Spectropolarimeter on board the Aditya-L1: polarization modulation and demodulation

Area of Science:

• Solar Physics
• Coronal Magnetometry
• Space Instrumentation

Background:

• Aditya-L1 mission's Visible Emission Line Coronagraph (VELC) payload aims to map coronal magnetic fields.
• Accurate measurement of magnetic fields requires high signal-to-noise ratio (SNR) spectropolarimetric observations.

Purpose of the Study:

• To address challenges in achieving high SNR for VELC's spectropolarimeter, specifically data volume increase and modulation matrix variations.
• To optimize data acquisition and processing for routine coronal magnetic field mapping.

Main Methods:

• Utilizing the infrared channel's polarimeter for full Stokes spectropolarimetric observations in the Fe xiii line (1074.7 nm).
• Implementing a dual-beam setup with a continuously rotating wave plate as a polarization modulator.
• Analyzing Zeeman and Hanle effects for magnetic field detection.

Main Results:

• Demonstrated that optimizing samples per half rotation can manage data volume.
• Proposed a method to account for modulation matrix variations across cycles.
• Ensured feasibility of high SNR measurements despite photon limitations and instrument dynamics.

Conclusions:

• The proposed methods enable efficient and accurate coronal magnetic field measurements using VELC.
• The study provides a pathway for routine magnetic field mapping, enhancing solar physics research.
• Optimized data handling is crucial for the success of advanced space-based coronagraph instruments.