Of the four resolutions associated with satellite imagery, radiometric resolution is probably the one that receives the least amount of attention. It is the least variable--most sensors have similar radiometric resolutions (or dynamic ranges), and only a few have a higher (or lower) resolution than the 'norm' (which is 256 levels of resolution, or, as it is also referred to, 8-bits per pixel). However, modern sensors (e.g., GeoEye-1) are increasingly collecting data with 10- or 11-bits per pixel, and converting that to 8 or 16-bit data. Radiometric resolution is closely tied to the word size of computer operating systems. Radiometric values are commonly referred to as Digital Numbers (DN) (scroll down to the discussion on pixels and intensity values)

• The Canadian Centre for Remote sensing has a brief discussion on radiometric resolution.
• An introduction to bits per pixel (albeit from a photographic perspective).
• A brief report on the Ikonos sensor and its 11-bit resolution. (How Ikonos performs radiometric instrument calibration: "The agile pointing capability of Ikonos is being utilized for instrument calibration. Solar, lunar and stellar scenes serve as radiometric instrument calibration sources. The ecliptic portion of the orbit is being used for stellar calibration. Absolute calibration of the Ikonos sensors is performed by comparing the total digital numbers found in the stellar image, to the absolute in-band spectral radiance of several radiometrically characterized stars. The radiometric calibration provides relative and absolute corrections for detector channel responsivity differences.")
• For those interested in learning how complex issues can become when working with radiometric values, reading over this paper will provide an insight.

Text: Chapter 2.5.1: Sensing properties