9-5. The Mars Climate for a Photovoltaic System Operation JOSEPH APPELBAUM & DENNIS J. FLOOD Summary Detailed information on the climatic conditions on Mars are very desirable for the design of photovoltaic systems for establishing outposts on the Martian surface. This paper addresses the distribution of solar insolation (global, direct and diffuse) and ambient temperature. These data are given at the Viking landers' locations and can also be used, to a first approximation, for other latitudes. The insolation data is based on measured optical depth of the Martian atmosphere derived from images taken of the sun with a special diode on the Viking cameras; and computation based on multiple wavelength and multiple scattering of the solar radiation. The ambient temperature (diurnal and yearly distribution) is based on direct measurements with a thermocouple at 1.6 m above the ground at the Viking lander locations. The insolation and ambient temperature information are short-term data. New information about Mars may be forthcoming in the future from new analysis of previously collected data or from future flight missions. The Mars climate data for photovoltaic system operation will thus be updated accordingly. Introduction NASA, through its Project Pathfinder, has put in place a wide-ranging set of advanced technology programs to address future needs of manned space exploration. Included in the mission set under study is the establishment of outposts on the surface of Mars. The Surface Power Program in Pathfinder is aimed at providing ultralightweight photovoltaic array technology for such an application (as well as for the lunar surface). Detailed information on the climatic conditions on Mars at the photovoltaic system location is very desirable. This includes the distribution of solar insolation; ambient temperature; albedo; and wind speeds and directions; with latitude, season, and time of day. In addition, the effect of dust accumulation on the photovoltaic panels and radiation damage causing degradation of the output power needs to be assessed. As on Earth, solar insolation on the surface of Mars is composed of two components: the direct beam, and diffuse component. The direct beam is affected by scattering and absorption along the path from the top of the Martian atmosphere to the Martian surface. Measurement of the optical depth [1,2] of the Martian atmosphere allows an estimate of the absorption and scattering out of the beam. These estimates were derived from images taken of the Sun and Phobos with a special diode on the Joseph Appelbaum and Dennis J. Flood, National Aeronautics and Space Administration, Lewis Research Center, Cleveland, Ohio 44135, USA. Paper number IAF-ICOSP89-9-5.
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