Receiver Selection and Calibration Unit for EHT-SPT (RESCUES)

Abstract

The Event Horizon Telescope (EHT) uses a technique known as Very Long Baseline Interferometry (VLBI) to combine radio telescopes all over the world into the equivalent of an Earth-size mirror. It will directly image the immediate surroundings of Sagittarius A* (Sgr A*), the supermassive black hole (SMBH) at the center of our galaxy. The 10-m South Pole Telescope (SPT) will provide EHT with its longest baselines, which will significantly improve EHT resolution. To prepare SPT for EHT, a VLBI receiver was built with its own optics system. The third mirror in the system requires a removable and repeatable mount that can rotate, while being light and compact with excellent thermal insulation. In addition, the VLBI receiver needs to have a motorized and remotely-controlled thermal calibration system to aid with data analysis. This project, titled Receiver Selection and Calibration Unit for EHT-SPT (RESCUES), presents a mount design that successfully satisfies the listed requirements. Finite Element Analysis (FEA) predicted that RESCUES had high performance with deformation on the scale of μm, which is within the tolerance of the optics system. Physical tests agreed with FEA simulations, confirming RESCUES reliability. RESCUES was installed at the SPT and first light was detected in 2015.