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Though the performance was optimized for each instrument, all CCDs have the same electrical format and were designed to operate at lower voltages than normal. This facilitates provision of drive electronics and also reduces the power demand on the spacecraft. The camera electronics were built in the United Kingdom by e2v’s project partners at the Rutherford Appleton Laboratory.
“CCDs provide a uniformity of image,” says Peter Pool, a chief engineer with e2v. “They’re absorbed into the silicon. With CMOS, the detection takes place on each pixel, so you could get pixel variability. One attribute of CMOS is that it’s very hard against ionizing radiation. We’ve developed a CCD that can survive one megarad of gamma rays. In the space environment, dominant damage is from high-energy protons displacing an atom from the silicon lattice which effectively impedes the movement of change.”
The telescopes’ wavelength bands will focus the image on the surface of the CCD, which must be very flat. The CCD will hold it in a static state to accumulate the charge from the illumination and collect pixels after a short integration time. “The read noise is extremely loud,” Pool says. “We can achieve read noise of less than two electrons [15 electrons RMS] which gives a great deal of precision.”
The cameras for HMI and AIA were built at Rutherford Appleton Laboratory (Chilton, Oxfordshire, England) while the camera for EVE was built by the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado (Boulder).
The AIA instrument is designed to provide an unprecedented view of the solar corona, taking images that span at least 1.3 solar diameters in multiple wavelengths nearly simultaneously, at a resolution of about 1 arcsec and at a cadence of 10 seconds or better. The Atmospheric Imaging Assembly will produce data required for quantitative studies of the evolving coronal magnetic field, and the plasma that it holds, both in quiescent phases and during flares and eruptions; the AIA science investigation is designed to use the data in a comprehensive research program to provide new understanding of the processes and, ultimately, to guide development of advanced forecasting tools needed by the user community of the Living With a Star program.