An asynchronous web application to visualise large sky surveys

Large sky surveys from dedicated survey telescopes allow astronomers to access large swathes of the optical and near-infrared sky at high spatial resolution. The increasingly large volume of multi-wavelength imaging and catalogue photometry data products they generate are a cumbersome data management burden for survey teams. Even the simplest of tasks like visual inspection can quickly become out of reach when trying to apply the traditional astronomical software toolkit familiar to most astronomers. More complex tasks like quality assurance and scientific exploitation demand interactive visualisation of data products alone (e.g. catalogues overlaid on imaging) and in conjunction with multi-wavelength data from other surveys. Here we introduce a web application that effortlessly performs these tasks for the reprocessed imaging (>20TB) and catalogues (>100GB) of the VISTA Hemisphere Survey. The application is powered by the asynchronous architecture developed for Data Central's Data Aggregation Service that can query and receive several data streams simultaneously. Users can inspect a single target or navigate multiple targets from an uploaded list. Survey images are dynamically converted from FITS to HiPS format before being loaded into an Aladin Lite instance. Multiple catalogues are retrieved and accurately drawn in Aladin Lite using markers and ellipses. Dynamically generated tables summarise catalogue metadata with links to full record information. Users requiring more than the provided visualisation and adjustable image scaling can download image and catalogue cutouts for closer inspection. With further science-oriented refinement we plan to release the application as part of the Data Central science platform.