The Atacama Cosmology Telescope: Measurement and Analysis of 1D Beams for DR4

Understand

We describe the measurement and treatment of the telescope beams for the Atacama Cosmology Telescope's fourth data release, DR4.

• Observations of Uranus are used to measure the central portion (<12') of the beams to roughly -40 dB of the peak.
• Such planet maps in intensity are used to construct azimuthally averaged beam profiles, which are fit with a physically motivated model before being transformed into Fourier space.
• We investigate and quantify a number of percent-level corrections to the beams, all of which are important for precision cosmology.