星载光学传感器在轨同步定标需要地面同步光谱测量作为数据支撑，准确的地物反射率是得到高精度定标结果的重要前提之一。传统的野外地面反射率测量采用单光谱仪法依次对目标及参考板进行测量。在辐射条件连续剧烈变化的情况下，传统测量方法无法保证目标及参考板辐射条件的一致性。利用双光谱仪法进行野外地物反射率时间序列测量，避免了传统方法测量中可能出现的辐射条件不一致问题。将测量结果与单光谱仪法比较，二者相关系数达到0.998，而且双光谱仪法反射率曲线更符合实际光谱，从而验证了该方法的可行性。

The in-orbit synchronous calibration of a spaceborne optical sensor needs to use the ground synchronous spectral measurement as the data support. The accurate surface reflectance is one of the important prerequisites for obtaining high-precision calibration results. The traditional field ground reflectance measurement methods use a single spectrometer to measure a target and a reference panel in turn. In the case of dramatic irradiation change, the traditional measurement methods cannot keep the radiation condition of the target and reference panel to be consistent. By using a dual-spectrometer method to measure the reflectance-time series of the ground objects in the field, the problem of inconsistent radiation condition occurred possibly in the traditional methods is avoided. By comparing the measurement result of the dual-spectrometer method with that of the single-spectrometer method, the correlation coefficient is up to 0.998. Moreover, the reflectance curve obtained by the dual-spectrometer method is closer to the actual spectrum. Thus, the feasibility of the dual-spectrometer method is verified.