From the linked PDF report: "Nominal orbit: Halo orbit about the Sun-Earth L2 point." The linked report also answers the "why there" question I immediately had

From the linked PDF report: "Nominal orbit: Halo orbit about the Sun-Earth L2 point." The linked report also answers the "why there" question I immediately had. > The HDST spacecraft and its operations will likely share many commonalities with the JWST architecture and operations. For HDST, as for JWST, an L2 halo orbit is preferable to a geosynchronous orbit (and most others, including low-earth orbit), because it is thermally stable and has lower fuel requirements for station-keeping https://static1.squarespace.com/static/558adc44e4b002a448a04c1a/t/55a411dee4b0543aa4ede4f2/1436815838795/hdst_report2_071315.pdf https://static1.squarespace.com/static/558adc44e4b002a448a04... (if that link expires, it was from here: http://www.hdstvision.org/report http://www.hdstvision.org/report )