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Gaia CCDs: charge transfer inefficiency measurements between five years of flight

Ahmed, S; Hall, D; Crowley, C; Skottfelt, J; Dryer, B; Seabroke, G; Hernandez, J; (2020) Gaia CCDs: charge transfer inefficiency measurements between five years of flight. In: Holland, AD and Beletic, J, (eds.) X-Ray, Optical, and Infrared Detectors for Astronomy IX. SPIE: Online conference. Green open access

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Abstract

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.

Type: Proceedings paper
Title: Gaia CCDs: charge transfer inefficiency measurements between five years of flight
Event: SPIE Astronomical Telescopes + Instrumentation, 2020
Open access status: An open access version is available from UCL Discovery
DOI: 10.1117/12.2562162
Publisher version: https://doi.org/10.1117/12.2562162
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/10120482
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