The mid-infrared spectrometer and camera transit spectrometer (MISC-T) is one of the three baseline instruments for Origins Space Telescope (Origins) and provides the capability to assess the habitability of nearby exoplanets and search for signs of life. MISC-T employs a densified pupil optical design, and HgCdTe and Si:As detector arrays. This optical design allows the instrument to be relatively insensitive to minor line-of-sight pointing drifts and telescope aberrations, and the detectors do not require a sub-Kelvin refrigerator. MISC-T has three science spectral channels that share the same field-of-view by means of beam splitters, and all channels are operated simultaneously to cover the full spectral range from 2.8 to 20 μm at once with exquisite stability and precision (<5 ppm between 2.8 to 11 μm, <20 ppm between 11 and 20 μm). A Lyot-coronagraph-based tip–tilt sensor located in the instrument fore-optics uses the light reflected by a field stop, which corresponds to 0.3% of the light from the target, to send fine pointing information to the field steering mirror in the Origins telescope. An additional MISC Wide Field Imager (WFI) is studied as an upscope option for the Origins. MISC-WFI offers a wide field imaging (3 ′ × 3 ′ ) and low-resolution spectroscopic capability with filters and grating-prisms (grisms) covering 5 to 28 μm. The imaging capability of the MISC-WFI will be used for general science objectives. The low-resolution spectroscopic capability in MISC-WFI with a resolving power R ( = λ / Δλ) of a few hundreds will be used to measure the mid-infrared dust features and ionic lines at z up to ∼1 in the Origins mission’s Rise of Metals and Black Hole Feedback programs. The MISC-WFI also serves as a focal plane pointing and guiding instrument for the observatory, including when the MISC-T channel is performing its exoplanet spectroscopy observations.
We are developing a high-resolution near-infrared spectrograph for exoplanet searches with telescopes in Suther- land, South Africa; the South Africa Near-infrared Doppler (SAND) instrument. It covers the z- and Y -bands (0.83–1.10 µm) simultaneously with a maximum spectral resolution of 55, 000. This specification enables the precise radial velocity (RV) measurements to search for both giant planets around young stars and habitable planets around nearby M-dwarfs. The SAND is a fiber-fed instrument and, therefore, can be installed into several telescopes at the same site by changing the fiber connection. It will be operated mainly on the PRIME telescope, which is newly developed by Osaka University in Japan. The InfraRed Survey Facility (IRSF) and the Southern African Large Telescope (SALT) are also candidate telescopes for the installation. Inside the SAND spectrograph, a star image ejected from the fiber is sliced half and each sliced image is spectrally dispersed by an echelle grating. As a reference source for the wavelength calibration, light transmitted from a Fabry-Perot Etalon is simultaneously injected into the spectrograph and share the almost identical optical pass. The SAND is expected to realize RV-measurements for targets in large stellar associations at the southern sky, with exclusive and flexible use of the telescope time.
The total integrated emission from galaxies, known as the Extragalactic Background Light (EBL), is an important observable for understanding the history of star formation over the history of the universe. Spatial fluctuations in the infrared EBL as measured by the Cosmic Infrared Background ExpeRiment (CIBER), Spitzer and AKARI exceed the predicted signal from galaxy clustering alone. The CIBER-2 project seeks to extend CIBER observa- tions of the EBL throughout the near infrared into the optical, through measurements above Earth's atmosphere during a suborbital sounding rocket flight. The experiment has a LN2-cooled 28.5 cm Cassegrain telescope along with three optical paths and dichroic beamsplitters, which are used to obtain three wide-field images in six broad spectral bands between 0.5-2.0 μm. The three focal planes also contain linear variable filters (LVFs) which simultaneously take spectra with resolution R=20 across the same range. CIBER-2 is scheduled to y multiple times on a Black Brant IX sounding rocket from White Sands Missile Range in the New Mexico desert. For the first flight, scheduled for early 2021, we have completed a variety of pre-flight optical tests, which we use to make focus adjustments, spectral response measurements, and absolute photometric calibrations. In this paper, we describe the methods behind these tests and present their results for pre-flight performance evaluation. In particular, we present measurements of the PSF for each broad spectral band, along with absolute calibration factors for each band and the LVF. Through monochromator scans, we also measure the spectral responsivity of each LVF as a function of position.
Extragalactic background light (EBL) consists of entire radiation emitted throughout the cosmic history and is one crucial observable quantity to study astrophysics in the early universe, such as first stellar objects or primordial black holes. In the visible and near-infrared, zodiacal light (ZL), sunlight scattered by interplanetary dust, is the brightest foreground for observer in the near-earth orbit and its uncertainty limits accuracy of the EBL measurement. To overcome this problem, observations from heliocentric distance beyond 5 au, where the ZL is negligible, is promising. To achieve the EBL observation in deep space, we have been developing EXo- Zodiacal Infrared Telescope (EXZIT) onboard a solar sail spacecraft to Jovian Trojans planned in Japan around 2030. According to our mission study, a three-mirror reflective telescope optics design with a 90mm × 50mm effective aperture and 16 deg × 8 deg field of view (FoV) followed by a focal plane array HAWAII-2RG with a linear variable filter makes available to detect the EBL at high significance in 0.4–1.6 μm with specific wavelength resolution of ∼ 20 . In the present study, we develop test optics to demonstrate optical performance in room temperature for the future observation. By adopting only mirrors of aspherical surface, we design the optics whose aberration is minimized to show point spread function (PSF) of approximately 3 pix × 3 pix on the focal plane. The mirrors are fabricated by machining aluminum alloy A6061 with a honeycomb processing on the back surface to reduce the mirror mass. After integrating and aligning the mirrors with support jigs, we measure the PSF on the focal plane by a visible camera by inserting collimated beam of different angle of incidence, covering the whole FoV. We evaluate the PSF size by analyzing encircled energy in comparison with that expected from the ray-trace simulation of the optics. Throughout the FoV of the optics, the measured PSF size is comparable to the simulation. The present study demonstrates the precision machining of the aspherical mirrors and the optical performance of the designed optics. As a next step, we plan to develop thermal structure of EXZIT to demonstrate the optical performance in low temperature.
The Mid-infrared Imager, Spectrometer, Coronagraph (MISC) is one of the instruments studied both for the Origins Space Telescope (OST) Mission Concept 1 and 2. The MISC for OST Mission Concept 1 consists of the MISC imager and spectrometer module (MISC I and S), the MISC coronagraph module (MISC COR) and the MISC transit spectrometer module (MISC TRA). The MISC I and S offers (1) a wide field (3 arcminx3 arcmin) imaging and low-resolution spectroscopic capability with filters and grisms for 6-38 μm, (2) a medium-resolution (R~1,000) Integral Field Unit (IFU) spectroscopic capability for 5- 38 μm and (3) a high-resolution (R~25,000) slit spectroscopic capability for 12-18 μm and 25-36 μm. The MISC COR module employs PIAACMC coronagraphy method and covers 6-38 μm achieving 10-7 contrast at 0.5 arcsec from the central star. The MISC TRA module employs a densified pupil spectroscopic design to achieve 3-5 ppm of spectro-photometric stability and covers 5-26 μm with R=100-300. The MISC for OST Mission Concept 2 consists of the MISC wide field imager module (MISC WFI) and the MISC transit Spectrometer module (MISC TRA). The MISC WFI offers a wide field (3 arcmin ×3 arcmin) imaging and low-resolution spectroscopic capabilities with filters and grisms for 6-28μm. The MISC TRA module in the OST Mission Concept 2 also employs the densified pupil spectroscopic design to achieve <5 ppm of spectro-photometric stability and covers 4-22 μm with R=100-300. The highest ever spectrophotometric stability achieved by MISC TRA enables to detect bio-signatures (e.g., ozone, water, and methane) in habitable worlds in both primary and secondary transits of exoplanets and makes the OST a powerful tool to bring an revolutionary progress in exoplanet sciences. Combined with the spectroscopic capability in the FIR provided by other OST instruments, the MISC widens the wavelength coverage of OST down to 5μm, which makes the OST a powerful tool to diagnose the physical and chemical condition of the ISM using dust features, molecules lines and atomic and ionic lines. The MISC also provides the OST with a focal plane guiding function for the other OST science instruments as well as its own use.
The Mid-infrared Imager, Spectrometer Coronagraph (MISC) instrument studied for the Origins Space Telescope (OST) Mission Concept 1 is designed to observe at mid-infrared (MIR) wavelengths ranging from 5 to 38 microns for OST. In the OST Mission Concept 1 study, MISC consists of three separate optical modules providing imaging, spectroscopy, and coronagraph capabilities. The MISC Coronagraph module (MISC COR) employs Phase-Induced Amplitude Apodization (PIAA) coronagraph (Guyon et al. 2014) in which pupil apodization is modified by reflection on mirrors and central starlight is blocked by focal plane mask and Lyot mask. The performance target of MISC COR is to achieve 10-7 contrast at 0.5” from the central star with covering wavelength of 6-38 microns using 2 optical channels. MISC COR will be a powerful tool to bring a revolutionary progress in exoplanet sciences. In this paper, we present detailed design of its optics and optomechanics, and discuss expected performances for a variety of combination of focal plane mask and Lyot mask.
Cosmic Infrared Background ExpeRiment-2 (CIBER-2) is an international project to make a rocket-borne measurement of the Cosmic Infrared Background (CIB) using three HAWAII-2RG image sensors. Since the rocket telemetry is unable to downlink all the image data in real time, we adopt an onboard data storage board for each sensor electronics. In this presentation, the development of the data storage board and the Ground Station Electronics (GSE) system for CIBER2 are described. We have fabricated, integrated, and tested all systems and confirmed that all work as expected, and are ready for flight.
The extragalactic background light (EBL) is the integrated emission from all objects outside of the Milky Way galaxy. Imprinted by the history of stellar emission, the EBL in the near infrared traces light back to the birth of the first stars in the Universe and can allow tight constraints on structure formation models. Recent studies using data from the Spitzer Space Telescope and the first Cosmic Infrared Background ExpeRiment (CIBER-1) find that there are excess fluctuations in the EBL on large scales which have been attributed to either high redshift galaxies and quasars, or to stars that were stripped from their host galaxies during merging events. To help disentangle these two models, multi-wavelength data can be used to trace their distinctive spectral features. Following the success of CIBER-1, CIBER-2 is designed to identify the sources of the EBL excess fluctuations using data in six wavebands covering the optical and near infrared. The experiment consists of a cryogenic payload and is scheduled to launch four times on a recoverable sounding rocket. CIBER-2 has a 28.5 cm telescope coupled with an optics system to obtain wide-field images in six broad spectral bands between 0.5 and 2.5 μm simultaneously. The experiment uses 2048 × 2048 HAWAII-2RG detector arrays and a cryogenic star tracker. A prototype of the cryogenic star tracker is under construction for a separate launch to verify its performance and star tracking algorithm. The mechanical, optical, and electrical components of the CIBER-2 experiment will have been integrated into the payload by mid-2018. Here we present the final design of CIBER-2 and our team’s instrument characterization efforts. The design and analysis of the optical focus tests will be discussed. We also report on the performance of CIBER-2 support systems, including the cooling mechanisms and deployable components. Finally, we outline the remaining tasks required to prepare the payload for launch.
We present the concept, design, fabrication, and evaluation of a new deformable mirror (DM), which is latchable, compact, and designed to be applicable for cryogenic environments. The main body of a prototype DM was fabricated from a monolithic cuboid of aluminum using wire electrical discharge machining (EDM). A flexible structure was constructed inside the block by 3-dimensionally crossed hollowing using the EDM. The prototype has 6 × 6 channels, and its volume is 27 mm × 27 mm × 30 mm. The mirror was formed on the surface of the aluminum block using a highprecision NC lathe. The surface figure of the mirror was evaluated and 34 nm rms was obtained. The evaluated surface roughness for the center and off-center areas of the mirror was 9.2 nm rms and 7.6 nm rms, respectively Screws set at the back of the block deform the mirror via springs and the internal flexible structure. We present our first demonstration of deformation of the mirror carried out at ambient temperature. The relationship between the displacement of the screws and the deformation of the mirror was evaluated. Consequently, a linear relationship was confirmed, and no significant hysteresis was found. The application of such mirrors to telescopes used for various different objectives is discussed. We conclude that a DM based on our concept can be used for wavefront correction of space-borne telescopes, especially in the infrared wavelength region.
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