Spec_SurfaceForce_SolarRadiation.md

Surface Force: Solar Radiation Pressure disturbance

1. Overview

1. Functions

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

2. Related files

• 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.

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

4. note

• NA

3. Results of verifications

1. Verification of perfect reflection case

1. overview

• In the perfect reflection case, the direction of the SRP force will be opposite from the direction of the sun.

2. conditions for the verification

• We assumed that the structure of the spacecraft is a 50-cm cube whose optical property is the perfect specular reflection($\nu=\mu=1$).

3. results

• We confirmed that the direction of the SRP force is opposite from the direction of the sun at the body frame.

4. References

1. NA