Introduction

Charge-coupled devices, or CCDs, were invented at Bell Laboratories, New Jersey, in 1969. The advantages of CCDs for optical astronomy over the previous technologies were quickly realized and the use of CCDs revolutionized astronomy in the 1980s due to their sensitivity and linear brightness response. CCD cameras are now the most common detector at optical observatories around the world and are the sensing element in nearly all commercial digital cameras.

It was also recognized early on that CCDs were sensitive to X-ray radiation as well as optical light, although optimizing the technology for X-ray use took longer. The first suborbital rocket flight equipped with an X-ray CCD camera was launched in 1987 to observe SN 1987A. Japan's ASCA (Tanaka et al., 1994), launched in 1993, was the first satellite with an X-ray CCD camera. Since that time, CCDs have become ubiquitous in X-ray astronomy and are part of the focal-plane instrumentation in almost all recent past, current, and planned missions. The CCD detectors on the largest of the currently operating missions are ACIS (Garmire et al., 2003) on Chandra, EPIC (Turner et al., 2001; Strüder et al., 2001) and RGS (den Herder et al., 2001) on XMM–Newton and XIS (Koyama et al., 2007) on Suzaku. Other CCD detectors on currently operating missions are XRT (Burrows et al., 2000) on Swift and SSC on MAXI (Matsuoka et al., 2009).

Understanding the basic principles of CCD operation and some of the resultant features encountered in data analysis is important for accurate interpretation.