This model was created to estimate solar power generation during different attitude modes. The numerical estimates can be seen on the page below
The power generated by a CubeSat's solar panels depends on its orientation relative to the sun, the surface area of each face exposed to sunlight, and the efficiency of the solar cells. Power estimates are calculated based on a few extreme cases of CubeSat orientation. In practice, the satellite’s orientation will likely be a combination of these scenarios, so the actual power generated will result from a superposition of the power estimates from these cases. However, these extreme cases help establish the upper and lower bounds of power generation.
This document presents power generation estimates for the following cases: nadir pointing (-z always facing the earth), tumbling around a single axis that is perpendicular to the sun vector, sun-pointing on a single face with the most solar panels, and sun-pointing on two faces at an optimal angle to maximize power generation.
| Case Description | Sides exposed to sun | Description |
|---|---|---|
| Nadir Pointing x | +x, +z, -x | In this orientation, the CubeSat's -Z face is consistently pointed toward Earth (nadir), and only the +x, -x, and +z faces face the sun during the orbit. |
| Nadir Pointing y | +y, +z, -y | Same as above, but only the +y, -y, +z faces get exposure |
| Tumbling about x | +y, -y, +z, and -z | Here, the CubeSat is tumbling around its x-axis which is perpendicular to the sun vector, meaning that the +x and -x faces remain roughly parallel to the sun, and therefore, do not get direct sunlight. Instead, the +y, -y, +z, and -z faces alternate in receiving sunlight as the satellite rotates. The tumbling motion exposes four faces equally, allowing each to receive sunlight in sequence. |
| Tumbling about y | +x, -x, +z, and -z | Same as above, but the y faces are always parallel to the sun rays |
| Tumbling about z | +x, -x, +y, and -y | Same as above, but the z faces are always parallel to the sun rays |
| Sun pointing -y face | -y | The side with the most solar panels (-y face) remains pointing towards the sun |
| Sun pointing optimized | -y, x | The -y and x faces both face the sun at a certain angle to maximize power generation |
An extreme nadir pointing case (Nadir X), where only the +x, +z, and -x faces receive sun exposure
The power generation can be estimated using this equation
$P = G \times A \times \eta \times \cos(\theta)$
Where: