INTER-UNIVERSITY  CENTRE  FOR  ASTRONOMY  AND  ASTROPHYSICS
(An Autonomous Institution of the University Grants Commission)

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  SEMINAR

 

MS. RAMYA ANCHE

Indian Institute of Astrophysics, Bangalore
 
Optical polarimetry using next-generation 30 m class telescopes
 
 

Polarimetry is a powerful technique for studying various astrophysical processes. The measurements are typically taken using a polarimeter placed at the telescope focus. The instrumental polarization (IP) and polarization cross-talk arising due to the reflections from the mirror surfaces of the telescope affect the polarization measurements and can seriously limit the science capabilities of the instrument. Hence, it is very important to estimate and minimize the IP and cross talk due to the telescope optics before designing a polarimeter, especially for high precision science goals (e.g. studies of exoplanet) where the polarimetric signals are weak. The polarization model for one of the future generation telescope, the Thirty Meter Telescope (TMT) will be presented. The polarization ray tracing model gives the complete Mueller matrices of all the mirrors of the telescope. The IP and crosstalk are found to be varying significantly with the field of view of the telescope, zenith angle, and the position of the instrument ports due to the inclined tertiary mirror of the telescope. The speaker will also discuss briefly on the polarization aberrations arising due to the non-normal incidences and coating and its effect on the point spread function of the telescope and effects of the segments and coating non-uniformities. The impact of these polarization effects on the science case requirements will also be discussed. This analysis will help in achieving precise requirements for future instruments with polarimetric capability for the next-generation telescopes.

 
IUCAA Lecture Hall, Bhaskara 3
July 10, 2019, 11:00 hrs.