The NASA fact sheet lists the solar irradiance at Mars as 586.2 W/m2, at the planet's mean distance from the Sun. [1] A flat panel does not collect that number. The screen here is area times that irradiance times an efficiency you type, times the cosine of the zenith angle, times an exponential dust term. Tau is the vertical optical depth, and you type it.
There is no stored clear-air tau and no stored dust-storm tau. Dust storms on Mars is why a storm can matter. This page will not pick a storm for you. A global dust storm can starve a solar mission. That sentence is a warning, not a tau.
Screen
One square meter, 100 percent efficiency, overhead Sun, and tau 0 must return 586.2 W/m2. If that check fails, the form refuses. A zenith of 90 degrees or more returns 0 W. Efficiency is a percent you type. 100 percent is the arithmetic check, not a cell. The exponent is exp(-tau / mu), and mu is not allowed below 0.05 in the divisor, so a very low Sun does not divide by zero. That floor is a numerical guard, not a measured atmosphere.
Class D instrument
Power is area times 586.2 W/m2 times efficiency times max(cos(zenith), 0) times exp(-tau / max(cos(zenith), 0.05)), and 0 when the zenith is 90 degrees or more. The 0.05 floor only keeps the divisor from hitting zero.
What this does not size
No array area for a crew, no battery, no night, no latitude climate, and no seasonal optical-depth curve. Oxygen from air does not size the power a crew oxygen plant would draw. Regolith shield is the soil column, and it does not use this irradiance.
See also
What links here
References
- NASA Goddard Space Flight Center. Mars Fact Sheet. Solar irradiance. Updated 19 May 2025. https://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html