The Hobby-Eberly telescope completion project

The Hobby-Eberly Telescope (HET) is a fixed-elevation, 9.2-m telescope with a spherical primary mirror and a tracker at prime focus to follow astronomical objects. The telescope was constructed for $13.9M over the period 1994-1997. A number of telescope performance deficiencies were identified and corrected following construction. Remaining problems included: 1) Dome seeing, 2) inadequate initial mirror segment alignment accuracy, and 3) mirror segment misalignment with time. The HET Completion Project was created in May 2001 to attack these problems and to identify and solve the next tier of problems. To address dome seeing, large louvers were installed and in operation by May 2002. Efforts are also underway to eliminate or suppress heat sources within the dome environment. To address segment alignment accuracy, a prototype Shack-Hartmann device, the Mirror Alignment Recovery System (MARS), was built and is in routine use at HET. The Segment Alignment Maintenance System (SAMS) is in early operation and has markedly improved telescope performance. Two Differential Image Motion Monitor (DIMM) telescopes were brought into regular operation in July 2001 to quantify atmospheric seeing at HET. As these improvements have been implemented, telescope image quality has improved significantly. Plans are in place to address additional performance issues.