We receive about 1kw of sunlight per square meter on Earth, and earth is 149M km from the sun. From napkin math, it should rather be ~45MW/sqm on the sun to receive 1kw/sqm on Earth (surface of the sphere of radius 149M km divided by surface of the sun gives ~45000, so 1 watt from the sun becomes 1/45000 watt when it reaches the Earth)
Where am I wrong ?
It's pretty amazing that you can have a spacecraft in nearly 20x direct sunlight, permanently and still have it actually work.
Total solar power output = 4 * π * (1.5e11 [m])² * 1361 [W] = 3.85e26 W/m²
Sun's "surface" irradiance = TSPO / (4 * π * (6.96e8 [m])²) = 6.32e9 W/m²
At Solar Orbiter's perihelion, assuming the distance from the Sun's point center rather than the Sun's surface = TSPO / (4 * π * (4.2e10 [m])²) = 1.74e4 W/m².
^ Except for Earth's irradiance and the distances, these are theoretical rough values rather than observed ones because reality is messier than simplified models.
The usual sense involves integration and derivation but look at senses 2 & 4. It also means any calculation.