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## Homework Statement

A spacecraft is protected from the Sun’s radiation by a planar baffle whose size is much greater than that of the spacecraft itself. The baffle is aligned perpendicular to the direction of the Sun. Show that the equilibrium temperature of the baffle is $$T_b=\Big(\frac{\alpha_d^2}{8}\Big)^{\frac{1}{4}}T_s$$ where T_s is the heat of the sun and is 5800K, $\alpha_d$ is the angular diameter of the Sun as seen from the spacecraft.

## Homework Equations

Flux of the sun = L / $2\pi d^2$ where $d$ is the distance of the Sun from the baffle and L is the luminosity of the Sun.

Any classical equations involving thermal equilibriums etc.

## The Attempt at a Solution

I was thinking of using the flux of the Sun stated above, and then the flux of the Sun's radiation on the baffle, considering the Sun's rays projected onto the baffle. Some form of ratios may help, but I didn't get anywhere.

I also tried using some geometries involving the angular diameter but could not successfully isolate $\alpha$. Perhaps we need to take a small angle approximation?