There are 4 X-ray Imaging Spectrometers (XISs) on Suzaku. Each XIS has its own X-ray Telescope that focuses X-rays onto it. The detector is a 1024 by 1024 pixel X-ray sensitive Charge Coupled Device (CCD).
Three XIS units use one type of CCD, and are sensitive to X-rays with energies between 0.4 and 12 keV. The fourth XIS uses a different type of CCD that covers 0.2-12 keV.
Many people use CCDs every day – they are used in digital cameras and camcorders. If your cell phone has a camera, it uses a CCD. The CCDs most people are familiar with are used to count up the number of visible light photons that land on each pixel while the camera's shutter is open. However, CCDs are also good at detecting X-rays, but in this case, they don't count the number of X-ray photons – they measure the energy of each X-ray photon. In other words, CCDs measure X-ray spectra.
