The Polarimeter to Unify the Corona and Heliosphere (PUNCH) mission is a four-spacecraft observatory designed for low earth orbit observations of the Sun to understand better the solar wind. Each of the four observatories carries a Teledyne e2V 230-82 CCD controlled by a Rutherford Appleton Laboratories (RAL) detector controller and a filter wheel that allows for the selection of different polarization vectors and a blank off to monitor detector health. The CCD is 2kx4k pixels and has a store shield covering half the device to serve as a charge storage region. The CCDs are operated in pseudo frame transfer mode. We present here the laboratory optical calibration data for the four flight detector systems.
We discuss the final assembly, integration, and testing of the Star-Planet Activity Research CubeSat. SPARCS is a 6U CubeSat mission designed to monitor the dual-channel, far-UV (153-176 nm) and near-UV (258-308 nm) photometric activity of nearby low mass stars to advance our understanding of their evolution, activity, and the habitability of surrounding exoplanets. This paper details the assembly of the SPARCS instrument and the testing process to characterize and validate the performance of the payload prior to spacecraft integration. To test SPARCS, we have established a customized CubeSat AIT laboratory and thermal vacuum chamber at ASU equipped to handle CubeSats requiring meticulous contamination control for work in the FUV. After a brief overview of these facilities and the testing plan, we will detail the methods and data used to verify the performance of SPARCS and generate calibration products to reduce raw flight data to high-quality science products. The result will be the delivery of the first highly sensitive FUV astrophysics CubeSat which will inform exoplanet environments and future observations of these systems by facilities like the Habitable Worlds Observatory.
At Southwest Research Institute (SwRI), the ultraviolet (UV) calibration lab successfully tested First Contact Polymer (FCP) cleaning solution on unprotected gold mirrors in the UV region. This investigation proved that the cleaning solution meets the contamination threshold of < 100 ng/cm² and passes the relative reflectance differences threshold of <10% difference. Future internal research funding would include UV testing with other optics (mirrors/lenses with different coatings and substrates, diffraction gratings, and freeform optics) to establish its effectiveness over a variety of optical elements.
The Star-planet activity research CubeSat (SPARCS) is a 6U CubeSat mission focused on dual channel, SPARCS farUV (153-171 nm) and near-UV (260-300 nm), photometric monitoring of nearby M-stars. These data will advance our understanding of the typical day-to-day UV environments around M stars and how these conditions evolve over the stars’ multibillion-year lifespans; critical factors that constrain the potential habitability of planets orbiting M stars, informing the search for life in the galaxy. This paper lays out the detailed plan for the SPARCS science payload assembly, integration, and testing (AIT), including the optical calibration and performance measurement methods for the science telescope, thermal vacuum bakeouts for part cleaning, ongoing contamination monitoring methods, and spectral performance measurements of the assembled payload camera. We will provide updates on AIT proceedings at ASU and the SPARCS thermal vacuum chamber (TVAC) test facility built for UV CubeSat missions at Arizona State University’s School of Earth and space exploration.
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 for all points on the grating, the design is not constrained by the limitations of ensuring that the grooves follow a single parametrized function. The grooves are then written with e-beam fabrication techniques onto a silicon substrate.
We present the results from our project to fabricate aberration-correcting gratings using direct writing in silicon. Two gratings were produced as part of this work, one is a demonstration a Fresnel plate to verify that the grating was fabricated as intended. The second grating was designed as part of a Raman spectrograph and provides excellent optical performance over the designed passband.
The University of Colorado led Extreme-ultraviolet Stellar Characterization for Atmospheric Physics and Evolution (ESCAPE) small explorer mission concept is designed to measure the extreme- and far-ultraviolet (EUV; 80 - 560 A, 600 - 825 A, FUV; 1280 - 1650 A) irradiance and are activity of exoplanet host stars; essential measurements for assessing the stability of rocky planet atmospheres in the liquid-water habitable zone. The ESCAPE design consists of a fixed optical configuration with a grazing incidence Gregorian, or "Hetterick- Bowyer", telescope feeding grazing and normal incidence spectroscopic channels. The telescope is provided by a joint NASA Marshall Space Flight Center and Smithsonian Astrophysics Observatory team. The grazing incidence gratings have a radial profile and are ruled into single-crystal silicon using electron-beam lithography in the nanofabrication laboratory at Pennsylvania State University. Normal incidence gratings have aberration correcting holographic solutions and are supplied by Horiba Jobin Yvon. Spectra are imaged onto a curved microchannel plate detector supplied by the University of California, Berkeley. ESCAPE utilizes the Ball Aerospace BCP spacecraft. The simple, fixed configuration design of ESCAPE is projected to exceed the effective area of the last major EUV astrophysics spectrograph, EUV E-DS/S, by more than a factor of 50, providing unprecedented sensitivity in this essential bandpass for exoplanet host-star characterization. We report on the ESCAPE design, projected performance and mission implementation plan, as well as the trade studies carried out over Phase A to scope the first NASA EUV astrophysics mission in nearly 30 years. If selected, ESCAPE will launch in Fall 2025.
The Star-Planet Activity Research CubeSat (SPARCS) is positioned to revolutionize our understanding of M-dwarf star evolution, activity, variability, and the habitability of surrounding exoplanets. SPARCS will be the first mission to observe M stars for long periods of time simultaneously using a dual channel FUV (153 – 171 nm) and NUV (260 - 300 nm) imaging system. Anticipated to launch in 2023, SPARCS will provide key UV context to future observations by TESS and JWST, and the spaceflight application of advanced new detector technologies will pave the way for their implementation into future missions like LUVOIR and HabEx. To realize the scientific potential of SPARCS against the challenges of the ultraviolet spectrum, we are developing the specialized facilities, procedures, and tests necessary to assemble, integrate, and test the SPARCS science payload and spacecraft. A thorough testing campaign will verify the performance of individual payload components and obtain calibration baselines from the fully assembled science instrument that are vital to the data reduction process and in-flight contamination monitoring. SPARCS requires extensive contamination control to maintain its sensitivity in the FUV and NUV, which means all of AIT must occur in controlled and precisely monitored environments. This work will result in: (1) The delivery of the assembled and tested SPARCS spacecraft for launch in 2023. (2) A comprehensive performance validation and calibration baseline for SPARCS including a measurement of system throughput to for every wavelength across the SPARCS bandpasses, maps of NUV and FUV sensitivity across the payload field of view, and a full set of calibration products like flatfield images and dark current measurements for data reduction and comparison with calibration products acquired in orbit to monitor spacecraft conditions. (3) The establishment of a fully operational CubeSat AIT laboratory at ASU equipped to handle CubeSats up to 6U in size requiring meticulous contamination control up to the levels required for working in the FUV. This paper presents the work completed so far on the development and early operation of assembly, integration, and testing facilities for SPARCS. A custom thermal vacuum (TVAC) chamber facility was created and one of Arizona State University’s cleanroom environments was retrofitted to accommodate a 6U ultraviolet CubeSat requiring strict contamination control. We will describe the TVAC facility design and early testing, the cleanroom operation and contamination monitoring, and the development of an optical system and procedures to characterize the optical performance.
The Star-Planet Activity Research CubeSat (SPARCS) is a 6U CubeSat under construction that is devoted to the photometric monitoring of M stars in the far-UV (FUV) and near-UV (NUV), to measure the time-dependent spectral slope, intensity and evolution of low-mass star high-energy radiation. We report on the progress made in the assembly, integration and test of the instrument payload at Arizona State University using a custom TVAC chamber and optical stimulus that provides calibration light sources and the custom contamination control environment that the FUV demands. The payload consists of a custom 90mm clear aperture telescope developed by Hexagon/Sigma Space, combined with a dichroic plate to separate the FUV and NUV beams developed by Teledyne Acton and Materion, married with twin focal plane array cameras separately optimized for their bandpasses as developed by JPL.
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.
KEYWORDS: Ultraviolet radiation, Stars, Atmospheric modeling, Space operations, Space telescopes, Planets, Telescopes, Sensors, Exoplanets, Control systems
Roughly 40 billion M dwarfs in our galaxy host at least one small planet in the habitable zone (HZ). The stellar ultraviolet (UV) radiation from M dwarfs is strong and highly variable, and impacts planetary atmospheric loss, composition and habitability. These effects are amplified by the extreme proximity of their HZs (0.1–0.4 AU). Knowing the UV environments of M dwarf planets will be crucial to understanding their atmospheric composition and a key parameter in discriminating between biological and abiotic sources for observed biosignatures. The Star-Planet Activity Research CubeSat (SPARCS) will be a 6U CubeSat devoted to photometric monitoring of M stars in the far-UV and near-UV, measuring the time-dependent spectral slope, intensity and evolution of low-mass star high-energy radiation.
The Colorado Ultraviolet Transit Experiment (CUTE) is a near-UV (2550 to 3300 Å) 6U CubeSat mission designed to monitor transiting hot Jupiters to quantify their atmospheric mass loss and magnetic fields. CUTE will probe both atomic (Mg and Fe) and molecular (OH) lines for evidence of enhanced transit absorption, and to search for evidence of early ingress due to bow shocks ahead of the planet’s orbital motion. As a dedicated mission, CUTE will observe ≳100 spectroscopic transits of hot Jupiters over a nominal 7-month mission. This represents the equivalent of >700 orbits of the only other instrument capable of these measurements, the Hubble Space Telescope. CUTE efficiently utilizes the available CubeSat volume by means of an innovative optical design to achieve a projected effective area of ∼28 cm2, low instrumental background, and a spectral resolving power of R∼3000 over the primary science bandpass. These performance characteristics enable CUTE to discern transit depths between 0.1% and 1% in individual spectral absorption lines. We present the CUTE optical and mechanical design, a summary of the science motivation and expected results, and an overview of the projected fabrication, calibration, and launch timeline.
We have worked to define the compelling next generation General Astrophysics science that the 4m implementation of the HabEx mission concept might enable. These science drivers have been used to define requirements for a far ultraviolet (FUV) spectrograph design for the telescope design that meets the needs of these programs. We describe both the drivers and the baseline design for the instrument, the modes it might support, and the choices that were made to optimize the performance. The operational performance of the instrument in cooperation with the rest of the telescope design is also discussed.
The Colorado Ultraviolet Transit Experiment (CUTE) is a near-UV (2550 - 3300 Å) 6U cubesat mission designed to monitor transiting hot Jupiters to quantify their atmospheric mass loss and magnetic fields. CUTE will probe both atomic (Mg and Fe) and molecular (OH) lines for evidence of enhanced transit absorption, and to search for evidence of early ingress due to bow shocks ahead of the planet’s orbital motion. As a dedicated mission, CUTE will observe ⪆ 60 spectroscopic transits of hot Jupiters over a nominal seven month mission. This represents the equivalent of > 700 orbits of the only other instrument capable of these measurements, the Hubble Space Telescope. CUTE efficiently utilizes the available cubesat volume by means of an innovative optical design to achieve a projected effective area of ∼ 22 cm2 , low instrumental background, and a spectral resolving power of R ∼ 3000 over the entire science bandpass. These performance characteristics enable CUTE to discern a transit depth of ⪅1% in individual spectral absorption lines. We present the CUTE optical and mechanical design, a summary of the science motivation and expected results, and an overview of the projected fabrication, calibration and launch timeline.
Recent years have seen a rise in the development of concepts for constellations of SmallSats or Cubesats for Earth Observation remote sensing. These constellations focus on visible RGB imagery or multi-band imagery from a handful of wide-bands in the visible or near infrared wavelengths.
Mid-wave infrared (MWIR) data provides a unique measurement, able to be operated both for day and night imaging. Recent developments in infrared detectors and the miniaturization of cryocooler technology enable this instrument be packaged in a Cubesat form-factor. Data products derived from the MWIR measurement have been shown to be beneficial in agricultural decision making process, specifically in irrigation and water use.
Planetary Resources is developing a MWIR instrument operating across the 3-5um wavelength for the purpose of prospecting near-Earth asteroids. In turning the gaze of the sensors to nadir from low-Earth orbit, a unique dataset is created that is currently lacking from existing commercial Earth observation platforms.
This paper presents the MWIR instrument, its measurement from low-Earth orbit and its potential for near-Earth asteroid exploration.
We present the Compact Holographic Aberration-corrected Platform (CHAP) instrument, designed and developed at Planetary Resources Development Corporation. By combining a dispersive element with the secondary of a telescope, we are able to produce a relatively long focal length with moderate dispersion at the focal plane. This design enables us to build a capable hyperspectral imaging instrument within the size constraints of the Cubesat form-factor. The advantages of our design revolves around its simplicity: there are only two optical elements, producing both a white light and diffracted image. With the use of a replicated grating, we can produce a long focal length hyperspectral imager at a price point far below other spaceflight instruments. The design is scalable for larger platforms and since it has no transmitting optics and only two reflective surfaces could be designed to function at any desired wavelength. Our system will be capable of spectral imaging across the 400 to 900 nm spectral range for use in small body surveys.
Over the past few years the advent of atomic layer deposition (ALD) technology has opened new capabilities to the field of coatings deposition for use in optical elements. At the same time, there have been major advances in both optical designs and detector technologies that can provide orders of magnitude improvement in throughput in the far ultraviolet (FUV) and near ultraviolet (NUV) passbands. Recent review work has shown that a veritable revolution is about to happen in astronomical diagnostic work for targets ranging from protostellar and protoplanetary systems, to the intergalactic medium that feeds gas supplies for galactic star formation, and supernovae and hot gas from star forming regions that determine galaxy formation feedback. These diagnostics are rooted in access to a forest of emission and absorption lines in the ultraviolet (UV)[1], and all that prevents this advance is the lack of throughput in such systems, even in space-based conditions. We outline an approach to use a range of materials to implement stable optical layers suitable for protective overcoats with high UV reflectivity and unprecedented uniformity, and use that capability to leverage innovative ultraviolet/optical filter construction to enable astronomical science. These materials will be deposited in a multilayer format over a metal base to produce a stable construct. Specifically, we will employ the use of PEALD (plasma-enhanced atomic layer deposition) methods for the deposition and construction of reflective layers that can be used to construct unprecedented filter designs for use in the ultraviolet.
The Colorado High-resolution Echelle Stellar Spectrograph (CHESS) is a far ultraviolet (FUV) rocket-borne experiment designed to study the atomic-to-molecular transitions within translucent interstellar clouds. CHESS is an objective echelle spectrograph operating at f/12.4 and resolving power of 120,000 over a band pass of 100 – 160 nm. The echelle flight grating is the product of a research and development project with LightSmyth Inc. and was coated at Goddard Space Flight Center (GSFC) with Al+LiF. It has an empirically-determined groove density of 71.67 grooves/mm. At the Center for Astrophysics and Space Astronomy (CASA) at the University of Colorado (CU), we measured the efficiencies of the peak and adjacent dispersion orders throughout the 90 – 165 nm band pass to characterize the behavior of the grating for pre-flight calibrations and to assess the scattered-light behavior. The crossdispersing grating, developed and ruled by Horiba Jobin-Yvon, is a holographically-ruled, low line density (351 grooves/mm), powered optic with a toroidal surface curvature. The CHESS cross-disperser was also coated at GSFC; Cr+Al+LiF was deposited to enhance far-UV efficiency. Results from final efficiency and reflectivity measurements of both optics are presented. We utilize a cross-strip anode microchannel plate (MCP) detector built by Sensor Sciences to achieve high resolution (25 μm spatial resolution) and data collection rates (~ 106 photons/second) over a large format (40mm round, digitized to 8k x 8k) for the first time in an astronomical sounding rocket flight. The CHESS instrument was successfully launched from White Sands Missile Range on 24 May 2014. We present pre-flight sensitivity, effective area calculations, lab spectra and calibration results, and touch on first results and post-flight calibration plans.
The High-ORbit Ultraviolet-visible Satellite (HORUS) is a 2.4-meter class space telescope that will conduct a
comprehensive and systematic study of the astrophysical processes and environments relevant for the births and life
cycles of stars and their planetary systems, to investigate and understand the range of environments, feedback
mechanisms, and other factors that most affect the outcome of the star and planet formation process. HORUS will
provide 100× greater imaging efficiency and combines the resolution of STIS with the throughput of COS. The HORUS
mission will contribute vital information on how solar systems form and whether habitable planets should be common or
rare. It also will investigate the structure, evolution, and destiny of galaxies and the universe. This program relies on
focused capabilities unique to space that no other planned NASA mission will provide: near-ultraviolet (UV)/visible
(200-1100nm) wide-field (14′ square), diffraction-limited imaging; and high-sensitivity, high-resolution FUV (100-
320nm) spectroscopy. From its baseline orbit at L2 HORUS will enjoy a stable environment for thermal and pointing
control, and long-duration target visibility. The core HORUS design will provide wide field of view imagery and high
efficiency point source far-ultraviolet (FUV) spectroscopy using a combination of spectral selection and field sharing.
We present the fabrication and testing of the Sub-orbital Local Interstellar Cloud Experiment (SLICE), a rocket-borne
payload for ultraviolet astrophysics in the 1020 to 1070 Å bandpass. The SLICE optical system is composed of an
ultraviolet-optimized telescope feeding a Rowland Circle spectrograph. The telescope is an 8-inch Classical Cassegrain
operating at F/7, with Al optics overcoated with LiF for enhanced far-ultraviolet reflectivity. The holographically-ruled
grating focuses light at an open-faced microchannel plate detector employing an opaque RbBr photocathode. In this
proceeding, we describe the design trades and calibration issues confronted during the build-up of this payload. We
place particular emphasis on the technical details of the design, modifications, construction, and alignment procedures
for SLICE in order to provide a roadmap for the optimization of future ruggedized experiments for ultraviolet imaging
and spectroscopy.
We present the flight performance and preliminary science results from the first flight of the Sub-orbital Local
Interstellar Cloud Experiment (SLICE). SLICE is a rocket-borne far-ultraviolet instrument designed to study the diffuse
interstellar medium. The SLICE payload comprises a Cassegrain telescope with LiF-coated aluminum optics feeding a
Rowland Circle spectrograph operating at medium resolution (R ~ 5000) over the 102 – 107 nm bandpass. We present a
novel method for cleaning LiF-overcoated Al optics and the instrumental wavelength calibration, while the details of the
instrument design and assembly are presented in a companion proceeding (Kane et al. 2013). We focus primarily on
first results from the spring 2013 launch of SLICE in this work. SLICE was launched aboard a Terrier-Black Brant IX
sounding rocket from White Sands Missile Range to observe four hot stars sampling different interstellar sightlines. The
instrument acquired approximately 240 seconds of on-target time for the science spectra. We observe atomic and
molecular transitions (HI, OI, CII, OVI, H2) tracing a range of temperatures, ionization states, and molecular fractions in
diffuse interstellar clouds. Initial spectral synthesis results and future plans are discussed.
We present a conceptual design for a high-resolution optical spectrograph appropriate for mounting at Cassegrain on a large aperture telescope. The design is based on our work for the Gemini High Resolution Optical Spectrograph (CUGHOS) project. Our design places the spectrograph at Cassegrain focus to maximize throughput and blue wavelength coverage, delivering R=40,000 resolving power over a continuous 320–1050 nm waveband with throughputs twice those of current instruments. The optical design uses a two-arm, cross-dispersed echelle format with each arm optimized to maximize efficiency. A fixed image slicer is used to minimize optics sizes. The principal challenge for the instrument design is to minimize flexure and degradation of the optical image. To ensure image stability, our opto-mechanical design combines a cost-effective, passively stable bench employing a honeycomb aluminum structure with active flexure control. The active flexure compensation consists of hexapod mounts for each focal plane with full 6-axis range of motion capability to correct for focus and beam displacement. We verified instrument performance using an integrated model that couples the optical and mechanical design to image performance. The full end-to-end modeling of the system under gravitational, thermal, and vibrational perturbations shows that deflections of the optical beam at the focal plane are <29 μm per exposure under the worst case scenario (<10 μm for most orientations), with final correction to 5 μm or better using open-loop active control to meet the stability requirement. The design elements and high fidelity modeling process are generally applicable to instruments requiring high stability under a varying gravity vector.
We present the design and system calibration results from the fabrication of a charge-coupled device (CCD) based
imaging system designed using a modified modular imager cell (MIC) used in an ultraviolet sounding rocket mission.
The heart of the imaging system is the MIC, which provides the video pre-amplifier circuitry and CCD clock level
filtering. The MIC is designed with standard four-layer FR4 printed circuit board (PCB) with surface mount and
through-hole components for ease of testing and lower fabrication cost. The imager is a 3.5k by 3.5k LBNL p-channel
CCD with enhanced quantum efficiency response in the UV using delta-doping technology at JPL. The recently released
PCIe/104 Small-Cam CCD controller from Astronomical Research Cameras, Inc (ARC) performs readout of the
detector. The PCIe/104 Small-Cam system has the same capabilities as its larger PCI brethren, but in a smaller form
factor, which makes it ideally suited for sub-orbital ballistic missions. The overall control is then accomplished using a
PCIe/104 computer from RTD Embedded Technologies, Inc. The design, fabrication, and testing was done at the
Laboratory for Astronomical and Space Instrumentation (LASI) at Arizona State University. Integration and flight
calibration are to be completed at the University of Colorado Boulder before integration into CHESS.
Current FUV instrumentation is seriously compromised by poor reflectivity. The best existing coatings for the 90 – 115 nm range are SiC (30% reflectivity across the band) and LiF/Aluminum (60% reflectivity from 100 nm to 115 nm). An improved coating therefore would enable the production of vastly more sensitive instruments in the 90 – 200 nm range. An additional goal in the development of an alternate FUV coating is to overcome the well-documented hygroscopic behaviors of LiF coatings, which currently impose handling concerns that in turn drive cost and schedule. The coatings we will develop in this effort must also function well through the conventional silicon-based detector bandpass (200 nm to 1100 nm). By ensuring that these new coatings are usable at many wavelengths, we will make it possible to incorporate ultraviolet instruments into future large missions without compromising the science capability of other instruments or increasing cost and risk due to handling issues. We present new results of the coating process and discuss our new ALD processes.
A key astrophysical theme that will drive future UV/optical space missions is the life cycle of cosmic matter, from the
flow of intergalactic gas into galaxies to the formation and evolution of exoplanetary systems. Spectroscopic systems
capable of delivering high resolution with low backgrounds will be essential to addressing these topics. Towards this
end, we are developing a rocket-borne instrument that will serve as a pathfinder for future high-sensitivity, highresolution
UV spectrographs. The Colorado High-resolution Echelle Stellar Spectrograph (CHESS) will provide 2 km
s-1 velocity resolution (R = 150,000) over the 100 - 160 nm bandpass that includes key atomic and molecular spectral
diagnostics for the intergalactic medium (H I Lyman-series, O VI, N V, and C IV), exoplanetary atmospheres (H I
Lyman-alpha, O I, and C II), and protoplanetary disks (H2 and CO electronic band systems). CHESS uses a novel
mechanical collimator comprised of an array of 10 mm x 10 mm stainless steel tubes to feed a low-scatter, 69 grooves
mm-1 echelle grating. The cross-disperser is a holographically ruled toroid, with 351 grooves mm-1. The spectral orders
can be recorded with either a 40 mm cross-strip microchannel plate detector or a 3.5k x 3.5k δ-doped CCD. The
microchannel plate will deliver 30 μm spatial resolution and employs new 64 amp/axis electronics to accommodate high
count rate observations of local OB stars. CHESS is scheduled to be launched aboard a NASA Terrier/Black Brant IX
sounding rocket from White Sands Missile Range in the summer of 2013.
Current FUV instrumentation is seriously compromised by poor reflectivity. The best existing coatings for the 90 - 115
nm range are SiC (30% reflectivity across the band) and LiF/Aluminum (60% reflectivity from 100 nm to 115 nm). An
improved coating therefore would enable the production of vastly more sensitive instruments in the 90 - 200 nm range.
An additional goal in the development of an alternate FUV coating is to overcome the well-documented hygroscopic
behaviors of LiF coatings, which currently impose handling concerns that in turn drive cost and schedule. The coatings
we will develop in this effort must also function well through the conventional silicon-based detector bandpass (200 nm
to 1100 nm). By ensuring that these new coatings are usable at many wavelengths, we will make it possible to
incorporate ultraviolet instruments into future large missions without compromising the science capability of other
instruments or increasing cost and risk due to handling issues.
We present the Colorado High-resolution Echelle Stellar Spectrograph (CHESS) sounding rocket payload. The
design uses a mechanical collimator made from a grid of square tubing, an objective echelle grating, a holographically-ruled
cross-disperser, a new 40 mm MCP with a cross strip anode or a delta-doped 3.5k x 3.5k CCD detector. The optics
are suspended using carbon fiber rods epoxied to titanium inserts to create a space frame structure. A preliminary design
is presented.
The Far-ultraviolet Imaging Rocket Experiment (FIRE) is a sounding rocket payload that was designed to image the
Whirlpool Galaxy (M51) from 900-1000A and search for young, hot stars. Selected to match the GALEX mission
capabilities, FIRE has a resolution of 8 arcseconds with a 54 arcminute field-of-view. To achieve the desired wavelength
limits, FIRE utilized a single parabolic mirror coated with silicon carbide, an indium filter and a detector coated with
rubidium bromide. In combination, they gave a throughput of approximately 2% from 900-1000A with a throughput of
less than 10-5 at the major source of noise, 1216A Lyman-alpha. To ensure that the 2000A thick indium filter survived
launch, the filter and detector were encased in a vacuum canister where the pressure was maintained with a small ion
pump and opened after ascent to allow data collection. FIRE launched for the first time on January 28th, 2011 from
Poker Flat Research Range in northern Alaska with M51 as a primary target and G191B2B as a calibration target. This
flight culminated in the first ever astronomical image taken at the wavelengths of 900-1000A and was successful in all its
technology demonstration goals. This paper will describe the scientific motivation, design considerations and initial
results.
The Star Formation Camera (SFC) is a wide-field (~19'×~15', >280 arcmin2), high-resolution (18 mas pixels) UV/optical
dichroic camera designed for the Theia 4-m space-borne space telescope concept. SFC will deliver diffraction-limited
images at λ > 300 nm in both a blue (190-517nm) and a red (517-1075nm) channel simultaneously. The goal is to
conduct a comprehensive and systematic study of the astrophysical processes and environments relevant for the births
and life cycles of stars and their planetary systems, and to investigate the range of environments, feedback mechanisms,
and other factors that most affect the outcome of star and planet formation.
FIRE (Far-ultraviolet Imaging Rocket Experiment) is a sounding rocket payload telescope designed to image
between 900-1100Å. It is scheduled to launch on January 29th, 2011 from the Poker Flats complex in northern Alaska.
For its first flight, it will target G191B2B, a white dwarf calibration source, and M51 (the Whirlpool Galaxy), the
science target, to help determine the number of hot, young O stars, as well as the intervening dust attenuation. FIRE
primary consists of a single primary mirror coated in silicon carbide, a 2000Å thick indium filter and a micro-channel
plate detector coated with rubidium bromide. Combined, these create a passband of 900-1100Å for the system and reject
the hydrogen Lyman-α to approximately a factor of 10-4. To ensure that the filter survives the launch, a small vacuum
chamber has been built around it to keep the pressure at 10-8 torr or lower.
As-fabricated free-standing indium foils were found to have transmission in the 90nm to 120nm
band ranging from 10% to 70% of modeled values based on pure indium. Auger depth profiling of
the as-deposited indium showed little surface contamination and high purity. However, final freestanding
filters were found to have heavy contamination, particularly on the surface. An
argon/hydrogen plasma bombardment was developed which improved EUV transmission by 50% to
500% in the finished filters without causing significant pinholes to develop in the foils or
appreciably affecting blocking characteristics.
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 discuss the design of a new high-efficiency, high-resolution far ultraviolet echelle spectrograph. Our project
concentrates on utilizing new technologies for gratings and detectors to reduce the impact of scattered light and
maximize quantum efficiency over a large bandpass. This program will enable advances in a vast number of
astrophysical subjects. Topics ranging from protoplanetary disks to the intergalactic medium can be addressed by
incorporating such a spectrograph into a future, long-duration mission.
We present the results of developing a Lyman alpha blind detector for (λ 1000-1100 Å). This detector has potential
applications to astrophysical FUV emission observations, particularly the O VI doublet at 1037.62 and 1031.93 Å. By
filling the detector with a gas whose ionization potential is above the energy of the bright Lyα airglow line at 10.2eV we
hoped to produce an FUV detector that is Lyα blind. Propane (C3H8 ) and acetylene (C2H2) were tested as potential gas
fillers. Both gases were found to have significant sensitivity to the Lyα line, either because of impurities in the gas or
from dissociation products formed from Lyα photons, and therefore the detector did not provide the ~107 suppression of
Lyα that is necessary to directly detect faint, diffuse FUV emission. When filled with acetylene the detector is 13 times
more sensitive to Ar 1067 Å (a proxy for the O VI 1038 and 1032 Å doublet lines) than to Lyα and when filled with
propane the detector is 3 times more sensitive to the argon line. The detector has a quantum efficiency of about 7% at
1067 Å with either gas and may hold promise for a completely Lyα blind FUV detector if a suitable gas is found.
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.
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.
We present deep scatter measurements on a sinusoidal profile, high groove density, holographically ruled, large format
grating. With long exposures and a low-noise detector, we were able to measure scatter at levels of 1 * 10-6/Ly α/nm at
100 nm. The result has potential impacts in the prospect of high sensitivity measurements of very faint objects at FUV
wavelengths. Any instrument sensitive to hydrogen Lyman α, a bright geo-coronal airglow line, must control the scatter
to make astrophysically significant measurements. Measurements of very faint emission line source - particularly ones
that do not have known redshifts (i.e. wavelength solution), Lyman α scatter may be the dominant source of error.
Therefore, characterization of the actual value of scatter is crucial to the success of future missions that will use
diffraction-based measures for detecting very faint targets.
Paul Scowen, Rolf Jansen, Matthew Beasley, Brian Cooke, Shouleh Nikzad, Oswald Siegmund, Robert Woodruff, Daniela Calzetti, Steven Desch, Alex Fullerton, John Gallagher, Sangeeta Malhotra, Mark McCaughrean, Robert O'Connell, Sally Oey, Debbie Padgett, James Rhoads, Aki Roberge, Nathan Smith, Daniel Stern, Jason Tumlinson, Rogier Windhorst
The Star Formation Observatory (SFO) is a 1.65m space telescope that addresses pivotal components in the 2007 NASA
Science Plan, with a primary focus on Cosmic Origins. The design under consideration provides 100 times greater
imaging efficiency and >10 times greater spectroscopic efficiency below 115 nm than existed on previous missions. The
mission has a well-defined Origins scientific program at its heart: a statistically significant survey of local, intermediate,
and high-redshift sites and indicators of star formation, to investigate and understand the range of environments,
feedback mechanisms, and other factors that most affect the outcome of the star and planet formation process. This
program relies on focused capabilities unique to space and that no other planned NASA mission will provide: near-
UV/visible (20-1100 nm) wide-field, diffraction-limited imaging; and high-efficiency, low- and high- resolution (R~40,000) UV (100-175 nm) spectroscopy using far-UV optimized coatings and recent advances in Micro-Channel Plate
(MCP) detector technology. The Observatory imager has a field of view in excess of 17' × 17' (>250 arcmin2) and uses a
dichroic to create optimized UV/blue and red/near-IR channels for simultaneous observations, employing detectors that
offer substantial quantum efficiency gains and that suffer lower losses due to cosmic rays.
We have completed a conceptual design study of the High Resolution Optical Spectrograph for the Thirty Meter Telescope project. We propose the use of a fiber fed integral field unit and a dichroic tree to achieve R=100,000 spectroscopy from 310 to 1100 nm independent of AO performance. The system relies on the dichroic tree to provide coarse wavelength selection, and 32 first order spectro-graph benches. This approach allows for simultaneous optimization of grating and detector performance for all wavelengths, resulting in high efficiency, near uniform dispersion, and reduced program risk and cost due to the high degree of component commonality. We present projected performance and design details.
We present a conceptual design for a High Resolution Optical Spectrograph (HROS) for the Thirty Meter Telescope, a 30-m primary aperture ground-based telescope currently under development (www.tmt.org). To decouple downstream optics sizes from the size of the seeing disk and/or AO performance, we use fiber fed IFUs to generate a 0.1" pseudo-slit. The use of multiple IFUs instead of a slit also allows for spatially resolved spectroscopy, multi-object spectroscopy, positionable sky sampling, and insertion of a simultaneous wavelength calibration signal into the beam. Instead of a cross-dispersed echelle design, our concept uses a dichroic tree to provide spectral separation. The dichroics feed 32 independent first-order spectrographs that cover the 310 to 1100 nm optical waveband at a nominal spectral resolution of R=100,000. This approach allows for the optimization of coatings and on-blaze grating performance in each channel, resulting in high efficiency, near-uniform dispersion, and reduced program risk and cost due to the high degree of component commonality. We also discuss the general applicability of this concept for achieving high resolution spectroscopy in the next generation of ground-based instrumentation.
The Orion MIDEX mission is a 1.2m UV-visual observatory orbiting at L2 that will conduct the first-ever high spatial
resolution survey of a statistically significant sample of visible star-forming environments in the Solar neighborhood in
emission lines and continuum. This survey will be used to characterize the star and planet forming environments within
2.5 kpc of the Sun, infer global properties and star formation histories in these regions, understand how environment
influences the process of star and planet formation, and develop a classification scheme for star forming regions. Based
on these findings a similar survey will be conducted of large portions of the Magellanic Clouds, extending the
classification scheme to new types of regions common in external galaxies, allowing the characterization of low mass
star forming environments in the Magellanic Clouds, study of the spatial distribution of star forming environments and
tracing of star formation history. Finally the mission will image a sample of external galaxies out to ~5 Mpc. The
distribution of star forming region type will be mapped as a function of galactic environment to infer the distribution
and history of low-mass star formation over galactic scales, and characterize the stellar content and star formation
history of galaxies. We present in this paper an update on the development of the mission and the hardware necessary
to deliver its required performance.
Astronomical surveys have demonstrated an enormous capability for increasing our understanding of the universe around us. There are significant wavelength regions, which for various reasons are poorly sampled. Powerful diagnostics of hot gas in the universe are well understood, but there are few instruments capable of making measurements at the wavelengths of the most important lines (103 nm, 123 nm, and 155 nm, the lithium-like series of O, N, and C). No complete survey has been done with moderate spatial resolution in emission even though virtually all measurements capable of detecting the presence of lithium-like oxygen do so. We present a technique to eliminate the spectral-spatial confusion inherent in a wide field imaging spectrograph based on a type of imaging spectrograph that takes advantage of the large, well-corrected field of view from a three-mirror anastigmat (TMA) in conjunction with aberration-corrected holography applied to the tertiary.
KEYWORDS: Stars, Galactic astronomy, Clouds, Ultraviolet radiation, Planets, Planetary systems, Spatial resolution, Sun, Space operations, System on a chip
The ORION MIDEX mission is a 1.2m UV-visual observatory orbiting at L2 that will conduct the first-ever high spatial resolution survey of a statistically significant sample of visible star-forming environments in the Solar neighborhood in emission lines and continuum. This survey will be used to characterize the star and planet forming environments within 2.5 kpc of the Sun, infer global properties and star formation histories in these regions, understand how environment influences the process of star and planet formation, and develop a classification scheme for star forming regions. Based on these findings a similar survey will be conducted of large portions of the Magellanic Clouds, extending the classification scheme to new types of regions common in external galaxies, allowing the characterization of low mass star forming environments in the Magellanic Clouds, study of the spatial distribution of star forming environments and tracing of star formation history. Finally the mission will image a sample of external galaxies out to ~5 Mpc. The distribution of star forming region type will be mapped as a function of galactic environment to infer the distribution and history of low-mass star formation over galactic scales, and characterize the stellar content and star formation history of galaxies.
To fulfill the National Aeronautic and Space Administration's some of the goals of the Origins program, we present the candidate Middle Class Explorer, ORION. ORION will image all the nearby star forming regions at high resolution at several astrophysically relevant emission lines. By imaging the nearby star forming regions ORION will answer profound questions about the origin of stars like the Sun, and therefore the planets that may contain life elsewhere in the universe. To compete with existing instruments, both in space and on the ground, we make use of new technologies and our ability to optimize the design for a single purpose.
The most powerful diagnostics of hot gas in the universe are well understood, but there are few instruments capable of making measurements at the wavelengths of the most important lines (103 nm, 123 nm, and 155 nm, the lithium-like series of O, N, and C). No complete survey has been done with moderate spatial resolution in emission even though virtually all measurements capable of detecting the presence of lithium-like oxygen do so. We present a type of imaging spectrograph that takes advantage of the large, well-corrected field of view from a three-mirror anastigmat (TMA) in conjunction with aberration-corrected holography applied to the tertiary. The combination of a TMA and aberration-corrected holography allows a large well-corrected field of view in diffracted light, potentially providing an excellent basis for an instrument capable of the first large scale survey from 100 nm to 150 nm.
We have repaired and reflown an existing sounding rocket payload to observe the OVI 1032 Å, 1038 Å emission doublet from a non-radiative shock in the NE section of the Cygnus Loop supernova remnant. We will analyze the images to determine the distance between the OVI-emitting gas and the shock front in visible light, as well as measuring the morphology of OVI across the shock. This will provide a measure of the temperature equilibration length, which can then be used to constrain models of the physical processes causing temperature equilibrium of charged particles in the hot shocked gas of the interstellar medium.
Small satellites with their low thermal capacitance are vulnerable to rapid temperature fluctuations. Therefore, thermal control becomes important, but the limitations on mass and electrical power require new approaches. Possible solutions to actively vary the heat rejection of the satellite in response to variations in the thermal load and environmental condition are the use of a variable emissivity coating (VEC), micro-machined shutters and louvers, or thermal switches. An elegant way the radiate heat is to switch the thermal contact between the emitting surface and the radiator electrostatically. This paper describes the design and fabrication of an active radiator for satellite thermal control based on such a micro electromechanical (MEMS) thermal switch. The switch operates by electrostatically moving a high emissivity surface layer in and out of contact with the radiator. The electromechanical model and material considerations for the thermal design of the MEMS device are discussed. The design utilizes a highly thermal conductive gold membrane supported by low-conductance SU-8 posts. The fabrication process is described. Measured actuation voltages were consistent with the electrostatic model, ranging from 8 to 25 volts.
We present the optical design and predicted performance of the Extreme Ultraviolet Spectrometer (EUVS) developed for the Jupiter Magnetospheric Explorer (JMEX) mission. JMEX was proposed as small explorer (SMEX) mission designed to observe the Jovian system to study the dynamical relationship between Jupiter's magnetosphere and Io, the primary source of material for the Io plasma torus. NASA selected JMEX as one of six SMEX missions for detailed technical study. While JMEX was ultimately not selected for flight, the EUVS instrument design has a unique set of performance characteristics that may be useful for other applications, such as a multi-object spectrometer, a push-broom spectrometer for diffuse objects, or an imaging spectrometer with high spatial resolution.
The EUVS is an imaging spectrograph originally designed to observe the Io plasma torus. EUVS provides moderate resolution (~0.1 nm) spectra between 64 to 114 nm over +/- 260" with 2" spatial resolution. The optical design is based on an off-axis Gregorian telescope, where the secondary mirror is replaced with an aberration-corrected holographic grating. The grating diffracts and focuses the UV light onto a cross-delay line microchannel plate detector with a potassium bromide photocathode. The primary mirror and grating are coated with boron carbide to maximize the normal incidence reflectivity at the shortest wavelengths. This high throughput, two-element design provides a compact instrument suitable for a small spacecraft while maintaining an efficient optical path that provides 7-12 cm2 of effective area.
We present a new instrument for narrow band imaging without the use of conventional interference filters. This instrument will image the OVI doublet at 103.2 and 103.8 nm, the brightest astrophysical emission line from diffuse gas at 300,000 degrees. Gases at this temperature, formed mostly by supernovae blast waves, are key to understanding the energy budget of the galaxy. To date, there are no high spatial resolution narrow-band images of OVI, although some low spatial resolution narrow maps have been acquired with conventional spectrographs. Using the imaging power of a conventional two-optic Gregorian telescope in conjunction with aberration-corrected holography, we can acquire narrow band images with subarcsecond spatial resolution. An aberration-corrected holographically ruled grating in place of the secondary optic is used to diffract the ultraviolet light to stigmatic focus. Additionally, the use of few optical surfaces minimizes the light loss from poor reflectivity of materials in the far ultraviolet (FUV), thereby maximizing instrument sensitivity. This instrument is the first to use aberration-corrected holographic gratings to produce a narrow-band imaging capability in this fashion. We are now developing a rocket payload to demonstrate the power of this technique with particular application to non-radiative shocks in the interstellar medium. We present the optical design, instrument performance, and relevant scientific simulations.
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