What is the Radiance of Solar Radiation at Earth Orbit?

[fredrick08]

Homework Statement

given that T(sun)=5771.4, S(Earth)=1370, D(Earth)=1.5x10^8km, R(sun)=7x10^5km

calculate the radiance of solar radiation at Earth orbit

Homework Equations

Irradiance=Radiance/Solid Angle
Solid Angle=Area/Distance^2
I=sigma*T^4

The Attempt at a Solution

Radiance=1370/solid angle... but how do i find the solid angle... i get answers that's are very large... but I am as confused as hell what to use

 

[fredrick08]

is it 1370/(pi*R(Sun)^2/D(earth)^2)=2x10^7 Wm^-2st-1?