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NASA NTRS2014

Performance Simulations for a Spaceborne Methane Lidar Mission

Future spaceborne lidar measurements of key anthropogenic greenhouse gases are expected to close current observational gaps particularly over remote, polar, and aerosol-contaminated regions, where actual in situ and passive remote sensing observation techniques have difficulties. For methane, a "Methane Remote Lidar Mission" was proposed by Deutsches Zentrum fuer Luft- und Raumfahrt and Centre National d'Etudes Spatiales in the frame of a German-French climate monitoring initiative. Simulations assess the performance of this mission with the help of Moderate Resolution Imaging Spectroradiometer and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations of the earth's surface albedo and atmospheric optical depth. These are key environmental parameters for integrated path differential absorption lidar which uses the surface backscatter to measure the total atmospheric methane column. Results showthat a lidar with an average optical power of 0.45W at 1.6 μm wavelength and a telescope diameter of 0.55 m, installed on a low Earth orbit platform(506 km), will measure methane columns at precisions of 1.2%, 1.7%, and 2.1% over land, water, and snow or ice surfaces, respectively, for monthly aggregated measurement samples within areas of 50 × 50 km2. Globally, the mean precision for the simulated year 2007 is 1.6%, with a standard deviation of 0.7%. At high latitudes, a lower reflectance due to snow and ice is compensated by denser measurements, owing to the orbital pattern. Over key methane source regions such as densely populated areas, boreal and tropical wetlands, or permafrost, our simulations show that the measurement precision will be between 1 and 2%.

methane↗

NASA NTRS1974

A parameterization for the absorption of solar radiation in the earth's atmosphere

A method is described for rapidly computing the amount of solar energy absorbed at the earth's surface and in the atmosphere as a function of altitude. The method is a parametric treatment, but the form of the solution and the coefficients involved are based on accurate multiple-scattering computations. In this treatment the absorption varies with the amount and type of clouds, the humidity, the zenith angle of the sun, and the albedo of the earth's surface. Within the stratosphere the absorption also depends on the vertical distribution of ozone. This parameterization for solar radiation is being used in current versions of the global atmospheric circulation model developed at the Goddard Institute for Space Studies.

Lacis, A. A.↗

NASA NTRS2005

Earth-Image Tracking in the IR for Deep Space Optical Communications

Sub-microradian level laser beam pointing to an Earth-based receiver is required for deep space optical communications. This requires a beacon emanated from Earth towards the spacecraft. The beacon could be a laser or reflected sunlight from Earth. Earth image tracking in the visible is hampered by significant albedo variations and/or crescent Earth image yielding large central errors. Here, we report results of Earth-image tracking in the infrared (8 to 13 micron) region of the spectrum with the aim of substantially alleviating the two challenges mentioned earlier.

earth image tracking↗

NASA NTRS1988

Study of the effect of cloud inhomogeneity on the earth radiation budget experiment

The Earth Radiation Budget Experiment (ERBE) is the most recent and probably the most intensive mission designed to gather precise measurements of the Earth's radiation components. The data obtained from ERBE is of great importance for future climatological studies. A statistical study reveals that the ERBE scanner data are highly correlated and that instantaneous measurements corresponding to neighboring pixels contain almost the same information. Analyzing only a fraction of the data set when sampling is suggested and applications of this strategy are given in the calculation of the albedo of the Earth and of the cloud-forcing over ocean.

Smith, Phillip J.↗

NASA NTRS1963

Earth Reflected Solar Radiation Incident upon an Arbitrarily Oriented Spinning Flat Plate

A general derivation is given for the earth reflected solar radiation input to a flat plate--a solar cell paddle, for example--which is spinning about an axis coincident with the axis of symmetry of the satellite to which it is affixed. The resulting equations are written for the general case so that arbitrary orientations of the spin axis with respect to the earth-satellite line and arbitrary orientations of the normal to the plate with respect to the spin axis can be treated. No attempt is made to perform the resulting integrations because of the complexity of the equations; nor is there any attempt to delineate the integration limits for the general case. However, the equations governing these limits are given. The appendixes contain: the results, in graphical form, of two representative examples; the general computer program for the calculation is given in Fortran notation; and the results of a calculation of the distribution of albedo energy on the proposed Echo II satellite. The value of the mean solar constant used is 1.395 times 10 (sup 4) ergs per centimeters-squared per second; the mean albedo of the earth is assumed to be 0.34; and the earth is assumed to be a diffuse reflector.

SOLAR RADIATION↗

NASA NTRS2011

Investigation of Seasonal Landscape Freeze/Thaw Cycles in Relation to Cloud Structure in the High Northern Latitudes

The seasonal freezing and thawing of Earth's cryosphere (the portion of Earth's surface permanently or seasonally frozen) has an immense impact on Earth's climate as well as on its water, carbon and energy cycles. During the spring, snowmelt and the transition between frozen and non-frozen states lowers Earth's surface albedo. This change in albedo causes more solar radiation to be absorbed by the land surface, raising surface soil and air temperatures as much as 5 C within a few days. The transition of ice into liquid water not only raises the surface humidity, but also greatly affects the energy exchange between the land surface and the atmosphere as the phase change creates a latent energy dominated system. There is strong evidence to suggest that the thawing of the cryosphere during spring and refreezing during autumn is correlated to local atmospheric conditions such as cloud structure and frequency. Understanding the influence of land surface freeze/thaw cycles on atmospheric structure can help improve our understanding of links between seasonal land surface state and weather and climate, providing insight into associated changes in Earth's water, carbon, and energy cycles that are driven by climate change.Information on both the freeze/thaw states of Earth's land surface and cloud characteristics is derived from data sets collected by NOAA's Special Sensor Microwave/Imager (SSM/I), the Advanced Microwave Scanning Radiometer on NASA's Earth Observing System(AMSR-E), NASA's CloudSat, and NASA's SeaWinds-on-QuickSCAT Earth remote sensing satellite instruments. These instruments take advantage of the microwave spectrum to collect an ensemble of atmospheric and land surface data. Our analysis uses data from radars (active instruments which transmit a microwave signal toward Earth and measure the resultant backscatter) and radiometers (passive devices which measure Earth's natural microwave emission) to accurately characterize salient details on Earth's surface and atmospheric states. By comparing the cloud measurements and the surface freeze-thaw data sets, a correlation between the two phenomena can be developed.

clouds↗

NASA NTRS2024

Optimized bandpasses for the Habitable Worlds Observatory's exoEarth survey

A primary scientific goal of the future Habitable Worlds Observatory will be the direct detection and characterization of Earth-like planets. Estimates of the exoplanet yields for this concept will help guide mission design through detailed trade studies. It is therefore critical that yield estimation codes optimally adapt observations to the mission’s performance parameters to ensure accurate trade studies. To aid in this, we implement wavelength optimization in yield calculations for the first time, allowing the yield code to determine the ideal detection and characterization bandpasses. We use this capability to confirm the observational wavelength assumptions made for the large UV/Optical/IR surveyor, design B (LUVOIR-B) study, namely that the optimum detection wavelength is 500 nm for the majority of targets and the optimum wavelength to detect water is near 1000 nm, given LUVOIR-B’s assumed instrument performance parameters. We show that including the wavelength-dependent albedo of an Earth twin as a prior provides no significant benefit to the yields of exoEarth candidates and caution against tuning observations to modern Earth twins. We also show that coronagraphs whose inner working angles are similar to step functions may benefit from wavelength optimization and demonstrate how wavelength-dependent instrument performance can impact the optimum wavelengths for detection and characterization. The optimization methods we implement automate wavelength selection and remove uncertainties regarding these choices, helping to adapt the observations to the instrument’s performance parameters.

telescopes↗

NASA NTRS2000

Satellite Mapping of the Earth's Ozone and Sulfur Dioxide

The Total Ozone Mapping Spectrometer (TOMS) instruments are spatially-scanning UV spectrometers that have produced daily global images of total ozone over the last 21 years since the launch of the Nimbus 7 satellite. The instruments use a total ozone retrieval algorithm pioneered by J.V. Dave and C. L. Mateer for the Nimbus 4 Backscatter Ultraviolet (BUV) instrument, designed by D.F. Heath. The TOMS ozone maps have revealed the relations between total ozone and atmospheric dynamics, and shown the dramatic losses of ozone in the Antarctic ozone hole and the Northern hemisphere. The accepted long-term trends in global, regional, and local ozone are derived from data from the Nimbus 7 TOMS and three successive TOMS flights on Russian, Japanese, and American satellites. The next TOMS flight will be launched in 2000. The contiguous mapping design and fortuitous choice of TOMS wavelengths bands also permitted imaging of a second atmospheric gas, sulfur dioxide, which is transient due to its short lifetime. The importance of this measurement was first realized after the eruption of El Chichon volcano in 1982. The extreme range of sizes of volcanic eruptions and the 'associated danger require observations from a distant observing platform. The first quantitative time series of the input of sulfur dioxide by explosive volcanic eruptions into the atmosphere thus was developed from the TOMS missions. Finally, the Rayleigh and aerosol scattering spectral characteristic and reflectivity complete the four dominant pieces of information in the near UV albedo of the Earth. The four parameters are derived with a linear algorithm, the absorption coefficients of the gases, and effective paths computed from radiative transfer tables. Absorbing aerosol clouds (smoke, dust, volcanic ash) are readily identified by their deviation from a Rayleigh signature. The greatest shortcoming of the TOMS dataset is the 24 hour time resolution that is produced by the polar orbit of the satellite. Dynamic phenomena, such as upper air fronts that modulate total ozone and volcanic eruptions of sulfur dioxide and ash, cannot be adequately resolved. It is hoped that UV observations from geostationary satellites will soon be made to test the value of this unique information in weather forecasting and aviation safety.

Krueger, Arlin↗

NASA NTRS2000

Satellite Mapping of the Earth's Ozone and Sulfur Dioxide

The Total Ozone Mapping Spectrometer (TOMS) instruments are spatially-scanning UV spectrometers that have produced daily global images of total ozone over the last 21 years since the launch of the Nimbus 7 satellite. The instruments use a total ozone retrieval algorithm pioneered by J.V. Dave and C. L. Mateer for the Nimbus 4 Backscatter Ultraviolet (BUV) instrument, designed by D.F. Heath. The TOMS ozone maps have revealed the relations between total ozone and atmospheric dynamics, and shown the dramatic losses of ozone in the Antarctic ozone hole and the Northern hemisphere. The accepted long-term trends in global, regional, and local ozone are derived from data from the Nimbus 7 TOMS and three successive TOMS flights on Russian, Japanese, and American satellites. The next TOMS flight will be launched in 2000. The contiguous mapping design and fortuitous choice of TOMS wavelengths bands also permitted imaging of a second atmospheric gas, sulfur dioxide, which is transient due to its short lifetime. The importance of this measurement was first realized after the eruption of El Chichon volcano in 1982. The extreme range of sizes of volcanic eruptions and the associated danger require observations from a distant observing platform. The first quantitative time series of the input of sulfur dioxide by explosive volcanic eruptions into the atmosphere thus was developed from the TOMS missions. Finally, the Rayleigh and aerosol scattering spectral characteristic and reflectivity complete the four dominant pieces of information in the near UV albedo of the Earth. The four parameters are derived with a linear algorithm, the absorption coefficients of the gases, and effective paths computed from radiative transfer tables. Absorbing aerosol clouds (smoke, dust, volcanic ash) are readily identified by their deviation from a Rayleigh signature. The greatest shortcoming of the TOMS dataset is the 24 hour time resolution that is produced by the polar orbit of the satellite. Dynamic phenomena, such as upper air fronts that modulate total ozone and volcanic eruptions of sulfur dioxide and ash, cannot be adequately resolved. It is hoped that UV observations from geostationary satellites will soon be made to test the value of this unique information in weather forecasting and aviation safety.

Krueger, Arlin↗

NASA NTRS1982

A parameterized model for global insolation under partially cloudy skies

A simple and efficient parameterization of insolation under partially cloudy skies is discussed and compared with a set of exact radiative transfer results for clear skies, an empirical equation and observations. The parameterization is physically based and requires, as input variables, the ozone path length, precipitable water, Angstrom turbidity, surface air pressure and albedo, fractional cloud-cover and cloud thickness. Multiple reflection between the surface and the overlying atmosphere, and clouds are considered. The albedo of the earth-atmosphere system is also formulated and compared with a set of exact radiative transfer results. As compared to the exact radiative transfer results, the errors in the insolations are generally less than 1 percent, and in the albedo of the earth-atmosphere system less than 10 percent. The errors in the calculated insolations using climatological data are 2-3 percent when compared with many years averaged observations at Maudheim (Antarctica) and at Rockville (U.S.A.). A parametric equation for calculating directly the daily total insolation is also given.

Choudhury, B.↗

NASA NTRS1973

LAGEOS mission analyses

Two error sources are found to be compatible and significant for the parameters affecting the LAGEOS mission. The first error source is the uncertainty in the gravity model, and the second error source is the radiation pressure which includes direct radiation, albedo radiation, and earth shine. Retrograde orbits increase the number of passes per day over the tracking stations at the expense of also increasing the number of time gaps when no station is observing. It is shown that relativistic effects are significant and must be included in orbit computation and determination systems for this mission. If station locations are known only to one meter, the error in the satellite orbits is comparable with solar pressure induced errors.

Squires, R. K.↗

NASA NTRS1975

Apollo 17 mission Report. Supplement 6: Calibration results for gamma ray spectrometer sodium iodide crystal

A major difficulty in medium energy gamma-ray remote sensing spectroscopy and astronomy measurements was the high rate of unwanted background resulting from the following major sources: (1) prompt secondary gamma-rays produced by cosmic-ray interactions in satellite materials; (2) direct charged-particle counts; (3) radioactivity induced in the detector materials by cosmic-ray and trapped protons; (4) radioactivity induced in detector materials by the planetary (e.g., earth or moon) albedo neutron flux; (5) radioactivity induced in the detector materials by the interaction of secondary neutrons produced throughout the spacecraft by cosmic-ray and trapped proton interactions; (6) radioactivity induced in spacecraft materials by the mechanisms outlined in 3, 4, and 5; and (7) natural radioactivity in spacecraft and detector materials. The purpose of this experiment was to obtain information on effects 3, 4, and 5, and from this information start developing calculational methods for predicting the background induced in the crystal detector in order to correct the Apollo gamma-ray spectrometer data for this interference.

Dyer, C.↗

NASA NTRS1980

Scattering by nonspherical particles of size comparable to wavelength - A new semi-empirical theory and its application to tropospheric aerosols

A semiempirical theory is developed which is based on simple physical principles and comparisons with laboratory measurements. The ultimate utility of this approach rests on its ability to successfully reproduce the observed single-scattering phase function for a wide variety of particle shapes, sizes and refractive indices. This approximate theory is developed for evaluating the interaction of randomly oriented, nonspherical particles with the total intensity component of electromagnetic radiation. Mie theory is used when the particle size parameter x (ratio of particle circumference to wavelength) is less than some upper bound x sub zero (about 5). For x greater than x sub zero, the interaction is divided into three components: diffraction, external reflection and transmission. The application of the theory is illustrated by considering the influence of the shape of tropospheric aerosols on their contribution to the earth's global albedo.

Pollack, J. B.↗

NASA NTRS1999

Validation of Landsat-7 ETM+ MEM Thermal Improvement in Thermal Vacuum Tests and in Flight Due to Lower Louver Set Points

The Enhanced Thematic Mapper Plus (ETM+) Main Electronics Module (MEM) power supply heat sink temperature is critical to the Landsat-7 mission. It is strongly dependent on the thermal louver design. A lower power supply heat sink temperature increases the reliability of the MEM, and reduces the risk of over heating and thermal shut-down. After the power supply failures in ETM+ instrument thermal vacuum tests #1 and #2, the author performed detailed thermal analyses of the MEM, and proposed to reduce the louver set-points by 7C. At the 1998 Intersociety Energy Conversion Engineering Conference (IECEC), the author presented a paper that included results of thermal analysis of the MEM. It showed that a 70C reduction of the louver set points could reduce the maximum power supply heat sink temperature in thermal vacuum test and in flight to below 20"C in the cooler outgas mode and in the nominal imaging mode, and has no significant impact on the standby heater duty cycle. It also showed that the effect of Earth infrared and albedo on the power supply heat sink temperature is small. The louver set point reduction was implemented in June 1998, just prior to ETM+ thermal vacuum test #3. Results of the thermal vacuum tests, and temperature data in flight validate the MEM thermal performance improvement due to the 70C reduction of the louver set points.

Choi, Michael K.↗

NASA NTRS1960

Thermal Irradiation of an Earth Satellite

The radiations that significantly affect the thermal balance of an earth satellite are: (1) Direct solar radiation. (2) Solar radiation reflected from the earth. (3) Thermal radiation from the earth. The total energy and the spectrum of the direct solar radiation are known to adequate accuracy. The solar radiation reflected from the earth is known with considerably less certainty. The earth's average albedo is about 35 percent. Different latitudes, however, have average albedos above or below this value. Furthermore, there is considerable variation with time and place, since the reflectance of solar radiation is determined by the sun's elevation angle, the nature of the terrain (desert, forest, snow, water, etc.) and the weather (absolute humidity, cloudiness, height and nature of clouds, etc.). Accordingly, it would be desirable to have statistically reasonable upper and lower limits for the reflected solar radiation for use in thermal-balance design studies.

Katzoff, S.↗

NASA NTRS1994

Aerosol Effects on Radiation and Climate: Column Closure Experiments with Towers, Aircraft, and Satellites

Many theoretical studies have shown that anthropogenic aerosol particles can change the radiation balance in an atmospheric column and might thereby exert a significant effect on the Earth's climate. In particular, recent calculations have shown that sulfate particles from anthropogenic combustion may already exert a cooling influence on the Earth that partially offsets the warming caused by the greenhouse gases from the same combustion. Despite the potential climatic importance of anthropogenic aerosols, simultaneous measurements of anthropogenic aerosol properties and their effect on atmospheric radiation have been very rare. Successful comparisons of measured radiation fields with those calculated from aerosol measurements - now referred to as column closure comparisons - are required to improve the accuracy and credibility of climate predictions. This paper reviews the column closure experiment performed at the Mt. Sutro Tower in San Francisco in 1975, in which elevated radiometers measured the change in Earth-plus-atmosphere albedo caused by an aerosol layer, while a lidar, sunphotometer, nephelometer, and other radiometers measured properties of the responsible aerosol. The time-dependent albedo calculated from the measured aerosol properties agreed with that measured by the tower radiometers. Also presented are designs for future column closure studies using radiometers and aerosol instruments on the ground, aircraft, and satellites. These designs draw upon algorithms and experience developed in the Sutro Tower study, as well as more recent experience with current measurement and analysis capabilities.

Russell, Philip B.↗

NASA NTRS2002

Thermal Orbital Environmental Parameter Study on the Propulsive Small Expendable Deployer System (ProSEDS) Using Earth Radiation Budget Experiment (ERBE) Data

The natural thermal environmental parameters used on the Space Station Program (SSP 30425) were generated by the Space Environmental Effects Branch at NASA's Marshall Space Flight Center (MSFC) utilizing extensive data from the Earth Radiation Budget Experiment (ERBE), a series of satellites which measured low earth orbit (LEO) albedo and outgoing long-wave radiation. Later, this temporal data was presented as a function of averaging times and orbital inclination for use by thermal engineers in NASA Technical Memorandum TM 4527. The data was not presented in a fashion readily usable by thermal engineering modeling tools and required knowledge of the thermal time constants and infrared versus solar spectrum sensitivity of the hardware being analyzed to be used properly. Another TM was recently issued as a guideline for utilizing these environments (NASA/TM-2001-211221) with more insight into the utilization by thermal analysts. This paper gives a top-level overview of the environmental parameters presented in the TM and a study of the effects of implementing these environments on an ongoing MSFC project, the Propulsive Small Expendable Deployer System (ProSEDS), compared to conventional orbital parameters that had been historically used.

Sharp, John R.↗

NASA NTRS2003

Corrosion of Highly Specular Vapor Deposited Aluminum (VDA) on Earthshade Door Sandwich Structure

High-resolution infrared (IR) imaging requires spacecraft instrument design that is tightly coupled with overall thermal control design. The JPL Tropospheric Emission Spectrometer (TES) instrument measures the 3-dimensional distribution of ozone and its precursors in the lower atmosphere on a global scale. The TES earthshade must protect the 180-K radiator and the 230-K radiator from the Earth IR and albedo. Requirements for specularity, emissivity, and solar absorptance of inner surfaces could only be met with vapor deposited aluminum (VDA). Circumstances leading to corrosion of the VDA are described. Innovative materials and processing to meet the optical and thermal cycle requirements were developed. Examples of scanning electronmicroscope (SEM), atomic force microscope (AFM), and other surface analysis techniques used in failure analysis, problem solving, and process development are given. Materials and process selection criteria and development test results are presented in a decision matrix. Examples of conditions promoting and preventing galvanic corrosion between VDA and graphite fiber-reinforced laminates are provided.

Plaskon, Daniel↗