WALOP-South: A wide-field one-shot linear optical polarimeter for PASIPHAE survey

Siddharth Maharana; John A. Kypriotakis; A. N. Ramaprakash; Pravin Khodade; Chaitanya Rajarshi; Bhushan Joshi; Pravin Chordia; Ramya M. Anche; Shrish Mishra; Dmitry Blinov; Hans Kristian Eriksen; Tuhin Ghosh; Eirik Gjerløw; Nikolaos Mandarakas; Georgia V. Panopoulou; Vasiliki Pavlidou; Timothy J. Pearson; Vincent Pelgrims; Stephen B. Potter; Anthony C. S. Readhead; Raphail Skalidis; Konstantinos Tassis; Ingunn K. Wehus

doi:10.1117/12.2554396

13 December 2020 WALOP-South: A wide-field one-shot linear optical polarimeter for PASIPHAE survey

Siddharth Maharana, John A. Kypriotakis, A. N. Ramaprakash, Pravin Khodade, Chaitanya Rajarshi, Bhushan Joshi, Pravin Chordia, Ramya M. Anche, Shrish Mishra, Dmitry Blinov, Hans Kristian Eriksen, Tuhin Ghosh, Eirik Gjerløw, Nikolaos Mandarakas, Georgia V. Panopoulou, Vasiliki Pavlidou, Timothy J. Pearson, Vincent Pelgrims, Stephen B. Potter, Anthony C. S. Readhead, Raphail Skalidis, Konstantinos Tassis, Ingunn K. Wehus

Author Affiliations +

Proceedings Volume 11447, Ground-based and Airborne Instrumentation for Astronomy VIII; 114475E (2020) https://doi.org/10.1117/12.2554396
Event: SPIE Astronomical Telescopes + Instrumentation, 2020, Online Only

Conference Poster

Abstract

WALOP (Wide-Area Linear Optical Polarimeter)-South, to be mounted on the 1m SAAO telescope in South Africa, is first of the two WALOP instruments currently under development for carrying out the PASIPHAE survey. Scheduled for commissioning in the year 2021, the WALOP instruments will be used to measure the linear polarization of around 10⁶ stars in the SDSS-r broadband with 0.1 % polarimetric accuracy, covering 4000 square degrees in the Galactic polar regions. The combined capabilities of one-shot linear polarimetry, high polarimetric accuracy (< 0.1 %) and polarimetric sensitivity (< 0.05 %), and a large field of view (FOV) of 35 35 arcminutes make WALOP-South a unique astronomical instrument. In a single exposure, it is designed to measure the Stokes parameters I, q and u in the SDSS-r broadband and narrowband filters between 500-700 nm. During each measurement, four images of the full field corresponding to the polarization angles of 0°, 45°, 90° and 135° will be imaged on four detectors and carrying out differential photometry on these images will yield the Stokes parameters. Major challenges in designing WALOP-South instrument include- (a) in the optical design, correcting for the spectral dispersion introduced by large split angle Wollaston Prisms used as polarization analyzers as well as aberrations from the wide field, and (b) making an optomechanical design adherent to the tolerances required to obtain good imaging and polarimetric performance under all temperature conditions as well as telescope pointing positions. We present the optical and optomechanical design for WALOP-South which overcomes these challenges.

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Siddharth Maharana, John A. Kypriotakis, A. N. Ramaprakash, Pravin Khodade, Chaitanya Rajarshi, Bhushan Joshi, Pravin Chordia, Ramya M. Anche, Shrish Mishra, Dmitry Blinov, Hans Kristian Eriksen, Tuhin Ghosh, Eirik Gjerløw, Nikolaos Mandarakas, Georgia V. Panopoulou, Vasiliki Pavlidou, Timothy J. Pearson, Vincent Pelgrims, Stephen B. Potter, Anthony C. S. Readhead, Raphail Skalidis, Konstantinos Tassis, and Ingunn K. Wehus "WALOP-South: A wide-field one-shot linear optical polarimeter for PASIPHAE survey", Proc. SPIE 11447, Ground-based and Airborne Instrumentation for Astronomy VIII, 114475E (13 December 2020); https://doi.org/10.1117/12.2554396

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