HDST meaning in General ?

The Large Ultraviolet Optical Infrared Surveyor, commonly known as LUVOIR (), is a multi-wavelength space telescope concept being developed by NASA under the leadership of a Science and Technology Definition Team. It is one of four large astrophysics space mission concepts being studied in preparation for the National Academy of Sciences 2020 Astronomy and Astrophysics Decadal Survey. While LUVOIR is a concept for a general-purpose observatory, it has the key science goal of characterizing a wide range of exoplanets, including those that might be habitable. An additional goal is to enable a broad range of astrophysics, from the reionization epoch, through galaxy formation and evolution, to star and planet formation. Powerful imaging and spectroscopy observations of Solar System bodies would also be possible. LUVOIR would be a Large Strategic Science Mission and will be considered for a development start sometime after 2020. The LUVOIR Study Team has produced designs for two variants of LUVOIR: one with a 15.1 m diameter telescope mirror (LUVOIR-A) and one with an 8 m diameter mirror (LUVOIR-B). LUVOIR can observe ultraviolet, visible, and near-infrared wavelengths of light. The Final Report on the 5-year LUVOIR mission concept study was publicly released on 26 August 2019.