Inputs
Orbit
Solar array
Results
Power at distance 190.5W
Power at Earth (1 AU) 190.5W
Ratio to Earth 1
Irradiance at distance 1,361W/m²
Sun distance 1AU
Method
The inverse-square solar flux model: beginning-of-life output at a fixed Sun distance and incidence angle.
Pd = (S0 / d²) · A · η · cos θ S0 = 1361 W/m², the solar constant, total irradiance at 1 AU.
Derivation
1
Scale the solar constant to the distance The Sun radiates into an expanding sphere, so irradiance falls with the square of the radius. This step is pure geometry: no spacecraft properties enter it. Sd = S0 / d²
2
Project the flux onto the panel A tilted panel presents a smaller cross-section to the Sun. The projected area is the cosine of the angle between the panel normal and the Sun vector. Aproj = A · cos θ
3
Convert intercepted flux to electrical power Cell efficiency is the fraction of intercepted flux the junction converts. Pd = Sd · Aproj · (η / 100)
4
Compare against the same array at Earth Panel area, efficiency, and incidence angle all cancel in the ratio, leaving only the distance, which is why the same array sized for LEO loses 96% of its output at Jupiter. R = Pd / P⊕ = 1 / d²
Symbols
| Input | Description | Unit |
|---|---|---|
| d | Distance from the Sun | AU |
| θ | Incidence angle from the panel normal | deg |
| A | Effective panel area: cell area, not panel outline | m² |
| η | Cell conversion efficiency | % |
| S0 | Solar constant at 1 AU: 1361, fixed | W/m² |
| Derived | Description | Unit |
|---|---|---|
| Sd | Solar irradiance at that distance | W/m² |
| Aproj | Projected area facing the Sun | m² |
| P⊕ | Power generated at Earth (1 AU) | W |
| Pd | Power generated at the distance | W |
| R | Ratio to Earth: 1/d², pure geometry | — |
Reference values
First-order figures for sanity-checking inputs.
| Body | Distance AU | Irradiance W/m² |
|---|---|---|
| Mercury | 0.387 | 9,083 |
| Venus | 0.723 | 2,602 |
| Earth | 1.000 | 1,361 |
| Mars | 1.524 | 586 |
| Jupiter | 5.203 | 50.3 |
| Saturn | 9.537 | 15.0 |
| Uranus | 19.19 | 3.70 |
| Neptune | 30.07 | 1.51 |
| Cell technology | Efficiency % |
|---|---|
| Silicon (space-qualified) | 15–18 |
| Thin-film (a-Si, CIGS) | 8–13 |
| Single-junction GaAs | 18–22 |
| Triple-junction GaInP/GaAs/Ge | 28–30 |
| Inverted metamorphic (IMM) | 32–34 |
This is beginning-of-life output at a single instant: no radiation or UV degradation, no temperature derating, no eclipse, no pointing error budget, and no harness or regulator losses. Real end-of-life sizing carries all of them plus margin. Treat these results as first-pass sizing, not a power budget.