FIRESS is the multi-purpose spectrometer proposed for the PRobe far-Infrared Mission for Astrophysics (PRIMA). The sensitive spectrometer on the cold telescope provide factors of 1,000 to 100,000 improvement in spatial-spectral mapping speed relative to Herschel, accessing galaxies across the arc of cosmic history via their dust-immune far-infrared spectral diagnostics. FIRESS covers the 24 to 235 micron range with four slit-fed grating spectrometer modules providing resolving power between 85 and 130. The four slits overlap in pairs so that a complete spectrum of any object of interest is obtained in 2 pointings. For higher-resolving-power studies, a Fourier-transform module (FTM) is inserted into the light path in advance of the grating backends. The FTM serves all four bands and boosts the resolving power up to 4,400 at 112 microns, allowing extraction of the faint HD transition in protoplanetary disks. FIRESS uses four 2016-pixel arrays of kinetic inductance detectors (KIDs) which operate at the astrophysical photon background limit. KID sensitivities for FIRESS have been demonstrated, and environmental qualification of prototype arrays is underway.
The PRobe Infrared Mission for Astrophysics (PRIMA) will be a multi-mode, cryogenic, far-infrared space-based observatory consisting of a 1.8 meter collecting telescope followed by multiple spectrometer and imager instruments. There is a Fourier Transform Module (FTM) that is optionally inserted between the telescope and Far-Infrared Enhanced Survey Spectrometer (FIRESS), which consists of an objective group that receives the collimated beam from the scan mirror and creates a focus at the slit for all spectrometers. A total of four spectrometers, working in different spectral bands, disperse the light and create a focus at FPAs. Most commonly, imaging spectrometers work at 1:1 magnification between slit and FPA, but in PRIMA the magnification of the four spectrometers ranges from 0.6x to 1.8x. The non-unity magnification led to a configuration trade for the spectrometer optics, and required the use of low-order Zernike aspheres (freeform surfaces) to achieve the requirements on wavefront error, keystone error, and smile. This paper describes the requirements, configuration trade and development, preliminary optical design, and performance analysis of FIRESS.
KEYWORDS: Mirrors, Telescopes, Spectroscopy, Imaging systems, Equipment, James Webb Space Telescope, Design and modelling, Space mirrors, Optomechanical design, Cryogenics
The PRIMA (Probe Far-Infrared Mission for Astrophysics) system will be a 1.8 meter, multi-mode, cryogenic, far-infrared space-based observatory consisting of a collecting afocal telescope followed by multiple spectrometer and imager instruments. The afocal telescope collects light from targets across a total field of view that is selectable by means of two different internal scan mirrors, one each for the spectrometers and the imagers. The primary and secondary mirrors are common to both instrument groups, and working with an angular field offset between instruments. The optics after the secondary and up to the scan mirrors are separate. The telescope provides two separate collimated and demagnified beams emerging from the scan mirrors to the spectrometer and imager instrument groups. Design-driving factors include the need to demagnify the entrance beam to fit a heritage scan mirror, and the need for an accessible field stop located clear of any mirror. This paper describes the requirements, configuration trade and development, preliminary optical design, and performance analysis of the telescope.
We present a design for an active telescope for space astronomy. The telescope is capable of both exoplanet work and general astronomy over wavelengths from ∼100 nm up to 5 μm. The primary mirror is 6 m in diameter, formed by 16 mirror segments that are precisely phased and supported on rigid body actuators and with segment optical surface figures fine-tuned using surface figure actuators. The active primary forms a large deformable mirror (DM) with wavefront error (WFE) correction at the entrance pupil. Thus the largest source of WFE can be removed at the source and is corrected over the entire field of view. This enables diffraction-limited performance at 400 nm and a more efficient optical system over a broader wavelength range than could be achieved by a small DM at a downstream relayed pupil. The telescope is passively cooled to below 100 K at Sun–Earth L2, enabling astronomical-background-limited observations out to 5 μm. Launched on a SpaceX Starship or alternatively National Aeronautics and Space Administration’s Space Launch System, the telescope requires minimal deployments. A 72-m-diameter starshade provides a contrast ratio better than 10 − 10 for exoplanet science. Near the visible region, with a 108% working bandwidth from 300 to 1000 nm, a working distance of 120 Mm provides a 51-mas inner working angle (IWA). This band can be moved to shorter or longer wavelengths by adjusting the starshade range from the telescope. Our first-ever thermal analysis of such a starshade shows that a temperature below 100 K can be achieved over a broad range of observing directions, permitting the possibility of working into the infrared. We model the yield in exoplanets that can be observed. A starshade and associated spectrograph offer significant advantages for exoplanet characterization. They enable a much broader instantaneous spectral bandwidth (here 108%) than current coronagraphs (∼10 % to 20% bandwidth), allow both polarizations to be observed simultaneously, and have higher throughput. The IWA is twice as small as can be achieved with a coronagraph and there is no outer working angle. These differences are particularly pronounced in the UV, where coronagraph performance would be strongly affected by throughput losses, wavefront aberrations, Fresnel polarization effects at surfaces, and thermal instability.
The Galaxy Evolution Probe (GEP) is a concept for a mid- and far-infrared space observatory to measure key properties of large samples of galaxies with large and unbiased surveys. GEP will attempt to achieve zodiacal light and Galactic dust emission photon background-limited observations by utilizing a 6-K, 2.0-m primary mirror and sensitive arrays of kinetic inductance detectors (KIDs). It will have two instrument modules: a 10 to 400 μm hyperspectral imager with spectral resolution R = λ / Δλ ≥ 8 (GEP-I) and a 24 to 193 μm, R = 200 grating spectrometer (GEP-S). GEP-I surveys will identify star-forming galaxies via their thermal dust emission and simultaneously measure redshifts using polycyclic aromatic hydrocarbon emission lines. Galaxy luminosities derived from star formation and nuclear supermassive black hole accretion will be measured for each source, enabling the cosmic star formation history to be measured to much greater precision than previously possible. Using optically thin far-infrared fine-structure lines, surveys with GEP-S will measure the growth of metallicity in the hearts of galaxies over cosmic time and extraplanar gas will be mapped in spiral galaxies in the local universe to investigate feedback processes. The science case and mission architecture designed to meet the science requirements is described, and the KID and readout electronics state of the art and needed developments are described. This paper supersedes the GEP concept study report cited in it by providing new content, including: a summary of recent mid-infrared KID development, a discussion of microlens array fabrication for mid-infrared KIDs, and additional context for galaxy surveys. The reader interested in more technical details may want to consult the concept study report.
We consider the scientific benefits and technical feasibility of a 6-m, non-deployed, cold space telescope mission concept, covering the ultraviolet, visible, near-infrared, and mid-infrared wavebands, for direct imaging of exoplanets and a broad range of astronomical investigations. The concept uses the largest practical aperture size that can be launched without deployment, for lower risk and cost. An innovative, rigid outer barrel and sunshield control temperature and stray light in a compact, Spitzer-like configuration that provides a 100-K telescope. Additional active and passive thermal features provide millikelvin temperature stability. The ultraviolet and visible instruments are based on the suite developed for the Habitable Exoplanet Observatory concept. The cold telescope enables the scientifically important addition of mid-infrared imaging and spectroscopy modes, providing background-limited imaging to 5 um wavelength. The telescope uses actively-controlled mirrors to compensate for cool-down aberrations, other optical uncertainties, and tolerances or errors that may occur in manufacturing, assembly, launch, and on-orbit operations. A starshade provides high-dynamic-range imaging and spectroscopy of exoplanets, potentially augmented by a coronagraph for exoplanet search and orbit measurement. Special attention has been paid to contamination control, assessing the feasibility of UV imaging with a cryogenic telescope. The paper will provide design details and assessment of scientific yield and technology readiness, while addressing real and perceived issues for a space telescope capable of covering this wide wavelength range.
The WFIRST Coronagraph Instrument will perform direct imaging of exoplanets via coronagraphy of the host star. The Phase B optical design fits within a new allocated instrument enclosure and accommodates both Hybrid Lyot and Shaped Pupil coronagraphs. It provides optical path and space for accessible focal planes for occulting masks and field stops. It provides accessible pupil planes for shaped pupil and Lyot masks. It accommodates ten active optical assemblies, including one fast steering mirror, on focusing mirror, two deformable mirrors, and six precision alignment mechanisms. We present the optical design and analyses for the Direct Imaging channel, including polarization imaging. We also present the performance analysis of pupil imaging for starlight illumination and diffused light illumination of the pupil.
The HabEx mission concept is intended to directly image planetary systems around nearby stars, and to perform a wide range of general astrophysics and solar system observations. The baseline HabEx design would use both a coronagraph and a starshade for exoplanet discovery and characterization. We describe a lower-cost alternative HabEx mission design, which would only use a starshade for exoplanet science. The starshade would provide excellent exoplanet science performance, but for a smaller number of detected exoplanets of all types, including exoEarth candidates, and a smaller fraction of exoplanets with measured orbits. The full suite of HabEx general astrophysics and solar-system science would be supported.
Characterizing exoearths at wavelength about 10 micron offers many benefits over visible coronagraphy. Apart from providing direct access to a number of significant bio-signatures, direct-imaging in the mid-infrared can provide 1000 times or more relaxation to contrast requirements while greatly shortening the time-scales over which the system must be stable. This in turn enables tremendous relief to optical manufacturing, control and stability tolerances bringing them inline with current technology state of the art. In this paper, we explore a reference design that co-optimizes a large, segmented, linearized aperture telescope using one-dimensional phase-induced aperture apodization to provide highcontrast imaging for spectroscopic analysis. By rotating about a parent star, the chemical signatures of its planets are characterized while affording additional means for background suppression.
The HabEx mission concept is intended to directly image planetary systems around nearby stars, and to perform a wide range of general astrophysics and solar system observations. Its main goal is the discovery and characterization of Earthlike exoplanets through high-contrast imaging and spectroscopy. The baseline HabEx concept would use both a coronagraph and a starshade for exoplanet science. We describe an alternative, “HabEx Lite” concept, which would use a starshade (only) for exoplanet science. The benefit is lower cost: by deleting the complex coronagraph instrument; by lowering observatory mass; by relaxing tolerances and stability requirements; by permitting use of a compact on-axis telescope design; by use of a smaller launch vehicle. The scientific penalty of this lower cost option is a smaller number of detected exoplanets of all types, including exoEarth candidates, and a smaller fraction of exoplanets with measured orbits. Our approach uses a non-deployed segmented primary mirror, whose manufacture is within current capabilities.
This paper describes the use of freeform optical surfaces to control distortion to lower levels than achievable with rotationally symmetric polynomial aspheres. The magnitude of the improvement is illustrated using three different common reflective imager configurations.
The Hubble Space Telescope 1st Servicing Mission carried with it a total of 14 corrective mirrors, four in wide field (WF) 2 and the planetary (PC) 2 (three WF and one PC), two each for the three axial SIs (FOS red and blue), faint object camera (f48 and f/96), and Goddard high resolution spectrograph, which were packaged in a single module, corrective optics space telescope axial replacement (COSTAR). This paper presents the fabrication and validation of these mirrors that were the cornerstone of strategy to recover the telescope performance. The COSTAR optics were particularly challenging and represented one of the earliest examples of anamorphic aspheric mirrors fabricated to <0.005 waves RMS of surface figure residual. Other firsts included one of the earliest applications of phase stepping interferometry, now an industry standard. Insights into the corrective designs, the mirror figure shapes, and the technology used in the validation of the mirrors are presented.
The Astrophysics Focused Telescope Assets (AFTA) study in 2012-2013 included a high-contrast stellar coronagraph to complement the wide-field infrared survey (WFIRST) instrument. The idea of flying a coronagraph on this telescope was met with some skepticism because the AFTA pupil has a large central obscuration with six secondary mirror struts that impact the coronagraph sensitivity. However, several promising coronagraph concepts have emerged, and a corresponding initial instrument design has been completed. Requirements on the design include observations centered 0.6 deg off-axis, on-orbit robotic serviceability, operation in a geosynchronous orbit, and room-temperature operation (driven by the coronagraph’s deformable mirrors). We describe the instrument performance requirements, the optical design, an observational scenario, and integration times for typical detection and characterization observations.
A retrosphere (either a convex ball or a concave mirror) is a convenient element to use in the
interferometric optical test of an objective. However, under some conditions the retrosphere can cause
ambiguities in the interferogram due to the effects of Fresnel diffraction. This paper provides diffracted
beam propagation analysis and results showing the magnitude of these effects for a range of system f- numbers
and retrosphere radii. The paper also presents an alternative retroreflector design concept that
avoids the ambiguities.
An optical system application required a high speed laser scanning subsystem that produced high quality extended
images focused at 32 discrete separated positions along a line, rather than continuously varying positions along the line
as in more familiar scanning systems. This paper describes the optical design trades and selection of a grating-based
scan element that produces this unusual type of scan, and the optical design methods that corrected aberrations produced
by the scan element. A variety of different grating-based scan element designs were explored, in a flat disk geometry,
but these produced excessive aberrations, both in the absolute level and in the magnitude of variation with scan. A ring-shaped
scan element geometry was identified, which greatly minimized the scan-varying aberrations and brought them
to near acceptable levels. Additional cylindrical corrector elements were added near the ring scan element to reduce the
astigmatism of the ring substrate, and cylindrical lenslets were placed near the focus to provide further independent
correction of astigmatism in each scan position. The resulting design achieved diffraction limited wavefront quality
across the scan range.
The primary, secondary and tertiary mirrors of the Thirty Meter Telescope (TMT), taken together, have approximately
12,000 degrees of freedom in optical alignment. The Alignment and Phasing System (APS) will use
starlight and a variety of Shack-Hartmann based measurement techniques to position the segment pistons, tips,
and tilts, segment figures, secondary rigid body motion, secondary figure and the tertiary figure to correctly align
the TMT. We present a conceptual design of the APS including the requirements, alignment modes, predicted
performance, software architecture, and an optical design.
We present the current status of the Canarias InfraRed Camera Experiment (CIRCE) an all-reflective near-IR,
imager, spectrograph, and polarimeter for the 10.4-meter Gran Telescopio Canarias (GTC). In particular, we
review the progress of the opto- and cryo- mechanical design and manufacture, focusing on the custom filter,
lyot, and grism wheels, lightweight optics, and mirror brackets. We also outline our progress with the optical
bench. Finally, we discuss a number of CIRCE's features that both complement and augment the planned suite
of GTC facility instruments.
Mid-infrared polarimetry remains an underexploited technique; where available it is limited in spectral coverage from
the ground, and conspicuously absent from the Spitzer, JWST and Herschel instrument suites. The unique characteristics
of SOFIA afford unprecedented spectral coverage and sensitivity in the mid-infrared waveband. We discuss the
preliminary optical design for a 5-40μm spectro-polarimeter for use on SOFIA, the SOFIA Mid-InfraRed Polarimeter
(SMIRPh). The design furthers the existing 5-40μm imaging and spectroscopic capabilities of SOFIA, and draws on
experience gained through the University of Florida's mid-IR imagers, spectrometer and polarimeter designs of T-ReCS
and CanariCam. We pay special attention to the challenges of obtaining polarimetric materials suitable at both these
wavelengths and cryogenic temperatures. Finally, we (briefly) present an overview of science highlights that could be
performed from a 5-40μm imaging- and spectro-polarimeter on SOFIA. Combined with the synergy between the
possible future far-IR polarimeter, Hale, this instrument would provide the SOFIA community with unique and exciting
science capabilities, leaving a unique scientific legacy.
Refractive infrared optical designs have traditionally covered modest FOVs in one spectral band. The design of a fast, extreme fisheye lens imaging 360° azimuth by 120° elevation over the full 3-12 micron band is described. The various relevant tradeoffs that were explored are detailed and the advantages and disadvantages of each approach are discussed. In particular, the applicability of reflective and diffractive solutions is described.
This paper describes a concept for a compact high-demagnification afocal telescope that feeds separate imaging channels of widely different spectral bands, without the need for a dichroic beamsplitter or a switch mirror.
We report on the design status of the Canarias InfraRed Camera Experiment (CIRCE), a near-infrared visitor
instrument for the 10.4 meter Gran Telescopio Canarias (GTC). In addition to functioning as a 1-2.5 micron
imager, CIRCE will have the capacity for narrow-band imaging, low-and moderate- resolution grism spectroscopy,
and imaging polarimetry. CIRCE's all-reflective aspheric optical design offers excellent throughput and
image quality. We present an analysis of the optical layout and the progress of the opto-mechanical design and
manufacture.
We report on the design, fabrication, and on-sky performance of the Florida Image Slicer for Infrared Cosmology and Astrophysics (FISICA) - a fully-cryogenic all-reflective image-slicing integral field unit for the FLAMINGOS near-infrared spectrograph. Designed to accept input beams near f/15, FISICA with FLAMINGOS provides R~1300 spectra over a 16x33-arcsec field-of-view on the Cassegrain f/15 focus of the KPNO 4-meter telescope, or a 6x12-arcsec field-of-view on the Nasmyth or Bent Cassegrain foci of the Gran Telescopio Canarias 10.4-meter telescope. FISICA accomplishes this using three sets of "monolithic" powered mirror arrays, each with 22 mirrored surfaces cut into a single piece of aluminum. We review the optical and opto-mechanical design and fabrication of FISICA, as well as laboratory test results for FISICA integrated with the FLAMINGOS instrument. Finally, we present performance results from observations with FISICA at the KPNO 4-m telescope and comparisons of FISICA performance to other available IFUs on 4-m to 8-m-class telescopes.
We report on the design status of the Canarias InfraRed Camera Experiment (CIRCE), a near-infrared visitor instrument for the 10.4-meter Gran Telescopio Canarias (GTC). Besides functioning as a 1-2.5 micron imager, CIRCE will have the capacity for narrow-band imaging, low- and moderate- resolution grism spectroscopy, and imaging polarimetry. Other design features include fully cryogenic filter, slit, and grism wheels, high-speed photometry modes, and broad-band imaging in J, H, and Ks filters. We anticipate that a myriad of scientific projects will benefit from CIRCE's unique combination of capabilities.
We report on the design and status of the Florida Image Slicer for Infrared Cosmology and Astrophysics (FISICA) - a fully-cryogenic all-reflective image-slicing integral field unit for the FLAMINGOS near-infrared spectrograph. Designed to accept input beams near f/15, FISICA with FLAMINGOS provides R~1300 spectra over a 16x33-arcsec field-of-view on the Cassegrain f/15 focus of the KPNO 4-meter telescope, or a 6x12-arcsec field-of-view on the Nasmyth or Bent Cassegrain foci of the Gran Telescopio Canarias 10.4-meter telescope. FISICA accomplishes this using three sets of “monolithic” powered mirror arrays, each with 22 mirrored surfaces cut into a single piece of aluminum. We review the optical and opto-mechanical design and fabrication of FISICA, as well as laboratory test results for FISICA integrated with the FLAMINGOS instrument. We also discuss plans for first-light observations on the KPNO 4-meter telescope in July 2004.
We discuss the design, fabrication, assembly, and testing of the prototype Florida Image Slicer for Infrared Cosmology and Astrophysics (FISICA) Integral Field Unit (IFU). FISICA is intended for large telescopes with f/numbers close to f/15, such as the KPNO 4-m and GTC 10.4-m telescopes. It implements an image slicing approach, wherein the initial image plane is optically sliced into thin strips and the strips are optically rearranged end-to-end, whereupon the composite slit image is fed into a conventional spectrograph. We divide the field of view into 22 slices, while accommodating the entire f/15 viewing solid angle. The all-reflective instrument resides in a cryogenic dewar at the initial focal plane, and places the composite slit image output precisely at the initial focus, allowing it to interface to the existing FLAMINGOS spectrograph. The mirrors were diamond turned using various tool geometries and state-of-the-art, multi-axis tool control. The mirrors are made from a single billet of aluminum, and the optical bench and mounts are made of the same alloy as the mirrors for optimum performance during cryogenic cooling. We discuss the key design efforts, emphasizing tradeoffs among performance, volume, fabrication difficulty, and alignment requirements. We describe the fabrication, and present preliminary laboratory test results.
This paper reviews unobscured multiple-mirror imaging designs ranging from two to many mirrors, the ranges of operating conditions of each configuration, their strengths and limitations, and areas of application.
This paper describes the optical design of a 10x zoom objective lens for the visible wavelength band that was required to fit within a limited envelope. The paper describes the design approach and results, including some practical issues that must be addressed when a design is to be fabricated and deployed. The scope of the paper includes discussion of generating a starting point, optimization for best overall configuration and for maximum MTF, glass selection considering both chromatic and thermo-optical issues, configuration choices for minimum tolerance sensitivity, boresight error analysis, and lens length budgeting.
The optical design of the main laser and transport mirror sections of the National Ignition Facility are described. For the main laser the configuration, layout constraints, multiple beam arrangement, pinhole layout and beam paths, clear aperture budget, ray trace models, alignment constraints, lens designs, wavefront performance, and pupil aberrations are discussed. For the transport mirror system the layout, alignment controls and clear aperture budget are described.
James McCarthy, Judith Cohen, Brad Butcher, John Cromer, Ernest Croner, William Douglas, Richard Goeden, Tony Grewal, Barry Lu, Harold Petrie, Tianxiang Weng, Bob Weber, Donald Koch, J. Michael Rodgers
This paper summarizes the optical, mechanical, electrical, and software design of LRIS-B, the blue channel of the Keck Low Resolution and Imaging Spectrograph. The LRIS-B project will shortly be completing the existing LRIS instrument through the addition of dichroic beamsplitters, grisms to disperse light on the blue channel, broad-band u, B, and V photometric filters, a blue and near-UV transmitting camera lens, and a large format blue-sensitive CCD detector. LRIS-B will also introduce piezoelectric xy-actuation of the CCD detector inside its Dewar, in order to compensate for flexure in the existing instrument; ultimately the red-side CCD detector will be similarly equipped, its PZT xy-stage being independently programmed. The optical design of the LRIS-B camera uses only fused silica and calcium fluoride elements, and includes a decentered meniscus element to compensate for coma introduced by the LRIS off-axis paraboloid collimator. The design of the blue channel grisms have been optimized for maximum blaze efficiency, the highest dispersion grism having a groove density of 1200 gr/mm. Optical elements not in use at any given time will be stowed in carousels externally mounted to the instrument sidewalls. The entire instrument is designed to permit remote operation.
Preliminary optical designs have been developed for the blue channel of the Low Resolution Imaging Spectrograph (LRIS) for the Keck Ten Meter Telescope. This paper discusses the configuration- driving factors and performance of the designs, as well as coating and fabrication issues.
All-reflective, unobscured optical designs were developed to help identify a candidate first- generation system to be used in soft x-ray projection lithography. The resolution goal for all designs was 0.1 micrometers , or better, at a design wavelength of 13 nm. Different design aspects including usable field size, image distortion, number of mirrors, telecentricity, surface shape (spherical versus aspheric), and system packaging were explored. Trade-off studied between systems requiring scanning and full-format nonscanning systems were made. The tolerance sensitivity analysis for a representative design demonstrated that as-built performance will be driven by the mirror surface irregularity tolerance; the required tolerance levels are briefly discussed.
An all-reflective unobscured flat-field low-distortion telecentric optical design has been developed for non-scanning reduction soft x-ray lithography application. 1. 0
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.