The Solar ALMA Science Archive (SALSA): First release, SALAT, and FITS header standard

Abstract

In December 2016, the Atacama Large Millimeter/submillimeter Array (ALMA) carried out the first regular observations of the Sun. These early observations and the reduction of the respective data posed a challenge due to the novelty and complexity of observing the Sun with ALMA. The difficulties with producing science-ready, time-resolved imaging products in a format familiar to and usable by solar physicists based on the measurement sets delivered by ALMA had limited the availability of such data to this point. With the development of the Solar ALMA Pipeline, it has now become possible to routinely reduce such data sets. As a result, a growing number of science-ready solar ALMA data sets are now offered in the form of the Solar ALMA Science Archive (SALSA). So far, SALSA contains primarily time series of single-pointing interferometric images at cadences of one or two seconds, accompanied by the respective single-dish full-disc solar images. The data arrays are provided in FITS format. We also present the first version of a standardised header format that accommodates future expansions and fits within the scope of other standards including the ALMA Science Archive itself and SOLARNET. The headers include information designed to aid the reproduction of the imaging products from the raw data. Links to co-observations, if available, with a focus on those of the Interface Region Imaging Spectrograph, are also provided. SALSA is accompanied by the Solar ALMA Library of Auxiliary Tools (SALAT), which contains Interactive Data Language and Python routines for convenient loading and a quick-look analysis of SALSA data.