Two novel approaches for determining the sky position of an unstacked, segmented-mirror telescope

Gregory D. Wirth; Nicolas Flagey; Michael S. Gordon; Brian A. Hicks; D. Scott Acton; J. Scott Knight; Paul A. Lightsey

doi:10.1117/12.2629036

27 August 2022 Two novel approaches for determining the sky position of an unstacked, segmented-mirror telescope

Gregory D. Wirth, Nicolas Flagey, Michael S. Gordon, Brian A. Hicks, D. Scott Acton, J. Scott Knight, Paul A. Lightsey

Proceedings Volume 12180, Space Telescopes and Instrumentation 2022: Optical, Infrared, and Millimeter Wave; 121803W (2022) https://doi.org/10.1117/12.2629036
Event: SPIE Astronomical Telescopes + Instrumentation, 2022, Montréal, Québec, Canada

Abstract

Segmented-mirror telescopes such as JWST and Keck provide a particular challenge when first pointed to the sky: to access a suitably isolated star with which to align the mirror segments, one must first determine the sky location to which the telescope is pointed. Prior to stacking, the primary mirror segments each produce a separate image of the sky; the expected result is a confusing image in which the star field is convolved with the randomly pointed segments so that each star appears multiple times. To establish the initial sky pointing of JWST, we have developed a pair of novel and complementary approaches for identifying the field. The first approach uses image pairs in which a single primary mirror segment is tilted from its initial pointing by a small amount. This motion of the segment produces a corresponding motion of the stellar images from that segment, allowing us to resolve the ambiguity between the array of stellar images and the array of segment images. The second performs a pattern match within a single image to identify the repeating pattern of the segment array (i.e., the star pattern in the field of view) which can then be matched against an astrometric catalog. Both algorithms produce a resulting array of star positions from which the astrometry.net engine can identify the sky location. We describe the application of these algorithms to both simulated JWST NIRCam images and actual images acquired with MOSFIRE on Keck I, explain how we employed these approaches during the initial stage of JWST primary mirror commissioning, and speculate on future applications for mirrors with more segments.

Citation Download Citation

Gregory D. Wirth, Nicolas Flagey, Michael S. Gordon, Brian A. Hicks, D. Scott Acton, J. Scott Knight, and Paul A. Lightsey "Two novel approaches for determining the sky position of an unstacked, segmented-mirror telescope", Proc. SPIE 12180, Space Telescopes and Instrumentation 2022: Optical, Infrared, and Millimeter Wave, 121803W (27 August 2022); https://doi.org/10.1117/12.2629036

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

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.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available

Members: $17.00

Non-members: $21.00 ADD TO CART

PROCEEDINGS
20 PAGES

DOWNLOAD PAPER SAVE TO MY LIBRARY

GET CITATION

RIGHTS & PERMISSIONS

Get copyright permission Get copyright permission on Copyright Marketplace

KEYWORDS

Image segmentation

Stars

Telescopes

James Webb Space Telescope

Mirrors

Image processing

Device simulation

Show All Keywords

Keywords/Phrases

Search In:

Publication Years