Performance of the GHRS Pt-Ne hollow-cathode lamps after their return from space and comparison with archival data

Abstract

The Space Telescope European Co-ordinating Facility (ST-ECF) and National Institute of Standards and Technology (NIST) are collaborating to study hollow cathode calibration lamps as used onboard the Hubble Space Telescope (HST). As part of the STIS Calibration Enhancement (STIS-CE) Project we are trying to improve our understanding of the performance of hollow cathode lamps and the physical processes involved in their long term operation. The original flight lamps from the Faint Object Spectrograph (FOS) and the Goddard High Resolution Spectrograph (GHRS) are the only lamps that have ever been returned to Earth after extended operation in space. We have taken spectra of all four lamps using NIST's 10.7-m normal-incidence spectrograph and Fourier transform spectrometer (FTS) optimized for use in the ultraviolet (UV). These spectra, together with spectra archived from six years of on-orbit operations and pre-launch spectra, provide a unique data set--covering a period of about 20 years--for studying aging effects in these lamps. Our findings represent important lessons for the choice and design of calibration sources and their operation in future UV and optical spectrographs in space. Our results will be directly used for planning science operations of the Cosmic Origins Spectrograph (COS) which is going to be installed on the HST during the next servicing mission.