The SPICA coronagraphic instrument (SCI) for the study of exoplanets

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Abstract

We present the SPICA Coronagraphic Instrument (SCI), which has been designed for a concentrated study of extra-solar planets (exoplanets). SPICA mission provides us with a unique opportunity to make high contrast observations because of its large telescope aperture, the simple pupil shape, and the capability for making infrared observations from space. The primary objectives for the SCI are the direct coronagraphic detection and spectroscopy of Jovian exoplanets in infrared, while the monitoring of transiting planets is another important target. The specification and an overview of the design of the instrument are shown. In the SCI, coronagraphic and non-coronagraphic modes are aplicable for both an imaging and a spectroscopy. The core wavelength range and the goal contrast of the coronagraphic mode are 3.5–27 μm, and 10−6, respectively. Two complemental designs of binary shaped pupil mask coronagraph are presented. The SCI has capability of simultaneous observations of one target using two channels, a short channel with an InSb detector and a long wavelength channel with a Si:As detector. We also give a report on the current progress in the development of key technologies for the SCI.

Section snippets

Background and scientific objective

We regard the systematic study of extra-solar planets (exoplanets) to be one of the most important tasks to be undertaken in space science in the near future. The enormous contrast between the parent star and the planet presents us with a serious problem. Therefore, there is a requirement for special instruments using techniques specifically designed to improve the contrast in order to perform a systematic observation of exoplanets. There are a number of different techniques currently used to

Specification

The specification of the instrument is summarized in Table 1. An overview of the current optical design of the SCI is shown in Fig. 2. The requirement that gives us the limiting short wavelength (3.5 μm) is derived for the direct detection and spectroscopy of Jovian exoplanets. As shown in Fig. 1, it is expected that the Spectral Energy Distribution (SED) of Jovian exoplanets has a peak in the 3.5–5 μm wavelength region (Burrows2003). So this wavelength region is one of the most appropriate

Key technologies

The SCI requires challenging technologies to realize high contrast for both imaging and spectroscopy over a wide MIR wavelength range. One of the critical technologies is the design, development and manufacture a coronagraph which can yield a high contrast PSF. We focused on a coronagraph using a 1-dimensional barcode mask (Enya and Abe, 2010) which is a type of binary shaped pupil mask (e.g., Vanderbei et al., 2004, Kasdin et al., 2005, Tanaka et al., 2006). Another key technology is the

Acknowledgments

We deeply thank and pay our respects to all the pioneers in this field, especially R. Vanderbei and J. Kasdin. This work is supported by JAXA.

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