ThirdBodyDisturbances.h

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//////////////////////////////////////////////////////////////////////////////////////////////////
/*! \file ThirdBodyDisturbances.h
*  \brief Environmental disturbances due to Third Bodies.
*  \author $Author: jayhawk_hokie $
*  \version $Revision: 1.2 $
*  \date    $Date: 2005/06/10 12:53:28 $
*//////////////////////////////////////////////////////////////////////////////////////////////////
/* 
*/
//////////////////////////////////////////////////////////////////////////////////////////////////

#ifndef __OSESSAME_THIRDBODY_PERTUBATIONS_H__
#define __OSESSAME_THIRDBODY_PERTUBATIONS_H__
#include <matrix/Matrix.h>
#include <utils/Time.h>
#include <orbit/OrbitState.h>
#include <Attitude.h>
#include <Environment.h>
#include <vector.h>
using namespace std;
using namespace O_SESSAME;

/*! \brief The third body force disturbance due to gravity.
* @ingroup EnvironmentForceFunctions
*
* 
* @param _currentTime current simulation time
* @param _currentOrbitState current orbit state, including representation and reference frame
* @param _currentAttitudeState current attitude state, including rotation and reference frame
* @param _parameterList EnvFuncParamaterType parameter list for external variables, [CentralBody* orbiting central body, CentralBody* third-body]  
* @return This force functions returns a 3-element vector of forces (x,y,z) due to gravity using a 
*       two-body simplified force model.
*/
Vector ThirdBodyForceDisturbance(const ssfTime &_currentTime, const OrbitState  &_currentOrbitState, const AttitudeState &_currentAttitudeState, const EnvFuncParamaterType &_parameterList)
{
    static Vector Forces(3);
    static Vector Position(3); 
    static CentralBody* pOrbCB, pThirdBody;
    pOrbCB = reinterpret_cast<CentralBody*>(_parameterList[0]);
    pThirdBody = reinterpret_cast<CentralBody*>(_parameterList[1]);
    
    static double massThirdBody = pThirdBody->GetMass();
    static Vector vectorOrbCB2ThirdBody = pOrbCB->GetVector2Body(pThirdBody);
    static Vector vectorThirdBody2Satellite(3); 
        vectorSat2ThirdBody = - pThirdBody->GetVector2Body(_currentOrbitState); // negative to "switch the head" around
    static double B = norm2(vectorOrbCB2ThirdBody) / norm2(vectorSat2ThirdBody) - 1;  
    static double beta = pow(1+B, 3);
    
    Position(_) = _currentOrbitState.GetState()(_(VectorIndexBase,VectorIndexBase+2));
    Forces = - c_GravitationalConstant * massThirdBody / pow(vectorOrbCB2ThirdBody, 3) * (Position(_) - beta * vectorSat2ThirdBody);
    return Forces;
}

#endif
// Do not change the comments below - they will be added automatically by CVS
/*****************************************************************************
*       $Log: ThirdBodyDisturbances.h,v $
*       Revision 1.2  2005/06/10 12:53:28  jayhawk_hokie
*       Changed header file format to make it easier to link to the spacecraft code by only having to specify dsacss/dep/spacecraft/src (ex. "file.h" changed to <dir/file.h> where dir is a folder in src).
*       
*       Revision 1.1.1.1  2005/04/26 17:40:56  cakinli
*       Adding OpenSESSAME to DSACSS distrib to capture fixed version.
*       
*       Revision 1.2  2003/10/18 21:37:28  rsharo
*       Removed "../utils" from all qmake project paths. Prepended "utils
*       /" to all #include directives for utils. Removed ".h" extensions from STL header
*       s and referenced STL components from "std::" namespace.  Overall, changed to be
*       more portable.
*       
*       Revision 1.1  2003/06/12 17:58:42  nilspace
*       Initial Submission.
*       
*       
******************************************************************************/

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