Polarization Properties of the John A. Galt 26-m Radio Telescope A Workshop Celebrating the Career of John A. Galt Polarization Properties of the John A. Galt 26-m Radio Telescope Xuan Du Sep 23, 2014

Challenges in Astronomical Polarimetry The Polarized Sky Instrumental Polarization The polarized emission from the Galactic plane T.L.Landecker et al, A&A, 2010, 520, A80

Simulate a Randomly Polarized source CST Model the Feed Pattern GRASP Surface Roughness Model the Reflector Mesh Leakage Simulate a Randomly Polarized source Ng et al, 2005, Radio Science, 40, 5014

Simulate a Randomly Polarized source CST Model the Feed Pattern GRASP Surface Roughness Model the Reflector Mesh Leakage Simulate a Randomly Polarized source Ng et al, 2005, Radio Science, 40, 5014

Total Intensity Patterns

Total Intensity Patterns T.L.Landecker et al, Radio Sci 1991, 363

Total Intensity Patterns

Polarization Patterns

Intensity Patterns Radial Average Aperture Efficiency & Beam Efficiency Beam Efficiency Strut scatter cones Spillover Lobes Aperture Efficiency

Ground Radiation (1400 MHz) 0.4 k 4.2 k Add arrows showing the fluctuation 𝑇 𝑔𝑟𝑜𝑢𝑛𝑑 = 1 Ω 𝑓 𝜃,𝜙 𝑇 𝐺 𝜃,𝜙 𝑑𝜔 0.6 k 𝑇 𝐺 𝜃,𝜙 = 300 [K] (80°<𝜃<180°)

Atmospheric Emission (1400MHz) 0.015k 3.5 k 𝑇 𝑎𝑡𝑚 = 1 Ω 𝑓 𝜃,𝜙 𝑇 𝜃,𝜙 𝑑𝜔 0.004k 𝑇 𝐴 𝜃,𝜙 = 2⋅sec(z) [K] (0°≤𝜃<80°) Gibbins, C.J. 1986, Radio Science, 21, 949

Ground temperature Profile Measurements Computation is not perfect Strut Modeling Ground Modeling Ground temperature Profile

Footer Text 4/22/2019

Conclusions GRASP can successfully predict polarization profile. Strut scattering and spillover contribute to the instrumental polarization. Aperture efficiency was calculated for GMIMS calibration. The ground contribution to the instrumental polarization is predicted.