Gaia CCDs: charge transfer inefficiency measurements between five years of flight
Gaia CCDs: charge transfer inefficiency measurements between five years of flight
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DOI：
10.1117/12.2562162
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发表时间：
2020-12
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影响因子：
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通讯作者：
Saad Ahmed;D. Hall;C. Crowley;J. Skottfelt;B. Dryer;G. Seabroke;J. Hernandez;A. Holland
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文献类型：
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作者：
Saad Ahmed;D. Hall;C. Crowley;J. Skottfelt;B. Dryer;G. Seabroke;J. Hernandez;A. Holland
欧洲航天局的盖亚航天器于2013年12月发射，已在地球-太阳拉格朗日点2（L2）的轨道上运行了6年多。该航天器测量银河系及其他地区约10亿颗恒星的位置、距离、空间运动和许多其他物理特征。它有一个由106个电荷耦合器件（CCD）组成的焦平面，这些器件都表现良好，但由于星际辐射造成的非电离能量损失（NIEL）损害，它们的性能会随着时间的推移而下降。这种NIEL损伤产生陷阱缺陷，其可以从信号捕获电荷并降低数据的质量。盖亚最初的使命寿命计划为5年左右，飞行前测试和辐射损伤分析是围绕这些时间尺度以及发射前预计的太阳活动量身定制的。在接近发射时间和盖亚的轨道年期间，人们注意到太阳活动比最初预测的要低。根据2016年对飞行数据的分析，计算出盖亚遭受的辐射损伤比预测的要小一个数量级。本文介绍了分析电荷校准数据和相应的电荷转移效率（CTI）测量从飞行中的CCD，无论是接近开始的使命，并在轨道上超过5年后，以量化辐射损伤的影响。这些结果可以与飞行前试验的结果进行比较，这些结果可以用来评估和了解地面和飞行中结果之间的差异。
The European Space Agency’s Gaia spacecraft was launched in December 2013 and has been in orbit at the Earth-Sun Lagrange point 2 (L2) for over 6 years. The spacecraft measures the positions, distances, space motions and many other physical characteristics of around one billion stars in the Milky Way and beyond. It has a focal plane of 106 Charge-Coupled Devices (CCDs) which have all been performing well but have been measuring a small but quantifiable degradation in performance in time due to Non-Ionizing Energy Loss (NIEL) damage from interstellar radiation. This NIEL damage produces trap defects which can capture charge from signals and reduces the quality of the data. Gaia’s original mission lifetime was planned to be around 5 years and the pre-flight testing and radiation damage analysis was tailored around those timescales as well as with the projected solar activity before launch. Closer to the time of launch and during Gaia’s years of orbit, it has been noted that the solar activity was lower than what was initially predicted. From the previous analysis of in-flight data in 2016, it was calculated that Gaia was experiencing an order of magnitude less radiation damage than was predicted. This paper describes the analysis of charge calibration data and corresponding Charge Transfer Inefficiency (CTI) measurements from the in-flight CCDs, both near the beginning of the mission and after more than 5 years in orbit to quantify the radiation damage impact. These sets of results can be compared with those from the pre-flight tests which can be used to evaluate and understand the differences between the on-ground and in-flight results.