Radiation damage in the Gaia focal plane: in-orbit data, charge-transfer simulations, and the impact on the astronomy achievable

2013年12月启动的欧洲航天局盖亚任务有一个雄心勃勃的目标，即在其5年（加上1-4年的延长）寿命内绘制10亿个天文物体的地图。盖亚焦平面由106块定制的e2v ccd组成。探测器在轨道上受到辐射损伤，到目前为止的结果表明这种损伤比发射前预测的要低得多。造成这种较低程度损害的因素仍未得到证实，尽管有几种可能的变异。其一是由于光纤和挡板末端的冰散射光而增加的光学背景。另一个影响是设备在轨道上的辐照温度比发射前的测试活动低100多K。俄勒冈大学目前的研究表明，这两个因素对受到的伤害程度都有重大影响。为欧几里得任务开发的模拟使用了类似的探测器（Skottfelt），尽管设计不同，但在帮助理解这些探测器辐射损伤过程背后的物理过程方面显示出很大的希望。虽然欧空局对盖亚辐射运动数据（霍尔和烘干机）的发射前研究已经结束，但数据现在正在从轨道返回。利用这些信息，除了开发盖亚探测器的OU模拟外，学生将能够获得有关在轨ccd中发展的陷阱的真实信息，并将这些信息反馈给其他任务研究（例如欧euclid， SMILE， WFIRST等）。然后，学生将继续从天文学的角度来看，在任务期间，辐射损伤将如何影响盖亚RVS的输出（诺顿）。由CCD辐射损伤引起的涂布可能导致感兴趣的物体与较暗的背景物体的混合增加，因此可能导致径向速度测量的不确定性增加。随着时间的推移，辐射的损害也会增加，因此，对这种影响的分析和可能的纠正方法（与欧氏欧几里得和SMILE的研究相联系）将是主要的兴趣。这种损害对盖亚天文研究的影响将构成论文的最后一部分，连接学院的空间仪器和天文学研究，并将对其他空间天文学任务如欧几里得和柏拉图任务有好处。这项研究的成果将有额外的好处，它们将进入S818：空间科学与技术硕士课程。盖亚案例研究由安德鲁·诺顿和大卫·霍尔共同撰写，通过教学将天文学和探测器技术联系起来。通过这一跨学科研究，在博士期间考虑其中一个对另一个的影响，不仅可以进一步联系天文学和空间仪器研究，而且可以进一步联系空间科学与技术硕士（S818）的教学和研究。

Launched in December 2013, the ESA Gaia mission has the ambitious aim of mapping a staggering 1 billion astronomical objects over its 5 year (plus 1-4 year extension) lifetime. The Gaia focal plane is formed of 106 custom-designed e2v CCDs. The detectors are subject to radiation damage whilst in orbit and the results so far suggest that this damage is much lower than that predicted pre-launch.The contributing factors to this lower level of damage are still unconfirmed, although there are several candidates for this variation. One is the increased optical background from light scattering from fibres and ice on the end of the baffle. Another is the impact of the devices being irradiated in-orbit more than 100 K lower in temperature than in the pre-launch test campaigns. Current research at the OU suggests that both factors have a major impact on the level of damage received. Simulations developed for the ESA Euclid mission using similar detectors (Skottfelt), albeit of a different design, are showing great promise in aiding an understanding of the physics behind the processes of radiation damage in these detectors. Although the OU's pre-launch research on Gaia radiation campaign data (Hall and Dryer) has ended, data is now being returned from orbit. Using this information, alongside developing the OU simulations to the Gaia detectors, the student will be able to get real information on traps developing in the CCDs in-orbit, feeding this information back into other mission research (e.g. Euclid, SMILE, WFIRST etc).The student will then go on to look at how the radiation damage will affect the Gaia RVS output from an astronomy perspective during the mission (Norton). Smearing caused by CCD radiation damage can lead to an increased blending of the object of interest with fainter background objects and this could therefore lead to an increased uncertainty in the radial velocity measurements. As the radiation damage builds over time, the uncertainties will also increase and an analysis of this effect and a possible way to correct for it (linking with OU Euclid and SMILE research), would therefore be of major interest. Impacts of this damage on the astronomy research made possible by Gaia will form the final part of the thesis, linking between the Space Instrumentation and Astronomy research in the School, and will have benefits to other space astronomy missions such as ESAs Euclid and PLATO missions.The outputs of this research would have the added benefit that they would feed into S818: Masters in Space Science and Technology. The Gaia case study, co-written by Andrew Norton and David Hall, provides a link between astronomy and detector technology through teaching. Consideration of the impact of one on the other during the PhD through this cross-disciplinary research would provide further links not only between astronomy and space instrumentation research, but also between the teaching and research in the Masters in Space Science and Technology (S818).