We report progress on the United States Naval Observatory, Navy Prototype Optical Interferometer, Astrometric Catalog
(UNAC). This catalog uses observations from eight astrometric observation runs (Jan. 2005 - Nov. 2009) at the Navy
Prototype Optical Interferometer (NPOI). The goal of the first release of the UNAC is to provide an astrometric catalog
of at least 100 bright (V < 6) stars with precise positions accurate to < 16 milliarcseconds. In this paper we report on
some of the data processing methods used to obtain absolute astrometric positions from optical interferometer data. We
also discuss plans for assessing the accuracy of our interferometrically derived absolute astrometric positions.
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.
This paper provides an overview of technology development for the Terrestrial Planet Finder Interferometer
(TPF-I). TPF-I is a mid-infrared space interferometer being designed with the capability of detecting Earth-like
planets in the habitable zones around nearby stars. The overall technology roadmap is presented and progress
with each of the testbeds is summarized.
This paper provides an overview of technology development for the Terrestrial Planet Finder Interferometer
(TPF-I). TPF-I is a mid-infrared space interferometer being designed with the capability of detecting Earth-like
planets in the habitable zones around nearby stars. The overall technology roadmap is presented and progress
with each of the testbeds is summarized. The current interferometer architecture, design trades, and the viability
of possible reduced-scope mission concepts are also presented.
KEYWORDS: Planets, Stars, Space operations, Interferometers, Nulling interferometry, Computer simulations, Interferometry, Robots, Telescopes, Control systems
The interferometric version of the Terrestrial Planet Finder (TPF-I) has the potential to find and characterize earth-sized
planets in the habitable zones of over 250 nearby stars and to search for life using biomarkers in the atmospheres of any
planets found. The scientific case for such a mission continues to be strengthened by on-going progress in the detection
of planets via indirect means. This paper summarizes the status of TPF-I, illustrative scientific requirements for the
mission, and its enabling technologies.
The technical status of the Navy Prototype Optical Interferometer (NPOI) since the last
SPIE meeting is summarized along with the current science programs. The instrument is
operated in an automatic observational mode, obtaining over 10,000 stellar observations
in the period, June 2004 through March 2006. The scientific program has been directed
at astrometry, TPF candidate stars, binary stars and other interesting targets such as Be
stars. A significant database of NPOI observations obtained in 1997-2004 is being
analyzed for binaries and single stars such as rapid rotating stars: Altair and Vega.
We present preliminary results from an ongoing survey for multiplicity among the bright stars using the Navy Prototype Optical Interferometer (NPOI). While the NPOI has previously concentrated on producing "visual" orbits of known close speckle and spectroscopic binaries, we have now embarked on a broader survey to detect new binary/multiple systems. We first present a summary of previous NPOI observations of known binary and multiple systems to illustrate the instrument's detection sensitivity for binaries at large magnitude differences over the range of angular separation detectable by the NPOI (currently 3 - 300 mas). We then discuss early results of the survey of bright stars north of declination -20°. This survey, which compliments previous surveys of the bright stars by speckle interferometry, initially emphasizes stars in a proposed Terrestrial Planet Finder (TPF) target list. To date, 29 of the 60 brightest TPF candidate stars (V ≤ 4.3) have each been observed on multiple nights. Preliminary analysis of these data indicates the possible detection of stellar companions to several of these stars.
We describe recent science projects that the Navy Prototype Optical Interferometer (NPOI) scientific staff and collaborators are pursuing. Recent results from the wide angle astrometric program and imaging programs (rapid rotators, binaries and Be stars) will be summarized. We discuss some of the technology that enables the NPOI to operate routinely as an observatory astronomical instrument.
Over the last year, a set of well defined science requirements has been established for the Terrestrial Planet Finder (TPF) mission. They consist of top level specifications, such as the number and characteristics of stars to be observed, the planetary sizes and orbital phase spaces to be searched for, the desired completeness of the search, etc. For each of the concurrent observing techniques considered - thermal infrared nulling interferometry and optical coronagraphy-, dedicated spectroscopy requirements have also been formulated. On the interferometry side, the most promising design studied so far consists of a free flyer assembly of four 4m class telescopes. It basically allows to thoroughly search for planets in the habitable zone of ~ 160 nearby main sequence F,G and K dwarfs in 1 year of continuous integration (~ 2 years of operation). Over 1.5 year of subsequent observation, this design would also enable low resolution (20) spectroscopic characterization of up to 10 exo-planetary atmospheres in the [6.5 - 17] micron range, assuming 260K exo-planets with Earth albedo, and at least half the Earth area
are present around the target stars. With only minor additions to the nulling design, and taking advantage of a spatial resolution 10 to 50 times higher than JWST, the free flyer design would also provide fantastic contributions in the fields of comparative planetology, the study of very young stellar objects and high-z galaxies.
In order to extend the US Naval Observatory (USNO) small-angle astrometric capabilities to near infrared wavelengths we have designed and manufactured a 1024 x 1024 InSb re-imaging infrared camera equipped with an array selected from the InSb ALADDIN (Advanced Large Area Detector Development in InSb) development
program and broadband and narrowband 0.8 - 3.8 μm filters. Since the USNO 1.55-m telescope is optimized for observations at visible wavelengths with an oversized secondary mirror and sky baffles, the straylight rejection capabilities of the ASTROCAM Lyot stop and baffles are of critical importance for its sensitivity and flat-
fielding capabilities. An Offner relay was chosen for the heart of the system and was manufactured from the same melt of aluminum alloy to ensure homologous contraction from room temperature to 77 K. A blackened cone was installed behind the undersized hole (the Lyot stop) in the Offner secondary. With low distortion, a well-sampled point spread function, and a large field of view, the system is well suited for astrometry. It is telecentric, so any defocus will not result in a change of image scale. The DSP-based electronics allow readout of the entire array with double-correlated sampling in 0.19 seconds, but shorter readout is possible with single sampling or by reading out only small numbers of subarrays. In this paper we report on the optical, mechanical, and electronic design of the system and present images and results on the sensitivity and astrometric stability obtained with the system, now operating routinely at the 1.55-m telescope with a science-grade ALADDIN array.
The Astrophysics of Reference Frame Tie Objects Key Science program will investigate the underlying physics of SIM grid objects. Extragalactic objects in the SIM grid will be used to tie the SIM reference frame to the quasi-inertial reference frame defined by extragalactic objects and to remove any residual frame rotation with respect to the extragalactic frame. The current realization of the extragalactic frame is the International Celestial Reference Frame (ICRF). The ICRF is defined by the radio positions of 212 extragalactic objects and is the IAU sanctioned fundamental astronomical reference frame. This key project will advance our knowledge of the physics of the objects which will make up the SIM grid, such as quasars and chromospherically active stars, and relates directly to the stability of the SIM reference frame. The following questions concerning the physics of reference frame tie objects will be investigated. What is the origin of optical emission in quasars? Are the optical photo-centers of quasars compact and positionally stable on the micro-arcsecond level? Are binary black hole mergers responsible for quasars? What is (are) the emission mechanism(s) responsible for generating radio emission in chromospherically active stars. What causes the transition of spherically symmetric Asymptotic Giant Branch (AGB) stars to asymmetric planetary nebulae (PNe)?
The Full-sky Astrometric Mapping Explorer (FAME) space mission will perform an all sky astrometric survey with unprecedented accuracy. FAME will produce an astrometric catalog of 40 million stars between 5th and 15th visual magnitude. For the bright stars (5th to 9th magnitude), FAME will determine the positions and parallaxes to better than 50 μas, with proper motion errors of 70 μas per year. For the fainter stars (between l0th and 15th magnitude), FAME will determine positions and parallaxes accurate to better than 500 μas with proper motions errors less than 500 μas per year. FAME will also collect photometric data on the 40 million stars. The accuracy of a single observation of a 9th magnitude star will be 1 mmag.
The FAME mission will impact almost all areas of astrophysics. It will find planets revolving around nearby stars, further studies of stellar evolution, determine the location of dark matter in the Milky Way galaxy, and measure the size and age of the universe. It will also establish a celestial reference frame with an accuracy better than a microarcsecond.
Scott Horner, Marvin Germain, Frederick Harris, Mark Johnson, Kenneth Johnston, David Monet, Marc Murison, James Phillips, Robert Reasenberg, P. Kenneth Seidelmann, Sean Urban, Richard Vassar
The Full-sky Astrometric Mapping Explorer (FAME) is a MIDEX class Explorer mission designed to perform an all-sky, astrometric survey with unprecedented accuracy, determining the positions, parallaxes, proper motions, and photometry of 40 million stars. It will create a rigid, astrometric catalog of stars from an input catalog with 5 < mv < 15. For bright stars, 5 < mv < 9, FAME's goal is to determine positions and parallaxes accurate to < 50 (mu) as, with proper motion errors < 50 (mu) as/year. For fainter stars, 9 < mv < 15, FAME's goal is to determine positions and parallaxes accurate to < 500 (mu) as, with proper motion errors < 500 (mu) as/year. It will also collect photometric data on these 40 million stars in four Sloan DSS colors.
The Navy Prototype Optical Interferometer contains two major subarrays: one for imaging the surface of stars, the other for measuring the precise positions of bright stars. In order to image the surface of stars, six 50 cm elements which can be reconfigured to sample many spatial frequencies using 32 spectral channels equally spaced in wavenumber between 450 and 850 nanometers. The imaging array elements are distributed on a 'Y' with a maximum spacing for imaging of 437 m, yielding a spatial resolution of 0.2 mas. The positions of stars will be measured using four fixed 50 cm siderostats with element spacings from 19 to 38 meters. The delay line compensation and beam paths are in vacuum to eliminate the effects of atmospheric dispersion. The astrometric goal is an accuracy of 2 mas over wide angles.
Newcomb is a design concept for an astrometric optical interferometer with nominal single-measurement accuracy of 100 microseconds of arc ((mu) as). In a 30-month mission life, it will make scientifically interesting measurements of O-star, RR Lyrae, and Cepheid distances, probe the dark matter in our Galaxy via parallax measurements of K giants in the disk, establish a reference grid with internal consistency better than 50 (mu) as, and lay groundwork for the larger optical interferometers that are expected to produce a profusion of scientific results during the next century. With an extended mission life, Newcomb could do a useful search for other planetary systems.
The Navy Prototype Optical Interferometer (NPOI) at the Lowell Observatory near Flagstaff, Arizona is a tri-baseline stellar interferometer with specific design characteristics for astrometry and imaging. All major construction has been completed. Installation of scientific instrumentation began in July 1993 with first light expected during the Spring 1994. Here we present a description of the location, physical plan, and construction of the interferometer.
Newcomb is a design concept for an astrometric optical interferometer with nominal single- measurement accuracy of 100 microseconds of arc ((mu) as). In a three-year mission life, it will make scientifically interesting measurements of O-star, RR Lyrae, and Cepheid distances, establish a reference grid with internal consistency better than 100 (mu) as, and lay groundwork for the larger optical interferometers that are expected to produce a profusion of scientific results during the next century. With an extended mission life, Newcomb could do a useful search for other planetary systems. The instrument is a highly simplified variant of POINTS. It has three (or four) interferometers stacked one above the other. All three (four) optical axes lie on a great circle, which is also the nominal direction of astrometric sensitivity. The second and third axes are separated from the first by fixed 'observation angles' of 40.91 and 60.51 deg. The fourth axis would be at either 70.77 or 78.60 deg from the first. Each interferometer detects a dispersed fringe (channeled spectrum), which falls on a CCD detector array nominally 8 k elements long and a small number of elements wide. With a nominal baseline length of 30 cm and optical passband from 0.9 to 0.3 microns, the Nyquist limit is reached by a star +/- 21 arcmin from the optical axis. The instrument will be constructed of stable materials such as ULE glass, and have neither internal moving parts nor laser metrology.
For the first time, four spectroscopic binaries have been directly resolved with the Mark III Stellar Interferometer. Observations in 1988 and 1989 were analyzed, and visual orbits for four binaries have been determined. The semimajor axes for Beta Tri, Alpha Equ, Alpha And and Beta Ari are approximately 0.008 arcsec, 0.012 arcsec, 0.024 arcsec and 0.037 arcsec, respectively. The magnitude differences between two components are 0.5, 0.7, 1.8 and 2.6 mag, respectively. All of the orbital elements for Alpha And and Beta Ari were determined from interferometric data only, and agree well with spectroscopic observations. Predictions of relative position between the two components for these binaries are consistent with the measurements to less than 0.001 arcsec. Combined with data from spectroscopy, masses and distance for the double-lined spectroscopic binary Beta Ari are derived, and the results indicate that both components of Beta Ari agree well with the empirical mass-luminosity relation.
Reliable stellar angular diameters can now be determined using the Mark III Optical Interferometer located on Mt. Wilson, California. The Mark III is a Michelson Interferometer capable of measuring the interferometric fringe visibility for stars using interferometer baselines varying from 3 to 31.5 meters in length. Angular diameters measured with the Mark III Optical Interferometer are presented for 12 stars at wavelengths of 450 and 800 nm.
This paper describes the design and the capabilities of the Naval Research Laboratory Big Optical Array (BOA), an interferometric optical array for high-resolution imaging of stars, stellar systems, and other celestial objects. There are four important differences between the BOA design and the design of Mark III Optical Interferometer on Mount Wilson (California). These include a long passive delay line which will be used in BOA to do most of the delay compensation, so that the fast delay line will have a very short travel; the beam combination in BOA will be done in triplets, to allow measurement of closure phase; the same light will be used for both star and fringe tracking; and the fringe tracker will use several wavelength channels.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.