There is a growing consensus that a substantial fraction of the matter in the universe, especially what we think of as normal baryonic matter, exists in a tenuous, hot filamentary intergalactic medium often referred to as the Cosmic Web. Improving our understanding of the web has been a high priority scientific goal in NASA's planning and roadmapping activities. NASA recently supported an Origins Probe study that explored the observable phenomenology of the web in detail and developed concepts for the instrumentation and mission. The Baryonic Structure Probe operates in the ultraviolet spectral region, using primarily O VI (λλ 1032, 1038 angstrom) and HI Ly α (λ 1216 angstrom) as tracers of the web. A productive investigation requires both moderate resolution (R = λ/Δλ ~ 30000) absorption line spectroscopy using faint background quasars as continuum sources, and imaging of the diffuse filaments in emission lines of the same ions.
Spectroscopic sensitivity to quasars as faint as V ~ 19 will probe a large number of sight lines to derive physical
diagnostics over the redshift range 0 < z < 1. Spectral imaging with a wide field of view and sensitivity to a redshift
range 0 < z < 0.3 will map the filaments in a large volume of the universe after the web had evolved to near its modern
structure. This paper summarizes the scientific goals, identifies the measurement requirements derived from them, and
describes the instrument concepts and overall mission architecture developed by the BSP study team.
The Terrestrial Planet Finder Coronagraph (TPF-C) is a future NASA mission to search for earth-like planets around nearby stars. Detecting a planet that is almost 10 billion times fainter than its parent star is extremely difficult, and it has been shown that polarization effects can cause stellar leakage which threatens that sensitivity goal. Building on our earlier work, we now show the combination of basic polarization effects with a representative coronagraph masking system, the eighth order linear field mask and Lyot stop, results in adequate performance.
The Airborne Imaging Radiometer (AIR) is a small, low mass and power sensor being developed by Ball Aerospace for studies of atmospheric and surface processes. AIR is designed to be a well calibrated, high spatial resolution multispectral imaging sensor. It has been proposed to be built and flown as part of a larger compliment of instrumentation for the High-performance Instrumented Airborne Platform for Environmental Research (HIAPER) under development by the National Science Foundation. The sensor design as currently envisaged will fit within the wing pod 18-inch diameter cylindrical envelope. The sensor is configured as a pushbroom-imager with an 8-km swath width at the nominal 12.5-km flight altitude of HIAPER. It will provide 50-meter resolution thermal imagery in ten spectral bands for the determination of surface and cloud top temperature, cirrus cloud properties, and layer averaged distributions of atmospheric temperature, water vapor and column ozone. A companion visible camera provides 25-meter imagery to aid in the analysis of the infrared imagery. AIR is designed around a Raytheon 320x240 element, 25 um pitch uncooled microbolometer detector array. This technology has advantages over other infrared detector technologies for airborne applications because it does not require a mechanical cryocooler or liquid nitrogen-filled dewar to achieve the necessary longwave response simplifying optical, thermal and mechanical design.
The optical telescope for a spaceborne coronagraph to detect terrestrial to Jovian-sized planets has unusually stringent phase and amplitude requirements - far exceeding a "conventional" telescope like Hubble or the James Webb Space Telescope. The key engineering requirements will be summarized based on probable mission science objectives and an engineering solution with a monolithic primary mirror on the order of 6 meters by 4 meters. We will also present an optical design for a sub-scale coronagraphic simulator as a logical and essential step in examining the system sensitivities. Testbed simulations will include F, G, and K stars and companion planets ranging in size from earth-like up to Jovian-like.
One of NASA's two planet-finding missions will be an optical coronagraph. Due to the stringent science requirements, i.e., detecting a planet that is more than a billion times fainter than its parent star, effects that normally do not enter into instrument design must now be considered. One such effect is polarization. This paper has several goals. First, we review scalar diffraction theory (PSFs and Strehl ratios) and extend it to include polarization. Second, we employ a systems-engineering approach to subdivide and categorize instrumental effects, ultimately concentrating on polarizing non-coronagraph components (mirrors). Third, we push the limits of Code-V commercial optical-engineering software to model the polarization behavior for on- and off- axis configurations, using protected-silver and bare-gold mirror coatings at four wavelengths. Last, we present a brief discussion of future tasks: easing polarization requirements, source polarization, and coronagraph masks and stops.
The Wide Field Camera 3 (WFC3) instrument was designed and built to replace the Hubble Space Telescope (HST) instrument Wide Field and Planetary Camera 2 (WFPC2) and to provide improved ultra-violet through near infra-red imaging capability during the extended HST mission. The WFC3 instrument consists of a two-channel instrument providing diffraction-limited imaging across an average 160 arc second square field of view over 200 to 1000 nm on a 4k x 4k Si detector and an average 135 arc second square field of view over 850 to 1700 nm on a 1k x 1k HgCdTe detector. We describe the optical design and predicted performance of WFC3.
The Wide Field Camera 3 (WFC3) instrument was designed and built to replace the Hubble Space Telescope (HST) instrument Wide Field and Planetary Camera 2 (WF/PC2) and to provide improved ultra-violet through near infrared imaging capability over the extended HST mission. We describe the optical component integration, alignment, and performance testing of the optical bench assembly.
The telescope for a Terrestrial Planet Finder (TPF) coronagraph has exceedingly stringent phase and amplitude requirements, especially for the large, monolithic primary mirror (possibly as large as 4 meters by 10 meters). The pertinent derived engineering requirements will be summarized based on a described set of science objectives to simulate solar type stars and their companion earth-size planets. We will also present an optical design for a sub-scale coronagraphic testbed as an essential step in examining the system sensitivities. The major subassemblies of the testbed include: 1) a star/planet simulator that affords variation in contrast, adjustable relative separation and angular orientation and 2) a relay optical system representative of a TPF 3-mirror telescope that allows the imposition of known optical perturbations over the desired wavefront spatial frequencies. We will compare these TPF testbed mirror wavefront requirements with levels recently achieved on the Advanced Mirror System Demonstrator and planned for the James Webb Space Telescope (JWST).
An instrument concept for an Imaging Multi-Order Fabry-Perot Spectrometer (IMOFPS) has been developed for measuring tropospheric carbon monoxide (CO) from space. The concept is based upon a correlation technique similar in nature to multi-order Fabry-Perot (FP) interferometer or gas filter radiometer techniques, which simultaneously measure atmospheric emission from several infrared vibration-rotation lines of CO. Correlation techniques provide a multiplex advantage for increased throughput, high spectral resolution and selectivity necessary for profiling tropospheric CO. Use of unconventional multilayer interference filter designs leads to improvement in CO spectral line correlation compared with the traditional FP multi-order technique, approaching the theoretical performance of gas filter correlation radiometry. In this implementation, however, the gas cell is replaced with a simple, robust solid interference filter. In addition to measuring CO, the correlation filter technique can be applied to measurements of other important gases such as carbon dioxide, nitrous oxide and methane. Imaging the scene onto a 2-D detector array enables a limited range of
spectral sampling owing to the field-angle dependence of the filter transmission function. An innovative anamorphic optical system provides a relatively large instrument field-of-view for imaging along the orthogonal direction across the detector array. An important advantage of the IMOFPS concept is that it is a small, low mass and high spectral resolution spectrometer having no moving parts. A small, correlation spectrometer like IMOFPS would be well suited for global observations of CO2, CO, and CH4 from low Earth or regional observations from Geostationary orbit. A prototype instrument is in development for flight demonstration on an airborne platform with potential applications to atmospheric chemistry, wild fire and biomass burning, and chemical dispersion monitoring.
Two Hamamatsu photodiode array detectors of the type that will be flown in the MASCS instrument on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission to Mercury were subjected to proton radiation to verify survival in the mission radiation environment and quantify expected levels of radiation-induced degradation of the dark field response during the mission. These same detector types were also evaluated for susceptibility to latch-up due to ionizing radiation.
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