Our environment is pretty clear to a spread of radio frequencies, however not completely clear. Astronomers have to know the radio opacity of the sky to know the right way to account for it of their observations. However how do you measure the opacity of our environment? The traditional methodology is called tipping scans, the place a radio antenna scans the sky whereas quickly tipping the antenna’s elevation from low to excessive (or vice versa). Tipping scans have been used to measure the opacity of the sky on the web site of the Very Massive Array, however these have been finished earlier than the observatory adopted the information processing software program generally known as Frequent Astronomy Software program Purposes (CASA).
Atmospheric opacity at totally different frequencies throughout the yr. Credit score: Pedro Beaklini, et al.
In new work, NRAO’s Pedro Beaklini and his colleagues have developed a CASA process that may use knowledge from tipping scans to measure the opacity of the VLA sky. They discovered that for some frequencies the opacity can range considerably over the course of the yr. For instance, at round 22 GHz, atmospheric opacity could be 3 times increased in summer season than in winter. These outcomes will assist astronomers higher course of their radio knowledge.
Pedro offered these findings at AAS 242.