Prof. Vasiliki Pavlidou Profile

Prof. Vasiliki Pavlidou

at Univ of Crete

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Author

Publications (7)

Proceedings Article | 25 July 2024 Presentation + Paper

The WALOP software

John Kypriotakis, Bhushan Joshi, Dmitry Blinov, Sebastian Kiehlmann, Siddharth Maharana, Chaitanya Rajarshi, A. Ramaprakash, Artem Basyrov, Myrto Falalaki, Tuhin Ghosh, Eirik Gjerløw, Ioannis Liodakis, Nikolaos Mandarakas, Georgia Panopoulou, Vasiliki Pavlidou, Timothy Pearson, Vincent Pelgrims, Stephen Potter, Anthony C. Readhead, Raphael Skalidis, Konstantinos Tassis, Namita Uppal

Proceedings Volume 13101, 131011A (2024) https://doi.org/10.1117/12.3018100

KEYWORDS: Databases, Calibration, Polarizers, Observatories, CCD cameras, Control software, Web services, Control systems, Robotics, Internet imaging, Instrumentation control

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Proceedings Article | 18 July 2024 Poster + Paper

Improving polarimetric accuracy of RoboPol to < 0.05 % using a half-wave plate calibrator system

Siddharth Maharana, Dmitry Blinov, A. N. Ramaprakash, Vasiliki Pavlidou, Konstantinos Tassis

Proceedings Volume 13096, 130963A (2024) https://doi.org/10.1117/12.3021523

KEYWORDS: Polarimetry, Calibration, Polarization, Equipment, Stars, Telescopes, Design, Astrophysics, Observatories

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Proceedings Article | 18 July 2024 Poster + Paper

Systems design, assembly, integration, and lab testing of WALOP-South Polarimeter

Siddharth Maharana, A. Ramaprakash, Chaitanya Rajarshi, Pravin Khodade, Bhushan Joshi, Pravin Chordia, Abhay Kohok, Ramya Anche, Deepa Modi, John Kypriotakis, Amit Deokar, Aditya Kinjawadekar, Stephen Potter, Dmitry Blinov, Hans Kristian Eriksen, Myrto Falalaki, Hitesh Gajjar, Tuhin Ghosh, Eirik Gjerløw, Sebastian Kiehlmann, Ioannis Liodakis, Nikolaos Mandarakas, Georgia Panopoulou, Vasiliki Pavlidou, Timothy Pearson, Vincent Pelgrims, Anthony C. Readhead, Raphael Skalidis, Konstantinos Tassis, Namita Uppal, Ingunn Wehus

Proceedings Volume 13096, 130967P (2024) https://doi.org/10.1117/12.3016144

KEYWORDS: Equipment, Cameras, Polarimetry, Polarizers, Collimators, Telescopes, Cements, Polarization, Calibration, Optomechanical design, Optical design, Calcite

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Wide-Area Linear Optical Polarimeter (WALOP)-South is the first wide-field and survey-capacity polarimeter in the optical wavelengths. On schedule for commissioning in 2024, it will be mounted on the 1 m SAAO telescope in Sutherland Observatory, South Africa to undertake the PASIPHAE sky survey. PASIPHAE program will create the first polarimetric sky map in the optical wavelengths, spanning more than 2000 square degrees of the southern Galactic region. In a single exposure, WALOP-South’s innovative design will enable it to measure the linear polarization (Stokes parameters q and u) of all sources in a field of view (FoV) of 35 × 35 arc-minutes-squared in the SDSS-r broadband and narrowband filters between 500-750 nm with 0.1 % polarization accuracy. The unique goals of the instrument place very stringent systems engineering goals, including on the performance of the optical, polarimetric, optomechanical, and electronic subsystems. In particular, the major technical hurdles for the project included the development of: (a) an optical design to achieve imaging quality PSFs across the FoV, (b) an optomechanical design to obtain high accuracy optical alignment in conjugation with minimal instrument flexure and stress birefringence on optics (which can lead to variable instrumental polarization), and (c) an on-sky calibration routine to remove the strong polarimetric cross-talk induced instrumental polarization to obtain 0.1% across the FoV. All the subsystems have been designed carefully to meet the overall instrument performance goals. As of May 2024, all the instrument optical and mechanical subsystems have been assembled and are currently getting tested and integrated. The complete testing and characterization of the instrument in the lab is expected to be completed by August 2024. While the instrument was initially scheduled for commissioning in 2022, it got delayed due to various technical challenges; WALOP-South is now on schedule for commissioning in second half of 2024. In this paper, we will present (a) the design and development of the entire instrument and its major subsystems, focusing the instrument’s opto-mechanical design which has not been reported before, and (b) assembly and integration of the instrument in the lab and early results from lab characterization of the instrument’s optical performance.

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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