Beyond Jupiter’s distance, solar panels cannot produce enough power to operate a spacecraft … layers in place for both direct lighting and mesh-reduced lighting experiments. CASSINI SCIENCE INVESTIGATION National Aeronautics and Space Administration Educational Product Educators& Students Grades 5-12 Educational Brief EB-2001-12-022-JPL EB-2001-12-022-JPL JPL 400-1037 05/02 Can a Spacecraft Use Solar Panels at Saturn? Objective To demonstrate the effect of the inverse square law of illumination with distance.

Solar panels convert solar energy directly to electricity using photovoltaic cells. When sunlight strikes the photovoltaic cell, a small voltage is generated. Wires connected to the cell permit an electric current to flow through circuits to power various electrical and electronic components. Electricity generated this way is used on Earth and on spacecraft to power electronics, motors, and science instruments. Missions to Mars and Venus, as well as satellites in Earth orbit, have solar panels. However, at increasing distance from the Sun, the amount of available sunlight drops below the level at which the use of solar panels is practical. Either the spacecraft must be very small or the solar panels must be very large. Beyond Jupiter’s distance, solar panels cannot produce enough power to operate a spacecraft, no matter what size the panels and spacecraft are. Facts You Need •Earth is 149,600,000 kilometers (92,970,000 miles) from the Sun. •Saturn is 1,429,400,000 kilometers (888,200,000 miles) from the Sun (9.555 times more distant than Earth). •Cassini needs 628 watts of power to operate all its systems at Saturn. Procedure 1. Measure the dimensions of the power-generating area of the solar cell with a millimeter ruler (sometimes the protective case is much larger than the actual working area). 2. Attach the leads of the solar cell to the same color leads of the digital multimeter (red is positive, black is negative; no damage will be done if the leads are mismatched). Alligator or wire clips on the multimeter leads will be easier to use than standard probes, or use alligator clip jumpers (also available from electronics parts stores) to make the connections. 3. Set the multimeter to current (or voltage) and turn it on….

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