100 additional senior scientists are formally associated with the program, most of these through written agreement with the Principal Investigators. Beyond this, many Principal Investigators have informal arrangements with other scientists for assistance in analysis or in assessing the significance of the results. Overall, it is expected that more than 700 senior scientists and engineers will have a direct function in the analysis and reporting of Skylab data. Over 2,500 astronaut hours wil be allocated to the performance of these investigations, more than three times the total amount available in all prior U.S. Earth Orbit missions. The crew will operate more than 50 different assemblies of sophisticated equipment to acquire an unprecedented amount and variety of data from a single scientific facility. This magnitude of participation and scientific interest emphasizes the importance of the Skylab experiments and investigations. Attention is now focused on each of the more significant disciplinary areas. SOLAR ASTRONOMY The study of the Sun (figure 100) goes back to the beginnings of civilization, • LEARN MORE ABOUT THE UNIVERSE SPACE ENVIRONMENT AND THE SOLAR SYSTEM AND THEIR EFFECT ON EARTH AND MANK ND WE DATA ON SOLAR PHENOMENA WITH INCREASED FIGURE 100 when prehistoric astronomers first used its motion to predict the seasons and tell the best times for planting and harvesting. Their successors, modern solar astronomers, seek to understand and explain the remarkable phenomena within and around the Sun itself. In part, this is scientific research in its purest form, but there is also a strong awareness that better knowledge of solar processes may lead the way to new means for generating and controlling energy for use on Earth. There is also the problem of explaining mechanisms by which solar events affect the Earth (figure 101) (see p. 384), particularly in the streams of high energy particles associated with solar flares. For example, it is assumed that these flares are responsible for the auroras and the associated disruption of ionospheric radio transmission. Since it is known that sunspot activity correlates with variations in the profiles of temperature and density in the upper atmosphere, it is conceivable that the injection of energy in the upper atmosphere by solar particles may trigger world-wide weather phenomena as well. The solar instruments on Skylab afford an unmatched opportunity to gain new knowledge of the Sun. Operating beyond the limitations of the atmosphere, these solar telescopes will make observations of the Sun not accessible from ground observations, particularly in the ultraviolet and X-ray regions. Their size and sensitivity make it possible to observe details of form and spectral composition not attainable by the satellite solar observatories orbited to date, and their operation under the direct control of an astronomer-astronaut allows them to be aimed selectively at specific details on the solar disc. The observing program to be carried out on Skylab embodies coordinated attacks on specific problems of solar physics, such as: magnetic fields and circulation in the solar atmosphere; active regions, analogous to storm centers, associated with sunspots; solar flares, giant eruptions associated with active regions; prominences and filaments, hundreds of tons of matter suspended in the solar atmosphere; and expulsion of solar matter toward the Earth. In addition, the properties of the Earth's atmosphere will be probed by observing the extinction of solar radiation as the spacecraft passes from night to day. The series of three Skylab missions will provide over 500 hours of astronaut controlled solar observations. While the first solar astronomy mission can be considered exploratory in nature, to separate the ordinary from the extraordinary and to refine the skills of the integrated astronaut/ground support team, the second and third missions will make it possible to close the cycle of observation, interpretation, and new observation, and to follow-up on the new discoveries that are anticipated. In planning a thorough and world-wide attack on solar physics, the Principal Investigators have established agreements for joint investigations with over 50 astronomers and physicists in the United States and abroad. Concurrent groundbased observations in accessible wavelength regions, and X-ray and gamma-ray spectroscopy from sounding rockets and balloons will provide needed supporting data to the space-borne observing programs and will multiply the solar physics return from both activities. To allow other interested scientists to coordinate their own observations with the solar astronomy program without a formalized agreement, the Principal Investigators also established procedures for world-wide communications which will inform interested ground-based observers what the scheduled solar astronomy observing activities are to be, on a daily basis. It is expected that over 200 observatories and scientists will take advantage of this opportunity. The unique combination of a manned solar observatory and simultaneous world-wide ground observations provides a powerful tool for obtaining new knowledge of the Sun that will benefit many areas of study. EARTH RESOURCES Space as a vantage point for observing the Earth (figure 102) has been PERFORM PHOTOGRAPHIC ANALYSIS OF CROPS FORESTRY UNDERGROUND WATER SNOW COVER GEOLOGY ATE AND EVALUATE AIR AND WATER POLLUTION AND SEA XAMINE OCEAN SURFACES ICE AND CLOUD FORMATIONS FIGURE 102 amply demonstrated by the photography returned by Gemini and Apollo flights and the weather information provided routinely by automated satellites for many years. The Earth Resources Technology Satellite (ERTS) launched last July and the Skylab Earth Resources Experiments Package (EREP) are experimental efforts directed towards demonstrating the feasibility of using space to gather more detailed information and apply it to the problems of the environment, our diminishing resources, and the rapidly growing world population. The data provided by ERTS and EREP are to be used, for example, to study crop and forest inventory, crop health, oceans, mineral resources, water resources, and air and water pollution. More specifically, EREP will be used to acquire selective data for 146 investigations in 46 task areas (figure 103) (see p. 386) which can use remotely sensed data from space. For instance, the tasks under "Crop Inventory" in the "Agriculture/Range/Forestry" discipline include studies in Arizona, California, Colorado, Michigan, Mississippi, Louisiana, and Texas; and in Iran, Brazil, Mexico, Argentina, the Sudan and Colombia. These studies should provide the basis for evaluating the feasibility of routine assessment of the major food crops of the world. The Skylab instruments generally provide higher spectral and spatial resolution (figure 104) (see p. 386) than is available with ERTS. In the lower regions of |