在轨绝对辐射定标是光学遥感卫星数据定量化应用的前提。载荷上天后，由于星上定标基准传递链路复杂，实现难度大，而以地面目标测量为参照基准的场地定标受尺度效应、大气条件、环境变化等不确定因素影响，时至今日，遥感载荷在轨定标的精准性、一致性、可追溯性问题，仍属亟待解决的国际难题。对此瓶颈问题的突破在于利用“定标星”搭载空间辐射基准载荷，通过与其他卫星载荷同时观测目标场景的方式，将高精准的空间辐射测量基准从天基标准辐射定标系统向光学遥感业务卫星传递，并准确核算传递路径中各环节的不确定因素，保证不同遥感卫星数据产品质量的高一致、可追溯。本文从光学遥感在轨辐射定标技术需求出发，回顾了星上定标、场地定标、交叉定标、月球定标等光学遥感卫星主要在轨辐射定标方法的发展历程及技术挑战，介绍了当前国际前沿的空间辐射测量基准传递定标技术，其将可溯源至SI的辐射基准源引入少量基准卫星，通过同时观测相同地月目标场景的交叉定标方式将统一的高精度空间辐射测量基准传递至多系列卫星，在大幅度提升定标整体水平的同时，保证多源卫星数据质量的高一致性与高稳定性。

On-orbit absolute radiometric calibration is an important prerequisite for the quantitative applications of optical remote sensing satellite data. Due to complicated transfer chain of radiometric benchmark which is hard to be realized, and traditional field calibration (which takes at-ground measured target characteristics as a radiometric benchmark) inevitably may be affected by uncertainty factors such as scale effect, atmospheric condition and space environment perturbation, up to this day, the accuracy, consistency and traceability of on-orbit radiometric calibration are still difficulties to be solved in the world. To break through these bottleneck problems, we can make use of the "calibration benchmark satellite" to carry spaceborne radiometric benchmark sensors, and transfer their high-accuracy radiometric measurement values to other operational optical remote sensing satellites by the way of synchronously observing the same at-ground targets/scenes. Through precisely assessing uncertainties introduced in various steps in the whole transfer chain, the high consistency and traceability among different satellite remote sensing products could be achieved. In this paper, starting with technical requirements of on-orbit radiometric calibration for optical remote sensing satellites, the authors overviewed and described those developing processes and technical challenges related to some common methods for on-orbit radiometric calibration, such as on-board calibration, field calibration, cross-calibration and lunar-based calibration. Furthermore, currently most advanced calibration technology - space-borne radiometric benchmark transfer calibration, was also illustrated in this paper. In this advanced calibration scheme, radiometric benchmark sources traceable to SI are installed in a small number of benchmark satellites, then consistent high-accuracy on-board radiometric benchmarks can be transferred to multi-series of operational satellites, by way of cross-calibration based on synchronous observation of earth/moon scenes. This calibration scheme is expected to extensively improve international technical level of calibration, and also can guarantee high consistent and high stable data quality for multi-source satellite data.