Optics design and performance for the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS)

The CHIPS observatory was launched on 12 January 2003, and is the first UNEX (NASA Goddard Spaceflight Center University Explorer class) mission. It is currently on-orbit and performing diffuse spectroscopy in the 90-260a wavelength band. The instrument is integrated with a custom 3-axis stabilized mini-satellite, designed for roughly one year of operation. The purpose of the observatory is examination of details of the local bubble thermal pressure, spatial distribution and ionization history. The spectrometer consists of six spectrograph channels which deliver >lambda/100 resolution spectra to a single detector. Cost constraints of UNEX led to a design based on a traditional aluminum structure, and an instrument with a large field of view (5° x 26°) for the dual purpose of increasing sensitivity in the photon-starved 90-260a band, and to reduce requirements on spacecraft pointing. All optomechanical systems on the spectrometer, including coalignment, thermal, front cover and vacuum door release are performing well on orbit. We discuss design, test and operational performance of these systems, as well as launch loads and thermal system considerations.