bands.

MODIS↗
NASA NTRS1973

Absolute calibration of Apollo lunar orbital mass spectrometer.

Recent experiments were conducted in Langley Research Center's molecular beam system to perform an absolute calibration of the lunar orbital mass spectrometer which was flown on the Apollo 15 and 16 missions. Tests were performed with several models of the instrument using two test gases, argon and neon, in the 1 ntorr to .1 picotorr range. Sensitivity to argon at spacecraft orbital velocity was .00028 A/torr enabling partial pressures in the .01-picotorr range to be measured at the spacecraft altitude. Neon sensitivity was nearly a factor of 5 less. Test data support the feasibility of using the lunar orbital mass spectrometer as a tool to gather information about the lunar atmosphere.

Yeager, P. R.↗
NASA NTRS2016

A Comparison of Radiometric Calibration Techniques for Lunar Impact Flashes

Video observations of lunar impact flashes have been made by a number of researchers since the late 1990's and the problem of determination of the impact energies has been approached in different ways (Bellot Rubio, et al., 2000 [1], Bouley, et al., 2012.[2], Suggs, et al. 2014 [3], Rembold and Ryan 2015 [4], Ortiz, et al. 2015 [5]). The wide spectral response of the unfiltered video cameras in use for all published measurements necessitates color correction for the standard filter magnitudes available for the comparison stars. An estimate of the color of the impact flash is also needed to correct it to the chosen passband. Magnitudes corrected to standard filters are then used to determine the luminous energy in the filter passband according to the stellar atmosphere calibrations of Bessell et al., 1998 [6]. Figure 1 illustrates the problem. The camera pass band is the wide black curve and the blue, green, red, and magenta curves show the band passes of the Johnson-Cousins B, V, R, and I filters for which we have calibration star magnitudes. The blackbody curve of an impact flash of temperature 2800K (Nemtchinov, et al., 1998 [7]) is the dashed line. This paper compares the various photometric calibration techniques and how they address the color corrections necessary for the calculation of luminous energy (radiometry) of impact flashes. This issue has significant implications for determination of luminous efficiency, predictions of impact crater sizes for observed flashes, and the flux of meteoroids in the 10s of grams to kilogram size range.

Suggs, R.↗