Calibration and Field Flattening for Single Dish Astronomical Phased Array Feed Radio Camera Imaging

A primary advantage of phased array feeds (PAFs) is the ability to operate as a "radio camera," forming an image with a single dish pointing. Each pixel corresponds to one of many simultaneously formed beams covering the field of view. However, variations in gain and noise levels across these beams hinder weak source detection. We present new calibration and beamformer design approaches to reduce these beam-to-beam variations, including a dual constraint beamformer which simultaneously satisfies beam gain and noise response constraints, and a dish rim calibration system to control spillover pattern variations.