A coronagraph using a digital micromirror device as an adaptive occultation mask: Design and observational result

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

We have developed a new coronagraph using digital micromirror device (DMD) to observe faint emissions close to a bright objects in our solar system such as water plumes on Europa and Enceladus, plasma emissions in giant planet's magnetospheres, escaping plasma and neutrals from Venus and Mars, and so on. The focal plane DMD mask enables us to occult planet's disks and their moons even when their angular dimeter and geometry vary with time. The coronagraph composed of a DMD as an occulting mask on a telescope focal plane, a pupil stop, a narrow-band filter, and others. The DMD located at the focal plane produces color dispersion of entrance aperture on a pupil plane for an extended light-source. Thus, we designed a proper shape of pupil mask to reduce remaining from the occulted light-source considering wavelength and bandwidth of observations. The coronagraph was installed on a Cassegrain focus of the Tohoku 60-cm telescope at Haleakala observatory in Hawaii. We have been using the coronagraph for observing sulfur ion emissions [SII] 671.6 and 673.1 nm from Io plasma torus since 2018. The DMD occultation reduces light from Jupiter disk and Galilean moons by 2.6×10-3. The system throughput is 56 % of a previous conventional coronagraph. In observation of Io plasma torus, north-south position of [SII] brightness peak shifted by 0.07 jovian radii toward the magnetic equator during three days. Increase of flesh pickup ion possibly makes higher anisotropy or higher ion perpendicular temperature causing the observed magnetic-equatorward shift of the plasma torus.

Original languageEnglish
Title of host publicationGround-Based and Airborne Instrumentation for Astronomy VIII
EditorsChristopher J. Evans, Julia J. Bryant, Kentaro Motohara
PublisherSPIE
ISBN (Electronic)9781510636811
DOIs
Publication statusPublished - 2020
EventGround-Based and Airborne Instrumentation for Astronomy VIII 2020 - Virtual, Online, United States
Duration: 2020 Dec 142020 Dec 22

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume11447
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X

Conference

ConferenceGround-Based and Airborne Instrumentation for Astronomy VIII 2020
Country/TerritoryUnited States
CityVirtual, Online
Period20/12/1420/12/22

Keywords

  • Coronagraph
  • DMD
  • High dynamic range
  • Io plasma torus
  • Lyot stop

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

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