/// <summary>
        /// J2积分器(惯性系中计算,无岁差章动),右函数采用J2Gravity模型
        /// <para>积分变量仅位置、速度</para>
        /// <para>给position仅添加J2项右函数</para>
        /// <para>RKF7(8)数值积分器,缺省绝对和相对精度皆为1e-13</para>
        /// <para>Epoch属性需手动赋值</para>
        /// </summary>
        /// <param name="position">PropagationNewtonianPoint,单位:m,m/s</param>
        /// <param name="centralBody"></param>
        /// <param name="gravitationalParameter">引力常数GM(m^3/s^2)</param>
        /// <param name="j2UnnormalizedValue">J2</param>
        /// <param name="referenceDistance">Re(m)</param>
        /// <param name="absTolerance">RKF7(8)的绝对精度</param>
        /// <param name="relRolerance">RKF7(8)的相对精度</param>
        public PropagatorDefinitionPureJ2(PropagationNewtonianPoint position, CentralBody centralBody, double gravitationalParameter = 3.986004418e14, double j2UnnormalizedValue = 0.001082629989052, double referenceDistance = 6378137.0, double absTolerance = 1e-13, double relRolerance = 1e-13)
        {
            //  中心天体的J2项引力摄动(含中心引力,中心天体的惯性系中计算),无岁差章动
            J2Gravity gravity = new J2Gravity(position.IntegrationPoint, centralBody, gravitationalParameter, j2UnnormalizedValue, referenceDistance);

            //  添加右函数
            position.AppliedForces.Clear();
            position.AppliedForces.Add(gravity);

            //  积分变量
            this.IntegrationElements.Add(position);

            //  RKF7(8)数值积分器
            RungeKuttaFehlberg78Integrator integrator = new RungeKuttaFehlberg78Integrator();

            integrator.AbsoluteTolerance = absTolerance;
            integrator.RelativeTolerance = relRolerance;
            integrator.InitialStepSize   = 60.0;
            integrator.StepSizeBehavior  = KindOfStepSize.Relative;
            integrator.MaximumStepSize   = 200.0;
            integrator.MinimumStepSize   = 1.0;
            //* This is STK's default and truncates each step to 3 decimal places
            integrator.StepTruncationOrder = -3;

            this.Integrator = integrator;
        }
        //#########################################################################################

        #region 构造函数
        /// <summary>
        /// 构造函数,缺省使用中心天体:地球(J2项系数为0)
        /// </summary>
        //public J2Gravity()
        //    : base(RoleOfForce.Principal, KindOfForce.NewtonianSpecificForce)
        //{
        //    CentralBodiesFacet fromContext = CentralBodiesFacet.GetFromContext();
        //    this.m_centralBody = fromContext.Earth;
        //    this.m_gravitationalParameter = WorldGeodeticSystem1984.GravitationalParameter;
        //    this.J2ZonalHarmonicCoefficient = 0.0;
        //    this.m_referenceDistance = m_centralBody.Shape.SemimajorAxisLength;
        //}

        /// <summary>
        /// 构造函数,缺省使用中心天体:地球(J2项系数为0)
        /// </summary>
        /// <param name="targetPoint">计算引力的瞬时点(位置、速度)</param>
        //public J2Gravity(Point targetPoint)
        //    : this()
        //{
        //    this.m_targetPoint = targetPoint;
        //}

        /// <summary>
        /// 构造函数,从已有对象复制
        /// </summary>
        /// <param name="existingInstance">已有对象</param>
        /// <param name="context">A CopyContext that controls the depth of the copy.</param>
        protected J2Gravity(J2Gravity existingInstance, CopyContext context)
            : base(existingInstance, context)
        {
            this.m_centralBody                = context.UpdateReference <CentralBody>(existingInstance.m_centralBody);
            this.m_gravitationalParameter     = existingInstance.m_gravitationalParameter;
            this.m_ignorePartials             = existingInstance.m_ignorePartials;
            this.m_targetPoint                = context.UpdateReference <Point>(existingInstance.m_targetPoint);
            this.m_j2ZonalHarmonicCoefficient = existingInstance.m_j2ZonalHarmonicCoefficient;
            this.m_referenceDistance          = existingInstance.m_referenceDistance;
        }
 /// <summary>
 /// 计算给定时刻的J2项引力(在坐标轴)
 /// </summary>
 /// <param name="date"></param>
 /// <returns></returns>
 public override Cartesian Evaluate(JulianDate date)
 {
     return(J2Gravity.CalculateAcceleration(this.m_position.Evaluate(date), this.m_gravity, this.m_j2ZonalHarmonicCoefficient, this.m_referenceDistance));
 }