Mr. Nikolaos Mandarakas Profile

Nikolaos Mandarakas

at Univ of Crete

SPIE Involvement:

Author

Publications (4)

SPIE Journal Paper | 6 September 2022

WALOP-South: a four-camera one-shot imaging polarimeter for PASIPHAE survey. Paper II – polarimetric modeling and calibration

Siddharth Maharana, Ramya Anche, Anamparambu Ramaprakash, Bhushan Joshi, Artem Basyrov, Dmitry Blinov, Carolina Casadio, Kishan Deka, Hans Kristian Eriksen, Tuhin Ghosh, Eirik Gjerløw, John Kypriotakis, Sebastian Kiehlmann, Nikolaos Mandarakas, Georgia V. Panopoulou, Katerina Papadaki, Vasiliki Pavlidou, Timothy Pearson, Vincent Pelgrims, Stephen Potter, Anthony C. Readhead, Raphael Skalidis, Trygve Leithe Svalheim, Konstantinos Tassis, Ingunn Wehus

JATIS, Vol. 8, Issue 03, 038004, (September 2022) https://doi.org/10.1117/12.10.1117/1.JATIS.8.3.038004

KEYWORDS: Polarimetry, Calibration, Polarization, Instrument modeling, Stars, Telescopes, Sensors, Zemax, Performance modeling, Systems modeling

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Proceedings Article | 29 August 2022 Presentation + Paper

Stress-induced birefringence in the lenses of Wide-Area Linear Optical Polarimeter-South

Ramya M. Anche, Siddharth Maharana, A. N. Ramaprakash, Pravin Khodade, Deepa Modi, Chaitanya Rajarshi, John A. Kypriotakis, Dmitry Blinov, Hans Kristian Eriksen, Tuhin Ghosh, Georgia V. Panopoulou, Vincent Pelgrims, Raphael Skalidis, Timothy J. Pearson, Eirik Gjerløw, Nikolaos Mandarakas, Vasiliki Pavlidou, Stephen B. Potter, Anthony C. S. Readhead, Konstantinos Tassis, Artem Basyrov, Katerina Papadaki, Trygve Leithe Svalheim, Ingunn K. Wehus

Proceedings Volume 12188, 121882C (2022) https://doi.org/10.1117/12.2629515

KEYWORDS: Birefringence, Polarization, Polarimetry, Telescopes, Finite element methods

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Two unique wide-field and high-accuracy polarimeters named WALOP (Wide-Area Linear Optical Polarimeter)- North and WALOP-South are currently under development at the Inter-University Center for Astronomy and Astrophysics (IUCAA), India, to create a large area optical polarization map of the sky for the upcoming PASIPHAE sky survey. These instruments are designed to achieve a linear polarimetric measurement accuracy of 0.1% across a field of view (FoV) of 30×30 arcminutes. The WALOP-South instrument will be installed first on a 1 m telescope at the Sutherland Observatory, where the temperatures during the night can vary between 10 to -5°C. These temperature variations and the instrument’s pointing to various non-zenithal positions in the sky can introduce stress birefringence in the lenses, leading to time-varying instrumental polarization. This work estimates stress-induced birefringence due to thermal, and gravity stresses on WALOP-South lenses. Using the optomechanical model of the WALOP-South, we carried out Finite Element Analysis (FEA) simulations in SolidWorks software to estimate the stresses for various scenarios of temperature, telescope pointing airmass, and lens mount material (aluminum and titanium). Further, we use the stress tensor analysis to estimate the principal stresses and their directions and consequent birefringence and retardance introduced in the lenses. The stressinduced birefringence will change the optical path length for orthogonal polarization states of the beam passing through the lenses and introduce phase retardation. Overall, with the lens mount design of the instrument, we find that the retardation and consequent instrumental polarization will be within the instrumental accuracy requirements. Additionally, the stress birefringence is found to be higher for aluminum compared to titanium mounts. We further incorporated this retardance in the instrument Mueller matrix estimation to understand its effects on the polarization measurements.

SPIE Journal Paper | 9 March 2021

WALOP-South: a four-camera one-shot imaging polarimeter for PASIPHAE survey. Paper I—optical design

Siddharth Maharana, John Kypriotakis, Anamparambu Ramaprakash, Chaitanya Rajarshi, Ramya Anche, Shrish Shrish, Dmitry Blinov, Hans Eriksen, Tuhin Ghosh, Eirik Gjerløw, Nikolaos Mandarakas, Georgia Panopoulou, Vasiliki Pavlidou, Timothy Pearson, Vincent Pelgrims, Stephen Potter, Anthony C. Readhead, Raphael Skalidis, Konstantinos Tassis, Ingunn Wehus

JATIS, Vol. 7, Issue 01, 014004, (March 2021) https://doi.org/10.1117/12.10.1117/1.JATIS.7.1.014004

KEYWORDS: Polarimetry, Polarization, Sensors, Telescopes, Cameras, Prisms, Point spread functions, Optical design, Optical filters, Stars

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Proceedings Article | 13 December 2020 Poster + Presentation + Paper

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

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

Proceedings Volume 11447, 114475E (2020) https://doi.org/10.1117/12.2554396

KEYWORDS: Polarimetry, Polarization, Telescopes, Stars, Astronomy, Optical filters, Photometry, Prisms, Vignetting, Optomechanical design

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