Newsgroups: sci.space.news From: yee@atlas.arc.nasa.gov (Peter Yee) Subject: Altas Program Brochure (Forwarded) Message-ID: <1993Apr7.231156.6297@news.arc.nasa.gov> Organization: NASA Ames Research Center, Moffett Field, CA Date: Wed, 7 Apr 1993 23:11:56 GMT Lines: 1978 ATLAS PROGRAM BROCHURE TEXT TO GRAPHIC DESIGN OCTOBER 16, 1992 TABLE OF CONTENTS The Heritage of Environmental Inquiry The ATLAS Program Requisites for A Habitable Planet: Earth's Atmosphere and the Sun Warmth and Protection for the Blue Planet: The Middle Atmosphere Energy for the Blue Planet: The "Solar Constant" The ATLAS Instruments Mission Operations Beyond ATLAS Fact Sheets This document was prepared under the auspices of the Marshall Space Flight Center Payload Projects Office by Essex Corporation. Design: Brien O'Brien Illustration: Frank Kulczak, David Johnston, Brien O'Brien, and MSI, a Division of the Bionetics Corporation THE HERITAGE OF ENVIRONMENTAL INQUIRY Since its emergence, the human race has been fascinated by its environment, particularly the weather. Early peoples developed elaborate explanations for the natural phenomena they encountered, learning to predict the weather by the "signs" they came to recognize over years and years of observation. Furthermore, their abilities to react to long-term environmental changes preserved the species. When the glaciers of the ice ages approached, for example, they migrated toward the milder, equatorial latitudes. When the glaciers retreated, they moved into more temperate climes. Today, we are still intrigued by our surroundings and seek to understand all there is to know about our world. Like our ancestors, we observe and measure, then theorize and test the theories. In doing so, we have refined many of the explanations they developed and have generated a more scientific framework from which to interpret the physical world. In modern times, we have even succeeded in some of our strategies to reverse human-induced changes that despoil our environment. We have levied controls on toxic emissions, for instance; we have reclaimed nearly lifeless waters around major population centers of the Great Lakes and cleaned up the Hudson River. Our heritage of environmental focus has grown beyond its beginnings as a familial and tribal concern to a regional investment to today's multinational awareness. We acknowledge that humans now play a pivotal role in determining the intricate balance of environmental conditions that sustains life on this exquisite blue-and-white planet. Today, peoples of every nation are expressing concern over the health of Planet Earth. As a result, a variety of scientific, economic, and political interests have formed alliances to develop a better understanding of the workings of our home planet. One such cooperative effort is the National Aeronautics and Space Administration's (NASA's) series of Spacelab missions called ATLAS, the Atmospheric Laboratory for Applications and Science. The ATLAS program investigates the relationships between Earth's atmosphere and the Sun. THE ATLAS PROGRAM The primary goal of the ATLAS program is to help characterize the chemical and physical components of the middle part of Earth's atmosphere, including the energies of sunlight that affect the middle atmosphere. Because no single space mission can provide enough information to accomplish this goal, a series of ATLAS missions, carrying a core of seven instruments, has been planned. With these instruments, an international team of scientists will gather data under a variety of atmospheric conditions over both the Northern and Southern Hemispheres. Some of the instruments focus primarily on atmospheric observations; others measure solar energy. Both sets of data are indispensable if we are to develop a comprehensive understanding of the middle atmosphere, and each set contributes to the interpretation of the other. The ATLAS research projects have been selected primarily because of their abilities to make very sensitive measurements. The instruments chosen are calibrated before and after each mission so that the information they gather about the middle atmosphere and Sun will be accurate and precise. The ability to recalibrate equipment regularly is an important part of the ATLAS concept. The longer an instrument operates in space, the greater is the chance that high-energy radiation or other harsh conditions can damage the hardware and skew the data gathered. As a Space Shuttle-Spacelab payload, the ATLAS experiment hardware is returned to Earth after each mission for recalibration, refurbishment, or refinement. This benefits not only the ATLAS program but also related space investigations, since the ATLAS Shuttle instruments have identical or similar counterparts on free-flying satellites. Scientists can use the precise ATLAS instrument measurements to refine the satellite data. ATLAS and Spacelab The ATLAS program depends on Spacelab, a set of modular hardware that is arranged to form laboratories carried into orbit in the Shuttle's payload bay. The ATLAS instruments themselves are installed on Spacelab's U-shaped pallets, which are directly exposed to space. A pressurized canister, the Spacelab igloo, along with nearby pumps and power boxes, provides the science equipment with power, communication links, and environmental control. From the Shuttle's orbit high above the middle atmosphere, the ATLAS instruments will look down through the atmosphere to gather chemical and physical data. The orbiter's altitude also benefits those experiments that observe the Sun and measure solar output. To accomplish their science objectives, these instruments must operate above the relatively dense lower and middle atmospheric regions, which absorb many wavelengths of solar radiation. As a Spacelab mission, each flight also offers the ATLAS investigators the opportunity to interact with their experiments from the ground. Before the mission, the teams develop lists of commands that can be issued by the Spacelab computer system at specific times. Controlled by these commands, the science instruments perform their operations automatically and according to schedule. If the scientists want to modify their instrument's operations, they can change the list of commands and transmit the changes from the ground control center to the Spacelab computer. They can also consult with the trained science crew in space to modify the preplanned instrument operations, having the crew either change the command lists or perform the operations manually. In the Spacelab concept, crewmembers in space are integral parts of the science team. Mission Configuration On each mission, six ATLAS instruments will be mounted on a Spacelab pallet in the bay of the Shuttle. A seventh instrument and its electronics, a co-manifested payload, will be located in two canisters attached to the payload bay wall. Because the pallet, igloo, and canisters occupy less than a third of the space available in the Shuttle bay, the ATLAS mission may share Shuttle resources and space with other payloads. An International Endeavor The ATLAS experiments are sponsored by space organizations and institutions around the globe, underscoring the international nature of atmospheric concerns. Each of the seven core investigations provides information that will complement and enhance the interpretation of data gathered by the other investigations. The data gleaned on ATLAS missions will also be available to the larger science community involved in related studies. ATLAS and Mission to Planet Earth The ATLAS series is a crucial component of NASA's Mission to Planet Earth, a comprehensive initiative to study the interactions of Earth's life forms, waters, atmosphere, and land masses, known collectively as the Earth System. Investigations on Mission to Planet Earth spacecraft make short- and long-term worldwide measurements of these global environmental components to determine how such systems interact to produce our environment and how they are affected by natural and human-induced changes. ATLAS investigations aboard 7- to 10-day Shuttle flights augment Mission to Planet Earth's longer term, free-flying satellite missions. On the Shuttle, instruments collect complementary, highly calibrated information from which scientists can construct "snapshots" for "albums" of information -- data that provide a quick look at how conditions have changed from one mission to the next and that validate or complement satellite data. For instance, ATLAS 1 and 2 are underflights of the Upper Atmosphere Research Satellite and provide correlative measurements. These periodic checks on atmospheric conditions will also supplement both the early Mission to Planet Earth satellite flights, such as the Upper Atmosphere Research Satellite, and the later programs, such as the Earth Observing System. Mission to Planet Earth is NASA's contribution to the United States Global Change Research Program, a unified study of the planet and its components, from its deepest interior to its outermost atmospheric regions. In turn, the Global Change Research Program is a cooperative element of the International Geosphere/Biosphere Program, one of the most comprehensive scientific undertakings of all time. This program focuses on the ocean-atmosphere-land-life system, studying its interactions on timescales from decades to centuries. Coincident and Complementary Measurements While the ATLAS instruments make atmospheric and solar measurements in support of their individual investigations, the data also enhance other ground- and space-based programs, particularly those using free-flying satellites. Coincident and complementary measurements are especially valuable in solar and atmospheric studies. In coincident measurements, an ATLAS atmospheric instrument and an instrument that surveys the same parameter from another orbiting craft view the same air mass in the atmosphere at approximately the same time. These observations are especially important when comparing the calibrations of the two instruments. When analyzing data taken under these observing conditions, the scientists do not have to consider spatial, temporal, or temperature variations in the atmosphere. On the other hand, for the ATLAS solar instruments, it is critical only to make measurements of the Sun at the same time as the satellite instrument does, since atmospheric conditions do not affect space-based solar observations. Complementary measurements are compiled to add to our total body of knowledge about the atmosphere and the Sun. For instance, if an ATLAS instrument records the concentration of a particular trace gas at sunrise and sunset, while an instrument in a polar orbit makes the same measurement at local noon and midnight, scientists can better establish the diurnal variation of that trace gas by combining the two sets of data. If a satellite instrument studies a few related chemical species and the ATLAS instruments observe additional ones, the combined data define the chemical processes better than either set of information by itself. REQUISITES FOR A HABITABLE PLANET: EARTH'S ATMOSPHERE AND THE SUN As far as we know, Earth is the only planet in our solar system that supports life. The atmosphere, in combination with the Sun's energy and the magnetic fields emanating from our planet, creates the conditions making life on Earth possible. By warming the planet and transporting water and heat, the atmosphere moderates Earth's climate -- its long-term and prevailing meteorological conditions, such as temperature, wind patterns, and precipitation. Our climate is driven both by the solar energy reaching the planet and by the Earth System's responses to the infusions of energy. These combined influences produce global temperatures that are sufficiently warm to incubate and sustain plant and animal life. It is theorized that small, though significant, long-term changes in either solar output or atmospheric characteristics might produce noticeable changes in Earth's climate. For example, changes in the Sun's output would be reflected in the response of the Earth System and could be manifested as changes in mean global temperature and as disturbances in the water cycle. It is far from certain, however, what the magnitude of these changes might be and even less certain how they might affect life on Earth. Is there evidence of solar or atmospheric change? While further investigations are needed, measurements of solar energy indicate that it does indeed fluctuate in both amount of energy and wavelength distribution. Moreover, there is overwhelming evidence that humans exert significant influence on the atmosphere through the actions of our sizeable population. One impact of our activity can be traced to the beginning of the Industrial Revolution. As the industrialized nations developed, burning more fossil fuels and clearing land for industrial and agricultural expansion, the atmospheric concentrations of certain important trace species -- particularly carbon dioxide, one of the compounds that is effective in trapping the heat reradiated by Earth -- began to increase dramatically. Although we have no influence over changes in solar irradiance (the Sun's energy received by the planet), we can control our actions and choices that affect the atmosphere and our climate. To do this responsibly, we must first understand the cycles of the Sun and the role sunlight plays in atmospheric processes. How much energy does the Sun pour upon our protective atmospheric layers? Does the amount of solar energy reaching Earth's upper atmosphere change? If so, what portions of the radiation change and by how much? Where in the atmosphere are different wavelengths of radiation absorbed? How do solar variations affect chemical reactions in the atmosphere? Next, we must be knowledgeable about the intrinsic characteristics and behavior of the atmosphere under various solar conditions. What trace gases are present in Earth's atmosphere? Where do they originate? How are they distributed in the atmosphere and in what concentrations? How are the chemicals transported upward, downward, or over the globe? How do they interact with one another? NASA's ATLAS program seeks to provide answers to these questions to help distinguish human-caused changes from natural variations. With this knowledge, we will be able to make more responsible decisions about our use of resources and our strategies for protecting the atmosphere. The Greenhouse Effect Planet Earth moves through space within its own protective mantle: the atmosphere. This mantle contains gases and clouds that absorb or reflect certain portions of sunlight. Other solar wavelengths penetrate the atmosphere and reach Earth's surface. The warm Earth radiates energy back toward space, but clouds and atmospheric gases can prevent some of these energies from escaping. The balance of absorbed sunlight and trapped radiation determines Earth's temperatures. The gases most involved in the planet's radiation balance are called "greenhouse" gases. The primary ones are trace gases -- water vapor, carbon dioxide, methane, and nitrous oxide. Like the glass panes in a greenhouse, these gases let sunlight through to Earth's surface, yet prevent heat from escaping to space. This natural warming is called the greenhouse effect, and it makes life on Earth possible. Historical records show that the concentrations of greenhouse gases -- particularly those of carbon dioxide -- fluctuate naturally and moderate Earth's temperature accordingly. When greenhouse gas concentrations drop, the planet experiences a cooling period; when these gases increase in concentration, Earth's temperatures rise. Because of complicating factors, such as changes in cloud cover, this possible cause-and-effect relationship is not yet completely understood. In recent times, human populations have grown exponentially and, with them, the basic needs of an increasing population: more food, more potable water, more shelter. One of the impacts of our efforts to feed, clothe, house, and transport our growing numbers is that we increase emissions of the greenhouse gases into the air, thus affecting the chemical balance of the atmosphere. Using atmospheric models and historical temperature records, scientists are trying to determine whether these growing concentrations of gases will enhance the natural greenhouse effect, changing our climate and global temperatures. They are asking whether Earth's mean temperature is changing, and if it is, they want to know how rapidly it is rising or falling. What they discover in their investigations may have a far-reaching impact on our lives. Consider what warmer or cooler mean temperatures could mean to plant and animal populations. We might see one result along our coastlines. Sea levels could rise if polar ice caps melted, or the levels could fall if the glacial ice caps grew. How would possible changes in sea level affect the economy of people who live along today's coastlines? Would the coastal cities be inundated, or would their communities be landlocked? Other consequences of a mean global temperature change might be evident in vegetation patterns. Would plant populations be able to migrate toward a suitable environment? Would farmers have to grow different crops or adopt other agricultural practices? By characterizing temperatures and trace gas concentrations in the middle atmosphere, the ATLAS missions will contribute to our understanding of the natural greenhouse effect. With its measurements of solar energy, the ATLAS series will help us anticipate possible climatic changes and distinguish the changes that might be related to varying solar output. WARMTH AND PROTECTION FOR THE BLUE PLANET: THE MIDDLE ATMOSPHERE Characterizing processes in the middle atmosphere is the major focus of the ATLAS science program. In the middle atmosphere, the trace gas ozone, a form of oxygen made up of three oxygen atoms, shields life on Earth from the Sun's ultraviolet radiation. Scientists believe that certain chemicals introduced into the atmosphere by human activity are harming that protective ozone shield. Stratospheric Ozone Stratospheric ozone absorbs and scatters ultraviolet radiation from the Sun and, in doing so, performs two important functions. First, the interaction of ozone and ultraviolet radiation heats the middle atmosphere and contributes to the thermal balance of the planet. This profoundly influences atmospheric circulation and, hence, Earth's climate. Second, the ozone layer protects life by preventing ultraviolet radiation, which is lethal or damaging to plants, humans, and other animals, from reaching the planet's surface. Stratospheric ozone is an extremely effective ultraviolet filter, absorbing nearly all of the solar radiation reaching Earth's atmosphere in the wavelength range between 210 and 340 nanometers. Yet, if all the ozone molecules located mainly within the 40-kilometer (km) [25-mile (mi)] expanse of the stratosphere were under the pressure and temperature conditions of Earth's surface, they would form a layer only 2 to 5 millimeters (0.08 to 0.2 inches) thick. A part of the ATLAS mandate is to study the photochemistry of ozone and changes in global ozone levels. Since 1985, scientists have noted that ozone concentrations over the Antarctic have decreased significantly during spring in the Southern Hemisphere (September, October, and November) when light from the Sun begins to reach the polar regions. The cold conditions, sunlight, and atmospheric chemicals present over the South Pole combine to destroy large numbers of ozone molecules, thus permitting more ultraviolet radiation to penetrate through the lower atmosphere to Earth's surface. Much research has been directed toward determining the risks that ultraviolet radiation poses to living creatures, but the exact effects are not yet known. Of particular concern is the danger to oceanic plankton in the southern seas; because these tiny plants and animals form the basis of many food webs, they are important components of the ecosystem. Increased exposure to ultraviolet radiation can also reduce crop productivity, and health threats to humans include increased numbers of skin cancers and cataracts. The photochemistry of ozone is extremely complex. In the daylit atmosphere, solar ultraviolet light splits apart the three-oxygen ozone molecule, freeing a single oxygen atom and a two-oxygen molecule to react with other trace gases. Ultraviolet radiation also splits the oxygen molecule to produce two oxygen atoms. Simultaneously, some of the oxygen atoms and molecules recombine to produce ozone. The net result of this cycle of ozone destruction and production -- the number of ozone molecules -- determines how much ultraviolet light is blocked in the stratosphere. Some chemical reactions in the atmosphere, particularly those involving nitrogen and its compounds (nitric oxide and nitrogen dioxide, for example) and chlorine and its compounds, especially chlorine monoxide, not only destroy ozone but are also catalytic. One chlorine atom, for instance, may cause the destruction of thousands of ozone molecules before it is incorporated into a compound that does not react with ozone. In addition, water vapor plays an important role in ozone chemistry in the stratosphere. Ultraviolet radiation dissociates the molecules of water vapor, forming hydrogen and hydroxyl radicals. (Hydroxyl radicals are highly reactive molecules consisting of one oxygen and one hydrogen atom.) Both of these chemically active species can react rapidly with ozone or produce other compounds that help destroy ozone molecules. Further complicating ozone chemistry are the reactions between different families of compounds, such as nitrogen and chlorine species. In one case, for example, nitrogen dioxide will combine with chlorine monoxide to produce the relatively stable molecule chlorine nitrate, temporarily removing both the reactive nitrogen and chlorine compounds from the ozone-destroying cycles. Sources of Atmospheric Chemicals How do the trace chemicals that are so involved in ozone photochemistry enter the atmosphere? Many are transported from Earth's surface. The specific chemicals and their concentrations can be changed both by unpredictable natural occurrences and by the activities of daily human life (anthropogenic sources). Wind patterns, for instance, carry sea salt and dust into the atmosphere; volcanic eruptions spew sulfur, ash, and carbon dioxide and other chemicals into the middle atmosphere; and thunderstorms move water into the stratosphere. Among the anthropogenic sources of atmospheric trace gases, chlorofluorocarbons are of particular concern. Chlorofluorocarbons are used as refrigerants, foam-blowing agents, cleaners, and aerosol propellants. These compounds are stable at Earth's surface, but when they are carried into the middle atmosphere, sunlight breaks the molecules apart, freeing chlorine to destroy ozone. Sunlight and the Middle Atmosphere Many gases filter solar radiation as it passes through the atmosphere, absorbing or reflecting particular wavelengths. The components of sunlight that penetrate the upper regions to reach the mesosphere and stratosphere fuel the chemistry of the middle atmosphere, with the absorption of ultraviolet radiation by ozone being the primary driver. When the amounts of these radiant wavelengths vary, the chemical reactions in the atmosphere reflect the changes. Furthermore, if changes in the middle atmosphere are observed, it is important to understand which changes might be related to variations in the amount of ultraviolet sunlight. Characterizing the Middle Atmosphere To improve our understanding of how the atmosphere responds to chemical and solar variations, we must develop an extensive and thorough compilation of atmospheric and solar measurements. The suite of ATLAS instruments will investigate the chemistry of the middle atmosphere, studying atmospheric constituents and quantifying the solar radiation that drives middle atmospheric chemistry. The ATLAS investigations, along with ground-based measurements and others made by instruments aboard free-flying satellites, aircraft, balloons, and rockets, will provide a compendium of data that will improve our mathematical models of the middle atmosphere and its relationships with solar energy. These models are important tools that atmospheric scientists use to test and refine their theories of how Earth's atmosphere functions; they are also useful for predicting future changes. Conditions and dynamics of the middle atmosphere are of primary interest to ATLAS scientists, but what is the middle atmosphere? Earth's atmosphere is not uniform. It has several layers, four of which are distinguished by thermal characteristics, chemical composition, movement, and density. The layer in contact with Earth's surface is the troposphere, which extends to altitudes ranging from 8 to 15 km (5 to 9 mi). It is the most dense of the layers, and its temperatures drop with increasing altitude. Essentially all weather occurs within this region. Extending from just above the troposphere to 50 km (31 mi) is the relatively dry, less dense stratosphere, characterized by temperatures that gradually increase with altitude. The stratosphere contains the thin, but crucial, layer of ozone, which absorbs and scatters solar ultraviolet radiation, the major source of stratospheric heating. The next layer is the mesosphere [50 to 85 km (31 to 53 mi)]. In the mesosphere, temperatures again decrease with altitude. The region is also characterized by an abundance of chemicals that exist in excited states. In an excited state, atmospheric components contain more energy than in the conventional state; they act as energy reservoirs and play a major role in mesospheric chemistry. Atmospheric scientists refer to the stratosphere and mesosphere as the middle atmosphere. The fourth layer is the thermosphere, extending to about 600 km (372 mi). Here, temperatures soar as the Sun's energy ionizes atoms and molecules. Chemical reactions in this region also occur at a much faster rate than they do in the cooler layers closer to Earth. The transition zones between each of these layers is called the pause. The border between the mesosphere and the thermosphere, for example, is the mesopause. Nitrogen, oxygen, water, and a myriad of other elements and compounds make up the atmosphere. Nitrogen and oxygen constitute the bulk of the atmospheric ingredients, approximately 79 and 20 percent, respectively; yet, the other, less abundant components are far more influential than their concentrations might indicate. These trace elements often play very important roles in atmospheric chemistry. The ATLAS science teams are seeking to quantify and study specific trace elements and their roles. There are two other major atmospheric divisions: the ionosphere and the exosphere. The ionosphere is characterized by the presence of charged gases, or plasmas. Although the ionosphere is associated with and embedded in the thermosphere, plasmas move closer to Earth or farther away, depending on the time of day and magnetic conditions, and it is not uncommon for plasmas to cross borders of other atmospheric regions. The exosphere is the outermost layer of the atmosphere. It begins at the top of the thermosphere and extends until it merges with interplanetary gases. Hydrogen and helium predominate here, but their densities are very low, accounting for the extreme vacuum conditions of the region. Atmospheric Models Once the ATLAS experiment teams complete their measurements and data analysis, scientists from around the world will have access to the results of the ATLAS observations, such as the solar flux in a given wavelength region or the three- dimensional distribution of ozone in the stratosphere. For these data to be most useful, scientists usually interpret the information in the context of numerical models, which allow the researchers to test their understanding of atmospheric processes and to make predictions about the atmosphere. Models can calculate any number of occurrences, such as the expected change in stratospheric ozone and temperature in response to increases in chlorofluorocarbons, small variations in solar ultraviolet output, and large volcanic eruptions, which inject massive quantities of sulfur dioxide into the stratosphere. Such models are especially important because their results can be used to understand the atmospheric significance of international agreements, such as the Montreal Protocol, which regulate the production and emission of chlorofluorocarbons and their substitutes. Consider the case in which certain ATLAS instruments simultaneously measure the concentrations of several trace species in a given region of the atmosphere. How can scientists tell whether all these data are consistent with each other and with current knowledge of the chemical and meteorological processes in the atmosphere? They construct a numerical model that incorporates the known processes, such as chemical reactions, solar-driven dissociation of molecules, atmospheric heating and cooling, and meteorological events associated with winds. Each model is very complex and requires large, fast computers. Using both the model and data, scientists can search for inconsistencies that might identify errors in one of the measured quantities of the trace species or in their understanding of the rates of one or more of the processes assumed to affect that molecule's concentration. If the future state of the atmosphere is to be modeled, an accurate understanding of atmospheric processes is necessary. Models are validated by real measurements of the atmosphere, and the space-based measurements from the ATLAS missions will be an important part of this validation process. ENERGY FOR THE BLUE PLANET: THE "SOLAR CONSTANT" Sunlight provides the energy for many atmospheric processes; yet, the Sun's radiant output -- in terms of its total energy as well as its distribution of wavelengths -- fluctuates, from a maximum to a minimum and back again over an 11-year cycle. Within this 11-year cycle are embedded the short-term variations of the 27-day solar rotation period. Earth's atmosphere reflects both cycles, and one of the goals of the ATLAS program is to characterize these influences and the related atmospheric responses. The Sun's energy arrives at the top of Earth's atmosphere with a broad wavelength distribution that includes gamma rays, X-rays, ultraviolet radiation, visible light (where most of the energy is contained), infrared radiation, microwaves, and radio waves. For years, the total energy in this solar irradiance was thought to be unchanging; thus, it was named the "solar constant." As more sophisticated and sensitive equipment measured the solar constant with greater precision, it became apparent that the term was a misnomer: solar energy does indeed fluctuate. From our vantage point in the solar system, we receive visual evidence of the solar activities that influence total solar irradiance. Dark sunspots appear, move across the face of our star as it rotates, and disappear; tremendous and fascinating flares erupt from its surface. Historical records indicate that these phenomena occur in 11-year cycles. Recent measurements further indicate that the solar constant also may vary by about 0.1 percent over these cycles. While a 0.1-percent variation may seem inconsequential, such a small change over a long period may have great climatological significance. For example, the general cooling of the planet in the 400 years spanning the 15th and 19th centuries --a period known as the Little Ice Age -- is thought to have been caused by a 1 percent or less variation in total solar irradiance. It is, therefore, important to measure the total solar irradiance and its variations as precisely as possible so that we can identify evidence of long-term change and can anticipate the effects of these changes on Earth's climate. Before the ATLAS missions, the best estimate of the total solar irradiance was 1,367 watts per square meter; however, the precision of the measurements producing this estimate was not sufficient to predict climatological responses reliably. Two ATLAS core instruments will measure total solar irradiance. Using slightly different techniques, these highly calibrated instruments will gather data at selected times during each mission to identify short-term irradiance changes. Even though the ATLAS measurements will not be made over a long enough time to identify long-term changes, these readings will serve as a point of comparison for future solar irradiance measurements. Identical or similar instruments on satellites are also measuring the solar constant at the same time as the ATLAS instruments. By comparing the irradiance values determined by these instruments with ATLAS values, scientists will be able to obtain more accurate and precise measurements of the solar constant over the longer periods in which the satellites are active. Electromagnetic Spectrum To probe the mysteries of the atmosphere and the Sun, the ATLAS experiments rely on the information contained in radiant energy. Each instrument is designed either to record specific ranges of energy that reach its sensors or to quantify the total amount of that energy. The entire range of radiant energy -- radio waves, microwaves, infrared radiation, visible light, ultraviolet light, X-rays, and gamma rays -- is called the electromagnetic spectrum. The human eye is sensitive to the visible light portion of the spectrum. When visible light passes through a prism, we can discern its many component colors -- red, orange, yellow, green, blue, indigo, and violet. Each of these colors represents a specific segment of the visible light energy range, and our eye- brain connection interprets the different segments as different colors. In a similar fashion, the ATLAS instruments interpret some of the electromagnetic spectrum energies produced by the Sun -- particularly the ultraviolet, visible, infrared, and microwave ranges. The instruments distinguish the various "colors" of these spectral ranges and thus identify the chemical species producing (or absorbing) the energy. Radiation enters each instrument in the form of photons, or packets of energy. Photons are described in terms of their wavelengths, which are directly related to their energies. For example, some radio photons move in waves that crest at distances of hundreds of thousands of kilometers. These low-frequency photons contain less energy than higher frequency photons, such as ultraviolet photons that crest as often as every 100 millionth of a meter. The measuring nomenclature of the electromagnetic spectrum is based on photon wavelength. The radiant wavelengths of most interest to ATLAS investigators are those that range from the lower energy infrared, microwave, and visible to the higher energy ultraviolet. These ranges, in order of decreasing wavelength, are measured in millimeters [(mm), thousandths of meters], micrometers [(5m), millionths of meters], and nanometers [(nm), billionths of meters]. THE ATLAS INSTRUMENTS Seven instruments form the heart of the ATLAS program. Five of these --ATMOS, MAS, SSBUV, SOLSPEC, and SUSIM -- gather data critical to our understanding of the middle atmosphere; the other two -- ACRIM and SOLCON --measure total solar irradiance; their readings are complemented by the spectral measurement of SOLSPEC. Fact sheets located in the folder on the back cover of this publication describe each experiment and its specific mission objectives in more detail. Chemical Constituents of the Middle Atmosphere Three investigations determine the concentrations and distribution of trace gases by measuring either the radiation these gases emit or the wavelengths they absorb or scatter. The Atmospheric Trace Molecule Spectroscopy (ATMOS) and Millimeter- wave Atmospheric Sounder (MAS) instruments primarily study the composition of the middle atmosphere. Their findings will be used to characterize global, seasonal, and long-term changes in the concentrations of trace atmospheric species, particularly the chlorofluorocarbons and their resultant chlorine breakdown products and other chemicals involved in the photochemistry of ozone. Data from this research will help validate models of stratospheric chemistry. As the Shuttle's orbit carries the spacecraft into or out of Earth's shadow (orbital night), the ATMOS instrument views the Sun as it sets or rises through the atmosphere. The spectrometer measures changes in the infrared component of sunlight as the Sun's rays pass through the atmosphere. Because trace gases absorb very specific infrared wavelengths, the science team can determine what species are present, in what concentrations, and at what altitudes by identifying the wavelengths that are "missing" from their spectral data. Some species or reactions within Earth's atmosphere also emit characteristic wavelengths of radiation. The MAS instrument measures trace chemical concentrations using a parabolic antenna to receive millimeter-wave emissions from atmospheric gases. The information the MAS instrument gathers from these emissions will allow the determination of middle atmospheric temperatures and pressures and of the concentrations and distribution of chlorine monoxide, water vapor, and ozone. The primary objective of the Shuttle Solar Backscatter Ultraviolet (SSBUV) experiment is to measure stratospheric ozone concentrations. It does so by measuring the ultraviolet radiation scattered by the ozone layer and comparing that radiation with other readings it makes of the ultraviolet spectrum coming directly from the Sun. The SSBUV instrument is virtually identical to Earth-observing satellite instruments that monitor ozone globally and will make coincident measurements with them. Because SSBUV flies on the Shuttle, it can be rigorously calibrated after each flight and before the next to maintain its high precision; a built-in system also allows inflight calibration. From the data gathered by this highly calibrated instrument, scientists can adjust for any drifts in data received from the satellite instruments. Solar Radiation and the Middle Atmosphere Two core investigations study specific wavelengths of sunlight, particularly the ultraviolet energies, which are the primary energy source for chemical reactions in Earth's middle atmosphere. Their measurements are also compared with the SSBUV ultraviolet readings. The Solar Spectrum Measurement from 180 to 3,200 Nanometers (SOLSPEC) experiment collects solar ultraviolet, visible, and infrared radiation to determine how solar energy is distributed at these wavelengths. Data from this study will also help scientists understand how the energy distribution varies and help identify and quantify the connections between variations in solar energy and atmospheric changes. By comparing SOLSPEC data from one flight to another, these solar spectral ranges can be monitored. Since SOLSPEC's spectral range covers most of the Sun's energy output, its data can also be used in combination with ACRIM and SOLCON to study the solar constant. The Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) instrument team studies solar energy variations in the ultraviolet spectrum. It is important to know the absolute intensity of this wavelength range, since the ultraviolet light flux varies widely, affecting middle atmospheric chemistry. Of particular interest are the shorter ultraviolet wavelengths, which exhibit the greatest variation over a solar cycle. The SUSIM also undergoes a rigorous calibration program before, during, and after each flight, enabling the science team to assess changes in instrument accuracy. Data from the ATLAS SUSIM will be compared to data gathered by identical and similar satellite instruments: these comparisons can improve the quality of the longer term measurements since the satellite instruments are not able to undergo rigorous postflight calibration tests. Total Solar Irradiance Measurements Two other investigations seek to refine the value of the solar constant by measuring total solar irradiance, an important factor in the study of Earth's climate. Data from these investigations will also help establish the total solar radiation scale for the International System of Units. The ATLAS Active Cavity Radiometer Irradiance Monitor (ACRIM) is part of an ongoing effort to measure the total solar irradiance. The ACRIM provides measurements of the energy contained in the ultraviolet through infrared spectral ranges with a high degree of accuracy and precision. Its ATLAS readings are combined with those from identical instruments on satellites to compile a database of total solar irradiance measurements. To determine the total solar irradiance, the ACRIM measures the power required to maintain a specific temperature difference between two cavities when one is open and exposed to sunlight and when both are closed. The ACRIM is recalibrated after every mission to provide a benchmark of accuracy for satellite data. The Measurement of Solar Constant (SOLCON) instrument is also designed to improve the accuracy of measurements of total solar irradiance and to identify long-term variations in the value. In contrast to the ACRIM, the SOLCON instrument measures solar irradiance by determining the difference in power required to bring two cavities into thermal balance when one is open to the Sun and the other is closed. To ensure the accuracy of the instrument, the science team characterizes it precisely in a laboratory setting. They also compare the instrument to a set of ground-based models and other absolute radiometers before and after each flight. MISSION OPERATIONS The global relevance of the ATLAS series is reflected in the ongoing efforts of the participating international space agencies to focus the expertise of their science, engineering, and management communities on characterizing the middle atmosphere. The ATLAS missions themselves have evolved through years of careful planning, coordination, and preparation. The ATLAS program is sponsored by NASA's Office of Space Science and Applications, directed by the Earth Science and Applications Division, and implemented by the Flight Systems Division, all located at NASA Headquarters in Washington, D.C. Here, the program managers and program scientist define the overall science goals, select experiments, and budget funds for instrument teams, hardware development, payload integration, mission operations and planning, and the publication of scientific results from the U.S. instruments. The management of each ATLAS mission is the responsibility of the Marshall Space Flight Center in Huntsville, Alabama. Working closely with the program offices, the mission manager directs a civil service and contractor team effort to match science objectives, instrument requirements and capabilities, and Shuttle-Spacelab resources so that each flight is engineered to gather the maximum amount of science information. This effort also includes the preparation of a minute-by-minute schedule, called a timeline, that combines crew activities, experiment requirements, Spacelab resources, and Shuttle maneuvers into an efficient operating plan. The mission manager and team work with other NASA centers that prepare the Shuttle and Spacelab for launch and landing, conduct flight operations, and collect, process, and distribute data. The team also ensures that each crew is well trained in the mission's science objectives and hardware operations. The ATLAS science community, too, has certain mission planning responsibilities. The principal investigators of the experiments form an Investigator Working Group that meets regularly before the mission to advise the mission manager's team on science- related issues and payload operations. The working group is chaired by the mission scientist, a member of the mission manager's team. During the mission, the working group becomes the Science Operations Planning Group, meeting twice a day to evaluate science activities, solve problems, and recommend ways to take full advantage of any unplanned opportunities. After the investigator teams have qualified their instruments for flight with comprehensive tests ensuring that they can survive and operate in the space environment, each team sends its experiment hardware to the Kennedy Space Center in Florida for installation on the Spacelab pallet. Once integrated, the instruments are again tested as a payload to ascertain their readiness for flight. The payload is then fitted into the orbiter. By launch day, all the elements for a successful mission are in place, awaiting the flight. The ATLAS missions launch from Kennedy Space Center. Shortly after the Shuttle reaches its orbiting altitude, the payload bay doors are opened, and the crew activates the Spacelab systems and makes sure each is operating properly. Next, the master timeline of science commands is loaded into the computers, and the ATLAS instruments begin operations. The computer timeline and the minute-by-minute mission schedule can both be revised, if desired, to respond to additional science opportunities or to any problems encountered. Every ATLAS flight crew is divided into two teams, each of which works a 12-hour shift so that science operations can continue around the clock. At least one member of each team will have special training in both Spacelab and experiment operations and will oversee science activities on the shift. Most of the ATLAS instruments operate automatically, commanded by the Spacelab computers; however, the crewmembers can use keyboards to enter observation sequences if necessary. Another crewmember on each team is part of the orbiter crew and is responsible for maneuvering the Shuttle when an instrument requires precise pointing or must be operated in a specific attitude. During the mission, the management and science teams maintain a 24-hour vigil in the Spacelab Mission Operations Control/Payload Operations Control Center at Marshall Space Flight Center. This facility contains banks of computers, monitors, and communication consoles that keep the people on the ground and in space in contact with one another to monitor the payload, collect data, solve problems, and reschedule science activities as necessary. The mission management team at Marshall is also in contact with personnel at Johnson Space Center's Mission Control Center in Houston, Texas, who are responsible for the orbiter operations and the flight itself. The ATLAS instruments will gather data from about 4 hours after launch until about 12 hours before landing. At this time, the crew will deactivate the science hardware and Spacelab, and the payload bay doors will close for reentry. After landing, three other important phases of the ATLAS program begin: flight data processing, concentrated data analysis, and preparation for the next mission. The Goddard Space Flight Center is responsible for distributing the flight data to the scientists, who further process the data and start their analyses in earnest. A few months later, the investigators are ready to begin reporting their findings, publishing their results in journals and magazines, presenting papers at science and technology symposia and workshops, and releasing their information through database networks. The body of knowledge gained through their ATLAS efforts is thus shared with investigators worldwide. The teams also inspect and recalibrate their instruments to ensure that the hardware is accurate, in good operating condition, and ready for the next flight. If the instrument must be repaired or updated, it can be refurbished and reintegrated quickly. BEYOND ATLAS Throughout history, people have placed great importance on changes in the environment, making significant investments of physical, mental, and spiritual energies to adapt to these changes and to determine their causes and effects. Unlike our ancestors, we have the benefit of hundreds of years of record keeping that points out long-term trends in our environment. Today, we can explore within the atmosphere itself to characterize the intricate tangle of chemicals and sunlight that influences and determines our environment. We now occupy an historically unique position: we are one of the controlling factors in the evolution of our atmosphere. To understand our role in environmental change, we must know how the Sun, the atmosphere, and the rest of the Earth System are interwoven. The ATLAS program, with its emphases on Earth's middle atmosphere and the Sun's influence on climate, is but one of the multidisciplinary endeavors to conduct systematic and continuing studies of our environment. The ATLAS missions are laying the groundwork from which an accurate description of the atmosphere and the Sun's influence on it can evolve. As our understanding of the Earth System becomes more refined and detailed, we become better prepared to carry out our responsibilities as guardians of Planet Earth. ATLAS 2 MISSION ATLAS 2, the second of the Atmospheric Laboratory for Applications and Science missions, is scheduled for launch in 1993. This mission characterizes the chemical and physical components of Earth's middle atmosphere and the solar energy injected into the atmosphere, studies that began on ATLAS 1. Like its predecessor, ATLAS 2 is an integral part of the Spacelab contribution to NASA's Mission to Planet Earth. Seven instruments comprise the core payload. The Atmospheric Trace Molecule Spectroscopy (ATMOS) and Millimeter-wave Atmospheric Sounder (MAS) study atmospheric constituents. The Solar Spectrum Measurement from 180 to 3,200 Nanometers (SOLSPEC) and the Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) characterize the solar radiation that drives chemical reactions in the middle atmosphere. The Shuttle Solar Backscatter Ultraviolet (SSBUV)* experiment measures both solar ultraviolet output and stratospheric ozone. Two other instruments -- the Active Cavity Radiometer Irradiance Monitor (ACRIM) and the Measurement of Solar Constant (SOLCON) -- measure the total solar irradiance. The objectives of each ATLAS 2 experiment program and its instrument complement are described in detail in accompanying fact sheets. Scientists from six nations are participating in the ATLAS 2 mission, underscoring the worldwide importance of atmospheric and solar research. In addition to the United States, investigators represent Belgium, Germany, France, The Netherlands, and Switzerland. MISSION FACTS Flight number: STS-56 Launch: 1993 Launch site: Kennedy Space Center Prime landing site: Kennedy Space Center Shuttle altitude: 296 km (160 n. mi.) Orbital inclination: 57 degrees to the equator Shuttle attitudes: payload bay toward Sun payload bay toward Earth Number of crew members: 5 Mission duration: 8 days Payload operations: 24 hours/day Configuration:igloo, 1 pallet, 2 Get-Away-Special canisters The mission will fly while the Upper Atmosphere Research Satellite is also gathering atmospheric and solar data. The orbits of the two spacecraft will allow instruments to make a number of independent measurements of the same regions of the atmosphere at the same time. Data gathered during these opportunities will be compared to ascertain satellite instrument calibration. *SSBUV is co-manifested with ATLAS 2. Unique Science Opportunities The ATLAS 2 mission is scheduled for a night launch in the Northern Hemisphere's spring. The Shuttle's path will then carry the payload over Earth's Northern Hemisphere during darkness on the ascending part of the orbit. This orbit will allow scientists to study daily variations in the chemistry of the middle atmosphere over high northern latitudes. (ATLAS 1 flew over the high southern latitudes at night and over the high northern latitudes during daylight, detailing those atmospheric conditions.) ATLAS 2 measurements are particularly crucial in light of recent data from the Upper Atmosphere Research Satellite and the Second Airborne Arctic Stratospheric Expedition, which indicate unprecedented levels of chlorine monoxide at high northern latitudes during the winter of 1991-1992. Given these high concentrations, atmospheric models suggest that, under appropriate meteorological conditions, significant ozone depletion over the Arctic is possible. Many important chemicals involved in the photochemistry of ozone exhibit strong diurnal variations. For example, in sunlight, chlorine reservoir compounds break down and release chlorine, which destroys ozone; at night, the concentrations of the reservoir species increase, reducing the amount of chlorine available for chemical reactions. The best time to measure the effects of the nightly buildup is at sunrise; so, for scientists to measure the nighttime chemical concentrations over the Northern Hemisphere, the Shuttle must be entering orbital sunrise from a high northern latitude. The ATLAS 2 orbital path will permit measurement of these and other key species in the atmosphere over northern regions, and what is learned from measurements of the buildup of these concentrations will improve our understanding of ozone chemistry and our ability to test models of atmospheric behavior. Science Operations Plan The ATLAS 2 science operations plan calls for periods of atmospheric data gathering interspersed with orbits dedicated to solar observations. During the orbits designated for middle atmospheric measurements, the Shuttle will fly with its payload bay toward Earth, and the atmospheric instruments will operate almost continuously. ATMOS will take solar radiation absorption readings during each orbital sunrise and sunset, MAS will measure microwave emissions from Earth's limb throughout each orbit, and SSBUV will make its measurements of backscattered ultraviolet radiation in the daylight portions of these orbits. The ATMOS and MAS instruments will be inactive during solar observation periods. For solar observations, the Shuttle's payload bay will point toward the Sun in the daylit portion of each orbit. At these times, ACRIM and SOLCON will measure total solar irradiance, SUSIM and SOLSPEC will make solar spectral measurements, and SSBUV will gather its data on solar ultraviolet radiation. MISSION MANAGEMENT TEAM Mission Manager: Program Manager: Ms. Teresa Vanhooser Mr. Earl Montoya Marshall Space Flight Center NASA HQ Assistant Mission Manager Mr. Gerald Maxwell Marshall Space Flight Center Mission Scientist: Program Scientist: Dr. Timothy Miller Dr. Jack Kaye Marshall Space Flight Center NASA HQ Assistant Mission Scientist: Dr. Steve Smith Marshall Space Flight Center Chief Engineer: Ms. Angie Jackman Marshall Space Flight Center ATLAS 1: AN ENCOUNTER WITH PLANET EARTH In March of 1992, the Shuttle Atlantis carried the first Spacelab flight of the National Aeronautics and Space Administration's Mission to Planet Earth into orbit. In its payload bay were 13 sophisticated and complementary instruments designed to identify the chemical species in our atmosphere, to measure the Sun's energy falling on and entering the atmosphere, to study the behavior of charged particles in the electric and magnetic fields surrounding Earth, and to gather ultraviolet light from stars and galaxies. This first mission in the series of Spacelab flights called the Atmospheric Laboratory for Science and Applications is known as ATLAS 1. The very successful 9-day mission established a voluminous and historical scientific database on the middle atmosphere. Science teams will be analyzing this database for years to come; however, some preliminary results are available. Six atmospheric instruments were aboard Atlantis: the Atmospheric Lyman-Alpha Emissions (ALAE) instrument, the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument, the Grille Spectrometer (Grille), the Imaging Spectrometric Observatory (ISO), the Millimeter-wave Atmospheric Sounder (MAS), and the Shuttle Solar Backscatter Ultraviolet (SSBUV) instrument. *The ALAE team has reported the first detection of deuterium atoms at 85 km (53 mi), the mesospheric altitude at which ultraviolet light dissociates hydrogen or deuterium from water vapor molecules. The deuterium observation is an important indicator of the hydrogen chemistry of the mesosphere, and the data will be useful in determining the height of the turbopause, the altitude below which atmospheric constituents are distributed by turbulent mixing. *ATLAS 1 crewmembers observed a layer of tiny droplets of sulfuric acid and water in the atmosphere. This aerosol layer was produced by the eruption of the Mount Pinatubo volcano in 1991. The ATMOS team is studying how concentrations of ozone and other gases are affected by the presence of this aerosol layer, which is located between 20 and 28 km (12 to 17 mi) and coincides with the ozone layer. ATMOS data also indicate that the concentrations of all chlorofluorocarbons have increased significantly since 1985, when ATMOS measured the concentrations of the compound during Spacelab 3. *The Grille Spectrometer successfully mapped the distribution of 10 target chemical species, and early analysis is focusing on methane (a source of hydrogen with concentrations that have been increasing from 0.5 to 1 percent each year) and hydrogen chloride (the dominant chlorine reservoir in the stratosphere). *The ISO team acquired a database on upper atmospheric spectral emissions, ranging from the extreme ultraviolet to the near infrared. The instrument recorded spectra of the atomic oxygen green line, which had not been measured before in the daytime mesosphere, and also obtained basic measurements of the hydroxyl radical in the same region. Atomic oxygen, along with molecular oxygen, plays a major role in ozone production in the stratosphere and mesosphere. The hydroxyl molecule is another dominant player in mesospheric chemistry; it especially affects the concentrations of ozone and carbon monoxide. *The MAS instrument obtained excellent global coverage of middle atmospheric chlorine monoxide, water vapor, and ozone measurements over the latitudes ranging from 80 N to about 40 S. In general, chlorine monoxide data agree with previous measurements and with models of undisturbed stratospheric chemistry. As predicted, a large diurnal ozone variation occurs above 70 km (43 mi), with greater concentrations on the night side of the orbit. Also, the data indicate a large latitudinal gradient in mesospheric water vapor, which appears to be in higher abundance over the tropics than at mid-latitudes. *During 7 of its 40 Earth-view orbits, the SSBUV gathered unique data on ozone in the upper stratosphere. By looking at 3 ultraviolet wavelengths 4 times in a row (rather than at 12 wavelengths for a whole ozone profile) and by surveying an air column between 40 and 60 km (25 and 37 mi), rather than between 15 and 60 km (9 to 37 mi), scientists were able to study small-scale features of ozone. This special wavelength scanning mode yielded higher spatial resolution of ozone [50 km (31 mi) versus the usual 250-km (155-mi) detail]. These features should provide data on how ozone is transported. The SSBUV also measured solar ultraviolet radiation over four orbits. These data are being analyzed to identify changes in solar irradiance related to changes in solar activity measured on SSBUV's previous flights in 1989, 1990, and 1991. Scientists are using data from two of the solar instruments aboard ATLAS 1 --the Active Cavity Radiometer Irradiance Monitor (ACRIM) and the Measurement of the Solar Constant (SOLCON) -- to refine measurements of the total amount of the Sun's radiant energy that reaches the top of Earth's atmosphere. ACRIM and SOLCON scientists are now analyzing data from the 23 solar-viewing orbits of ATLAS 1 and will be comparing their measurements of the solar constant with one another and with information from the ACRIM II instrument aboard the Upper Atmosphere Research Satellite. The results of SOLCON's solar observations will also be compared to data from instruments aboard the Earth Radiation Budget and EURECA Satellites. These measurements are crucial to our ability to identify possible trends in solar irradiance variability. Two other instruments -- the Solar Spectrum Measurement from 180 to 3,200 Nanometers (SOLSPEC) and the Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) -- measured specific wavelengths of solar radiation to determine their absolute values very accurately. These measurements are used in models of the middle and upper atmospheric regions. The data will help determine not only how solar output varies by wavelength but will also be useful in inferring the response of Earth's atmosphere to such variations. *The preliminary analysis of SOLSPEC data indicates that the solar output magnitude values for the wavelengths of interest (ultraviolet, visible, and infrared) are close to the expected values. The results of subsequent and more detailed analysis will be helpful in validating models of the interaction of sunlight with the atmosphere. *The SUSIM team collected over 100 spectra. These data are also being compared to those from the SUSIM instrument on the Upper Atmosphere Research Satellite, a comparison that will establish a calibration factor for the satellite instrument. Three investigations explored the space plasma environment: the Atmospheric Emissions Photometric Imaging (AEPI), the Space Experiments with Particle Accelerators (SEPAC), and the Energetic Neutral Atom Precipitation (ENAP) investigations. *The AEPI recorded optical emissions from the SEPAC artificial auroras, natural auroras in the Southern Hemisphere, and airflow. Investigators are studying AEPI's images of auroral arcs to learn more about the chemical processes occurring in the arcs. The AEPI also produced clear images of atmospheric gravity wave structures from the emissions of atmospheric oxygen. (Gravity waves are disturbances that often originate from lower atmospheric activity and produce structured features in the airflow.) At least one of these structures was ~100 km (62 mi) long. *SEPAC used an electron beam accelerator to create 60 artificial auroras over the southern Pacific Ocean. These were the largest and brightest artificial auroras ever made: the optical emissions were brighter than expected and occurred over a much larger portion of the image. *The ENAP investigation used the ISO instrument to measure faint nighttime glows that occur above Earth's middle latitudes when neutral atoms from Earth's ring current rain down on the atmosphere. Although the brighter glows were observed south of Australia when Atlantis' orbit was nearest the southern auroral zone, the ENAP investigation detected faint glows all the way to the equator. Another region of brighter emissions was detected over the south Atlantic Ocean where trapped particles from the ring current penetrate to lower altitudes than elsewhere at these latitudes. The Far Ultraviolet Space Telescope (FAUST) obtained over 20 wide-field images of the far ultraviolet sky. These images contain information on galactic stars and dust, extragalactic objects, and even auroral and atmospheric emissions and reveal a wealth of newly discovered sources of ultraviolet radiation. Because they were produced by a new technique of counting photons electronically, the images show sources that are up to 10 times fainter than those from a previous ultraviolet survey of the same regions of the sky. THE ATLAS 2 CREW Commander Kenneth D. Cameron received a B.S. and an M.S. in aeronautics and astronautics from the Massachusetts Institute of Technology. He enlisted in the Marine Corps and then earned a commission. He was assigned to the Republic of Vietnam as a platoon comm