Ultraviolet (UV) spectroscopy is one of the most powerful tools used in a wide range of scientific fields from planetary science to astronomy. We propose a future UV space telescope, LAPYUTA (Life-environmentology, Astronomy, and PlanetarY Ultraviolet Telescope Assembly), selected as a candidate for JAXA’s 6th M-class mission in 2023. Launch is planned for the early 2030s. LAPYUTA will accomplish the following four objectives related to two scientific goals: understanding (1) the habitable environment and (2) the origin of structure and matter in the universe. Objective 1 focuses on the subsurface ocean environments of Jupiter's icy moons and the atmospheric evolution of terrestrial planets. Objective 2 characterizes the atmosphere of the exoplanets around the habitable zone and estimates their surface environment by detecting their exospheric atmosphere. In cosmology and astronomy, Objective 3 tests whether the structures of presentday galaxies contain ubiquitous Ly-α halos and reveals the physical origins of Ly-α halos. Objective 4 elucidates the synthesis process of heavy elements based on observations of ultraviolet radiation from hot gas immediately after neutronstar mergers. LAPYUTA will perform spectroscopic and imaging observations in the far-UV range of 110-190 nm with an effective area of >300 cm2 and a high spatial resolution of 0.1 arcsec. The apogee is 2,000 km, and the perigee is 1,000 km to avoid the influence of the geocorona when observing oxygen and hydrogen atoms and the Earth's radiation belt.
The 2-μm near-infrared (NIR) camera, IR2, onboard Japan’s Venus orbiter Akatsuki acquired Venus images after the successful orbit insertion in December 2015. IR2 utilizes a platinum silicide (PtSi) Schottky-barrier array sensor (1040×1040 pixels) in which photon is detected by the photo-electric effect. This is by nature not a very high efficiency mechanism therefore unused light is subjected to multiple reflection within the silicon substrate (400-μm thick in IR2). Because very intense day crescent (some ~3 orders of magnitudes brighter) of Venus exists in the same field of view when the night-side disk is imaged, light spread from the former significantly affects the photometry of the latter. To restore the night-side features to a level that can be measured photometrically, we have developed a simulation to model the point-spread function (PSF) of IR2 in which effect of multiple light reflection is accounted for. Different elements in the array sensor (the NIR-sensitive PtSi pixels, the vertical scanning lines, and the charge-sweep device area) are considered and the light reflection is traced until the beam becomes weaker than a threshold. While the multiple rings (the innermost one corresponds to the critical angle of total internal reflection) are successfully reproduced, the cross pattern did not show up from this simulation and we had to artificially add it. The concept of simulation may be useful for other sensors of which substrate is relatively transparent for the wavelengths of interest while the target objects contain large dynamic range.
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.