1,516 research outputs found
Wavefront sensing with a brightest pixel selection algorithm
Astronomical adaptive optics systems with open-loop deformable mirror control
have recently come on-line. In these systems, the deformable mirror surface is
not included in the wavefront sensor paths, and so changes made to the
deformable mirror are not fed back to the wavefront sensors. This gives rise to
all sorts of linearity and control issues mainly centred on one question: Has
the mirror taken the shape requested? Non-linearities in wavefront measurement
and in the deformable mirror shape can lead to significant deviations in mirror
shape from the requested shape. Here, wavefront sensor measurements made using
a brightest pixel selection method are discussed along with the implications
that this has for open-loop AO systems. Discussion includes elongated laser
guide star spots and also computational efficiency.Comment: 10 pages, 12 figures, accepted by MNRA
MECHANICALLY ASSISTED LANDMINE CLEARANCE AND DETECTION
In response to worldwide requirements for Humanitarian Demining, Schiebel Technology, Inc., an independent U.S. based corporation, has focused on the research, development, and production of the CAMCOPTER Unmanned Aerial Vehicle System particularly germane to mechanically assisted landmine detection and clearance
Empirical Study of Simulated Two-planet Microlensing Event
We undertake the first study of two-planet microlensing models recovered from
simulations of microlensing events generated by realistic multi-planet systems
in which 292 planetary events including 16 two-planet events were detected from
6690 simulated light curves. We find that when two planets are recovered, their
parameters are usually close to those of the two planets in the system most
responsible for the perturbations. However, in one of the 16 examples, the
apparent mass of both detected planets was more than doubled by the unmodeled
influence of a third, massive planet. This fraction is larger than, but
statistically consistent with, the roughly 1.5% rate of serious mass errors due
to unmodeled planetary companions for the 274 cases from the same simulation in
which a single planet is recovered. We conjecture that an analogous effect due
to unmodeled stellar companions may occur more frequently. For seven out of 23
cases in which two planets in the system would have been detected separately,
only one planet was recovered because the perturbations due to the two planets
had similar forms. This is a small fraction (7/274) of all recovered
single-planet models, but almost a third of all events that might plausibly
have led to two-planet models. Still, in these cases, the recovered planet
tends to have parameters similar to one of the two real planets most
responsible for the anomaly.Comment: 21 pages, 9 figures, 2 tables; submitted to ApJ; for a short video
introducing the key results, see https://www.youtube.com/watch?v=qhK4a6sbfO
An aperture masking mode for the MICADO instrument
MICADO is a near-IR camera for the Europea ELT, featuring an extended field
(75" diameter) for imaging, and also spectrographic and high contrast imaging
capabilities. It has been chosen by ESO as one of the two first-light
instruments. Although it is ultimately aimed at being fed by the MCAO module
called MAORY, MICADO will come with an internal SCAO system that will be
complementary to it and will deliver a high performance on axis correction,
suitable for coronagraphic and pupil masking applications. The basis of the
pupil masking approach is to ensure the stability of the optical transfer
function, even in the case of residual errors after AO correction (due to non
common path errors and quasi-static aberrations). Preliminary designs of pupil
masks are presented. Trade-offs and technical choices, especially regarding
redundancy and pupil tracking, are explained.Comment: SPIE 2014 Proceeding -- Montrea
Collagenases and aggrecanases: understanding the role of non-catalytic domains in cartilage matrix breakdown
Adaptive Optics for Astronomy
Adaptive Optics is a prime example of how progress in observational astronomy
can be driven by technological developments. At many observatories it is now
considered to be part of a standard instrumentation suite, enabling
ground-based telescopes to reach the diffraction limit and thus providing
spatial resolution superior to that achievable from space with current or
planned satellites. In this review we consider adaptive optics from the
astrophysical perspective. We show that adaptive optics has led to important
advances in our understanding of a multitude of astrophysical processes, and
describe how the requirements from science applications are now driving the
development of the next generation of novel adaptive optics techniques.Comment: to appear in ARA&A vol 50, 201
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