20 research outputs found
Development of a scalable generic platform for adaptive optics real time control
The main objective of the present project is to explore the viability of an
adaptive optics control system based exclusively on Field Programmable Gate
Arrays (FPGAs), making strong use of their parallel processing capability. In
an Adaptive Optics (AO) system, the generation of the Deformable Mirror (DM)
control voltages from the Wavefront Sensor (WFS) measurements is usually
through the multiplication of the wavefront slopes with a predetermined
reconstructor matrix. The ability to access several hundred hard multipliers
and memories concurrently in an FPGA allows performance far beyond that of a
modern CPU or GPU for tasks with a well defined structure such as Adaptive
Optics control. The target of the current project is to generate a signal for a
real time wavefront correction, from the signals coming from a Wavefront
Sensor, wherein the system would be flexible to accommodate all the current
Wavefront Sensing techniques and also the different methods which are used for
wavefront compensation. The system should also accommodate for different data
transmission protocols (like Ethernet, USB, IEEE 1394 etc.) for transmitting
data to and from the FPGA device, thus providing a more flexible platform for
Adaptive Optics control. Preliminary simulation results for the formulation of
the platform, and a design of a fully scalable slope computer is presented.Comment: Paper presented as part of SPIE ICOP 2015 Conference Proceeding
UNICS - An Unified Instrument Control System for Small/Medium Sized Astronomical Observatories
Although the astronomy community is witnessing an era of large telescopes,
smaller and medium sized telescopes still maintain their utility being larger
in numbers. In order to obtain better scientific outputs it is necessary to
incorporate modern and advanced technologies to the back-end instruments and to
their interfaces with the telescopes through various control processes. However
often tight financial constraints on the smaller and medium size observatories
limit the scope and utility of these systems. Most of the time for every new
development on the telescope the back-end control systems are required to be
built from scratch leading to high costs and efforts. Therefore a simple, low
cost control system for small and medium size observatory needs to be developed
to minimize the cost and efforts while going for the expansion of the
observatory. Here we report on the development of a modern, multipurpose
instrument control system UNICS (Unified Instrument Control System) to
integrate the controls of various instruments and devices mounted on the
telescope. UNICS consists of an embedded hardware unit called Common Control
Unit (CCU) and Linux based data acquisition and User Interface. The Hardware of
the CCU is built around the Atmel make ATmega 128 micro-controller and is
designed with a back-plane, Master Slave architecture. The Graphical User
Interface (GUI) has been developed based on QT and the back end application
software is based on C/C++. UNICS provides feedback mechanisms which give the
operator a good visibility and a quick-look display of the status and modes of
instruments. UNICS is being used for regular science observations since March
2008 on 2m, f/10 IUCAA Telescope located at Girawali, Pune India.Comment: Submitted to PASP, 10 Pages, 5 figure
Robotic Laser-Adaptive-Optics Imaging of 715 Kepler Exoplanet Candidates using Robo-AO
The Robo-AO Kepler Planetary Candidate Survey is designed to observe every
Kepler planet candidate host star with laser adaptive optics imaging to search
for blended nearby stars, which may be physically associated companions and/or
responsible for transit false positives. In this paper we present the results
from the 2012 observing season, searching for stars close to 715 representative
Kepler planet candidate hosts. We find 53 companions, 44 of which are new
discoveries. We detail the Robo-AO survey data reduction methods including a
method of using the large ensemble of target observations as mutual
point-spread-function references, along with a new automated
companion-detection algorithm designed for large adaptive optics surveys. Our
survey is sensitive to objects from 0.15" to 2.5" separation, with contrast
ratios up to delta-m~6. We measure an overall nearby-star-probability for
Kepler planet candidates of 7.4% +/- 1.0%, and calculate the effects of each
detected nearby star on the Kepler-measured planetary radius. We discuss
several KOIs of particular interest, including KOI-191 and KOI-1151, which are
both multi-planet systems with detected stellar companions whose unusual
planetary system architecture might be best explained if they are "coincident
multiple" systems, with several transiting planets shared between the two
stars. Finally, we detect 2.6-sigma evidence for <15d-period giant planets
being 2-3 times more likely be found in wide stellar binaries than smaller
close-in planets and all sizes of further-out planets.Comment: Accepted by ApJ. Minor updates & improved statistical analysis; no
changes to results. 15 pages, 13 figure
The Robo-AO software: fully autonomous operation of a laser guide star adaptive optics and science system
Robo-AO is the first astronomical laser guide star adaptive optics (AO) system designed to operate completely
independent of human supervision. A single computer commands the AO system, the laser guide star, visible and
near-infrared science cameras (which double as tip-tip sensors), the telescope, and other instrument functions.
Autonomous startup and shutdown sequences as well as concatenated visible observations were demonstrated in
late 2011. The fully robotic software is currently operating during a month long demonstration of Robo-AO at
the Palomar Observatory 60-inch telescope
A survey of the high order multiplicity of nearby solar-type binary stars with Robo-AO
We conducted a survey of nearby binary systems composed of main sequence
stars of spectral types F and G in order to improve our understanding of the
hierarchical nature of multiple star systems. Using Robo-AO, the first robotic
adaptive optics instrument, we collected high angular resolution images with
deep and well-defined detection limits in the SDSS band. A total of 695
components belonging to 595 systems were observed. We prioritized observations
of faint secondary components with separations over to quantify the
still poorly constrained frequency of their sub-systems. Of the 214 secondaries
observed, 39 contain such subsystems; 19 of those were discovered with Robo-AO.
The selection-corrected frequency of secondary sub-systems with periods from
to days is 0.120.03, the same as the frequency of such
companions to the primary. Half of the secondary pairs belong to quadruple
systems where the primary is also a close pair, showing that the presence of
sub-systems in both components of the outer binary is correlated. The
relatively large abundance of 2+2 quadruple systems is a new finding, and will
require more exploration of the formation mechanism of multiple star systems.
We also targeted close binaries with periods less than 100~yr, searching for
their distant tertiary components, and discovered 17 certain and 2 potential
new triples. In a sub-sample of 241 close binaries, 71 have additional outer
companions. The overall frequency of tertiary components is not enhanced,
compared to all (non-binary) targets, but in the range of outer periods from
to days (separations on the order of 500~AU), the frequency
of tertiary components is 0.160.03, exceeding by almost a factor of two
the frequency of similar systems among all targets (0.09)
Bringing the Visible Universe into Focus with Robo-AO
The angular resolution of ground-based optical telescopes is limited by the degrading effects of the turbulent atmosphere. In the absence of an atmosphere, the angular resolution of a typical telescope is limited only by diffraction, i.e., the wavelength of interest, λ, divided by the size of its primary mirror's aperture, D. For example, the Hubble Space Telescope (HST), with a 2.4-m primary mirror, has an angular resolution at visible wavelengths of ~0.04 arc seconds. The atmosphere is composed of air at slightly different temperatures, and therefore different indices of refraction, constantly mixing. Light waves are bent as they pass through the inhomogeneous atmosphere. When a telescope on the ground
focuses these light waves, instantaneous images appear fragmented, changing as a function of time. As a result, long-exposure images acquired using ground-based telescopes - even telescopes with four times the diameter of HST - appear blurry and have an angular resolution of roughly
0.5 to 1.5 arc seconds at best. Astronomical adaptive-optics systems compensate for the effects of atmospheric turbulence. First, the shape of the incoming non-planar wave
is determined using measurements of a nearby bright star by a wavefront sensor. Next, an element in the optical system, such as a deformable mirror, is commanded to correct the shape of the incoming light wave. Additional corrections are made at a rate sufficient to keep up with the
dynamically changing atmosphere through which the telescope looks, ultimately producing diffraction-limited images.
The fidelity of the wavefront sensor measurement is based upon how well the incoming light is spatially and temporally sampled. Finer sampling requires brighter reference objects. While the brightest stars can serve as reference objects for imaging targets from several to tens of arc seconds away in the best conditions, most interesting astronomical targets do not have sufficiently bright stars nearby. One solution is to focus a high-power laser beam in the direction of the astronomical target to create an artificial reference of known shape, also known as a 'laser guide star'. The Robo-AO laser adaptive optics system employs a 10-W ultraviolet laser focused at a distance of 10 km to generate a laser guide star. Wavefront sensor measurements of the laser guide star drive the adaptive optics correction resulting in diffraction-limited images that have an angular resolution of ~0.1 arc seconds on a 1.5-m telescope
Know The Star, Know the Planet. IV. A Stellar Companion to the Host star of the Eccentric Exoplanet HD 8673b
HD 8673 hosts a massive exoplanet in a highly eccentric orbit (e=0.723).
Based on two epochs of speckle interferometry a previous publication identified
a candidate stellar companion. We observed HD 8673 multiple times with the 10 m
Keck II telescope, the 5 m Hale telescope, the 3.63 m AEOS telescope and the
1.5m Palomar telescope in a variety of filters with the aim of confirming and
characterizing the stellar companion. We did not detect the candidate
companion, which we now conclude was a false detection, but we did detect a
fainter companion. We collected astrometry and photometry of the companion on
six epochs in a variety of filters. The measured differential photometry
enabled us to determine that the companion is an early M dwarf with a mass
estimate of 0.33-0.45 M?. The companion has a projected separation of 10 AU,
which is one of the smallest projected separations of an exoplanet host binary
system. Based on the limited astrometry collected, we are able to constrain the
orbit of the stellar companion to a semi-major axis of 35{60 AU, an
eccentricity ? 0.5 and an inclination of 75{85?. The stellar companion has
likely strongly in uenced the orbit of the exoplanet and quite possibly
explains its high eccentricity.Comment: Accepted to the Astronomical Journal, 6 Pages, 5 Figure