arXiv subjects

N. Jeremy Kasdin

Publications and source records attributed to N. Jeremy Kasdin.

76 records · Page 5Linked to original sources

arXiv2004

Bayesian Hypothesis Testing for Planet Detection

The past five years has seen a surge in research and innovative ideas for the imaging of extrasolar planets, particular terrestrial ones. We expect that within the next decade a space observatory will be launched with the objective of imaging earthlike planets. Because of the limited lifetime of such a mission and the large number of potential targets, integration time is a critical parameter. In fact, integration time is the primary metric in evaluating various design approaches for the high contrast imaging system. In this paper we present a new approach to determining the existence of a planet in an observed system using Bayesian hypothesis testing. Rather than perform photometry, or rely on vision to determine the existence of a planet, this approach evaluates the image plane data statistically under certain assumptions about the prior probability distributions. We show that extremely high confidence can be achieved in substantially shorter integration times than conventional photometric methods.

astro-ph↗

arXiv2004

Rectangular-Mask Coronagraphs for High-Contrast Imaging

We present yet another new family of masks for high-contrast imaging as required for the to-be-built terrestrial planet finder space telescope. The ``best'' design involves a square entrance pupil having a 4-vane spider, a square image-plane mask containing a plus-sign shaped occulter to block the starlight inside 0.6 lambda/D, and a Lyot-plane mask consisting of a rectangular array of rectangular opennings. Using Fraunhofer analysis, we show that the optical system can image a planet 10^{-10} times as bright as an on-axis star in four rectangular regions given by {(xi,zeta): 1.4 < | xi | < 20, 1.4 < | zeta | < 20}. Since the design involves an image plane mask, pointing error is an issue. We show that the design can tolerate pointing errors of about 0.05 lambda/D. The inclusion of a 4-vane spider in the entrance pupil provides the possibility to build a mirror-only on-axis system thereby greatly reducing the negative effects of polarization. Each of the masks can be realized as two masks consisting of stripes of opaque material with the stripes oriented at right angles to each other. We call these striped masks barcode masks. We show that it is sufficient for the barcode masks by themselves to provide 10^{-5} contrast. This then guarantees that the full system will provide the required 10^{-10} contrast.

astro-ph↗

arXiv2003

Circularly Symmetric Apodization via Starshaped Masks

Recently, we introduced a class of shaped pupil masks, called spiderweb masks, that produce point spread functions having annular dark zones. With such masks, a single image can be used to probe a star for extrasolar planets. In this paper, we introduce a new class of shaped pupil masks that also provide annular dark zones. We call these masks starshaped masks. Given any circularly symmetric apodization function, we show how to construct a corresponding starshaped mask that has the same point-spread function (out to any given outer working distance) as obtained by the apodization.

astro-ph↗

arXiv2003

Spiderweb Masks for High-Contrast Imaging

Motivated by the desire to image exosolar planets, recent work by us and others has shown that high-contrast imaging can be achieved using specially shaped pupil masks. To date, the masks we have designed have been symmetric with respect to a cartesian coordinate system but were not rotationally invariant, thus requiring that one take multiple images at different angles of rotation about the central point in order to obtain high-contrast in all directions. In this paper, we present a new class of masks that have rotational symmetry and provide high-contrast in all directions with just one image. These masks provide the required 10^{-10} level of contrast to within 4 lambda/D, and in some cases 3 lambda/D, of the central point, which is deemed necessary for exosolar planet finding/imaging. They are also well-suited for use on ground-based telescopes, and perhaps NGST too, since they can accommodate central obstructions and associated support spiders.

astro-ph↗