Surface Force: Solar Radiation Pressure disturbance

1. Overview

1. Functions

SolarRadiationPressureDisturbance class inherits SurfaceForce base class and calculates air drag disturbance force and torque.

solar_radiation_pressure_disturbance.cpp, solar_radiation_pressure_disturbance.hpp : The SolarRadiationPressureDisturbance class is defined.
surface_force.cpp, surface_force.hpp : The base class SurfaceForce is defined.
- Note: SurfaceForce class inherits SimpleDisturbance class, and SimpleDisturbance class inherits Disturbance class. So, please refer them if users want to understand the structure deeply.
disturbance.ini : Initialization file

3. How to use

Make an instance of the SolarRadiationPressureDisturbance class in InitializeInstances function in disturbances.cpp
- Create an instance by using the initialization function InitSolarRadiationPressureDisturbance
Set the parameters in the disturbance.ini
- Select ENABLE for calculation and logging

2. Explanation of Algorithm

1. `CalcCoefficients` function

1. overview

CalcCoefficients calculates the normal and in-plane coefficients for SurfaceForce calculation.

2. inputs and outputs

inputs
- $v_{s}$:Direction vector of the sun (spacecraft to the sun) at the body frame
- $P$ Solar pressure at the position of the spacecraft [N/m^2]
setting parameters
- $\nu$ : Total reflectance
  - $\nu = 1-\alpha$, where $\alpha$ is the absorption of the sun spectrum.
- $\mu$ : Specularity. Ratio of specular reflection inside the total reflected light.
- $A$ : Area of the surface
outputs
- $C_{n}$ and $C_{t}$

3. algorithm

$C_{n}$ and $C_{t}$ are calculated as follows:
- $\theta$ is the angle between the normal vector and the sun vector.

\[ \begin{align} C_{n} &= AP \left((1+\nu\mu)\cos^{2}{\theta}+\frac{2}{3}\nu(1-\mu)\cos{\theta} \right)\\ C_{t} &= AP(1-\nu\mu)\cos{\theta}\sin{\theta} \end{align} \]