Viking lander cameras. Since the cameras are sitting on the Martian surface, the measured intensity is directly related by Beer's law to the optical depth of the intervening atmospheric haze: where Go is the unattenuated insolation at the top of the Martian atmosphere; Gb is the direct beam insolation on Martian surface normal to the solar rays; T is the optical depth; and m(z) is the airmass determined by the zenith angle z. Earth-terrestrial insolation data are accumulated over many years at different locations around the world and are given as long-term average values. The optical depth data for Mars are derived for only 2 Mars years. Consequently, the calculated solar insolation corresponds to short-term data. Furthermore, the measured opacities (optical depth) and the calculated insolations pertain to just two locations on Mars, Viking lander 1 (VL1) is located at 22.3° N latitude and 47.9° W longitude, and Viking lander 2 (VL2) is located at 47.7° N latitude and 225.7° W longitude. The similarity in properties of the dust suspended above the two landing sites suggests that they are also representative of ones at other locations, at least, at latitudes not too far from the landers' sites. Data from lander VL1 may be used for latitudes 40° N to 40° S and data from lander VL2 for higher latitudes. Scatterers in the Martian atmosphere consists mainly of suspended dust particles, the amount of which vary daily, seasonally, and annually dependent on local and global storm intensities and duration. The optical depth of the atmosphere was determined from the measurements taken in the morning and in the afternoon. The afternoon values are more representative due to suspended dust particles, whereas the morning values are higher indicating the presence of a ground fog. Optical depth values given in the section entitled OPTICAL DEPTH are the afternoon values, and are assumed to be constant throughout the day. Large values of optical depth correspond to global storms, i.e. days with low insolation (‘dark days'). The albedo of the Martian surface varies in the range of about 0.1-0.4. The insolations derived in the section entitled SOLAR INSOLATION correspond to 0.1 albedo but can be also used for other values of albedo, to a first approximation. The ambient temperature at the Viking landers' locations was measured for more than two Martian years at a height of 1.6 m. The ambient temperature sensors are chromel-constantan thermocouples. Again, these are short-term data and pertain to the two Viking locations. In this paper we calculated the distribution of solar insolation and report the ambient temperature: the two major climatic components for photovoltaic system design. We do not report data on wind speed and direction, nor albedo and the effect of dust on the output power of the photovoltaic panels. New information about Mars may be forthcoming in the future from new analysis of previously collected data, from new Earth-based observation, or from future flight missions. The Mars climatic data for photovoltaic system design will thus be updated accordingly. Solar Cell Array The effect of temperature and insolation on the I— V characteristic of a solar cell array can be related to empirically observed properties of the type of solar cell used. The
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