Baranec, C., Lloyd-Hart, M., and Milton, N. M., 2007 Ground-layer wave front reconstruction from multiple natural guide stars ApJ 661, 1332-1338 (Instrumentation) Lloyd-Hart, M., Baranec, C., Milton, N., Stalcup, T., Snyder, M., 2007 Closed-loop results from the MMT's multi-laser guide star adaptive optics system Proceedings of the AMOS Technologies Conference, ed. S. Ryan, Wailea, HI, Sept. 12-15 2007, E66-E74 (Instrumentation) Baranec, C., Lloyd-Hart, M., Meyer, M., 2007 Loki: a ground-layer adaptive optics high-resolution near-infrared survey camera Astronomical Adaptive Optics Systems and Applications III (Proc. SPIE), eds. R. Tyson and M. Lloyd-Hart, 6691 (Instrumentation) Baranec, C., Lloyd-Hart, M., Milton, N. M., Stalcup, T., Snyder, M., Vaitheeswaran, V., McCarthy, D., Angel, R., 2007 Astronomical imaging using ground-layer adaptive optics Astronomical Adaptive Optics Systems and Applications III (Proc. SPIE), eds. R. Tyson and M. Lloyd-Hart, 6691 (Instrumentation) Milton, N. M., Lloyd-Hart, M., Bernier, J., Baranec, C., 2007 Real-time atmospheric turbulence profile estimation using modal covariance measurements from multiple guide stars Astronomical Adaptive Optics Systems and Applications III (Proc. SPIE), eds. R. Tyson and M. Lloyd-Hart, 6691 (Instrumentation) Lloyd-Hart, M., Angel, R., Green, R., Stalcup, T., Milton, N., Powell, K., 2007 Multi-laser-guided adaptive optics for the Large Binocular Telescope Astronomical Adaptive Optics Systems and Applications III (Proc. SPIE), eds. R. Tyson and M. Lloyd-Hart, 6691 (Instrumentation) Stalcup, T., Angel, R., Lloyd-Hart, M., Rademacher, M., 2007 Status of the MMT Observatory Multiple Laser Beacon Projector Astronomical Adaptive Optics Systems and Applications III (Proc. SPIE), eds. R. Tyson and M. Lloyd-Hart, 6691 (Instrumentation)
Lloyd-Hart is leading a team investigating the application of altitude-conjugated adaptive optics to current and future large telescopes. In a major breakthrough, first closed-loop results have been obtained from an AO system at the MMT that uses multiple laser guide stars, the first such system to be fielded at a telescope. Ground-layer AO, in which low-lying atmospheric turbulence is corrected to improve the seeing over a wide field of view, has been shown to work well over a 2 arc minute field, improving the seeing from the site's 65th percentile in K band to 15th percentile. Lloyd-Hart and graduate student N. M. Milton have demonstrated a technique similar to SLODAR in which the vertical profile of the atmospheric turbulence may be deduced from the wavefront sensor signals of a multi-beacon AO system. The technique may be applied while the system is in closed loop, allowing the real-time wavefront reconstructor algorithm to be optimized on the fly in response to changing atmospheric conditions. Lloyd-Hart has invented a technique for focal-plane wavefront sensing with particular application to the detection and study of extra-solar planets and other faint companions to bright stars. Residual atmospheric wavefront errors, detected by the wavefront sensor while in closed loop, can be analyzed in a manner similar to the phase diverse focal-plane technique to yield high fidelity maps of the wavefront phase distortion. Lloyd-Hart is Principal Investigator for a Steward-based team that is developing the design for the adaptive optics systems to be included in the Giant Magellan Telescope. Plans for the telescope call for an adaptive secondary mirror, facility instrumentation for diffraction limited operation in the near and thermal IR, ground-layer correction of an 8 arcmin field of view, and very high-fidelity correction of bright sources to enable imaging and spectroscopy of planets around other nearby stars. Detailed modelling of the AO systems is now underway. Lloyd-Hart is the Arizona Principal Investigator in an international collaboration, headed by the Max Planck Society, to equip the LBT with laser guide stars for its AO system. The work will build on pioneering effort at the MMT, putting four Rayleigh laser beacons on each half of the telescope. Initially, the system will implement GLAO in the near IR over the 4 arc minute field of the two LUCIFER imager/spectrographs. Hooks are designed into the system to allow upgrades to tomographic operation for correction to the diffraction limit, and for operation with the thermal infrared imaging capability of the LBT Interferometer.