The potential of Meudon spectroheliograph for investigating long term solar activity and variability

Observations of the chromosphere with Deslandres’s spectroheliograph started at Paris Observatory in 1893 and were followed by systematic observations at Meudon since 1908. The solar collection of H$\alpha$ and CaII K images is probably the longest available worldwide, with associated products such as synoptic maps and tables. Since 2018, Meudon spectroheliograph is the only instrument producing data-cubes of full line profiles of CaII H, CaII K and H$\alpha$, for each pixel of the solar disk. Slices of the cubes provide monochromatic images. We summarize in this paper the capabilities of the successive generations of the instrument, and explore the potential of the collection and products for analysis of rare events, investigations of past solar activity and studies of long term variability.     

天基星空背景观测覆盖范围计算方法研究

针对日趋复杂的空间环境，天基观测由于其分布灵活和全天候观测的特性受到越来越多的关注，该类问题为典型的星空背景观测（above-the-horizon，ATH）问题。基于分段积分思想，提出了一种ATH观测三维空间覆盖范围的计算方法，涵盖了该问题所有可能的10种积分形式，适用于因观测约束参数不同取值而形成的任意几何构型场景。不仅在二维平面覆盖问题上与现有方法进行了比较并验证，还首次解决了ATH在三维空间中覆盖体积的定量解析计算难题。仿真结果表明，平面和空间覆盖最大化所对应的最优观测轨道高度存在明显差异，空间覆盖计算模型能更为准确有效地表示卫星覆盖性能，同时能为星座优化设计提供参考。