ation and emitted infrared radiation. Over shorter time ... radiation balance of the entire Earth, ... Pluto. 10. 0.1. 100. 0.01. 1000. 0.001. 0.0001. Pressure. (atrn) scientists. ... outweighs their absorption of infrared radiation. The study of clouds will.
Computers in Physics Looking Ahead to EOS: The Earth Observing System Jeff Dozier Citation: Computers in Physics 4, 248 (1990); doi: 10.1063/1.4822913 View online: http://dx.doi.org/10.1063/1.4822913 View Table of Contents: http://scitation.aip.org/content/aip/journal/cip/4/3?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Looking ahead Am. J. Phys. 69, 741 (2001); 10.1119/1.1381425 In‐situ data in earth observing system (EOS) AIP Conf. Proc. 283, 50 (1993); 10.1063/1.44426 CERN looks ahead Phys. Today 17, 60 (1964); 10.1063/1.3051759 Looking ahead… Phys. Today 9, 22 (1956); 10.1063/1.3059775 Looking Ahead Phys. Today 7, 30 (1954); 10.1063/1.3061454
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Looking Ahead to EOS: The Earth Observing System Jeff Dozier
NASA prepares to handle a greater volume of data than that generated by all previous Earth-observing satellites combined lthough the Earth has been changing for millions of years, dramatic recent changes such as ozone depletion above Antarctica and increased atmospheric carbon dioxide demonstrate that human activities cause acceleration in the rate of change. It is difficult to predict the long-term effects of documented changes in atmospheric gases, however, because our understanding of the causes of natural variability is so poor. Data from Greenland ice cores, for example, show several episodes where climate and CO2 concentration seem to have changed by more than half of the full glacial-interglacial difference over a few decades, yet such rapid changes seem to be absent from Antarctic ice. Natural variability most affects mankind through variation in the hydrologic cycle. Changes in precipitation, evapotranspiration, and runoff, rather than changes in air temperature, most affect people. What is
A
Jeff Dozier is a Professor of Geography at the University of California, Santa Barbara and chairs the Science Advisory Panel for EOS Data and Information.
worrisome about projected global warming is the uncertainty about future precipitation patterns. If we had confidence that most of the details in current climate simulations were right, we could plan for the 21st century with recommendations about where to build reservoirs, where farming practices need to be modified, and so forth. But climate models do not account for precipitation well, and even in a stable climate, interannual variability causes farmers to need about a century to experimentally determine what crops to grow, when to plant and how to rotate. When anthropogenic change is superimposed on natural variability, the increased uncertainty is difficult to cope with. NASA's Earth Observing System (EOS) is a pivotal part of the U.S. Global Change Research Program;' and hence of the international effort to understand global change and the increasing demands of human activity.? EOS consists of a spacebased observing system, a Data and Information System (EOSDIS), and a scientific research program. The space component will consist of two series of polar-orbiting platforms, the
first scheduled for launch in late 1997, that will collect data for 15 years. EOS will be supplemented by European and Japanese platforms and continuing operational and commercial satellites. Development of EOSDIS will begin immediately, to support research and analysis of existing data by providing investigators with timely data at a marginal cost of reproduction. Some of these experts will analyze the data to provide geophysical and biological products, which will be available in EOSDIS for use by other scientists. In this way, EOS will open the capabilities of remote sensing data to a broader range of the scientific community, who will no longer need to possess detailed knowledge of instrument characteristics and electromagnetic interactions at the surface. The scientific research program was initiated this year, with funding for 28 interdisciplinary teams, to begin development of models that will use EOS data.
EOS SCIENCE GOALS Such incompatible gases as oxygen and methane coexist in the Earth's
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MEAN SURFACE TEMPERATURE FOR JUNE 1988 USING HIRS 2 AND MSU DATA
Fig.l: Mean surface temperature for June 1988, obtained from the infrared and microwave radiometers (HIRS/MSU) aboard NOAA meteorological satellites. Increasing temperatures are represented from blue to yellow to red. (M. T. Chahine, JPL, and J. Susskind, NASA GSFC)
atmosphere, and the disequilibrium for periods much longer than the residence times of the gases means that the atmosphere is used to transfer waste products and nutrients. To understand even the simplest part of the Earth system, therefore, requires knowledge of geophysics, geochemistry and biology. Thus the study of global-scale problems and global environmental change requires an interdisciplinary approach, "Earth System Science,":' that describes how the components of the Earth system and their interactions have evolved, how they function, and how they may be expected to continue to evolve. EOS supports Earth System Science with three distinct goals: 1. Establishment of long-term, reliable measurements from remote sensing of important geophysical and biological variables, so that global, regional, and local change over the present period and 15 years after launch can be documented; 2. Use of remote sensing data, from the EOS platform and from aircraft and other satellites, to identify and investigate the most important processes in Earth System Science; 3. Improvement of our predictive models, so that plausible changes
over the next century can be better understood.
Need for Integrated Observations Currently there are many gaps in our knowledge of the Earth. Such processes as rainfall and snowfall, primary biological productivity, localized fault motion and uplift, tropical winds in the troposphere, and phenology of terrestrial ecosystems are accurately measured only at local scales. Estimations of the total global amount of such variables as carbon input into the atmosphere currently have uncertainties of lOOX. Rainfall over the oceans is hardly measured at all, yet it causes surface-density variations that affect circulation. The instruments on the EOS platforms are designed to measure many variables for which data are not currently available over the whole Earth at the appropriate spatial and temporal scales. Many measurements and interpretations require simultaneous observations of coupled phenomena. Some of the more energetic processes are also highly variable. Particularly for measurements of atmospheric phenomena or correction of images of the surface for atmospheric effects,
complementary instruments must look through the same atmospheric column. Sensors that sample at a coarse global mapping resolution must be coupled to similar, simultaneous observations at finer scales, so that processes at interfaces can be studied and the effects of variation finer than the resolution of the coarser instrument can be examined. Our investigation of global change also requires long-term, consistent observations. Sustained measurements are needed that result in globally analyzed products of established accuracy. These are needed to document changes that are really occurring. A benchmark for our performance will be the quality and reliability of our measurements and our analyses, as seen from a future perspective: What will our successors think, 20 years from now, when they are making similar measurements and trying to determine whether the apparent changes are real or artifacts of instrument design, calibration, sampling, or treatment of the data? For almost every variable the required measurement system is composite, involving a blend of satellite and in situ observations, many of them not under the direct control of research
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emitted radiances. Precipitation will also be monitored, as will global distributions of important gases in the chemistry of the stratosphere and troposphere.
10000
1000
100
ICE
Venus.
WATER
Circulation of the Oceans and Atmosphere
10 Jupiter. Pressure (atrn)
• Earth
0.1
• Uranus • Pluto
0.01
WATER VAPOR
Mars.
0.001
0.0001
Mercury (daylight side).!.
-200
-100
o
100
200
300
400
500
Temperature, °C
Fig.2: Phase diagram of water, ice and water vapor and the average pressures and temperatures on the planets.
scientists. Few of the existing measurement and analysis systems are adequate, because of the dearth of information on long-term accuracy and lack of identified responsibility for reviewing or ensuring end-to-end performance.
Interdisciplinary Investigations EOS Interdisciplinary Investigations are listed in Table 1. Some of the EOS science goals are briefly described in the remainder of this section.2
Climate and the Earth's Radiation Balance Clouds playa critical role in the heat balance of the Earth, and our lack of ability to predict cloud formation is the major source of uncertainty in evaluating the effect of changes in atmospheric composition on climate. High clouds can have a net heating effect, by trapping emitted thermal infrared radiation and increasing the potential greenhouse effect. Low clouds can do just the opposite: their increased reflectance in the solar part of the electromagnetic spectrum outweighs their absorption of infrared radiation. The study of clouds will thus be central to several EOS investigations. For the Earth as a whole, and over long periods, there is a near balance between absorbed solar radi-
ation and emitted infrared radiation. Over shorter time scales, the temporal and spatial distribution of heating and cooling drives atmospheric and oceanic circulation. Radiative heating and cooling combine with sensible and latent heat transfer to determine the temperature of the surface and atmosphere. Increased amounts of absorbing gases--carbon dioxide and methane, for example--cause air temperature to rise; the warmer temperatures cause increased water vapor concentrations, further warming the air. Increased low cloudiness, a consequence of increased water vapor, would lower air temperatures. Thus understanding the behavior of clouds is a crucial element in evaluating plausible climatic consequences of human activities. Our present understanding of the three-dimensional structure of the Earth's radiation field is hampered by the fact that the properties of clouds and the radiation balance are measured separately. EOS instruments will provide observations of clouds at improved spatial resolution and high spectral resolution, along with more accurate profiles of atmospheric temperature and water vapor. At the same time, broad-band sensors will measure the radiation balance of the entire Earth, while also sampling the complete angular distribution of reflected and
Atmospheric and oceanic circulations distribute heat around the Earth. Atmospheric motion is driven by radiative heating and cooling, and the surface winds drive oceanic circulation and the exchange of heat and water vapor at the air-sea interface. The oceans and atmosphere probably transport roughly equal amounts of heat from tropical to polar regions, but attempts to measure oceanic heat transport have proven difficult. As we try to forecast weather over periods of several weeks or try to understand longer-term climate changes, improving our knowledge of the interaction between the ocean and atmosphere is essential. The heat content and time scales of motion are much larger in the ocean than in the atmosphere, so changes in oceanic circulation could lessen or heighten the climatic effects of greenhouse gases. Similarly, changes in the formation and circulation of the polar sea ice affect heat transport and deep-water formation. EOS, together with surface measurements, will provide for the first time the necessary simultaneous observations for accurate measurement on a global scale of heat transport in the atmosphere and oceans. In addition to profiles of atmospheric humidity and temperature, EOS will provide global wind profiles. Similarly, sea-surface temperature, sea-ice coverage, and surface currents will be observed simultaneously, improving estimates of heat exchange at the airsea interface (Fig. I). Coupled with better numerical models, these measurements will enhance our ability to understand and predict the role of oceanic and atmospheric circulation in climate change.
The Hydrologic Cycle Earth is unique among the planets in its abundance of water in all three phases (Fig.2). Through the hydrologic cycle, water is an essential element of most processes that determine global change. Global distributions of rainfall, snowfall, evaporation, and accumulated surface and subsurface
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TABLE 1. EDS Interdisciplinary Investigations Principal Investigator
Title
Coupled Atmosphere Ocean Processes and Primary Producti on in the Southern Ocean
Mark Abbott
Oregon State U.
Global Water Cycle: Extension Across the Earth Sciences
Eric Barron
Pennsylvania State U.
Development and Use of a Four-Dtrnensicnal Atmospheric/OCean/Land Data Assimilation System for EOS
Ray Bates
NASA Goddard
Long-Term Monitoring of the Amazon Ecosystems Through EOS: From Patterns to Processes
Getulio Batista Jeffrey Richie
INPE (Brazil) U. Washington
Biogeochem ical Fluxes at the OCean/Atmosphere Interface
Peter Brewer
Woods Hole
Quantifying the Vegetation of Canada : Carbon Budget and Succes sion Models
Josef Cihlar
CCRS (Canada)
NCAR Projecf to Interface Modeling on Global and Regional Scales with EOS Observations
Robert Dickinson
U. Arizona & NCAR
Hydrology, Hydrochemical Modeling, and Remote Sensing in Seasona lly SnowCovered Alpine Drainage Basins
Jeff Dozier
U. Calif. Santa Barbara
Observational and Modeling Studies of Radiative , Chemical , and Dynamical Interactions in the Earth's Atmosphere
William Grose
NASA Langley
Estimation of the Globa l Water Budget
Robert Gurney
U. Reading
Interannual Variability of the Global Carbon and Energy Cycles
James Hansen
NASAGISS
Interdisciplinary Studies of the Relationships Between Climate , Ocean Circulat ion, Biological Processes , and Renewable Resources
Graham Harris
CSIRO (Australia)
Climate Processes Over the Oceans
Dennis Hartmann
U. Washington
Tectonic/Climatic Dynamics and Crustal Evolution in the Andean Orogen
Bryan Isacks
Cornell U.
Hydrologic Cycle and Climatic Proces ses in Arid and Semi-Ar id Lands
Yann Kerr Soroosh Sorooshian
LERTS (France) U. Arizona
Role of Air-Sea Exchanges and OCean Circulation in Climate Variability
Timothy Liu
JPL
Use of a Cryospheric System (CRYSYS) to Monitor Global Change in Canada
Lyn McNutt
CCRS (Canada)
Changes in Biogeochemical Cycles
Berrien Moore
U. New Hampshire
Global Assessment of Active Volcanism, Volcanic Hazards , and Volcanic Inputs to the Atmosphere from EOS
Peter Mouginis-Mark
U. Hawaii
Investigation offhe Atmosphere/Ocean/Land System Related to Climati c Processes
Masat o Murakami
MRI (Japan)
Chemical, Dynamical , and Radiative Interactions Through the Middle Atmosphere and Thermosphere
John Pyle
Cambridge U.
Polar OCean Surface Fluxes: Interaction of Oceans , Ice, Atmosphere , and the Marine Biosphere
Drew Rothrock
U. Washington
Using Multi-Sensor Data to Model Factors Limiting Carbon Balance in Global Grasslands
David Schimel
Colorado State U.
Chemical and Dynamical Changes in the Stratosphere Up to and During the EOS Observ ing Period
Mark Schoebert
NASA Goddard
Biosphere -Atmosphere Interact ions
Piers Sellers
U. Maryland
Middle and High Latitudes OCeanic Variability Study (MAHLOVS)
Meric Srokosz
BNSC (U.K.)
Earth Systems Dynamics: Determination and Interpretation of the Global Angular Momentum Budget Using EOS
Byron Tapley
U. Texas
An Interdisciplin ary Investigation 01 Clouds and the Earth's Radiant Energy System
Bruce Wielicki
NASA Langley
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Fig.3: Estimates of sea ice and snow cover for February 1983, derived from the Nlmbus-? microwave radiometer. Sea ice is white, permanent ice sheets purple, and increasingly deep snow in shades of blue. (D. Hall and D. Cavalieri, NASA GSFC)
TABLE 2. EOS Facility Instruments Instrument
Team Leader
Atmosphe ric Infrared Sounder
AIRS
Moustafa Chah ine
JP L
Altime te r
ALT
Lee-Lueng Fu
JP L
Geoscience Laser Ranging System
GLRS
to be selected
High-Resolut ion Imaging Spectrometer
HIRIS
Alexande r Goetz
U. Colorado
Intermediate Thermal Infrared Radiometer
ITIR
Hiroji Tsu
Geological Survey of Japan
Laser Atmospheric Wind Sounder
LAWS
Wayman Baker
NOAA NMC
Modera te-Reso lutio n Imaging Spectrometer
MODIS
Vincent Salomonson
NASA Goddard
EOS Synthetic Aperture Radar
EOS SAR
Char les Elachi
JP L
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water affect the local extent and global distribution of biological productivity. The redistribution of heat depends on the transport and phase changes of water, and water movement couples the land with the oceans through the transport of solutes and sediment. Water is an essential part of all biogeochemical cycles and is needed to support vegetation. The amount and distribution of snow and ice (Fig.3) affect the Earth's sea level, polar oceans, and radiation balance. Because of the pervasive role of water in human affairs, its role at the local scale-primarily water supply and flood hazards-has been the focus of most research up to this time. But we are far from understanding how the hydrologic cycle will respond to a changing Earth system, or how water will influence other components of the system. The diversity of the effects of water in the Earth
system has limited the development of a comprehensive understanding of the global water cycle. Along with the Tropical Rainfall Measuring Mission (TRMM), to be flown around 1995, EOS will provide the first long-term, consistent global measurements of many key variables: precipitation, atmospheric water vapor, clouds, snow accumulation, sea ice, polar and alpine glaciers, soil moisture, vegetation, temperature and winds. These will provide the capability to investigate the processes that defineinteractions and feedbacks within the hydrologic cycle.
The Carbon Cycle Since 1850, atmospheric carbon dioxide has increased by 25%, atmospheric methane by more than 100%. Although we have data on atmospheric concentrations-the carbon
dioxide data set was the first piece of evidence of anthropogenic global change-we remain uncertain about the relative roles of terrestrial ecosystems and oceans in removing CO2 from the atmosphere. Hence we cannot predict future trends and effects. Current operational remote sensing systems can acquire data with which to estimate the rate of deforestation, but the available instruments cannot detect vegetation change under cloud cover and have limited spectral resolution, so they cannot discriminate subtle changes in disturbed ecosystems. EOS instruments will provide needed global coverage of ecosystem states, and a synthetic aperture radar can penetrate clouds and forest canopies to measure forest biomass and moisture status. The net flux of carbon dioxide into the oceans remains uncertain, and EOS instruments will provide dramatic improve-
TABLE 3. EOS Instrument Investigations Principal Investigator
Instrument Active Cavity Radiometer Irradiance Monitor
ACRIM
Richard Willson
JPL
Clouds and the Earth's Radiant Energy System
CERES
Bruce Barkstrom
NASA Langley
Energetic Neutra l Atom Camera for EOS
ENACEOS
Barry Mauk
APL
Earth Observing Scanning Polarimeter
EOSP
Larry Travis
NASA GISS
GPS Geoscience Instrument
GGI
William Melbourne
JPL
Geomagnet ic Observing System
GOS
Robert Langel
NASA Goddard
High-Resolution Microwave Spectrometer Sounder
HIMSS
Roy Spencer
NASA Marshall
High-Resolution Dynamics Limb Sounder
HiRDLS
John Barnett
Oxford U.
Ionospheric Plasma and Electrodynamics Instrument
IPEI
Roderick Heelis
U. Texas
Lightning Imaging Sensor
LIS
Hugh Christian
NASA Marshall
Multi-Angle Imaging Spectro -Radiomete r
MISR
David Diner
JPL
Microwave Limb Sounder
MLS
Joe Waters
JPL
Measurements of Pollution in the Troposphere
MOPITI
James Drummond
U. Toronto
POsitron Electron Magnet Spectrometer
POEMS
Paul Evenson
U. Delaware
Spectroscopy of the Atmosphere Using Far Infrared Radiation
SAFIRE
James Russell
NASA Langley
Stratospheric Aerosol and Gas Experiment III
SAGE III
Patrick McCormick
NASA Langley
Scatterometer
STIKSCAT
Michael Freilich
JPL
Solar Stellar Irradiance Comparison Experiment
SOLSTICE
Gary Rottman
U. Colorado
Stratospheric Wind Infrared Limb Sounder
SWIRLS
Daniel McCleese
JPL
Tropospheric Emission Spectrometer
TES
Reinhard Beer
JPL
Tropospheric Radiometer for Atmospheric Chemistry and Environmental Research
TRACER
Henry Reichle
NASA Langley
Tropical Rain Mapping Radar
TRAMAR
Gerald North
Texas A&M
X-Ray Imaging Experiment
XIE·
George Parks
U. Washington
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ments in our estimates of biological productivity in the upper ocean.
Ozone and Atmospheric Chemistry Observed recent changes in chemical composition of the atmosphere have been the reduction of stratospheric ozone by chlorofluorocarbons and the increase in greenhouse gases in the troposphere. Monitoring ozone depletion (Fig.4) requires measurements of global ozone profiles, along with measurements of the atmospheric chemicals, dynamic processes, and solar energy input that control ozone concentrations. The Upper Atmospheric Research Satellite (UARS) and the Total Ozone Mapping Spectrometer (TOMS) will provide data on ozone and dynamics through the mid-1990s. Then, during its IS-year life, EOS will allow measurements over enough annual cycles, biennial oscillations and ozone changes to help us address the problems of relating climate to changing atmospheric chemistry. Solid Earth Processes Volcanic eru ptions, earthquakes, floods, and landslides are well-documented hazards. Volcanoes introduce chemicals and aerosols into the atmosphere. Crustal movement results in earthquakes and sea-level variations. Erosion affects the hydrologic cycle and biological productivity . The motion of material deep within the Earth causes subtle changes in its rotation and length of day. Understanding these processes and linking them to global change on shorter time scales require a diversity of observations. EOS instruments will be used to characterize the composition and nature of volcanoes, and to monitor the mechanisms of plate motion. High-resolution geodetic observation and altimetry will help us examine regional uplift, subsidence, and changes in shape and volume of the large continental ice sheets in polar regions. Deeper processes within the Earth are best studied through the Earth's magnetic field. EOS INSTRUMENTS EOS will provide new capabilities for remotely sensing the Earth, and will make the data both physically and intellectually accessible to the broad scientific community. This comprehensive approach to observations of
TABLE 4. Categories of EDS Instruments Surface Imagers CERES EOSP HIMSS HIRIS ITIR MISR MODIS Tropospheric Sounders AIRS HIMSS MODIS
Radar/Lidar ALT GGI GLRS LAWS STIKSCAT EOS SAR Stra tospheric Chemistry HiRDLS MLS SAFIRE SAGE III SWIRLS
Tropospheric Chemislry LIS MOPITT TRACER TES Solar- Terrestrial Interactions GOS IPEI XIE Solar Irradiance ACRIM SOLSTICE Secondary Science ENACEO S POEMS
the Earth is unprecedented. The U.S. component of the program consists of two platform configurations. Platform A contains the surface imagers and tropospheric sounders and is scheduled for launch in 1997. Platform B, to follow 2~ years later, is mainly devoted to measurements of the upper atmosphere. Platform C, a duplicate of A, will follow B by 2~ years, and the sequence will be repeated for 15 years. The instruments are divided into two classes," and are briefly described in the sections that follow. 1. Facility instruments are designed to measure variables useful to a wide range of scientific disciplines. Each facility instrument has a team of 10 to 25 scientists who develop and code algorithms to estimate geophysical and biological quantities from the signals measured by the sensor. 2. Investigator instruments are designed by small groups of scientists to make observations of more specific phenomena. Each investigator instrument has a principal investigator and several co-investigators.
Facility Instruments EOS facility instruments are listed in Table 2. Atmospheric Infrared Sounder (AIRS) is a high-resolution infrared sounder that will measure reflected sunlight and infrared emissions from the atmosphere and surface in five wavelength-bands between 0.4 and 1.1 /-lm and 4,000 wavelength-bands between 3 and 17/-lm. Together with observations from the NOAA operational Advance Microwave Sound-
ing Unit (AMSU), which measures emissions at 20 frequencies between 20 and 90 GHz, AIRS will measure atmospheric temperature and humidity profiles with more accuracy and better resolution than are currently available. AIRS will also provide data on cloud cover, ozone and other trace gases, and surface temperature and albedo. Altimeter (ALT) is a nadirlooking radar altimeter, which will map the topography of the sea surface, from which velocity of surface currents can be inferred. The shape and strength of the radar pulse return provide measurements of wave height and wind speed. Because EOS will be in a polar orbit, ALT will also measure changes in volume of the polar ice sheets. EOS Synth etic Aperture Radar (EOS SAR) is a three-frequency multi-polarization instrument to monitor global deforestation, soil moisture, snow cover, wetness and water equivalence, canopy moisture and flood inundation, sea ice properties and motion. Because of its large mass, the EOS SAR will fly on its own dedicated platform. Geodynamics Laser Ranging System (GLRS) is a laser ranger and altimeter designed to measure crustal movements and deformation and altitude profiles over ice sheets and the land surface. High-Resolution Imaging Spectrometer (HIRIS) provides images at both high spectral and spatial resolution at any point on the Earth's surface in any two-day period. HIRIS covers the 0.4 to 2.45 /-lm spectral region in 192 spectral bands, with a
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pixel size of 30 m and a swath width of 24 km. The spectral resolution of HIRIS allows identification of materials and states at the Earth's surface, such as minerals, biochemical properties of vegetation, grain size and contaminants in snow, and nutrient
content of coastal and inland water. The spatial resolution, intermediate between the human and the global, provides the measurements at a scale suitable to study processes, examine interfaces, and link process studies to global interpretations.
Intermediate Thermal Infrared Radiometer (ITIR) , to be supplied by MITI, will image the surface and clouds with high spatial resolution (15 to 60 m) with multi-spectral wavelength-bands from the visible through infrared regions. Science ob-
Fig.4: Time series of stratospheric ozone for the month of October from 1979 to 1988 (left to right from top) and 1989 (large image). The data, collected by the TOMS sensor, shows the evolution of the "ozone hole" near Antarctica. (M. Schoeberl NASA GSFC) ,
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jectives include classification of some rock types, examination of the radiative properties of clouds, estimations of evapotranspiration from vegetation, and investigations of volcanic activity. Laser Atmospheric Wind Sounder (LAWS) is a Doppler lidar system for direct measurements of tropospheric winds. Global wind profiles from LAWS will help measure the transport of water vapor, gases and aerosols. Moderate-Resolution Imaging Spectrometer (MODIS) consists of two instruments: MODIS-N (nadirpointing) and MODIS-T (tilting). MODIS-N is an imaging spectrometer with a 2,300 km swath with pixel sizes of 214 m, 428 m, and 856 m. It samples the spectral ranges of 0.4 to 14.54 p,m in 36 bands and provides information about surface vegetation, surface temperature, snow cover, ocean color and atmospheric aerosols. MODIS-T is specifically designed for observations of ocean primary productivity, with 64 wavelength bands between 0.4 and 0.88 p,m. The tilt allows avoidance of sun glint, as well as enabling studies of the angular variation in surface reflectance over land.
Instrument Investigations To avoid making this paper unduly long, descriptions of the EOS instrument investigations, listed in Table 4, are brief. Active Cavity Radiometer Irradiance Monitor (ACRIM) has flown on previous satellites and will continue long-term monitoring of the variability of solar irradiance. Clouds and the Earth's Radiant Energy System (CERES), similar to previous Earth Radiation Budget Experiment (ERBE) instruments, will provide EOS with an accurate and consistent data base to continue longterm measurement of the Earth's radiation balance. Energetic Neutral Atom Camera for EOS (ENACEOS) will obtain images of the global structure and dynamics of the Earth's magnetosphere. Earth Observing Scanning Polarimeter (EOSP) will obtain global maps of the radiance and linear polarization of reflected and scattered
sunlight and will infer aerosol concentrations. GPS Geoscience Instrument (GGI) will provide precise positioning in support of other instruments. Geomagnetic Observing System (GOS) will measure the Earth's magnetic field. High-Resolution Microwave Spectrometer Sounder (HIMSS) will retrieve numerous atmospheric and oceanic parameters, including precipitation rates over land and ocean, oceanic-cloud water and water vapor content, surface wind speed and seasurface temperature, atmospheric temperature profile, snow water equivalence and the properties of vegetation. High-Resolution Dynamics Limb Sounder (HiRDLS) is an infrared limb scanning radiometer designed to sound the upper troposphere, stratosphere and mesosphere to determine temperature and concentration of nine gases. Ionospheric Plasma and Electrodynamics Instrument (IPEI) will remotely sense the electric fields generated in the lower atmosphere by interaction of the Earth with the interplanetary environment. Lightning Imaging Sensor (LIS) will investigate the distribution and variability of lightning over the Earth. Multi-Angle Imaging SpectroRadiometer (MISR) will obtain continuous multi-angle imagery of the Earth and its atmosphere and will thus measure aerosol loading, threedimensional structure of clouds, changes in structure, distribution and extent of forests and deserts, and atmosphere-biosphere interactions. Microwave Limb Sounder (MLS) will study and monitor processes that govern stratospheric and mesospheric ozone, through measurement of concentration profiles of 19 gases, temperature and pressure, mesospheric wind, and liquid water. Measurements ofPollution in the Troposphere (MOPITT) will measure concentrations of carbon monoxide and examine how it interacts with the surface and ocean. Positron Electron Magnet Spectrometer (POEMS) is an energetic particle detector which will study the nature and temporal variation of the charged particle radiation near the Earth.
Spectroscopy of the Atmosphere Using Far Infrared Radiation (SAFIRE)will study ozone in the middle atmosphere by measuring chemical, radiative, and dynamic processes that influence ozone changes. Stratospheric Aerosol and Gas Experiment III (SAGE III) will measure profiles of aerosols, several gases, and air density between cloud tops and the upper atmosphere. Solar Stellar Irradiance Comparison Experiment (SOLSTICE) provides precise measurements of solar ultraviolet irradiance; bright, early-type stars will be used as stable calibration sources. Scatterometer (STIKSCAT) is an active microwave radar designed to measure surface wind speed and direction over the ocean. Stratospheric Wind Infrared Limb Sounder (SWIRLS) focuses on stratospheric structure, dynamics and transport, and the influence of natural and anthropogenic forcing on stratospheric change, including changes in ozone. It will measure the vertical profiles of wind, temperature and abundances of ozone and nitrous oxide. Tropospheric Emission Spectrometer (TES) is a high spectral resolution infrared spectrometer that uses both limb and nadir viewing to measure concentration profiles of a wide variety of atmospheric gases. Tropospheric Radiometer for Atmospheric Chemistry and Environmental Research (TRACER) will measure the global distribution of carbon monoxide at multiple levels in the troposphere. Tropical Rain Mapping Radar (TRAMAR), to be flown as an attached payload on the manned Space Station, will provide accurate rainfall data over the tropical regions to improve our understanding of the hydrologic cycle, atmospheric circulation, climate models and mesoscale storm systems. X-Ray Imaging Experiment (XIE) will detect and determine the total particulate energy precipated into the Earth's atmosphere.
Categories of EOS Instruments A summary table of all EOS facility instruments and instrument investigations is given in Table 5.
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Schedule of Instruments for the EOS A and B Platforms Because of the constraints on resources (mass, power, data rate, cost etc.), there are various feasible combinations of instruments for the EOS A (1997 launch) and B (2000 launch) platforms. A preliminary recommendation for a suite of instruments is summarized in Table 6. These are subject to continued evaluation after their characteristics (cost, mass, power, risk etc.) have been thoroughly evaluated. THE EOS DATA AND INFORMATION SYSTEM (EOSDlS) Crucial to the success of the Earth Observing System is the EOS Data and Information System (EOSDIS).5 Achieving the goals of EOS will depend not only on its instruments and science investigations, but also on how well EOSDIS helps scientists integrate reliable, large-scale data sets of geophysical and biological measurements made from EOS data, and on how successfully EOS scientists interact with other investigators in Earth System Science. Current progress in the use of remote sensing for science is hampered by requirements that the scientist understand in detail the instrument, the electromagnetic properties of the surface, and a suite of arcane tape formats, and by the immaturity of some of the techniques for estimat-
ing geophysical and biological variables from remote sensing data. These shortcomings must be transcended if remote sensing data are to be used by a much wider population of scientists who study environmental change at both regional and global scales.
Scientific Information from EOSDlS What distinguishes EOSDIS from current remote sensing data systems is the commitment to provide usable scientificinformation to the geophysical, biogeochemical, ecological, and interdisciplinary communities. EOS data products will be used by a wide spectrum of scientists and the public during the IS-year life of the mission and the decades to follow. Standard, reliable data products, essential to distinguish natural and anthropogenic variations, will give the community access to independent measurements to validate and drive models of processes at local, regional, and global scales. The characterization will include algorithms for generating the products and descriptors of data quality, and each data set will include the identity of the responsible scientists. Standard products, created by algorithms that are certified by a peer-review process, will be available through EOSDIS for all cases for which the appropriate input data exists. Moreover, specialized products created by EOS scientists in their own computing facilities are to be archived and distributed by EOSDIS.
EOS data will continue existing measurements, some of which have been gathered for more than a decade. EOS Science begins now, not with the launch of the first EOS platform in 1997. Starting immediately, EOSDIS will develop current and previous data sets and measurements, and provide them to other investigators, so that the EOS community can gain experience with data-processing, archive and distribution centers. The few current centers where remote sensing data is intensively and routinely analyzed into scientific products provide the heritage for design and prototyping ofEOS data-processing and distribution, especially for data sets consisting of scientific interpretations rather than satellite-level radiance measurements.
Evolving Design and Architecture The important questions that drive the design and architecture of EOSDIS involve the procedures by which scientific products will be created and distributed, as well as how the styles of interaction with EOSDIS will change as EOS science matures. An EOS data-processing and distribution system, including visualization and browse capability for both image and non-image data and information derived from EOS sensors, requires an evolutionary, distributed design because of flexible research utilization of the data and because of rapid
TABLE 5. Possible Configurations for EOS A and B Platforms EOSA
EOS B
European platform
Japanese platform
LAWS
separate platform
AIRS
ITIR b
GGI
CERES
ALl"'
LIS
GLRS
GOS
CERES
MISR
ITIRb
EOS SAR
EOSP
MODIS
MLS
TRMM
GGI
MOPITII TRACER
SAFIRE
HIMSS HiRDLS
STIKSCAT
HIRIS
resources P9rmirtmg
ALT
IPEI
SAGE lII e
XIE
SAGE lII e SOLSTICE SWIRLS TES
a.
Is the plattorrn stability adequate lor ocean animetric measurements?
b.
Stereo imaging capability of instrument would be best implemented it it lIew with GLRS on B. Munispec1ral investigations would be best served it it lIew with HIRIS and MODIS on A.
c.
Measurements are 01 crucial importance : early launch on a separate plattorm would provide Ionger·term dat a.
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developments occurring in computer hardware and software. As EOS matures, specific algorithms will be formulated, mutual product dependencies resolved, and interdisciplinary data requirements defined. The process of producing and analyzing data will continue to lead to new methods of producing scientific products and new computing requirements. The system architecture must accommodate data from different kinds of sensors, changes in available computer hardware, software and communications. A system that can address the changing nature of both its tasks and the available hardware and software must be designed for easy, graceful evolution, both before and after launch of the EOS platforms.
Scientists' Participation The responsibility of EOSDIS to provide scientific information as well as raw data has significant implications for the time and requirements for support of many participating scientists. An EOS investigator who is responsible for a standard data product has a commitment for the life of the mission-including maintenance of the algorithm and code as the instrument and environment changes, as well as quality control and validation of the product. The investigator must also provide additional information (meta-data, browse products, documentation) that will enable others to identify and use the scientific products. The scientist must also be flexible about generating information the community needs even if not promised in the original proposal. For algorithms to be maintainable, the code must be readable and portable, and therefore written and documented using good scientific coding standards. Policy on Availability of Data EOSDIS policy specifies that all data and derived products be available to all users, with no preference given to EOS investigators and no period of proprietary restriction. Research users in the U.S. and participating countries will pay only the marginal costs for data reproduction and distribution; they will have to agree to publish their results and to make available supporting information, including methods of analysis and code
implementing the algorithms. Research users in non-participating countries may have the same access to EOS data by proposing cooperative projects and associated contributions, i.e similar access to their satellite, aircraft and surface data. For all data products, the documented scientific software that produced them will also be available. As much as possible, we want to apply the same policy to non-EOS data . Other U.S. agencies involved in EOS-NOAA and U.S. Geological Survey-have agreed. For data from the international platforms, discussions are under way between NASA Headquarters and the appropriate foreign government agencies. Expectations are that they will agree to the same data policy. Availability of commercial data (Landsat and SPOT) under the same policy will require a change in legislation.
System Architecture The current concept of EOSDIS is that as many as a dozen Distributed Active Archive Centers (DAACs) will fulfill all processing needs except algorithm development and individual scientists' investigations. Each will have Data Archive and DistributionSystems (DADS) that will be accessed by an Information Manage ment System (IMS) and that will distribute data sets to investigators. Instrument support software will be available for investigators to submit commands for instrument pointing and data acquisition. Explicit in this concept is that multiple facilities and generic classes of facilities can best fulfill these functions. Some functions are best handled by centralized, spacecraft-oriented or instrument-oriented facilities. "Raw" Level 0 products involve the space-
craft and data-relay satellites. Levell products , e.g. radiative measurements at the spacecraft, require intimate knowledge of instrument characteristics and need to be done quickly. For some functions, an instrument- or discipline-oriented facility would provide the most reliable products. The creation of geophysical Level 2 products usually, but not always, requires data from only one instrument and involves intimate knowledge of its characteristics. Some scientific products use data from more than one instrument, and some products may be developed by scientists who are not on an instrument science team. Higher-level (3 or 4) standard products may be most reliable if produced at a discipline-oriented facility or at the investigator's home institution. Many useful regional or global-scale scientific products are derived from a suite of instruments, and scientific expertise, cooperation, and interaction are needed. Separation of product generation into different nodes within EOSDIS is consistent with scientific goals and interdisciplinary research. In order for a networked Information Management System to succeed, standards for operating systems and data formats are crucial, and a single common catalog is needed. Any user should be able to investigate the availability and characteristics of all archived data, without having to use either separate catalogs for different instruments or to learn new access techniques. Scientific functions of EOSDIS-command and control of the spacecraft, data acquisition, distribution of instrument Level I data to investigators, information management, interaction among investigators, creation of geophysical and
TABLE G. Preliminary Selection of EDSDlS Distributed Active Archive Centers Alaska SAR Facility
NASA Marshall Space Flight Center
Consortium for International Earth Science Information Network
National Center for Atmospheric Research
Jet Propulsion Laboratory
National Snow and Ice Data Center
NASA Goddard Space Flight Center
U.S. Geological Survey, EROS Data Center
NASA Langley Research Center
University of Wisconsin
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biological products, and archiving and distribution of data and information-should be separately optimized. Smooth interfaces are also important. Where centralization is appropriate, we should build concentrated processing in a few institutional locations. For those functions where more distributed processing is best, we should use EOSDIS to provide networks, access to supercomputers, standards, maintenance and advice. Where processing can be routine, without continuous involvement of scientists, we should design a system to process efficiently, but where continuing scientific evaluation is needed in the creation of science products, we should not constrain this activity by an emphasis on "efficiency." Most scientists' concept of their ideal computing environment involves: • powerful workstations under their control; • painless and affordable access to data from big archives or from other investigators' workstations; • confidence that the geophysical and biological products they ob-
tain are produced by knowledgeable people and have established quality and reliability; • access to communications networks for easy exchange of information, without the arcane knowledge currently required to go between systems; and • occasional access to bigger and faster computers. The current selection of Distributed Active Archive Centers is listed in Table 6. In the next year, each potential DAAC will identify appropriate current and previous data and promote their rapid de velopment. They will also acquire experience with currently active data-processing centers and archives and begin development of interfaces between DAACs and between EOSDIS and other national and international archives. Acknowledgements: In this summary description of EOS and EOSDIS, I have borrowed freely from discussions with my colleagues and from published and unpublished documents circulating among EOS investigators. To name them all and identify
• Presentation X-V plotting, 2-D graphing
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I. Com mittee on Eart h Sciences, Our Changing Planet: The FY 1991 U.s. Global Change Research Program. 60 pp., Offi ce of Science and Technology Policy, Washington, D.C. , 1990. 2. EOS: A Mission to Planet Earth. 36 pp., NASA, Washin gton, D. C., 1990. 3. Eart h System Sciences Committ ee, NASA Advisory Council, Earth System Science: A Closer View. NASA, Washington, D. C., 1988. 4. EOS Ref erence Handbook. NASA Goddard Space Flight Ctr. , Greenbelt, MD , 1990. 5. Science Advisory Panel for EOS Data and Informat ion, Initial Scientific Assessment of the EOS Data and Inf ormation System (EOSDIS ). EOS-89-I, 43 pp., ASA Goddard Space Flight Ctr ., Greenbelt. MD , 1989.
• Integration; calcu lator-like math on tables • Fast Fourier transforms • Curve fits for data modeling
• Overlaid graphs, up to 1000; legend
• Data smoothing , sorting, and merging of files
.i • ~
References
• Labels: Greek, symbols, sub/super-scripts
f • Color con trols for color monitors ~
their individual contributions is too daunting, and I apologize here for the many omissions. Specifically though, I must thank Dixon Butler and Stanley Wilson of NASA Headquarters, James Baker of the Joint Oceanographic Institutions, Berrien Moore of the University of New Hampshire, David Dokken of the SM Systems and Research Corporation and my colleagues on the EOSDIS Advisory Panel. •
Plot scaling, shifting, zooming
• Dynamic cursor coordinates • PostScript™EPS output
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• Up to 1000 data tables of any length
~
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• Several file I/O formats (customizable) • Custom program your C-Ianguage analysis
Math ++:
Also 1.5 Mbytes C-source code numerical analysis library with example programs.
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