In the context of the SPHERE planet finder project, we further develop and characterize a recently proposed
method for the efficient direct detection of exoplanets from the ground using spectral and angular differential
imaging. The method, called ANDROMEDA, combines images appropriately into "pseudo-data", then uses all
of them in a Maximum-Likelihood framework to estimate the position and flux of potential planets orbiting
the observed star. The method's performance is assessed on realistic simulations of images performed by the
SPHERE consortium, and it is applied to experimental data taken by the VLT/NAOS-CONICA instrument.
HiCIAO is a near-infrared, high contrast instrument which is specifically designed for searches and studies for
extrasolar planets and proto-planetary/debris disks on the Subaru 8.2 m telescope. A coronagraph technique
and three differential observing modes, i.e., a dual-beam simultaneous polarimetric differential imaging mode,
quad-beam simultaneous spectral differential imaging mode, and angular differential imaging mode, are used
to extract faint objects from the sea of speckle around bright stars. We describe the instrument performances
verified in the laboratory and during the commissioning period. Readout noise with a correlated double sampling
method is 15 e- using the Sidecar ASIC controller with the HAWAII-2RG detector array, and it is as low as 5 e-
with a multiple sampling method. Strehl ratio obtained by HiCIAO on the sky combined with the 188-actuator
adaptive optics system (AO188) is 0.4 and 0.7 in the H and K-band, respectively, with natural guide stars that
have R ~ 5 and under median seeing conditions. Image distortion is correctable to 7 milli-arcsec level using
the ACS data as a reference image. Examples of contrast performances in the observing modes are presented
from data obtained during the commissioning period. An observation for HR 8799 in the angular differential
imaging mode shows a clear detection of three known planets, demonstrating the high contrast capability of
We present on-sky performance results of a new technique, speckle stabilization, with the Stabilized sPeckle
Integral Field Spectrograph Proof-Of-Concept (SPIFS-POC) instrument. The SPIFS-POC is an optical-imaging
instrument capable of high spatial resolutions much finer than the seeing-limit. It achieves this aim by measuring
speckle patterns in real time (through the use of an L3CCD), finding the highest quality speckle, and stabilizing
it onto a traditional, low readout speed science camera through the use of a fast steering mirror. This process
is repeated at ≈100 Hz over the course of long exposures resulting in a high-resolution core surrounded by a
diffuse halo. We show that in the Sloan z' bands, SPIFS is able to acquire spatial resolutions much greater than
the seeing limit, even approaching 3λ/D. We also discuss improvements for the next phase of the SPIFS project
where we fully expect to be able to recover diffraction-limited spatial resolutions in the optical.
We present the results of performance simulations characterizing the Stabilized sPeckle Integral Field Spectrograph (SPIFS). Our simulations of images distorted by Kolmogorov atmospheric turbulence confirm that stabilization of the single brightest speckle via a fast steering mirror (FSM) produces near-diffraction-limited spatial resolution for the red part of the visible spectrum (0.6 μm-1.0 μm). On a 10-meter class telescope this corresponds to an angle of ~13 mas. We also demonstrate that the Strehl ratio of the stabilized speckle will be between 1 and 3% for r0 = 20cm on a 10-meter class telescopes. The guide star limiting magnitude, through the use of a shutter, will be I=16.5. Simulations also reveal that the guide star can be as far away as 20" from the source and still recover tip-tilt information to drive SPIFS.
We describe an instrument concept and basic feasibility study for a new observational technique which we call
Stabilized-sPeckle Integral Field Spectroscopy (SPIFS). SPIFS will enable, under certain observational conditions and
constraints, low-to-modest-Strehl diffraction-limited imaging spectroscopy from large ground-based telescopes in the
optical bandpass (i.e. V, R, and I bands). SPIFS is capable of exploring important scientific niches which are not
currently available using existing high angular resolution techniques such as adaptive optics or speckle imaging, using
existing, relatively-inexpensive technology. Based on our simulations presented in a companion paper (Keremedjiev,
Eikenberry & Carson, 2008), SPIFS can provide integral field spectroscopy at ~15-mas resolution and ~3% Strehl over
the I-band with sky coverage of ~20% to 100% in the Galactic Plane and ~5% at the Galactic poles. We present an
overview of the SPIFS technique and simulated performance in realistic observations of the microquasar SS 433 to
demonstrate one simple example of the power of SPIFS.
We summarize here an experimental frame combination pipeline we developed for ultra high-contrast imaging with
systems like the upcoming VLT SPHERE instrument. The pipeline combines strategies from the Drizzle technique, the
Spitzer IRACproc package, and homegrown codes, to combine image sets that may include a rotating field of view and
arbitrary shifts between frames. The pipeline is meant to be robust at dealing with data that may contain non-ideal
effects like sub-pixel pointing errors, missing data points, non-symmetrical noise sources, arbitrary geometric distortions,
and rapidly changing point spread functions. We summarize in this document individual steps and strategies, as well as
results from preliminary tests and simulations.
We present a status report on a study on the effects of instrumental polarization on the fine structure of the stellar point spread function (PSF). These effects are important to understand because the the aberration caused by instrumental polarization on an otherwise diffraction-limited PSF will likely have have severe consequences for extreme high contrast imaging systems such as NASA's proposed Terrestrial Planet Finder (TPF) mission and the proposed NASA Eclipse mission. The report here, describing our efforts to examine these effects, includes two parts: 1) a numerical analysis of the effect of metallic reflection, with some polarization-specific retardation, on a spherical wavefront; 2) an experimental approach for observing this effect, along with a status report on preliminary laboratory results. The numerical analysis indicates that the inclusion of polarization-specific phase effects (retardation) results in a point spread function (PSF) aberration more severe than the amplitude (reflectivity) effects previously recorded in the literature. Preliminary in-lab results are consistent with our numerical predictions.
We present here results from an experimental and theoretical study in the use of graded focal-plane occulting masks to improve high-contrast astronomical imaging at near-infrared wavelengths. The study includes investigations of both high-energy beam sensitive (HEBS) glass (a product of Canyon Materials, San Diego, CA) and binary notch-filter technologies to create precision graded occulting masks. In conjunction with this investigation, we conduct computer simulations showing expected high-contrast levels for various graded masks being considered for installation in the PHARO camera of the Palomar 200-inch (5m) Hale Telescope Adaptive Optics (AO) system. Our results demonstrate that the implementation of a graded exponential mask in the Palomar system should improve high-contrast sensitivities by about 2.4-mag in K-band (2.0-2.4 μm), for 0.75-1.5 arcsec separations. We also demonstrate that both HEBS and binary notch-filter technologies present adequate platforms for necessary occulting requirements. We conclude with a discussion of theinsights our study yields for planned space-based high-contrast observatories such as NASA's planned Terrestrial Planet Finder Coronagraph (TPF-C) and the proposed Eclipse mission.
The availability of both large aperture telescopes and large
format near-infrared (NIR) detectors are making wide-field NIR
imaging a reality. We describe the Wide-field Infrared Camera
(WIRC), a newly commissioned instrument that provides the Palomar
200-inch telescope with such an imaging capability. WIRC features
a field-of-view (FOV) of 4.33 arcminutes on a side with its
currently installed 1024-square Rockwell Hawaii-I NIR detector. A
2048-square Rockwell Hawaii-II NIR detector will be installed and
commissioned later this year, in collaboration with Caltech, to
give WIRC an 8.7 arcminute FOV on a side. WIRC mounts at the
telescope's f/3.3 prime focus. The instrument's seeing-limited
optical design, optimized for the JHK atmospheric bands,
includes a 4-element refractive collimator, two 7-position filter
wheels that straddle a Lyot stop, and a 5-element refractive f/3
camera. Typical seeing-limited point spread functions are slightly
oversampled with a 0.25 arcsec per pixel plate scale at the detector. The entire optical train is contained within a cryogenic dewar with a 2.5 day hold-time. Entrance hatches at the top of the dewar allow access to the detector without disruption of the optics and optical alignment. The optical, mechanical, cryogenic, and electronic design of the instrument are described, a commissioning science image and performance analyses are presented.