OUL is a wide field imager designed as a small, additional payload to be attached to the Luna 26 mission. The instrument has a field of view of 20° × 20° and provides images with angular resolution 3 arcmin in several far ultraviolet bands, including Lyman-α, He II at 164nm and several continuum bands. The imager is designed to monitor the Earth’s exosphere and the ecliptic (+/-20°) primary at Lyman-α and in the 125-140 nm and 145-170 nm bands. In this contribution, the optical design of the instrument, its mechanical layout and the science program to be implemented will be described.
Many Earth-sized planets have been discovered and some of them are potentially in the habitable zone. In addition, several Earth-sized planets have been detected around low temperature stars near our solar system. However, it is difficult to characterize them as Earth-like or Venus-like, even though they are relatively very close to our solar system. We performed a conceptual design of an Ultraviolet Spectrograph for Exoplanet (UVSPEX) for World Space Observatory Ultraviolet (WSO-UV), which is 1.7-m UV space telescope being prepared by Russia. The spectral range is to exceed wavelengths from 115 nm to 135 nm to detect at least H Lyman alpha 121.6nm to O I 130 nm. The throughput is >4%. UVSPEX is planned to be a part of a Field Camera Unit (FCU). This additional instrument would enable us to observe ~20 Earth-like exoplanets and detect an oxygen exosphere if some of them have an Earth-like atmosphere.
There is a growing interest in lunar exploration fed by the perception that the Moon can be made accessible to low-cost missions in the next decade. The ongoing projects to set a communications relay in lunar orbit and a deep space gateway, as well as the spreading of commercial-of-the shelf technology for small space platforms such as the cubesats contribute to this perception. Small, cubesat size satellites orbiting the Moon offer ample opportunities to study the Moon and enjoy an advantage point to monitor the Solar System and the large-scale interaction between the Earth and the solar wind. We describe the technical characteristics of a 12U cubesat to be set in polar lunar orbit for this purpose and the science behind it. The mission is named Earth as an exoplanet (EarthASAP) and is submitted to the Lunar Cubesats for Exploration call in 2016. EarthASAP is designed to monitor hydrated rock reservoirs in the lunar poles and to study the interaction between the large Earth’s exosphere and the solar wind in preparation for future exoplanetary missions.
We present our development of high-efficiency reflective grating development by holographic processing. Its primary objective is to carry out exoplanet science studies in the ultraviolet (UV) wavelength region using space-borne telescopes. While the final development goal is aspheric grating, in this study, we manufactured planar grating samples with laminar and blazed grooves for our first step in order to establish processing conditions and to evaluate characteristics of each grating. Geometry of the manufactured gratings is 30×30×10 mm, and their groove density is 2400/mm. It was confirmed by Atomic Force Microscope (AFM) evaluation that laminar and blazed grooves were constructed on the surface of each grating. The measured absolute diffraction efficiency achieved by the brazed grating is 40.2% and 44.1% at wavelengths of 122 nm and 131 nm, respectively. These values are higher than values of the laminar grating by factor of ∼1.5.
The World Space Observatory for Ultraviolet (WSO-UV) is an orbital optical telescope with a 1.7-m diameter primary mirror currently under development. The WSO-UV is aimed to operate in the 115- to 310-nm UV spectral range. Its two major science instruments are UV spectrographs and UV imaging field cameras with filter wheels. The WSO-UV project is currently in the implementation phase, with a tentative launch date in 2023. As designed, the telescope field of view in the focal plane is not fully occupied by instruments. Recently, two additional instruments devoted to exoplanets have been proposed for WSO-UV, which are the focus of this paper. UVSPEX, a UV-spectrograph for exoplanets, aims to determine atomic hydrogen and oxygen abundance in the exospheres of terrestrial exoplanets. The spectral range is 115 to 130 nm, which enables simultaneous measurement of hydrogen and oxygen emission intensities during an exoplanet transit. A study of exosphere transit photometric curves can help differentiate among different types of rocky planets. The exospheric temperature of an Earth-like planet is much higher than that of a Venus-like planet because of the low mixing ratio of the dominant coolant (CO2) in the upper atmosphere of the former, which causes a large difference in transit depth at the oxygen emission line. Thus, whether the terrestrial exoplanet is Earth-like, Venus-like, or other can be determined. A Stellar Coronagraph for Exoplanet Direct Imaging (SCEDI) is aimed to directly detect the starlight reflected from exoplanets orbiting their parent stars or from the stellar vicinity including circumstellar disks, dust, and clumps. SCEDI will create an achromatic (optimized to 420- to 700-nm wavelength range), high-contrast stellocentric coronagraphic image of a circumstellar vicinity. The two instruments, such as UVSPEX and SCEDI, share common power and control modules. The present communication outlines the science goals of both proposed instruments and explains some of their engineering features.
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