We conducted the evaluation testing of the InGaAs image sensor for the future JASMINE mission. The InGaAs image sensor, which is manufactured by Hamamatsu Photonics K.K., has been updated with substrate removal to avoid fluorescence caused by cosmic rays. We introduce preliminary performance reports of the 128×128 arrayed small prototype at 170K, assuming space use, including dark current and relative quantum efficiency in the near-infrared. Notably, we confirmed that fluorescence is significantly mitigated with an exposure of about 10 minutes. Furthermore, the relative quantum efficiency in the visible wavelength is enhanced compared to previous evaluations in the literature. These results provide a good configuration for the test of the sensor for deployment and play an important role in the future development of infrared astronomical instruments.
Structural, Thermal and Optical Performance (STOP) analysis is performed to investigate the stability of the telescope to be onboard the Japan Astrometry Satellite Mission for INfrared Exploration (JASMINE). In order to perform one of the prime science objectives, high-precision astrometric observations in the wavelength range of 1.0–1.6 µm toward the Galactic center to reveal its central core structure and formation history, the JASMINE telescope is requested to be highly stable with an orbital change in the image distortion pattern being less than a few 10 µas after low-order correction. The JASMINE telescope tried to satisfy this requirement by adopting two design concepts. Firstly, the mirror and their support structures are made of extremely low coefficientof-thermal-expansion materials. Secondly, their temperatures are highly stabilized with an orbital variation of less the 0.1 ◦C by the unique thermal control idea. Through the preliminary STOP analysis, the structural and thermal structural feasibility of the JASMINE telescope is considered. By combining the results of the structural and thermal design, its thermal deformation is estimated. The optical performance of the JASMINE telescope after the thermal deformation is numerically evaluated. It is found that the thermal displacement of the mirrors in the current structural thermal design produces a slightly large focus-length change. As far as the focus adjustment is adequately applied, the orbital variation of the image distortion pattern is suggested to become acceptable after the low-order correction.
To investigate the evolution of our Galaxy, we plan to measure the distances and motions of stars in the Galactic center region. Additionally, our goal is to detect planets within the habitable zone around mid-M-type stars using transit phenomena. To achieve these objectives, we initiated the Japan Astrometry Satellite Mission for Infrared Exploration (JASMINE) project, targeting a 40 microarcsecond annual parallax measurement and aiming photometric accuracy of less than 0.3% for mid-M-type stars. A conceptual study of the observation instrument was conducted. As a result, the telescope is designed with high stability in orbit through carefully chosen materials and a special thermal design. A three-year operation is planned to collect sufficient data for annual parallax measurements. The telescope, with a diameter of 36 cm, covers wavelengths from 1.0 to 1.6 microns using InGaAs detectors. This paper will detail how instrument parameters were selected based on scientific objectives.
We describe scientific objective and project status of an astronomical 6U CubeSat mission VERTECS (Visible Extragalactic background RadiaTion Exploration by CubeSat). The scientific goal of VERTECS is to reveal the star-formation history along the evolution of the universe by measuring the extragalactic background light (EBL) in the visible wavelength. Earlier observations have shown that the near-infrared EBL is several times brighter than integrated light of individual galaxies. As candidates for the excess light, first-generation stars in the early universe or low-redshift intra-halo light have been proposed. Since these objects are expected to show different emission spectra in visible wavelengths, multi-color visible observations are crucial to reveal the origin of the excess light. Since detection sensitivity of the EBL depends on the product of the telescope aperture and the field of view, it is possible to observe it with a small but wide-field telescope system that can be mounted on the limited volume of CubeSat. In VERTECS mission, we develop a 6U CubeSat equipped with a 3U-sized telescope optimized for observation of the visible EBL. The bus system composed of onboard computer, electric power system, communication subsystem, and structure is based on heritage of series of CubeSats developed at Kyushu Institute of Technology in combination with high-precision attitude control subsystem and deployable solar array paddle required for the mission. The VERTECS mission was selected for JAXA-Small Satellite Rush Program (JAXA-SMASH Program), a new program that encourages universities, private companies and JAXA to collaborate to realize small satellite missions utilizing commercial small launch opportunities, and to diversify transportation services in Japan. We started the satellite development in December 2022 and plan to launch the satellite in FY2025.
JASMINE is a Japanese planned space mission that aims to reveal the formation history of our Galaxy and discover habitable exoEarths. For these objectives, the JASMINE satellite performs high-precision astrometric observations of the Galactic bulge and high-precision transit monitoring of M-dwarfs in the near-infrared (1.0—1.6 µm in wavelength). For feasibility studies, we develop an image simulation software named JASMINE-imagesim, which produces realistic observation images. This software takes into account various factors such as the optical point spread function (PSF), telescope jitter caused by the satellite’s attitude control error (ACE), detector flat patterns, exposure timing differences between detector pixels, and various noise factors. As an example, we report a simulation for the feasibility study of astrometric observations using JASMINE-imagesim. The simulation confirms that the required position measurement accuracy of 4 milliarcseconds for a single exposure of 12.5-mag objects is achievable if the telescope pointing jitter uniformly dilutes the PSF across all stars in the field of view. On the other hand, the simulation also demonstrates that the combination of realistic pointing jitter and exposure timing differences in the detector can significantly degrade accuracy and prevent achieving the requirement. This means that certain countermeasures against this issue must be developed. This result implies that this kind of simulation is important for mission planning and advanced developments to realize more realistic simulations help us to identify critical issues and also devise effective solutions.
The InfraRed Doppler (IRD) instrument is the Subaru telescope’s high-resolution (R > 70,000) spectrograph covering wavelengths from 1000 to 1700 nm. A laser frequency comb (LFC) spectrum simultaneously obtained with an object spectrum calibrates wavelength shifts caused by instrumental instability. We originally developed IRD to carry out precision radial velocity (RV) measurements at near-infrared wavelengths. The wide wavelength coverage of IRD, and the large mirror (8.2 m) of the Subaru Telescope enables IRD to provide the best sensitivities to detect a planet orbiting a cool M-type star. The first science operation of IRD was conducted in 2018 and the large strategic blind survey for planets orbiting cool M-type stars started in 2019. Since then, there have been many observations not only for exoplanet category but also for stellar physics, Galaxy, and high-energy astrophysics. IRD spectroscopy allowed for characterizing exoplanet atmospheres by measuring OH emissions, He absorptions, and spin-orbit obliquities. The IRD survey discovered a super-Earth in orbit near a habitable zone of Ross 508. The IRD RV measurements for many systems that host transiting planets, including TOI-2285 b and Gliese 12 b, helped confirm those and determine or constrain their masses. Using REACH, IRD can be combined with the extreme adaptive optics SCExAO, enabling the use of a single-mode fiber and characterizations of faint sub-stellar companions orbiting bright stars. In this proceeding paper, we review and highlight the scientific results achieved by the IRD observations.
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