Proceedings Article | 10 July 2018
KEYWORDS: Telescopes, Sensors, Reflectors, Optical instrument design, Temperature metrology, Polarization, Anisotropy, Microwave radiation, Reflector telescopes, Receivers
Advanced ACTPol (AdvACT) is a third generation upgrade to the Atacama Cosmology Telescope (ACT) designed to measure the temperature and polarization anisotropies of the Cosmic Microwave Background (CMB) across five frequency bands. ACT is an off-axis Gregorian telescope with a 6 m primary reflector and 2 m secondary reflector located at a remote site in the Chilean Atacama Desert. AdvACT repurposes the second generation ACTPol receiver, replacing elements where needed while upgrading to a set of kilo-pixel dichroic transition edge sensor bolometer arrays.
The AdvACT upgrade has been deployed in stages. The first new array was deployed in 2016, observing at 230 and 150 GHz. The following two arrays were deployed in 2017, observing at 150 and 90 GHz. These upgrades approximately doubled the number of detectors (to ~6,000) when compared to the second generation instrument, ACTPol. The fourth array, designed to observe at 39 and 27 GHz, will be the last to be deployed. The increase in detector count and wide frequency coverage enables a wide range of science goals which include improving constraints on dark energy, the sum of the neutrino masses, and primordial gravitational waves.
Command and control of the telescope is performed remotely. A team of collaboration members, referred to as remote observers, has formed to take shifts controlling the telescope throughout the season. Each shift lasts for 24 hours, during which the assigned remote observer is responsible for scheduling the day’s observations, coordinating with the engineering crew at the site, and recovering the telescope should it cease operations. To facilitate these tasks we have designed a set of web tools. The utility of these tools ranges from monitoring telescope systems, data flow, and computer status to scheduling observations and controlling the telescope itself. New tools are simple to integrate and are added as needed.
Science and housekeeping data collection, processing, and transfer are largely autonomous. The telescope control tools command the readout electronics which interface with the detectors. Data are collected on one of three computers, one for each detector array, and processed into a standardized, compressed format before being stored in a RAID near the site. A copy is then automatically made on a transport disk, which is used to transfer the data to North America where another copy is then made for data analysis.
AdvACT is now in its second season of observations. In this work we describe the status of the AdvACT project and discuss the telescope systems and operations.
