Anders Jorgensen, New Mexico Institute of Mining and Technology, A. M. Jorgensen, New Mexico Tech, H. R. Schmitt, Naval Research Laboratory, G. T. van Belle, Lowell Observatory, D. J. Hutter, Naval Observatory Flagstaff Station, J. Clark, Naval Research Laboratory, D. Mozurkewich, Seabrook Engineering, J. T. Armstrong, Naval Research Laboratory, E. K. Baines, Naval Research Laboratory, S. R. Restaino, Naval Research Laboratory
Keywords: npoi, imaging, stars, interferometry, coherent integration, bootstrapping
Abstract:
The Navy Precision Optical Interferometer (NPOI) has a unique layout which is particularly well-suited for high-resolution interferometric imaging. By combining the NPOI layout with a new data acquisition and fringe tracking system we are progressing toward a imaging capability which will exceed any other interferometer in operation. The project, funded by the National Science Foundation, combines several existing advances and infrastructure at NPOI with modest enhancements. For optimal imaging there are several requirements that should be fulfilled. The observatory should be capable of measuring visibilities on a wide range of baseline lengths and orientations, providing complete UV coverage in a short period of time. It should measure visibility amplitudes with good SNR on all baselines as critical imaging information is often contained in low-amplitude visibilities. It should measure the visibility phase on all baselines. The technologies which can achieve this are the NPOI Y-shaped array with (nearly) equal spacing between telescopes and an ability for rapid configuration. Placing 6-telescopes in a row makes it possible to measure visibilities into the 4th lobe of the visibility function. By arranging the available telescopes carefully we will be able to switch, every few days, between 3 different 6-station chains which provide symmetric coverage in the UV (Fourier) plane without moving any telescopes, only by moving beam relay mirrors. The 6-station chains are important to achieve the highest imaging resolution, and switching rapidly between station chains provides uniform coverage. Coherent integration techniques can be used to obtain good SNR on very small visibilities. Coherently integrated visibilities can be used for imaging with standard radio imaging packages such as AIPS. The commissioning of one additional station, the use of new data acquisition hardware and fringe tracking algorithms are the enhancements which make this project possible.
Date of Conference: September 15-18, 2015
Track: Poster