Merge pull request #440 from ut-issl/feature/add-earth-rotation-effec…

…t-for-air-drag

Add relative velocity of atmosphere

src/disturbances/air_drag.cpp

@@ -24,7 +24,12 @@ AirDrag::AirDrag(const std::vector<Surface>& surfaces, const libra::Vector<3>& c
 
 void AirDrag::Update(const LocalEnvironment& local_environment, const Dynamics& dynamics) {
  double air_density_kg_m3 = local_environment.GetAtmosphere().GetAirDensity_kg_m3();
- Vector<3> velocity_b_m_s = dynamics.GetOrbit().GetVelocity_b_m_s();
+
+ libra::Matrix<3, 3> dcm_ecef2eci =
+ local_environment.GetCelestialInformation().GetGlobalInformation().GetEarthRotation().GetDcmJ2000ToXcxf().Transpose();
+ libra::Vector<3> relative_velocity_wrt_atmosphere_i_m_s = dcm_ecef2eci * dynamics.GetOrbit().GetVelocity_ecef_m_s();
+ libra::Quaternion quaternion_i2b = dynamics.GetAttitude().GetQuaternion_i2b();
+ libra::Vector<3> velocity_b_m_s = quaternion_i2b.FrameConversion(relative_velocity_wrt_atmosphere_i_m_s);
  CalcTorqueForce(velocity_b_m_s, air_density_kg_m3);
 }