STIS 自动波长校正曝光状态
Status of the STIS Auto-wavecal Exposures
AI总结：
STIS波长校正曝光的现状分析，探讨灯源变暗对校准精度的影响及改进措施。
摘要：
我们讨论了与大多数 STIS 光谱学曝光一起获得的默认 ``wavecal'' 光谱的行为，这些光谱对于正确校准科学数据的波长至关重要。由于用于波长校正的 Pt/Cr-Ne 氖灯正在变暗（尤其是在最短波长处），近年来已对一些默认灯和/或曝光时间进行了修改，以保持准确的校准。为了评估是否需要进一步的修改，我们检查了从波长校正中获得的 SHIFTA1、SHIFTA2 值的分布（光谱图像在探测器上的 x 和 y 偏移），重新审视了灯的波长依赖性变暗情况，并进行了模拟以估计需要多长时间才能获得准确的 SHIFTA 值。尽管当前的波长校正似乎能产生合理的 SHIFTA 值，但为了确保灯继续变暗时的可靠波长零点，某些最短波长设置的默认曝光时间增加是有帮助的。
英文摘要：
We discuss the behavior of the default ``wavecal'' spectra obtained together with most STIS spectroscopic exposures, which are needed for proper wavelength calibration of the science data. Because the Pt/Cr-Ne lamps used for the wavecals have been fading (especially at the shortest wavelengths), some changes in the default lamp and/or exposure time have been implemented in recent years to maintain accurate calibrations. To assess whether additional changes might be appropriate, we examine the distribution of the SHIFTA1, SHIFTA2 values derived from the wavecals (the x and y offsets of the spectral image on the detector), we re-visit the wavelength-dependent fading of the lamps, and we perform simulations to estimate the exposure times that would be needed to obtain accurate SHIFTA values. While the current wavecals do appear to yield reasonable SHIFTA, increases in the default exposure times for some of the shortest-wavelength settings would help to ensure reliable wavelength zero points as the lamps continue to fade.
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