The Cosmic Hot Interstellar Plasma Spectrometer (CHIPS) observatory launched on 12 January 2003, and
was the first and only successful GSFC UNEX (NASA Goddard Spaceflight Center University Explorer
class) mission. The UNEX program was conceived by the National Aeronautics and Space Administration
(NASA) as a new class of Explorer mission charged with demonstrating that significant science and/or
technology experiments can be performed by small satellites with constrained budgets and a limited schedule.
The purpose of the observatory was to examine details of the local bubble thermal pressure, spatial
distribution and ionization history. The observatory was also used to observe solar spectra, both scattered
from the Lunar surface and via a fortuitous 2nd order scattering path. CHIPS confirmed that spectral features
within the 90-260Å band were much dimmer than was predicted by contemporary theories, and operated four
years beyond its design lifetime. The observatory was placed in an extended safe-hold mode in April of 2008
for budgetary purposes. The spectrometer consisted of six spectrograph channels which delivered >λ/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°). All optical and optomechanical
systems on the spectrometer performed flawlessly on orbit. We discuss the challenges, difficulties and
lessons learned during the design, fabrication and execution stages of the mission.
We describe the design and development of the CHIPS microchannel plate detector. The Cosmic Hot Interstellar Plasma Spectrometer will study the diffuse radiation of the interstellar medium in the extreme ultraviolet band pass of 90Å to 260Å. Astronomical fluxes are expected to be low, so high efficiency in the band pass, good out-of-band rejection, low intrinsic background, and minimal image non-linearities are crucial detector properties. The detector utilizes three 75mm diameter microchannel plates (MCPs) in an abutted Z stack configuration. A NaBr photocathode material deposited on the MCP top surface enhances the quantum detection efficiency. The charge pulses from the MCPs are centroided in two dimensions by a crossed-delayline (XDL) anode. A four panel thin-film filter array is affixed above the MCPs to reduce sensitivity to airglow and scattered radiation, composed of aluminum, polyimide/boron, and zirconium filter panes. The detector is housed in a flight vacuum chamber to preserve the hygroscopic photocathode, the pressure sensitive thin-film filters, and to permit application of high voltage during ground test.
We present a status report on CHIPS, the Cosmic Hot Interstellar Plasma Spectrometer. CHIPS is the first NASA University-Class Explorer (UNEX) project, and was launched on January 13, 2003.
The grazing incidence CHIPS spectrograph is surveying selected regions of the sky for diffuse emission in the comparatively unexplored wavelength band between 90 and 260 Å. These data are providing important new constraints on the temperature, ionization state, and emission measure of hot plasma in the "local bubble" of the interstellar medium.
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 90-260Å 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 90-260Å 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.
The Baryonic Extragalactic Structure Tracer (BEST) is a SMEX-class mission that is designed to map the hot million-degree diffuse intergalactic and interstellar gas with high spectral resolution. It consists of an imaging X-ray spectrometer that can, over a 1-2 year mission, map the entire sky and conduct deep pointed observations of selected regions to profoundly extend our understanding of hot matter in the Universe. BEST will be able to detect and characterize the missing baryons in the current epoch, which are primarily in moderately overdense intergalactic regions and are predicted to account for 10 - 20% of the soft X-ray background, and also determine the properties of the hot Galactic halo and the hot Galactic gas, crucial to understanding the evolution and dynamics of our Galaxy and its interstellar medium.
CHIPS is a NASA UNEX mission designed for diffuse background spectroscopy in the EUV bandpass from 90-260Å. The spectrometer is optimized for peak resolution near 170 Å, in order to study diffuse emissions from cooling million degree plasma. Details of local bubble thermal pressure, spatial distribution, and ionization history are the goals of CHIPS observations. We discuss the opto-mechanical design adopted to meet the throughput, signal to noise, and spectral resolution requirements within the mass, volume, and budgetary constraints of a UNEX Delta-II secondary payload. Mechanical tolerance requirements for the six spectrometer channels are discussed, along with details of the lightweight mounting scheme for CHIPS diffraction gratings, front cover slit mechanisms and thermal design. Finally, visible light and vacuum alignment techniques are discussed, as well as with methods employed to minimize stray light.
We present a status report on CHIPS, the Cosmic Hot Interstellar Plasma Spectrometer. CHIPS is the first NASA University-Class Explorer (UNEX) project. CHIPS was selected in 1998 and is now scheduled for launch in December of 2002. The grazing incidence CHIPS spectrograph will survey the sky and record spectra of diffuse emission in the comparatively unexplored wavelength band between 90 and 260 Å. These data will provide important new constraints on the temperature, ionization state, and emission measure of hot plasma in the "local bubble" of the interstellar medium.
We report the fabrication and evaluation of silicon diffraction gratings for use in the far- and extreme- ultraviolet. An interference technique was used to expose a layer of photoresist on a 10 cm silicon wafer in a series of parallel strips. V-shaped grooves were then etched into the wafer anisotropically. Diffraction efficiencies for a first pair of gratings at groove periods of 1.0 and 2.5 micrometers were measured. The process leaves much room for refinement, but shows promise in that the gratings produce clear diffraction orders with reasonable efficiency and have groove facets free of pitting or sharp ridges.
The Berkeley spectrometer aboard the ORFEUS payload achieved a variety of 'firsts' during its inaugural mission in September 1993. The instrument utilizes spherical gratings with mechanically ruled varied line-spacing, and curved microchannel plate detectors with delay- line anode readout systems, to cover the 390 - 1200 angstrom band at a resolution of lambda/5000. The instrument is discussed, and its performance illustrated with calibration and in-flight spectra. Science highlights from the ORFEUS-I mission are presented (oral presentation only). The payload is available for use by guest investigators during the ORFEUS-II mission currently scheduled for late 1996.
We have developed detectors design for high resolution spectroscopic imaging for the EUV spectrometer on the ORFEUS-SPAS mission. The detectors employ spherically curved microchannel plates and a delay line read out system. We present results from the testing and calibration of the detectors prior to their integration into the spectrometer. The design, MCP preconditioning, and imaging characteristics are discussed for 2 rectangular spectral detectors and for the fine guidance detector. Each spectral detector achieves a 30 X 100 micrometers FWHM resolution element size over a 95 mm X 25 mm anode format with good linearity (< 30 micrometers ) in the spectral direction. The fine guidance detector, used for drift corrections, achieves good resolution and will meet the necessary centroiding requirements.
A highly efficient EUV spectrograph is designed for high-resolution spectroscopic observation. The spectrograph is designed for point source astronomy in a 40-120 nm bandpass and is to be ORFEUS (Orbiting Retrievable Far and Extreme Ultraviolet Spectrometer), scheduled for launch as the first payload of a German space platform Astro-SPAS (Astronomy Shuttle Pallet Satellite). The design uses spherical varied line-space (SVLS) grating to minimize astigmatism, coma, and spherical aberration. The effectiveness and practical feasibility of the design is proved by an SVLS grating for visible use. The image focusing properties of the SVLS grating for ORFEUS are compared to those with toroidal uniform line-space (TULS) design. The SVLS design is superior to the TULS, theoretically in resolution and image concentration, but also practically with not only fabrication ease. Four SVLS gratings with nominal groove densities of 6000, 4550, 3450, and 2616 gr./mm, and a 200 mm x 200 mm ruled area have been ruled using a numerically controlled ruling engine for use in ORFEUS.