The Palomar Testbed Interferometer (PTI) is a near-infrared, long-baseline interferometer located at the Palomar Observatory. PTI obtained first fringes in 1995, and has been in routine scientific operations since 1998.
PTI was primarily designed as a technology demonstration experiment for the Keck Interferometer, and has been successful in demonstrating 100-uas-class differential astrometry and two-combiner phase referencing. In addition to its engineering development accomplishments, PTI has been extraordinarily scientifically productive, producing more than 25 refereed scientific papers to date. This contribution will provide an update on PTI’s operational, technical, and scientific status.
We discuss recent work from the Palomar Testbed Interferometer (PTI), including science results and system improvements. In the past two years PTI has been used to observe a wide range of scientifically interesting sources, including binaries, Cepheids and Miras. In addition PTI has been used to observe departures from spherical symmetry in several stars. Recent system improvements incude a new low read-noise camera based on a HAWAII infrared array, routine opteration in two baselines, and operation in the J band. Future developments include an upgrade to three-aperture combination and closure phase measurements, and double-Fourier interferometry.
The Interferometry Science Center (ISC) at the California Institute of Technology (Caltech) is chartered with providing science operations, data analysis support, and data archiving support for the suite of interferometry projects within the NASA Origins theme. Beginning with the Science Operations System (SOS) for the Keck Interferometer (KI), the ISC will design, implement, and operate a multi-mission facility to provide operations and support functions for NASA Origins interferometers and the scientists and engineers that use them. Future Origins interferometry projects such as the Space Interferometry Mission (SIM) will further use and extend the functionality of the ISC’s multi-mission base. In this talk I will introduce the functional elements in the KI SOS; describe the common SOS core elements that KI and SIM will share; and provide prospective users of these facilities an introduction to user support model that the ISC is implementing.
The Palomar Testbed Interferometer is a long-baseline near- infrared interferometer operating at Palomar Observatory, CA. The interferometer has a maximum baseline of 110 m, 40- cm collecting apertures, and active fringe tracking. It also incorporates a dual-star architecture to enable cophasing and narrow-angle astrometry. We will discuss recent system improvements and engineering results. These include upgrades to allow for longer coherent integration times, H band operation, and cophasing using delay line feedforward. Recent engineering tests of astrometry in dual-star mode have shown a night-to-night repeatability of 100 (mu) as on a bright test target. Several new observation planning tools have been developed, and data reduction tools have been automated to allow fully pipelined nightly reductions and archiving.
The Palomar Testbed Interferometer is a long-baseline, near-infrared astronomical interferometer capable of visibility measurement and narrow-angle differential astrometry. In this submission we consider the problem of fringe amplitude calibration as applied to the study of single and binary star systems with PTI. Methodologies for selecting appropriate calibration objects, and performing the calibrations to produce consistent multi-night datasets are considered. Applications of such calibrated datasets to binary orbit determination and stellar diameter measurements will be presented.
The Keck Interferometer is being developed by JPL and CARA as one of the ground-based components of NASA's Origins Program. The interferometer will combine the two 10-m Keck telescopes with four proposed 1.8-m outrigger telescopes located at the periphery of the Keck site on Mauna Kea. Incorporation of adaptive optics on the Keck telescopes with cophasing using an isoplanatic reference provides high sensitivity. Back-end instrumentation will include two-way combiners for cophasing and single-baseline measurements, a nulling combiner for high-dynamic range measurements, and a multi-way imaging combiner. Science objectives include the characterization of zodiacal dust around other stars, detection of hot Jupiters and brown dwarfs through multi- color differential-phase measurements, astrometric searches for planets down to Uranus-mass, and a wide range of IR imaging.
The Palomar Testbed Interferometer (PTI) is an infrared, phase-tracking interferometer in operation at Palomar Mountain since July 1995. It was funded by NASA for the purpose of developing techniques and methodologies for doing narrowangle astrometry for the purpose of detecting extrasolar planets. The instrument employs active fringe trackingin the infrared (2.0-2.4 μm) to monitor fringe phase. It is a dual-star interferometer; it is able to measure fringes on two separate stars simultaneously. An end-to-end heterodyne laser metrology system is used to monitor the optical path length of the starlight. Recently completed engineering upgrades have improved the initial instrument performance. These upgrades are:extended wavelength coverage, a single mode fiber for spatial filtering, vacuum pipes to relay the beams, accelerometers on the siderostat mirrors and a new baseline. Results of recent astrometry data indicate the instrument is approaching the astrometric limit as set by the atmosphere.
A key thrust of NASA's Origins program is the search for and detection of planetary systems about other stars. Pursuing this goal in a cost-effective and expedient manner from the ground has led NASA to begin work on the Keck Interferometer, which will add 4 1.8m 'outrigger' telescopes at the Keck Observatory on Mauna Kea. In addition to the imaging science to be performed by the Keck 10m telescopes with the outriggers, another one of the principal capabilities of the instrument will be the ability for the outriggers to conduct relative astrometry at the 25 microarcsecond level per root hour. Astrometry of this accuracy will enable the array to detect planetary systems composed of Uranus-mass or larger bodies orbiting at 5 AU solar mass stars at a distance of 20 pc; over 300 stars are to be surveyed by the outriggers annually. The astrometric capabilities of the Keck array can also be utilized other astrophysical investigations, such as characterization of spectroscopic binary orbits, and the measurement of the center-of-light shift of MACHO microlensing events, which will allow for a model-independent determinations of lens masses.
JPL and CARA are building a multi-element, IR interferometer for NASA to be situated at the twin Keck Observatories on Mauna Kea, Hawaii. Initially, the 10-m diameter Keck telescopes will be augmented with four fixed-location 2-m class outrigger telescopes resulting in 15 non-redundant baselines, the longest being approximately equals 110 m or nearly 5 X 10<SUP>7</SUP> ((lambda) /2.2micrometers )<SUP>-1</SUP> wavelengths. Fast adaptive optics and tip-tilt corrections will be used to phase up the Keck and outrigger apertures, respectively. The entire array will be co-phased by observing a relatively bright target on the photon rich Keck-Keck (K-K) and Keck- outrigger (K-O) baselines. When fully phased, the projected fringe phaser sensitivity for unresolved targets will be K- 22.0, 20.0 and 17.9 on the K-K, K-O and O-O baselines, respectively. Synthetic imaging capability will be available in the 1.6-10.0 micrometers atmospheric transmission bands at angular resolutions of 4.0 milli-arcseconds. In this article, we briefly outline the adopted methodology, imaging hardware, projected sensitivities and summarize the scientific potential of the instrument as an imaging interferometer.