The effect of radiation damage on optical CCDs operating in time-delay integration mode

Time-delay integration (TDI) mode or strip chart recording mode is a standard mode of operation of charge-coupled devices (CCDs), which record data whilst either the instrument or the object of interest is in motion. In this paper we examine the effects that radiation damage has on the centroiding accuracy of objects tracked by optical CCDs. Radiation damage not only affects the shape of objects being tracked as a result of charge trapping or charge release but also affects the intensity of the object being tracked, which in turn might affect the error in any photometric measurements. This effect may be exacerbated if filters are being used in any of the photometric measurements, since radiation interacting with the filter glass will alter the optical transmission properties of the glass. s paper we also present a description of the apparatus used to synchronise the projection and translation of sources of light onto a CCD with the charge transfer rate of the device. The facility and measurement technique described in this paper will provide the University of Leicester, Space Research Centre with a dedicated optical CCD test facility to support future space and ground-based instrument development programmes involving optical CCDs. This paper is aimed at supporting the contribution of the UK to the European Space Agencyʹs (ESA) Gaia programme. This paper will determine whether radiation effects place intrinsic limits on the centroiding accuracy and photometric efficiency achievable with optical CCDs operating in TDI mode.