From 2008 December to 2012 September, the NICI (Near-Infrared Coronagraphic Imager at the Gemini-South 8.1-m) Planet-Finding Campaign (Liu et al. 2010) obtained deep, high-contrast AO imaging of a carefully selected sample of over 200 young, nearby stars. In the course of the campaign, we discovered four co-moving brown dwarf companions: PZ Tel B (36±6 MJup, 16.4±1.0 AU), CD-35 2722B (31±8 MJup, 67±4 AU), HD 1160B (33+12 -9 MJup, 81± AU), and HIP 79797Bb (55+20-19MJup, 3 AU from the previously known brown dwarf companion HIP 79797Ba), as well as numerous stellar binaries. Three survey papers have been published to date, covering: 1) high mass stars (Nielsen et al. 2013), 2) debris disk stars (Wahhaj et al. 2013), and 3) stars which are members of nearby young moving groups (Biller et al. 2013). In addition, the Campaign has yielded new orbital constraints for the ~8-10 MJup planet Pic β (Nielsen et al. 2014) and a high precision measurement of the star-disk offset for the well-known disk around HR 4796A (Wahhaj et al. 2014). Here we discuss constraints placed on the distribution of wide giant exoplanets from the NICI Campaign, new substellar companion discoveries, and characterization both of exoplanets and circumstellar disks.
The Hokupa’a-85 curvature adaptive optics system components have been adapted to create a new AO-corrected
coud´e instrument at the 3.67m Advanced Electro-Optical System (AEOS) telescope. This new AO-corrected
optical path is designed to deliver an f/40 diffraction-limited focus at wavelengths longer than 800nm. A new
EMCCD-based dual-beam imaging polarimeter called InnoPOL has been designed and is presently being installed
behind this corrected f/40 beam. The InnoPOL system is a flexible platform for optimizing polarimetric
performance using commercial solutions and for testing modulation strategies. The system is designed as a
technology test and demonstration platform as the coud´e path is built using off-the-shelf components wherever
possible. Models of the polarimetric performance after AO correction show that polarization modulation at rates
as slow as 200Hz can cause speckle correlations in brightness and focal plane location sufficient enough to change
the speckle suppression behavior of the modulators. These models are also verified by initial EMCCD scoring
camera data at AEOS. Substantial instrument trades and development efforts are explored between instrument
performance parameters and various polarimetric noise sources.
Our team is carrying out a multi-year observing program to directly image and characterize young extrasolar
planets using the Near-Infrared Coronagraphic Imager (NICI) on the Gemini-South 8.1-meter telescope. NICI
is the first instrument on a large telescope designed from the outset for high-contrast imaging, comprising a
high-performance curvature adaptive optics (AO) system with a simultaneous dual-channel coronagraphic imager.
Combined with state-of-the-art AO observing methods and data processing, NICI typically achieves ≈2
magnitudes better contrast compared to previous ground-based or
space-based planet-finding efforts, at separations
inside of ≈2". In preparation for the Campaign, we carried out efforts to identify previously unrecognized
young stars as targets, to develop a rigorous quantitative method for constructing our observing strategy, and to
optimize the combination of angular differential imaging and spectral differential imaging. The Planet-Finding
Campaign is in its second year, with first-epoch imaging of 174 stars already obtained out of a total sample of
300 stars. We describe the Campaign's goals, design, target selection, implementation, on-sky performance, and
preliminary results. The NICI Planet-Finding Campaign represents the largest and most sensitive imaging survey
to date for massive
(>~ 1 MJup) planets around other stars. Upon completion, the Campaign will establish the best
measurements to date on the properties of young gas-giant planets at
-> 5-10 AU separations. Finally, Campaign
discoveries will be well-suited to long-term orbital monitoring and detailed spectrophotometric followup with
next-generation planet-finding instruments.
The effect of measurement noise on the phase reconstruction is here analyzed for curvature sensors. It is shown,
that for a fixed extra-focal distance the phase variance depends only on the number of photons and is independent
of the number of sensing elements.
The error propagation factor is further computed for three different sampling geometries: square and hexagonal
grids and the polar geometry commonly used for curvature sensors. The error propagation factor is seen to
be almost independent of the grid geometry.
CanariCam is the facility multi-mode mid-IR camera developed by the University of Florida for the 10-meter Gran
Telescopio Canarias (GTC) on La Palma. CanariCam has four science modes that provide the GTC community with an
especially powerful research tool for imaging, grating spectroscopy, coronagraphy, and dual-beam polarimetry.
Instrument commissioning in the laboratory at the University of Florida indicates that all modes perform as required, and
the next step is on-telescope commissioning. After commenting on the instrument status, we will review key features of
each of these science modes, with emphasis on illustrating each mode with science examples that put the system
performance, particularly the anticipated sensitivity, into perspective.
We discuss observing strategy for the Near Infrared Coronagraphic Imager (NICI) on the 8-m Gemini South
telescope. NICI combines a number of techniques to attenuate starlight and suppress superspeckles: 1) coronagraphic
imaging, 2) dual channel imaging for Spectral Differential Imaging (SDI) and 3) operation in a fixed
Cassegrain rotator mode for Angular Differential Imaging (ADI). NICI will be used both in service mode and
for a dedicated 50 night planet search campaign. While all of these techniques have been used individually in
large planet-finding surveys, this is the first time ADI and SDI will be used with a coronagraph in a large survey.
Thus, novel observing strategies are necessary to conduct a viable planet search campaign.
The goal of this project is to achieve exquisite image quality over the largest possible field of view, with a goal of a
FWHM of not more than 0.3" over a square degree field in the optical domain. The narrow PSF will allow detection of
fainter sources in reasonable exposure times. The characteristics of the turbulence of Mauna Kea, a very thin ground
layer with excellent free seeing allows very wide fields to be corrected by GLAO and would make such an instrument
unique. The Ground Layer AO module uses a deformable mirror conjugated to the telescope pupil. Coupled with a high
order WFS, it corrects the turbulence common to the entire field. Over such large fields the probability of finding
sufficiently numerous and bright natural guide sources is high, but a constellation of laser beacons could be considered
to ensure homogeneous and uniform image quality.
The free atmosphere seeing then limits the image quality (50% best conditions: 0.2" to 0.4"). This can be further
improved by an OTCCD camera, which can correct local image motion on isokinetic scales from residual high altitude
tip-tilt. The advantages of the OTCCD are not limited to improving the image quality: a Panstarrs1 clone covers one
square degree with 0.1" sampling, in perfect accordance with the scientific requirements. The fast read time (6 seconds
for 1.4 Gpixels) also leads to an improvement of the dynamic range of the images. Finally, the guiding capabilities of
the OTCCD will provide the overall (local and global) tip-tilt signal.
We present the coronagraphic and adaptive optics performance of the Gemini-South Near-Infrared Coronagraphic Imager (NICI). NICI includes a dual-channel imager for simultaneous spectral difference imaging, a dedicated 85-element curvature adaptive optics system, and a built-in Lyot coronagraph. It is specifically designed to survey for and image large extra-solar gaseous planets on the Gemini Observatory 8-meter telescope in Chile. We present the on-sky performance of the individual subsystems along with the end-to-end contrast curve. These are compared to our model predictions for the adaptive optics system, the coronagraph, and the spectral difference imaging.
CanariCam is the facility multi-mode mid-IR camera developed by the University of Florida (UF) for the 10.4-
meter Gran Telescopio Canarias (GTC). CanariCam contains a 320 × 240-pixel Raytheon array, which will
Nyquist-sample the diffraction-limited point-spread-function at wavelengths longer than 8 microns, yielding a
field of view of 26"×19". In Aug. 2007, the University of Florida instrument team held a successful Acceptance
Testing (AT) of CanariCam. We describe key performance requirements, and compare these to the actual performance
during formal AT. Among the results considered are detector noise characteristics, image quality, and
throughput. We focus particularly on the unique dual-beam polarimetric modes. We have demonstrated that
with a half-wave plate, it achieves or exceeds the design goals for imaging both polarization planes simultaneously.
The Near-Infrared Coronagraphic Imager (NICI) is a high-contrast AO imager at the
Gemini South telescope. The camera includes a coronagraphic mask and dual channel imaging
for Spectral Differential Imaging (SDI). The instrument can also be used in a fixed Cassegrain
Rotator mode for Angular Differential Imaging (ADI). While coronagraphy, SDI, and ADI have
been applied before in direct imaging searches for exoplanets. NICI represents the first time that
these 3 techniques can be combined. We present preliminary NICI commissioning data using
these techniques and show that combining SDI and ADI results in significant gains.
The Mauna Kea Observatory offers a unique opportunity to build a large and sensitive interferometer. Seven telescopes have diameters larger than 3 meters and are or may be equipped with adaptive optics systems to correct phase perturbations induced by atmospheric turbulence. The maximum telescope separation of 800 meters can provide an angular resolution as good as 0.25 milli-arcseconds in the J band. The large pupils and long baselines make 'OHANA very complementary to existing large optical interferometers. From an astrophysical point of view, it opens the way to imaging of the central part of faint and compact objects such as active galactic nuclei and young stellar objects. On a technical point of view, it opens the way to kilometric or more arrays by propagating light in single-mode fibers. First instruments have been built and tested successfully at CFHT, Keck I and Gemini to inject light into single-mode fibers thus partly completing Phase I of the project. Phase II is now on-going with the prospects of the first combinations of Keck I - Keck II in 2004 and Gemini - CFHT in 2005.
The University of Florida is developing a mid-infrared camera for the 10.4-meter Gran Telescopio CANARIAS. CanariCam has four science modes and two engineering modes, which use the same 320 x 240-pixel, arsenic-doped silicon, blocked-impurity-band detector from Raytheon. Each mode can be remotely selected quickly during an observing sequence. The pixel scale is 0.08 arcsec, resulting in Nyquist sampling of the diffraction-limited point-spread-function at 8 μm, the shortest wavelength for which CanariCam is optimized. The total available field of view for imaging is 26 arcsec x 19 arcsec. The primary science mode will be diffraction-limited imaging using one of several available spectral filters in the 10 μm (8-14 μm) and 20 μm (16-25 μm) atmospheric windows. Any one of four plane gratings can be inserted for low and moderate-resolution (R = 100 - 1300) slit spectroscopy in the 10 and 20-μm regions. Insertion of appropriate field and pupil stops converts the camera into a coronagraph, while insertion of an internal rotating half-wave plate, a field mask, and a Wollaston prism converts the camera into a dual-beam polarimeter.
The Near Infrared Coronagraphic Imager for Gemini South (NICI) is a dual beam coronagraphic camera operating over the 1.0 to 5.5 micrometer wavelength range with a dedicated adaptive optics system. NICI target science, design and capabilities will be described as an introduction to this instrument slated for deployment in mid 2005.
The Jovian Planet Finder (JPF) is a proposed NASA MIDEX mission to place a highly optimized coronagraphic telescope on the International Space Station (ISS) to image Jupiter-like planets around nearby stars. The optical system is an off-axis, unobscured telescope with a 1.5 m primary mirror. A classical Lyot coronagraph with apodized occulting spots is used to reduce diffracted light from the central star. In order to provide the necessary contrast for detection of a planet, scattered light from mid-spatial-frequency errors is reduced by using super-smooth optics. Recent advances in polishing optics for extreme-ultraviolet lithography have shown that a factor of >30 reduction in midfrequency errors relative to those in the Hubble Space Telescope is possible (corresponding to a reduction in scattered light of nearly 1000x). The low level of scattered and diffracted light, together with a novel utilization of field rotation introduced by the alt-azimuth ISS telescope mounting, will provide a relatively low-cost facility for not only imaging extrasolar planets, but also circumstellar disks, host galaxies of quasars, and low-mass substellar companions such as brown dwarfs.
Eclipse is a proposed Discovery-class mission to perform a sensitive imaging survey of nearby planetary systems, including a complete survey for Jupiter-sized planets orbiting 5 AU from all stars of spectral types A-K to distances of 15 pc. Eclipse is a coronagraphic space telescope concept designed for high-contrast visible wavelength imaging and spectrophotometry. Its optical design incorporates essential elements: a telescope with an unobscured aperture of 1.8 meters and optical surfaces optimized for smoothness at critical spatial frequencies, a coronagraphic camera for suppression of diffracted light, and precision active optical correction for suppression of light scattered by residual mirror surface irregularities. For reference, Eclipse is predicted to reduce diffracted and scattered starlight between 0.25 and 2.0 arcseconds from the star by at least three orders of magnitude compared to any HST instrument. The Eclipse mission offers precursor science explorations and critical technology validation in
support of coronagraphic concepts for NASA's Terrestrial Planet Finder (TPF). A baseline three-year science mission would provide a survey of the nearby stars accessible to TPF before the end of this decade, promising fundamental new insights into the nature and evolution of possibly diverse planetary systems associated with our Sun's nearest neighbors.
All existing night-time astronomical telescopes, regardless of aperture, are blind to an important part of the universe - the region around bright objects. Technology now exist to build an unobscured 6.5 m aperture telescope which will attain coronagraphic sensitivity heretofore unachieved. A working group hosted by the University of Hawaii Institute for Astronomy has developed plans for a New Planetary Telescope which will permit astronomical observations which have never before ben possible. In its narrow-field mode the off-axis optical design, combined with adaptive optics, provides superb coronagraphic capabilities, and a very low thermal IR background. These make it ideal for studies of extra-solar planets and circumstellar discs, as well as for general IR astronomy. In its wide-field mode the NPT provides a 2 degree diameter field for surveys of Kuiper Belt Objects and Near-Earth Objects, surveys central to current intellectual interests in solar system astronomy.
Imaging planets, brown dwarfs and disks around nearby stars is a challenging endeavor due to the required scene contrast. Success requires imaging down to m equals 20-25 within arcseconds of stars that are 4th-6th magnitude. Light scattered and diffracted from a variety of sources increases the background flux in the area of interest by orders of magnitude masking the target objects. As first shown by M. B. Lyot in 1939 masks can be placed in the focal pane and pupil planes of a camera to occult the bright central source making it possible to image the faint extensions around it. CoCo is an experiment in using a coronagraphic camera, for IR observations, on a large telescope in an effort to understand how a coronagraph can help and how to properly design one of the new generation of large telescopes. Recent result with CoCo show a factor of 5-10 reduction in background levels in the area from 2-7 arcseconds from the central object. This paper will describe those result and summarize what has been learned towards building coronagraphic cameras for today's large telescopes.
During the second servicing mission of the Hubble Space Telescope (HST), a newly refurbished fine guidance sensor (FGS-1R) was installed into the telescope's Radial Bay No. 1. The successful replacement of the existing FGS-1, whose degraded Star Selector Servo bearings were affecting the scheduling and acquisition of science data, was critical to continued success of the observatory. In addition to solving the bearing problem, the refurbished FGS-1R also provided an innovative approach to minimize the effects of spherical aberration on the interferometric signal generate by the FGS, hereafter referred to as an s-curve. Rather than try to remove the aberration from the wavefront over a very large field of view, FGS-1R was given the capability to realign the beam to the Koester's prism. A symmetric error, such as spherical aberration, which is divided perfectly at the beam center and folded onto itself, will have the effects of the aberration canceled. To this end, FGS-1R's FOld Flat No. 3 was retrofit with an Actuated Mechanisms Assembly (AMA), which allows on orbit correction of the beam alignment. This paper gives an overview of the theory of operation of the FGS, and characterizes the effects of spherical aberration on s-curve modulation. It discusses the theory of operation of the AMA, and how it is used to optimize the optical alignment. It describes the analysis tools and methods used to transform on orbit data into required adjustments of the AMA. Finally, it presents the result of the on orbit optimization of s-curve modulation, and briefly discusses some of the challenges faced in refurbishing the next FGS.
To achieve the highest accuracy boresight pointing performance the Hubble Space Telescope uses attitude feedback from the Fine Guidance Sensors (FGS). There are three FGS's on board HST. During normal operations, one sensor monitors spacecraft pitch and yaw, another monitors roll and the third is the redundant unit. Each FGS senses wavefront tilt interferometrically and converts that tilt into spacecraft pointing error. The presence of spherical aberration affects the signal from the instrument causing a reduction in acquisition and tracking performance on targets whose magnitudes are fainter than 14. This paper documents the efforts to optimize uplinkable, FGS parameters in order to increase the probability of target acquisition that is better than 98 percent over the entire field of view. To this end, the paper describes the Monte Carlo simulator used in deriving the optimized values for the FGS acquisition and discusses methods for testing the new parameters prior to on-orbit verification. It reports on improvements predicted by the acquisition simulator and evaluates on orbit performance with the optimized values. In addition, the paper discusses the commissioning of FGS 1R, installed during the February 1997 servicing mission, with regard to operational options predicted by the simulator. It also reports on how well the new FGS, with its on board alignment capability, is working with the new acquisition parameters determined by the simulator.
This paper describes the design of an IR cold coronagraph (CoCo) built by SETS Technology, Inc., for use at the NASA 3 m IR Telescope Facility (IRTF) at Mauna Kea Observatory, for the imaging of faint IR sources in proximity to bright sources. The coronagraph is designed to obtain high contrast photometric images by use of an occulting mask and a pupil mask. The coronagraph is to be used in combination with the IRTF NSFCAM, which covers 1-5 micrometers and uses a 256x256 InSb array. The platescale can be varied from 0.06'/pixel to 0.15'/pixel, covering a field of view of 14' and 38', respectively. Selectable apodized and hard occulting masks are mounted on a wheel as the first element in the system to reduce scattered light. Selectable pupil masks are cooled to 77K within the CoCo cryostat. The cryostat consists of a liquid nitrogen can for cooling the optics, masks, and baffles. The CoCo dewar is mounted on a slide in a housing to allow it to move out of the beam path so that the NSFCAM may be used with or without the coronagraph during the same observing period.
In order to explore the nature of the limits on direct extrasolar planet detection we have generated high accuracy broadband background models for several different cases. The simplest assumes an ideal diffraction limited background with shot and read noise errors. More complex models based on phase error maps drawn from real metrology data include the effects of scatter in the optical system. To these backgrounds a planet image can be added at various relative intensity levels. In the simples case, the background dominated by ideal diffraction is so smooth that a median filter is very effective at removing it locally, permitting planet detection at the limits of the flat field error of the detector. The use of more complex filters for the scatter limited case will be discussed.
The Astrometric Imaging Telescope will detect extra-solar planetary systems with imaging and astrometry. The optical system contains a high-efficiency coronagraph and scatter-compensated mirrors to detect Jupiter-size planets around nearby stars. The optical system also is distortion free, tolerant to misalignments, and tolerant to optical surface contamination. This allows for the astrometric precision to detect Uranus-mass planets. A focal plane guider and fine guidance sensor are other elements of the optical design.
Polarization analysis software that employs Jones matrix formalism to calculate the polarization sensitivity of an instrument design was developed at Hughes Danbury Optical Systems. The code is capable of analyzing the full ray bundle at its angles of incidence for each optical surface. Input is based on the system ray trace and the thin film coating design at each surface. The MODIS-N (Moderate Resolution Imaging Spectrometer) system is used to demonstrate that it is possible to meet stringent requirements on polarization insensitivity associated with planned remote sensing instruments. Analysis indicates that a polarization sensitivity less than or equal to 2 percent was achieved in all desired spectral bands at all pointing angles, per specification. Polarization sensitivities were as high as 10 percent in similar remote sensing instruments.
The sensitivity of image quality to various system and subsystem parameters has been studied in order to determine the utility of imaging phased telescope arrays to wide field of view (FOV) applications. An error budget tree is developed to include optical design errors, assembly and alignment errors, optical fabrication errors, and environmental errors. Trade studies, parametric analyses, and previous engineering experience permitted the derivation of design and engineering tolerances from error budget allocations based on known state-of-the-art performance characteristics. The FOV limitations of the residual optical design errors (off-axis aberrations) are investigated in detail. It is shown that the somewhat benign (for conventional optical systems) aberration of field curvature results in field-dependent relative phase (piston) and pointing (tilt) errors, which rapidly degrades the image quality of phased telescope arrays as the FOV is increased. Thus extremely light tolerances on residual field curvature are needed for telescope diameters larger than one meter.
The enhanced reflectance achieved by recent developments in x-ray multilayer technology has made normal-incidence x-ray/EUV telescopes feasible for many applications of interest. Conventional optical designs with obvious advantages over the somewhat cumbersome grazing incidence designs of Kirkpatrick, Baez, and Wolter can thus be utilized. Preliminary results of actual flight data suggest great promise of scientific achievement from this new technology. It is widely recognized that "supersmooth"
substrates are required since microroughness can decimate the reflectance of the multilayer. However, high x-ray reflectance is a necessary but not sufficient condition for producing high quality images. A second and equally important condition is the ability to concentrate the reflected radiation in a very small region in the focal plane. Optical substrates with satisfactory "figure" and "finish" for x-ray/EUV applications have been successfully demonstrated. However, small angle scatter from
"mid spatial frequency" optical fabrication errors will limit the practical resolution attainable from this promising new technology. The surface
power spectral density function over the entire range of relevant spatial frequencies is thus required to accurately predict image characteristics.
The results of parametric optical performance predictions indicate that subarcsecond resolution is possible provided sufficiently smooth layer
interfaces are maintained. However, optical fabrication tolerances imposed on the substrate may require advances over the current state of the art.