Hollow cathode lamps are well known light sources for calibration of ground based and space based instruments. Long life, high spectral purity, adaptability for specialized applications, and survivability in harsh environments are a few of the desirable features offered by hollow cathode lamps. Historically, hollow cathode lamps with platinum, or platinum chromium cathodes and neon fill gas have been used onboard the Hubble Space Telescope for NASA and the GOME instrument for ESA, as well as ground based experiments. Recent improvements have increased the usefulness of hollow cathode lamps for calibration in the ultraviolet and visible spectrum.