The HET is a telescope of the Arecibo design with an aperture of 9.2 m that is created by using an array of 91 mirror segments. These mirror segments essentially slot together to form one big mirror. (The primary motivation behind creating such a segmented mirror is the fact that it radically reduces the cost of the telescope.)
The HET is located at the McDonald Observatory at Mount Fowlkes near Austin, Texas.
HET was commissioned in 1997 and started science operations in 1999. It is a joint project between the University of Texas at Austin, Pennsylvania State University, Stanford University, the Ludwig Maximilians Universität and the Georg August Universität.