Sam Ragland Email and Phone Number

I’m currently playing a lead role in certain aspects of all Keck Adaptive Optics (AO) development projects including the more recent projects such as Keck All-sky Precision Adaptive optics system (KAPA), Next Generation Real-time Control System (NGRTC), Pyramid Wavefront Sensor (PWS), and Fiber Injection Unit (FIU) upgrades. I manage the Point Spread Function (PSF) Determination and AO Optimization projects at the W.M. Keck Observatory (WMKO). The reconstructed PSFs for the science verification observations are being critically evaluated in order to improve the photometric and astrometric accuracy of the science observations.

I managed the operations and the infrastructure of the Keck Interferometer (KI) including the interferometer budget and provided a science perspective of the interferometer to help guide the operation and continued development of the interferometer. I led the development-to-operations handover and operations of the interferometer science instruments to ensure the scientific and operational success of these instruments. I led the team in assuring robust and reliable operations of the Keck Interferometer in its various modes to a diverse community of science users, including the successful completion of the NASA Nuller Key Science Program to observe exozodiacal dust disk survey. I carried out scientific and engineering research using the interferometer, including (1) probing the circumstellar environment around young stellar objects, and (2) implementing the L-band science instrument that advances the scientific objectives of the Keck Observatory.

I led the development of the Differential Phase science instrument at WMKO and made significant contributions to the development of the other Keck Interferometer instruments. I was responsible for the AO and the Real-time Control systems for Keck Interferometer operation and development. I have developed many operational tools for the interferometer and the AO. I was the Principal Investigator and the Manager of "The Mira Imaging Project" (funded by NSF) at the WMKO. The outcome of the research includes direct detection of asymmetry in a sample of Asymptotic Giant Branch Stars (AGB) and characterization of the immediate surroundings of evolved stars using interferometric observations in the infrared and radio wavelengths.

I was involved in various instrumental and observational aspects of stellar interferometry in collaboration with Dr. Wesley Traub. I initiated a systematic observing program of late-type stars at IOTA to understand the atmospheres of these stars and address various unresolved problems in this area. I carried out several engineering and/or science observing runs at IOTA, and took closure phase and visibility amplitude measurements of 56 evolved stars. I made visibility amplitude and closure phase measurements of a few cool giants beyond the first null using baseline bootstrapping. Several targets show non-zero closure phase from these observations signifying the presence of surface asymmetry in these AGB stars. The variability phase and wavelength dependent angular size were also a topic of my interest. I took an active part in the efforts of the IOTA team in obtaining the first closure phase measurements of IOTA. I have also contributed to the development of observing strategy at IOTA and dealing with various calibration issues in order to make accurate closure phase and visibility amplitude measurements. I have extensively used the fiber optics based (FLUOR) and the integrated optics based (IONIC) beam-combiners at IOTA. I have designed a low-resolution spectrometer for the IOTA interferometer using ZEMAX. The spectrometer is designed to work with all three-telescope beams enabling spectrally resolved visibility amplitude and closure phase measurements in the continuum and molecular bands of the atmosphere of evolved stars at near-infrared wavelengths. The spectrometer has the flexibility to easily reconfigure for conventional broadband operations.