16978

Monitor the change in sensitivity over time with visits to the WD standard stars comma GD71 comma GD153 comma G191B2B comma and GRW+70 5824. Verify and refine the WFC photometric calibrations and repeatability measures. Single bright stars with photon statistical noise of virgul0.2% are a more precise and straightforward approach to measuring sensitivity changes than with the multitude of stars in 47 Tuc. This program has executed annually since Cycle 19.

通过观测白矮星（WD）标准星GD71、GD153、G191B2B及GRW+70 5824，监测灵敏度随时间的变化。验证并优化WFC光度校准及重复性测量结果。光子统计噪声约为0.2%的单颗亮星，相较于杜鹃座47（47 Tuc）中众多恒星，是测量灵敏度变化更精确、更直接的方法。该项目自第19周期（Cycle 19）起每年执行一次。