Cosmic Origins Spectrograph

Cosmic Origins Spectrograph. The Cosmic Origins Spectrograph is a powerful ultraviolet spectrograph installed on the Hubble Space Telescope. Designed to probe the large-scale structure of the universe, it studies the cosmic web of gas and filaments that form the foundation for galaxy formation. Its high sensitivity allows astronomers to analyze the composition and physical properties of distant intergalactic matter with unprecedented detail.

Overview

The instrument was conceived to address fundamental questions in modern astrophysics concerning the evolution of the universe. Developed under the leadership of principal investigator James C. Green of the University of Colorado Boulder, it was built by Ball Aerospace & Technologies Corp. under contract to NASA. The project involved collaboration with scientists from the Space Telescope Science Institute and several other research universities. Funding and oversight were managed through NASA's Goddard Space Flight Center, ensuring it met the rigorous standards for integration onto the Hubble Space Telescope.

Design and capabilities

The spectrograph utilizes two independent, parallel optical channels: the Far-Ultraviolet (FUV) channel and the Near-Ultraviolet (NUV) channel. This dual-channel design allows it to cover a broad spectral range from approximately 1150 to 3200 Ångströms. Key components include high-efficiency diffraction gratings and microchannel plate detectors developed by the Naval Research Laboratory. Its design prioritizes high sensitivity and spectral resolution, enabling the detection of extremely faint spectral lines from sources like distant quasars. The optical bench is constructed from a stable, lightweight material to maintain precise alignment in the microgravity environment of low Earth orbit.

Scientific objectives and discoveries

Primary objectives include mapping the distribution of ordinary baryonic matter in the cosmic web and studying the galactic halos of nearby galaxies. It has been instrumental in analyzing the circumgalactic medium around galaxies like the Andromeda Galaxy and the Milky Way. The spectrograph has provided critical data on the physical conditions and metallicity of gas in the intergalactic medium, shedding light on galaxy formation and evolution. Notable discoveries include detailed observations of the Lyman-alpha forest in quasar spectra and constraints on the temperature of the warm-hot intergalactic medium. It has also studied the atmospheric composition of exoplanets orbiting stars like GJ 1214 b.

Installation and operation on Hubble

The instrument was installed on the Hubble Space Telescope during STS-125, the final Space Shuttle servicing mission, in May 2009. Astronauts including John M. Grunsfeld and Andrew J. Feustel performed the complex spacewalk to remove the obsolete Corrective Optics Space Telescope Axial Replacement and install the new spectrograph. Following installation, a team at the Space Telescope Science Institute conducted an extensive period of commissioning and calibration. It has operated continuously since, with its observations scheduled and archived by the Mikulski Archive for Space Telescopes. The instrument's longevity has far exceeded its initial five-year design life.

Comparison with other spectrographs

Compared to its predecessor on Hubble, the Space Telescope Imaging Spectrograph, it offers significantly greater sensitivity in the far-ultraviolet, particularly for faint, diffuse sources. While the Hubble Space Telescope's Advanced Camera for Surveys excels at imaging, this spectrograph provides complementary, high-resolution spectroscopic data. For future missions, its capabilities in the ultraviolet are a precursor to those planned for the LUVOIR space telescope concept. Ground-based observatories like the Very Large Telescope cannot access the ultraviolet wavelengths this instrument specializes in, due to absorption by Earth's ozone layer. Its design philosophy of maximizing throughput influenced later instruments like those on the James Webb Space Telescope.

Category:Spectrographs Category:Hubble Space Telescope instruments Category:Space telescopes