We present the design for a far-UV integral field spectrograph for astronomy enabled by two-axis digital micromirror arrays. Techniques used for integral field spectroscopy in the Optical-IR bandpass either do not apply to the far-UV due to low material transmission, or have other UV-specific challenges. In order to circumvent this limitation, we have designed an all-reflective method of dynamically reformatting the focal plane of a telescope with micro-opto-electro-mechanical systems (MOEMS). The Adaptive Micromirror Array Demonstration Experiment for Ultraviolet Spectroscopy (AMADEUS) is a benchtop far-UV/Optical spectrograph designed to demonstrate that the stability, repeatability, and scattered light contamination are all sufficiently controlable to use these devices in a high sensitivity astronomical instrument. The use of MOEMS devices enables the focal plane mapping to be reconfigured at will, providing some field sampling and path length control advantages relative to conventional Optical/IR techniques for integral field spectroscopy. We report on the design of AMADEUS and present a spectrograph concept for a future sub-orbital mission.
Microchannel plate (MCP) detectors have been the detector of choice for ultraviolet (UV) instruments onboard many NASA missions. These detectors have many advantages, including high spatial resolution (<20 μm), photon counting, radiation hardness, large formats (up to 20 cm), and ability for curved focal plane matching. Novel borosilicate glass MCPs with atomic layer deposition combine extremely low backgrounds, high strength, and tunable secondary electron yield. GaN and combinations of bialkali/alkali halide photocathodes show promise for broadband, higher quantum efficiency. Cross-strip anodes combined with compact ASIC readout electronics enable high spatial resolution over large formats with high dynamic range. The technology readiness levels of these technologies are each being advanced through research grants for laboratory testing and rocket flights. Combining these capabilities would be ideal for UV instruments onboard the Large UV/Optical/IR Surveyor (LUVOIR) and the Habitable Exoplanet Imaging Mission (HABEX) concepts currently under study for NASA’s Astrophysics Decadal Survey.
The Alice far-ultraviolet spectrograph on board the Rosetta spacecraft currently operating around the comet 67P/Churyumov-Gerasimenko experiences an anomalistic feature (AF) that has proven nearly constant at comet separations below 450 km.1 This feature varies rapidly on the second time scale and displays no relation to any measured parameters with the exception of comet separation. Simulations showed that nanograins and ions could create the feature through a range of possible masses, velocities, charges, and energies. This paper builds on research published in Reference 1 that explored the behaviors and morphology of the AF. Observations taken on February 19th, 2016 during a dust outburst observed by several other instruments (Eberhard Grun, in prep) verified that the most common morphology of the AF is linked to dust and charged nanograins.
We present the Southwest Ultraviolet Imaging System (SwUIS), a compact, low-cost instrument
designed for remote sensing observations from a manned platform in space. It has two chief
configurations; a high spatial resolution mode with a 7-inch Maksutov-Cassegrain telescope, and a
large field-of-view camera mode using a lens assembly. It can operate with either an intensified CCD
or an electron multiplying CCD camera. Interchangeable filters and lenses enable broadband and
narrowband imaging at UV/visible/near-infrared wavelengths, over a range of spatial resolution.
SwUIS has flown previously on Space Shuttle flights STS-85 and STS-93, where it recorded multiple
UV images of planets, comets, and vulcanoids. We describe the instrument and its capabilities in
detail. The SWUIS’s broad wavelength coverage and versatile range of hardware configurations make
it an attractive option for use as a facility instrument for Earth science and astronomical imaging
investigations aboard the International Space Station.
The Southwest Research Institute Ultraviolet Reflectance Chamber (SwURC) is a highly capable UV reflectometer
chamber and data acquisition system designed to provide bidirectional scattering data of various surfaces and
materials. The chamber provides laboratory-based UV reflectance measurements of water frost/ice, lunar soils,
simulants, and analogs to support interpretation of UV reflectance data from the Lyman Alpha Mapping Project
(LAMP) Lunar Reconnaissance Orbiter (LRO). A deuterium lamp illuminates a monochromator with a nominal
wavelength range of 115 nm to 210 nm. The detector scans emission angles -85° to +85°in the principal plane. Liquid
nitrogen passed through the sample mount enables constant refrigeration of tray temperatures down to 78 K to form
water ice and other volatile samples. The SwURC can be configured to examine a wide range of samples and
materials through the use of custom removable sample trays, connectors, and holders. Calibration reference standard
measurements reported here include Al/MgF2 coated mirrors for specular reflection and Fluorilon for diffuse
reflectances. This calibration work is a precursor to reports of experiments measuring the far-UV reflectance of water
frost, lunar simulants, and Apollo soil sample 10084 in support of LRO-LAMP.
We have assembled and launched the Diffuse Interstellar Cloud Experiment (DICE), an instrument capable of
recording high resolution (λ/δλ = 30,000) spectra in the Far Ultraviolet (FUV). Absorption measurements toward nearby
bright stars can provide new insight into the processes governing warm-hot gas in the Local Interstellar Medium. It flew
on May 21st, 2010. An anomaly in the Black Brant motor subjected the payload to abnormally high vibration. As a
result, the optics were misaligned and no spectral data fell on the detector. Here we present the details of mechanical and
electrical integration with NASA launch systems, as well as optical alignment of the telescope and spectrograph. In
addition, we summarize the flight results.
We have designed a sounding rocket payload to perform high resolution far ultraviolet (FUV) spectroscopy. The payload will contain a modified Rowland spectrograph, achieving resolution (λ/δ λ) of 60,000 by adding a magnifying secondary optic. We will use this instrument to observe two stars on opposing sides of the Local Bubble wall. Obtaining spectra of the O VI doublet in absorption towards these stars will provide new insight into the processes governing hot gas near the cavity wall.
Perhaps the most compelling piece of science and exploration now under discussion for future space missions is the direct
study of planets circling other stars. Indirect means have established planets as common in the universe but have given us
a limited view of their actual characteristics. Direct observation holds the potential to map entire planetary systems, view
newly forming planets, find Earth-like planets and perform photometry to search for major surface features. Direct
observations will also enable spectroscopy of exoplanets and the search for evidence of simple life in the universe. Recent
advances in the design of external occulters - starshades that block the light from the star while passing exoplanet light -
have lowered their cost and improved their performance to the point where we can now envision a New Worlds Observer
that is both buildable and affordable with today's technology. We will summarize recent studies of such missions and
show they provide a very attractive alternative near term mission.
A new mission concept for direct imaging of exo-solar planets called New Worlds Observer (NWO) has been proposed. It involves flying a meter-class space telescope in formation with a newly-conceived, specially-shaped, deployable star-occulting shade several meters across at a separation of some tens of thousands of kilometers. The telescope would make its observations from behind the starshade in a volume of high suppression of incident irradiance from the star around which planets orbit. For an efficacious mission, the required level of irradiance suppression by the starshade is of order 0.1 to 10 parts per billion in broadband light. We discuss an experiment to accurately measure the irradiance suppression ratio at the null position behind candidate starshade forms to these levels. We also present results of broadband measurements which demonstrated suppression levels of less than 100 parts per billion in air using the Sun as a light source. A simulated spatial irradiance distribution surrounding the null from an analytical model developed for starshades is compared with a photograph of actual irradiance captured in situ behind a candidate starshade.
We present laboratory studies of scaled occulting starshades for the New Worlds Observer (NWO). A deep
reactive ion etched silicon starshade has been fabricated by NIST, designed to cover the same number of Fresnel zones
as in the proposed mission. The broadband shadow is mapped with a photometer in a dark vacuum tunnel fed by a
heliostat at HAO. CCD images provide direct contrast measurements of different features around the starshade.
Preliminary measurements reach 5x10-6 suppression in the center of the shadow at the focal plane. The two-dimensional
structure of the starshade diffraction pattern is compared to that produced by the Fresnel integral.
We present a new sounding rocket payload that will perform high resolution (R~100) x-ray spectroscopy of diffuse celestial x-ray sources. The instrument features a new geometry that allows for high resolution along with high throughput. A wire grid collimator constrains light from diffuse sources into a converging beam that feeds an array of diffraction gratings in the extreme off-plane mount. Starting with launch in 2006 we can obtain physical diagnostics of supernova remnants such as the Cygnus Loop and ultimately the hot phase of the interstellar medium.
We discuss the progress that has been made in the understanding of the use of external occulters to observe exoplanetary systems. We show how a starshade can be designed and built in a practical and affordable manner to fully remove starlight and leave only planet light entering a telescope. When coupled to a powerful observatory like the James Webb Space Telescope, an occulter can extinguish the starlight and reveal basic details of the planetary systems around our closest, neighboring stars.
High resolution and signal to noise spectral observations of AGN outflows in the UV demonstrate the need for using
covering factor models in calculating absorber column densities. We study the best X-ray data set of an AGN outflow,
the Chandra 900 kilosecond observation of NGC 3783, for similar effects in the strongly saturated line series of NeX and
OVII. Velocity-dependent covering factor generates much better fits to the OVII He-like series than full covering with
the same amount of column. There is also evidence for covering factor in strong L-shell Fe lines. With the low
resolution of the HETGS relative to absorption troughs, full covering and partial covering yield similar fits to the NeX
Lyman series. Still, both models produce NeX column densities 5 times higher than previous analyses. We generate
synthetic data for the future Con-X mission and compare to the Chandra 900 ks data. We calculate the necessary
resolution and effective area to correctly identify covering factor models.
The Constellation-X Reflection Grating Spectrometer (RGS) is designed to provide high-throughput, high-resolution spectra in the long wavelength band of 6 to 50 angstrom. In the nominal design an array of reflection gratings is mounted at the exit of the Spectroscopy X-ray Telescope (SXT) mirror module. The gratings intercept and disperse light to a designated array of CCD detectors. To achieve the throughput (Aeff > 1000 cm2 below 0.6 keV) and resolution (Δλ/λ > 300 below 0.6 keV) requirements for the instrument we are investigating two possible grating designs. The first design uses in-plane gratings in a classical configuration that is very similar to the XMM-Newton RGS. The second design uses off-plane gratings in a conical configuration. The off-plane design has the advantage of providing higher reflectivity and potentially, a higher spectral resolution than the in-plane configuration. In our presentation we will describe the performance requirements and the current status of the technology development.
The New Worlds Observer, currently studied under a NASA Institute for Advanced Concepts grant, will be a pinhole camera in space designed to directly detect and study extrasolar terrestrial planets. An apodized occultor or pinhole creates an image of the planetary system in the focal plane far away, where a second telescope craft orbits to detect the light. In this study we simulate the expected signal of NWO to find the optimal configuration and specifications of the two craft. The efficiency of direct detection through photometric imaging depends strongly on occulter and telescope size, while preliminary studies on absorption biomarker detection and photometric variability measurements are summarized.
James Beatty, H. Ahn, P. Allison, M. J. Choi, N. Conklin, Stephane Coutu, Michael DuVernois, O. Ganel, S. Jaminion, K. Kim, M. Lee, L. Lutz, Pier Marrocchesi, S. Minnick, S. Mognet, Kyung-wook Min, S. Nutter, H. Park, I. Park, K. Petska, E. Schindhelm, Eun-Suk Seo, Simon Swordy, J. Wu, J. Yang
The cosmic ray all-particle spectrum has a small steepening of its spectral slope, or 'knee', near 1015 eV. Changes in the nuclear composition of cosmic rays may be associated with the knee and provide clues concerning the origin of the spectral change. An ultra-long duration balloon experiment, Cosmic Ray Energetics and Mass (CREAM), is being constructed to measure cosmic ray elemental spectra at energies just below the knee to look for evidence of changes in composition. CREAM employs a thin calorimeter and transition radiation detector to provide multiple measures of the particle energy. A novel technique, the timing charge detector, is used to identify the charge of the incident primary cosmic ray in the presence of the albedo particles generated by interactions in the calorimeter.
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