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Crisp, David

Publications and source records attributed to Crisp, David.

At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

Earth as an Extrasolar Planet: Earth Model Validation Using EPOXI Earth Observations

The EPOXI Discovery Mission of Opportunity reused the Deep Impact flyby spacecraft to obtain spatially and temporally resolved visible photometric and moderate resolution near-infrared (NIR) spectroscopic observations of Earth. These remote observations provide a rigorous validation of whole disk Earth model simulations used to better under- stand remotely detectable extrasolar planet characteristics. We have used these data to upgrade, correct, and validate the NASA Astrobiology Institute s Virtual Planetary Laboratory three-dimensional line-by-line, multiple-scattering spectral Earth model (Tinetti et al., 2006a,b). This comprehensive model now includes specular reflectance from the ocean and explicitly includes atmospheric effects such as Rayleigh scattering, gas absorption, and temperature structure. We have used this model to generate spatially and temporally resolved synthetic spectra and images of Earth for the dates of EPOXI observation. Model parameters were varied to yield an optimum fit to the data. We found that a minimum spatial resolution of approx.100 pixels on the visible disk, and four categories of water clouds, which were defined using observed cloud positions and optical thicknesses, were needed to yield acceptable fits. The validated model provides a simultaneous fit to the Earth s lightcurve, absolute brightness, and spectral data, with a root-mean-square error of typically less than 3% for the multiwavelength lightcurves, and residuals of approx.10% for the absolute brightness throughout the visible and NIR spectral range. We extend our validation into the mid-infrared by comparing the model to high spectral resolution observations of Earth from the Atmospheric Infrared Sounder, obtaining a fit with residuals of approx.7%, and temperature errors of less than 1K in the atmospheric window. For the purpose of understanding the observable characteristics of the distant Earth at arbitrary viewing geometry and observing cadence, our validated forward model can be used to simulate Earth s time dependent brightness and spectral properties for wavelengths from the far ultraviolet to the far infrared.brightness

Robinson, Tyler D.↗
NASA NTRS2008

Opportunities for Coordinated Observations of CO2 with the Orbiting Carbon Observatory (OCO) and Greenhouse Gases Observing Satellite (GOSAT)

The Orbiting Carbon Observatory (OCO) and the Greenhouse Gases Observing Satellite (GOSAT) are the first two satellites designed to make global measurements of atmospheric carbon dioxide (CO2) with the precision and sampling needed identify and monitor surface sources and sinks of this important greenhouse gas. Because the operational phases of the OCO and GOSAT missions overlap in time, there are numerous opportunities for comparing and combining the data from these two satellites to improve our understanding of the natural processes and human activities that control the atmospheric CO2 and it variability over time. Opportunities for cross-calibration, cross-validation, and coordinated observations that are currently under consideration are summarized here.

climate↗
NASA NTRS2008

The NASA Orbiting Carbon Observatory (OCO) Mission: Objectives, Approach, and Status

The Orbiting Carbon Observatory (OCO) is a NASA Earth System Science Pathfinder (ESSP) mission that is currently under development at the Jet Propulsion Laboratory (JPL). OCO will make global, space-based measurements of atmospheric carbon dioxide (CO2) with the precision, resolution, and coverage needed to characterize regional-scale sources and sinks of this important greenhouse gas. The observatory consists of a dedicated spacecraft bus that carries a single instrument. The bus employs single-string version of Orbital Sciences Corporation (OSC) LEOStar-2 architecture. This 3-axis stabilized bus includes a propulsion system for orbit insertion and maintenance, provides power, points the instrument, receives and processes commands from the ground, and records, stores, and downlinks science and engineering data. The OCO instrument incorporates 3 oboresighted, high resolution grating spectrometers that will make coincident measurements of reflected sunlight in near-infrared CO2 and molecular oxygen (O2) bands. The instrument was designed and manufactured by Hamilton Sundstrand (Pomona, CA), and then integrated, flight qualified, and calibrated by JPL. It is scheduled for delivery to OSC (Dulles, VA) for integration with the spacecraft bus in the spring of 2008. OCO will be launched from the Vandenberg Air Force Base on a dedicated OSC Taurus XL launch vehicle in December 2008. It will fly in formation with the Earth Observing System Afternoon Constellation, a group of satellites that files in a 98.8 minute, 705 km altitude, sun-synchronous orbit. This orbit provides coverage of the sunlit hemisphere with a 16-day ground track repeat cycle. OCO will fly approx.4 minutes ahead of the EOS Aqua platform, with an ascending nodal crossing time of approx.1:26 PM. The OCO science data will be transmitted to the NASA Ground Network Stations in Alaska and Virginia, and then transferred to the OCO Ground Data System at JPL. There, the CO2 and O2 spectra will be analyzed by the OCO Science Team to provide spatially resolved estimates of the column-averaged CO2 dry air mole fraction, XCO2. These measurements are expected to improve our understanding of the nature and processes that regulate atmospheric CO2 enabling more reliable forecasts of CO2 buildup and its impact on climate change.

global measurements↗
NASA NTRS2006

The Orbiting Carbon Observatory: Mission Overview

OCO will acquire the space-based data needed to identify CO2 sources and sinks and quantify their variability over the seasonal cycle. Approach: a) Collect spatially resolved, high resolution spectroscopic observations of CO2 and O2 absorption in reflected sunlight; b) Use these data to resolve spatial and temporal variations in the column averaged CO2 dry air mole fraction, X cub CO2) over the sunlit hemisphere; and c) Employ independent calibration and validation approaches to produce X(sub CO2) estimates with random errors and biases no larger than 1-2 ppm (0.3-0.5%) on regional scales at monthly intervals.

CO2↗
NASA NTRS2006

The NASA Orbiting Carbon Observatory

Accurate forecasting of future climate requires an improved understanding of the global carbon cycle and its interaction with the Earth System OCO and GOSAT will make the first space-based measurements of CO2 with the accuracy needed to quantify sources and sinks of this important greenhouse gas. Continuing Cooperation between the OCO and GOSAT teams will improve the value of both missions to the science community.

Orbiting Carbon Obervatory (OCO) mission↗
NASA NTRS2006

The Orbiting Carbon Observatory: Sampling Approach and Anticipated Data Products

This viewgraph presentation reviews the mission and the architecture of NASA's Orbiting Carbon Observatory (OCO). It also discusses the method of making precise measurements of CO2 from space. Due to be launched in September of 2008, the OCO will fly 12 minutes ahead of the EOS Aqua platform in the Earth Observing System (EOS) Afternoon Constellation (A-Train). The OCO's mission is to identify the sources and sinks for atmospheric CO2.

CO2↗
NASA NTRS2006

Monitoring CO2 sources and sinks from space : the Orbiting Carbon Observatory (OCO) Mission

NASA's Orbiting Carbon Observatory (OCO) will make the first space-based measurements of atmospheric carbon dioxide (CO2) with the precision, resolution, and coverage needed to characterize the geographic distribution of CO2 sources and sinks and quantify their variability over the seasonal cycle. OCO is currently scheduled for launch in 2008. The observatory will carry a single instrument that incorporates three high-resolution grating spectrometers designed to measure the near-infrared absorption by CO2 and molecular oxygen (O2) in reflected sunlight. OCO will fly 12 minutes ahead of the EOS Aqua platform in the Earth Observing System (EOS) Afternoon Constellation (A-Train). The in-strument will collect 12 to 24 soundings per second as the Observatory moves along its orbit track on the day side of the Earth. A small sampling footprint (<3 km2 at nadir) was adopted to reduce biases in each sounding associated with clouds and aerosols and spatial variations in surface topography. A comprehensive ground-based validation program will be used to assess random errors and biases in the XCO2 product on regional to continental scales. Measurements collected by OCO will be assimilated with other environmental measurements to retrieve surface sources and sinks of CO2. This information could play an important role in monitoring the integrity of large scale CO2 sequestration projects.

carbon dioxide sources and sinks↗
NASA NTRS2005

Disk-averaged synthetic spectra of Mars

The principal goal of the NASA Terrestrial Planet Finder (TPF) and European Space Agency's Darwin mission concepts is to directly detect and characterize extrasolar terrestrial (Earthsized) planets. This first generation of instruments is expected to provide disk-averaged spectra with modest spectral resolution and signal-to-noise. Here we use a spatially and spectrally resolved model of a Mars-like planet to study the detectability of a planet's surface and atmospheric properties from disk-averaged spectra. We explore the detectability as a function of spectral resolution and wavelength range, for both the proposed visible coronograph (TPFC) and mid-infrared interferometer (TPF-I/Darwin) architectures. At the core of our model is a spectrum-resolving (line-by-line) atmospheric/surface radiative transfer model. This model uses observational data as input to generate a database of spatially resolved synthetic spectra for a range of illumination conditions and viewing geometries. The model was validated against spectra recorded by the Mars Global Surveyor-Thermal Emission Spectrometer and the Mariner 9-Infrared Interferometer Spectrometer. Results presented here include disk-averaged synthetic spectra, light curves, and the spectral variability at visible and mid-infrared wavelengths for Mars as a function of viewing angle, illumination, and season. We also considered the differences in the spectral appearance of an increasingly ice-covered Mars, as a function of spectral resolution, signal-to-noise and integration time for both TPF-C and TPFI/ Darwin.

Mars↗
NASA NTRS2005

The current development status of the Orbiting Carbon Observatory (OCO) instrument optical design

The status of the OCO instrument optical design is presented in this paper. The optical bench assembly comprises three cooled grating spectrometers coupled to an all-reflective telescope/relay system. Dichroic beam splitters are used to separate the light from a common telescope into the three spectral bands. The three bore sighted spectrometers allow the total column CO2 absorption path to be corrected for optical path and surface pressure uncertainties, aerosols, and water vapor. The design of the instrument is based on classic flight proven technologies.

global carb↗
NASA NTRS2005

In-situ exploration of Venus on a global scale : direct measurements of origins and evolution, meterology, dynamics, and chemistry by a long-duration aerial science station

Drifting in the strong winds of Venus under benign Earth-like temperature and pressure conditions, an instrumented balloon-borne science station presents a viable means to explore, in-situ, the Venusian atmosphere on a global scale. Flying over the ground at speeds exceeding 240 km/hour while floating in the Venusian skies near 55 km altitude for several weeks, such an aerostat can conduct a 'world tour' of our neighboring planet, as it circumnavigates the globe multiple times during its flight from equatorial to polar latitudes. Onboard science sensors can repeatedly and directly sample gas compositions, atmospheric pressures and temperatures and cloud particle properties, giving unprecedented insight into the chemical processes occurring within the sulfuric clouds. Additionally, interferometric tracking via Earth-based radio observatories can yield positions and windspeeds to better than 10 cm/sec over one-hour periods, providing important information for understanding the planet's meridional circulation and enigmatic zonal super-rotation, as well as local dynamics associated with meteorological processes. As well, hundreds of GCMS spectra collected during the flight can provide measurements of noble gas compositions and their isotopes with unprecedented accuracy, thereby enabling fundamental new insights into Venus's origin and evolution.

Venus↗
NASA NTRS2005

A Network of Geophysical Observatories for Mars

For the past 30 years there has been a strong consensus within the international scientific community in favor of sending a network of geophysical landers to Mars to characterize the near-surface weather and climate, determine the large-scale atmospheric dynamics and explore the interior structure and composition. Despite this scientific support, there has been an unbroken string of proposed missions over the past fifteen years which have failed for programmatic reasons to progress beyond the design stage (Mars Network Mission, MESUR, Marsnet, InterMarsnet, NetLander). In this presentation, we review the scientific rationale and technical requirements for such a mission, and discuss current activities aimed toward its implementation.

Banerdt, W. Bruce↗
NASA NTRS2003

The Earth System Science Pathfinder Orbiting Carbon Observatory (OCO) Mission

A viewgraph presentation describing the Earth System Science Pathfinder Orbiting Carbon Observatory (OCO) Mission is shown. The contents include: 1) Why CO2?; 2) What Processes Control CO2 Sinks?; 3) OCO Science Team; 4) Space-Based Measurements of CO2; 5) Driving Requirement: Precise, Bias-Free Global Measurements; 6) Making Precise CO2 Measurements from Space; 7) OCO Spatial Sampling Strategy; 8) OCO Observing Modes; 9) Implementation Approach; 10) The OCO Instrument; 11) The OCO Spacecraft; 12) OCO Will Fly in the A-Train; 13) Validation Program Ensures Accuracy and Minimizes Spatially Coherent Biases; 14) Can OCO Provide the Required Precision?; 15) O2 Column Retrievals with Ground-based FTS; 16) X(sub CO2) Retrieval Simulations; 17) Impact of Albedo and Aerosol Uncertainty on X(sub CO2) Retrievals; 18) Carbon Cycle Modeling Studies: Seasonal Cycle; 19) Carbon Cycle Modeling Studies: The North-South Gradient in CO2; 20) Carbon Cycle Modeling Studies: Effect of Diurnal Biases; 21) Project Status and Schedule; and 22) Summary.

carbon cycles↗