为了提供准确的空间相机外热流数据，提出一种在地磁坐标系下进行频繁姿态变换的空间相机瞬态外热流计算方法。首先，确定了在J2000坐标系下太阳—地球的相对位置及太阳辐照强度；其次，计算相机不同位置的地磁纬度，并采用二分法得到相机在轨运行时进出高磁纬地区(L≥60°)的轨道时间；然后，依据其地磁纬度，确定相机不同时刻下的在轨姿态。最后，采用蒙特卡洛法(MCM)计算相机的各环境映射面的轨道视角系数，进而得出整轨周期内各环境映射面接受的瞬时外热流。此方法与IDEAS/TMG软件的外热流结果能够较好的吻合。与姿态稳定的相机相比，空间相机姿态频繁变化会导致外热流数值的明显波动。尤其是入光口所在的+Z面，其波动范围为0~1 245.4 W/m2。

In order to provide the external heat flux of space camera accurately, a method was proposed to calculate the instantaneous external heat fluxes of a space camera with changing attitudes frequently depending on its position in the Geomagnetic Coordinate system(MAG). First, in J2000 Coordinate the relative position of the sun, earth and radiation intensity of sun was calculated. Second, geomagnetic latitudes of a camera and orbital times when camera entered or exited from high geomagnetic latitudes(L≥60°) were calculated. Then, the camera′s attitudes were ensured with geomagnetic latitudes. Finally, orbital view factors of six mapping planes were achieved by the Monte Carlo Method(MCM)and the instantaneous external heat fluxes was obtained during the on-orbit time. The external heat fluxes of this paper were consentaneous with the software IDEAS/TMG. Compared with the stable attitude camera, the attitude varieties of the camera take a relatively strong influence on the external heat flux, especially for the +Z-direction where optical entrance is located. The fluctuation range of the +Z-direction external heat flux is about 0-1 245.4 W/m2.