  This paper summarizes the introductory presentation for a workshop that
explored the challenges of making precision astronomical measurements using
deeply depleted (thick) CCDs. While thick CCDs provide definite advantages in
terms of increased quantum efficiency at NIR wavelengths, and reduced fringing
from atmospheric emission lines, these devices also exhibit undesirable
features that pose a challenge to precision determination of the positions,
fluxes, and shapes of astronomical objects, and features in astronomical
spectra. Many of the effects seen in these devices arise from lateral
electrical fields within the detector, that produce charge transport anomalies
that have been previously misinterpreted as quantum efficiency variations.
Performing simplistic flat-fielding introduces systematic errors in the image
processing pipeline. One measurement challenge is devising a calibration method
that can distinguish genuine quantum efficiency variations from charge
transport effects. Given the scientific benefits of improving both the
precision and accuracy of astronomical measurements, we need to identify,
characterize, and overcome these various detector artifacts. In retrospect,
many of the detector features first identified in thick CCDs also afflict
measurements made with more traditional CCD detectors, albeit often at a
reduced level. I provide a qualitative overview of the physical effects we
think are responsible for the observed device properties, and provide some
perspective for the work that lies ahead. Finally, I take this opportunity to
make a plea for establishing a clear and consistent vocabulary when describing
these various detector features, and make some suggestions for a standard
lexicon based on discussions at the workshop.
