We have developed the capability to optimize a diffraction grating with arbitrary groove density and direction as a function of location. The added degrees of freedom allow additional correction of optical aberrations beyond what is available to holographic recordings. Since the groove direction and density can be independent but continuous for all points on the grating, we are not constrained by the limitations of ensuring that the grooves follow a single parametrized function. By fabricating a grating with an e-beam in silicon, we are able to produce a coherent, continuous grating across a silicon substrate. Silicon substrates have a number of advantages for optical designers, with ready availability. Additional advances in fabrication are providing improved grating efficiency. The key advance we report here is the adaptation of existing semiconductor fabrication technology to create a grating with grooves that are functionally independent across the entire grating. By ensuring that the grooves are continuous and coherent, we are able to fabricate a grating with unprecedented optical performance at low cost. Work to date includes fabricated test pieces, testing of the pieces, and refinement of the modeling of the optical performance.
Southwest Research Institute's (SwRI's) "ALICE" line of ultraviolet spectrographs (UVS) is founded on a lightweight,
low power, and highly versatile instrument design. Generally small changes in detector photocathode, pixel size, slit
shape, optical coatings, pinhole aperture implementations, and other minor tweaks have enabled a wide variety of
applications for the ALICE design, including investigations of comets (Rosetta-ALICE), Pluto (New Horizons-ALICE),
the Moon (Lunar Reconnaissance Orbiter (LRO)-Lyman Alpha Mapping Project (LAMP)), and Jupiter (Juno-UVS).
ALICE's high capability and our experience with high radiation environment and outer solar system requirements make
this UVS a good choice for future planetary mission concepts.
We report accelerated vacuum aging tests on two Pt-Ne lamps identical and/or similar to those installed on
the Cosmic Origins Spectrograph (COS) to be installed in the Hubble Space Telescope (HST) in the fall of
2008. One additional lamp was aged in air at the National Institute of Standards and Technology (NIST). All
lamps were tested at a 50% duty cycle (30 s on/off) at flight nominal (10 mA) constant current until failure.
Calibrated spectra of all lamps were taken at NIST using the 10.7-m normal incidence vacuum spectrograph at
various points in the life of the lamps. In this paper we report the results of the photometric, electrical, and
thermal monitoring of the vacuum tested lamps, while the spectroscopic and air aging results are given in a
companion paper (Nave et al., 2008, SPIE 7011-134). We conclude that the lamps will satisfy the requirements
of the HST/COS mission in terms of lifetime, cycles, and thermal and spectral stability.
A second generation near-infrared instrument was built by the University of Colorado for the ARC 3.5 meter telescope and is being commissioned at the Apache Point Observatory. An initial engineering run, first light, commissioning observations, and initial facility science operations have been accomplished in the last year. Instrument imaging performance was good to excellent from first light and consortium observers began to employ the instrument on a shared-risk basis immediately after commissioning operations. Instrument optical and mechanical performance during this testing and operations phase are discussed. Detector system (Rockwell Hawaii-1RG 1024x1024 HgCdTe focal plane array with Leach controller) characteristics during these early operations are detailed along with ongoing efforts for system optimization. High resolution (R~10,000) spectroscopy is planned employing a Queensgate (now IC Optical) cryogenic Fabry-Perot etalon, though mechanical difficulties with the etalon precluded a system performance demonstration. The Consortium has decided that the instrument will retain the name NIC-FPS (Near Infrared Camera and Fabry-Perot Spectrometer) after commissioning.
A near-infrared instrument is being built for the ARC 3.5 meter telescope that will operate in both an imaging and a narrow band, full field spectroscopic mode. The 4.5' x 4.5' fild-of-view is imaged onto a new-generation, low-noise Rockwell Hawaii-1RG 1024x1024 HgCdTe detector. High resolution (R~10,000) spectroscopy is accomplished by employing a Queensgate (now IC Optical) cryogenic Fabry-Perot etalon. The instrument is housed in a large Dewar of innovative, light-weight design. This report describes the as-built opto-mechanical system for the instrument and the work remaining before deployment at Apache Point Observatory in New Mexico.
We present a new instrument for wide-field, narrow-band imaging of the O VI doublet at 1032, 1038 Å. This doublet constitutes the brightest astrophysical line emission from diffuse gas at 300,000 degrees K. Gases at this temperature are primarily formed by supernova blast waves, and are key in understanding the energy budget of the galaxy. We use a conventional Gregorian telescope design to provide excellent zero-order imaging, in conjunction with aberration-corrected holography to yield high-resolution images of O VI in first order. This instrument design uses only two reflective elements and no transmissions, minimizing the light lost due to the poor reflectivity and transmissivity of materials in the far ultraviolet. The holographic recording solution provides 4-9 arcsecond imaging over a 0.5 degree field of view. This instrument demonstrates the versatility of the holographic telescope concept by expanding is applicability to larger fields of view. We are developing a sounding rocket payload to demonstrate the power of this wide field holographic telescope design, particularly as a means of mapping shocked gas in the interstellar medium, at temperatures intermediate to those sampled in optical and X-ray emission. We present the optical design, instrument performance, image reconstruction techniques, and relevant scientific simulations.