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We present the status of site testing being done at and near the US Naval Observatory's Flagstaff Station (NOFS). Differential image motion monitors (DIMM) will be used to measure r 0 , the Fried seeing parameter, at each candidate site. DIMM results will be correlated with image quality as measured by the NOFS 1.55-m telescope. In addition, sky darkness measurements will be made and analysis of water column measurements made nearby by NOAA will be discussed. Site history, measurement methodology, and preliminary results will be presented.

Instrumentation developments at the Navy Precision Optical Interferometer (NPOI, formerly “Navy Optical Interferometer,” and “Navy Prototype Optical Interferometer”) since the last SPIE meeting in 2010 are summarized. The commissioning of new siderostat stations, progress towards the installation of four 1.8m telescopes, and other instrumentation and control systems upgrades, are reviewed.

Four 1.8 m outrigger telescopes were procured by NASA for use as part of the Keck Observatory Interferometer. Due to changes in NASA planning they will not be installed on Mauna Kea. The Navy Prototype Optical Interferometer (NPOI), a joint project of The U.S. Naval Observatory (USNO), The Naval Research Laboratory (NRL), and Lowell Observatory, located outside Flagstaff, Arizona, would like to upgrade the current siderostats on the project to larger apertures. The preliminary plans for integrating the Keck outrigger telescopes (OT) into NPOI are presented.

The instrumental status of the Navy Prototype Optical Interferometer (NPOI) since the last SPIE meeting in 2006 is summarized, along with the results of the current science programs. The commissioning of new stations and plans for greatly increased telescope apertures are discussed, along with other instrumentation upgrades. Recent results in the areas of wide-angle astrometry, binary stars, physical modeling of the circumstellar disks of early-type stars, improvements in coherent averaging, and phase-reference imaging are also reviewed.

The USNO 61" (1.55 m) astrometric reflector was state-of-the-art when it entered service in 1964. However, with a relatively small aperture, it now has limited research capability because it can not observe faint objects. The current facility, including dome and pier, offers significant resources upon which to build a larger telescope. Preliminary estimates indicate that a 3.5 m telescope could be retrofitted into the dome at a cost of ~$10-15 million; about half the cost of building on a new site. USNO has contracted with an engineering firm to perform a feasibility study of such a telescope upgrade, the results of which are summarized.

The alignment of a telescope consisting of 2 or more mirrors with powered surfaces is critical to system performance. For on axis images, secondary mirror tilt and decenter both predominately produce coma, and therefore, either can be used to correct coma. Consequently, for systems that operate over relatively narrow fields of view, it is not necessary to differentiate between secondary tilt and decenter. However, for systems utilizing wider fields of view, correcting tilt with decenter (or decenter with tilt) can result in large aberration variation off-axis. Details of a technique for differentiating between secondary mirror decenter and tilt through the use of off-axis wavefront sensing, aberration calculation, and alignment sensitivity modeling are presented.

An adaptive optics system is being developed by the U. S. Naval Observatory based on commercial, off-the-shelf components. This AO system will be used to experimentally test the influence of AO correction on precision astrometry across a wider-than-conventional field.

The reflectivity of mirror surfaces is a critical aspect of telescope performance. This is especially true of large adaptive optics systems and interferometers where twenty or more reflective surfaces may be encountered prior to reaching the final detector. The ability to accurately measure the reflectivity of mirrors in-situ allows not only for the determination of system throughput, but also helps to determine when optical elements need cleaning or recoating. We compare the performance of three commercially available, hand-held reflectometers by measuring calibrated reference surfaces of varying reflectivity and scatter characteristics. The reference surfaces are precisely calibrated for absolute reflectivity against NIST traceable standards using a state-of-the-art laboratory reflectometer. Through analysis of the reflectometer measurements of the precisely calibrated surfaces, we determine the relative ability of each reflectometer to measure reflectivity and differentiate scattered light from specular reflection.

In this paper we present results using a compact, portable adaptive optics system. The system was developed as a joint venture between the Naval Research Laboratory, Air Force Research Laboratory, and two small, New Mexico based-businesses. The system has a footprint of 18x24x18 inches and weighs less than 100 lbs. Key hardware design characteristics enable portability, easy mounting, and stable alignment. The system also enables quick calibration procedures, stable performance, and automatic adaptability to various pupil configurations. The system was tested during an engineering run in late July 2002 at the Naval Observatory Flagstaff Station one-meter telescope. Weather prevented extensive testing and the seeing during the run was marginal but a sufficient opportunity was provided for proof-of-concept, initial characterization of closed loop performance, and to start addressing some of the most pressing engineering and scientific issues. 1. Introduction Results are presented from a compact, portable Adaptive Optics (AO) system. The AO system was developed as a joint venture between the Naval Research Laboratory (NRL), Air Force Research Laboratory (AFRL), and two small, New Mexico-based businesses: Baker Adaptive Optics (BAO) and Narrascape. The initial results presented in this paper show data from a system whose design approach views the AO system as a self-contained instrument much like a camera or a spectrograph rather than as a part of the infrastructure of the telescope, which is the traditional view. The goal of this ongoing work is to create a versatile, accessible approach for various current users and various new users of adaptive optics technologies and those investigators interested in improving the response of their telescopes by correcting the effects of the atmosphere. Of specific interest, is the development of a compact, lightweight, low cost AO system that can be deployed on multiple telescopes configured as an interferometer. This system is characterized by flexibility and robustness that allows portability, simple mounting; ease of alignment and calibration procedures; and adaptability to readily exchange different types of Deformable Mirrors (DM) and wavefront sensors. Customized software and hardware combined with commercially available optics, camera, DM, and wavefront sensor provided a low cost, compact alternative to conventional systems.

While telescopes with segmented optics (currently Keck and HET and in the future GTC, CELT, GSMT, NGST, etc) present extra challenges in terms of optical alignment, they also present the opportunity for using an alignment technique not available to telescopes with monolithic optics. We present a technique for aligning telescope secondary mirrors utilizing the segmented nature of the primary. The data required is gathered in direct image mode and can be collected from science instrument detectors (as compared to a wavefront sensor). From this data aberrations (focus and coma) are calculated from which secondary piston and tip/tilt (or decenter) corrections are determined. In addition, tip/tilt corrections for each of the primary mirror segments can also be calculated. Furthermore, other aberrations are available to determine other alignment or support issues including differentiating secondary tip/tilt from decenter, focal surface tilt, and instrument aberrations. This technique has been used nightly on the Keck I and II telescopes over the last 8 years and has made a significant improvement in image quality.

Direct-imaging surveys require telescope designs which maximize the product of the primary mirror diameter times the field of view. While a 4.0-m telescope would not be considered "large" by modern standards, the provision of a 2.0-degree field corrector would make it comparable in imaging information-gathering capacity to an 8.0-m telescope with a 1.0-degree field corrector which is at or near the present state-of-the-art. We have explored plausible optical design options for such a 4.0-m telescope within the confines of a set of specifications which emphasize practical issues. These include realistic image quality requirements, mechanical simplicity, ease of construction, minimum cost and freedom from restrictive constraints on the primary mirror shape and the telescope structure, such that it could potentially be used in other optical configurations. We present a mechanically robust optical solution which uses a 4.0-m f/2.08 parabolic primary mirror and a refracting field corrector containing 4 powered lens elements with 2 mild aspherics located on softly curved surfaces, ample room for filter(s) and a shutter, with a flat vacuum dewar window and a flat 2.0-degree diameter field of view. We discuss or specifications and we provide a fully-quantitative system prescription as well as our analysis of the system's expected direct-imaging performance in the traditional Umod, B, V, R, (V+R) and I passbands. While we recongize that other optical designs may prove to be superior to ours by some standard(s) of measure, we believe that our solution provides a useful and realistic baseline design which is competitive for the intended purposes.

The construction and integration of the Keck AO system presented many interesting challenges, stemming from the program's unique scientific objectives and the size and shape of the Keck telescope primary mirror. In this paper, we will discuss several technical problems encountered during the design, construction, integration, and commissioning of the Keck AO system, and describe the solutions that have been implemented in the AO system.

Astronomical observations are now taking place on the Keck I telescope on a regular basis. We summarize here the status of the Keck I and II optics, and the current wavefront and image quality of the Keck I telescope as measured by in-telescope optical tests. Shack-Hartmann measurements of the individual primary mirror segments yield 80% encircled energy diameters that vary from 0.31 to 0.60 arc seconds. Full width at half maximum measurements of direct segment images obtained on a night of excellent seeing varied from 0.32 to 0.51 arcsec, and the combined image was 0.42 arcsec.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.