Adaptive Optics

Rotating RAdio Transients" (RRATs) are a newly discovered astronomical phenomenon, characterised by occasional brief radio bursts, with average intervals between bursts ranging from minutes to hours. The burst spacings allow identification of periodicities, which fall in the range 0.4 to 7 seconds. The RRATs thus seem to be rotating neutron stars, albeit with properties very different from the rest of the population. We here present the serendipitous detection with the Chandra Xray Observatory of a bright point-like X-ray source coincident with one of the RRATs. We discuss the temporal and spectral properties of this X-ray emission, consider counterparts in other wavebands, and interpret these results in the context of possible explanations for the RRAT population.

GMTNIRS, the Giant Magellan Telescope near-infrared spectrograph, is a first-generation instrument for the GMT that will provide detailed spectroscopic information about young stellar objects, exoplanets, and cool and/or obscured stars. The optical and mechanical design GMTNIRS presented at a conceptual design review in October 2011 covered all accessible parts of the spectrum from 1.12 to 5.3 microns at R=50,000 (1.12-2.5 microns) and R=100,000 (3-5.3 microns). GMTNIRS uses the GMT adaptive-optics system and has a single 85 milliarcsecond slit. The instrument includes five separate spectrographs for the different atmospheric windows. By use of dichroics that divide the incident light between five separate spectrographs, it observes its entire spectral grasp in a single exposure while having only one cryogenic moving part, a rotating pupil stop. Large, highly accurate silicon immersion gratings are critical to GMTNIRS, since they both permit a design within the allowable instrument volume and enable continuous wavelength coverage on existing detectors. We describe the effort during the preliminary design phase to refine the design of the spectrograph to meet the science goals while minimizing the cost and risk involved in the grating production. We discuss different design options for the individual spectrographs at R=50,000, 67,000, 75,000, and 100,000 and their impact on science return.

The goal of this unit was to consolidate the project for the construction of the high resolution spectrometer of the E-ELT (HIRES). The task included the development of scientific cases and tools to predict the instrumental performances. From the technical point of view it included several R&D activities in collaboration with highly specialized Italian companies; it culminated with the detailed design of a highly modular instrument based on well established technologies. From the management point of view it lead to the consolidation of a large international consortium that spans over 12 countries and includes most of the European and ESO-related institutes interested in high resolution spectroscopy.

We present Hα integral field spectroscopy of well resolved, UV/optically selected z~2 star-forming galaxies as part of the SINS survey with SINFONI on the ESO VLT. Our laser guide star adaptive optics and good seeing data show the presence of turbulent rotating star forming rings/disks, plus central bulge/inner disk components, whose mass fractions relative to total dynamical mass appears to scale with [NII]/Hα flux ratio and 'star formation' age. We propose that the buildup of the central disks and bulges of massive galaxies at z~2 can be driven by the early secular evolution of gas-rich 'proto'-disks. High redshift disks exhibit large random motions. This turbulence may in part be stirred up by the release of gravitational energy in the rapid 'cold' accretion flows along the filaments of the cosmic web. As a result dynamical friction and viscous processes proceed on a time scale of <1 Gyr, at least an order of magnitude faster than in z~0 disk galaxies. Early secular evolution thus drives gas and stars into the central regions and can build up exponential disks and massive bulges, even without major mergers. Secular evolution along with increased efficiency of star formation at high surface densities may also help to account for the short time scales of the stellar buildup observed in massive galaxies at z~2.

The purpose of this study was to use wavefront sensing as an objective method to detect and assess dynamic accommodation in subjects with accommodative dysfunctions and symptoms related to near-vision tasks. Sixty-three subjects were divided into control (N = 18), symptomatic without any accommodative dysfunction (SWD) (N = 18), infacility of accommodation (INFA) (N = 6), excess of accommodation (EA) (N = 9), and insufficiency of accommodation (INSA) (N = 12) groups. Accommodation was stimulated in different cycles of accommodation and disaccommodation while ocular aberrations were measured. Dynamic accommodation was computed from ocular wavefront aberrations and then analysed, including response time, peak velocity, and microfluctuations. Subjects with accommodative dysfunctions showed alterations in accommodative responses compared to the control group, characterized by slower and excessive/reduced responses, as well as an increase in accommodative microfluctuations and difficulty in relaxing accommodation to different accommodative demands. The SWD group showed significant changes compared to the control group, suggesting accommodative problems not previously detected in clinical examinations and explaining the symptoms reported by these subjects. The specific patterns of the characteristics of dynamic accommodation are presented for the different accommodative dysfunctions. The objective assessment of dynamic accommodation using wavefront sensing, analysed for different accommodative demands, provides a comprehensive approach to the detection and characterisation of accommodative dysfunctions. This method enables the improvement of the precision of the diagnosis of accommodative dysfunctions and allows its detection in cases that may not be detected by current clinical examinations. In addition, this method may contribute to personalized treatment planning, potentially improving patient outcomes in clinical practice.

An adaptive fibre-optic interferomety system based on a dynamic hologram recorded in a bismuth titanium oxide crystal is developed and studied. The system possesses a low cutoff frequency (4 mHz), making possible the adaptive detection of ultra-slow physical signals with an amplitude equivalent to fibre elongation of 5 nm.

Imaging faint companions (exoplanets and brown dwarfs) around nearby stars is currently limited by speckle noise. To efficiently attenuate this noise, a technique called simultaneous spectral differential imaging (SSDI) can be used. This technique consists of acquiring simultaneously images of the field of view in several adjacent narrow bands and in combining these images to suppress speckles. Simulations predict that SSDI can achieve, with the acquisition of three wavelengths, speckle noise attenuation of several thousands. These simulations are usually performed using the Fraunhofer approximation, i.e. considering that all aberrations are located in the pupil plane. We have performed wavefront propagation simulations to evaluate how out-of-pupil-plane aberrations affect SSDI speckle noise attenuation performance. The Talbot formalism is used to give a physical insight of the problem; results are confirmed using a proper wavefront propagation algorithm. We will show that near-focal-plane aberrations can significantly reduce SSDI speckle noise attenuation performance at several λ/D separation. It is also shown that the Talbot effect correctly predicts the PSF chromaticity. Both differential atmospheric refraction effects and the use of a coronagraph will be discussed.

The Large Synoptic Survey Telescope (LSST) is a three mirror modified Paul-Baker design with an 8.4m primary, a 3.4m secondary, and a 5.0m tertiary followed by a 3-element refractive corrector producing a 3.5 degree field of view. This design produces image diameters of <0.3 arcsecond 80% encircled energy over its full field of view. The image quality of this design is sufficient to ensure that the final images produced by the telescope will be limited by the atmospheric seeing at an excellent astronomical site. In order to maintain this image quality, the deformations and rigid body motions of the three large mirrors must be actively controlled to minimize optical aberrations. By measuring the optical wavefront produced by the telescope at multiple points in the field, mirror deformations and rigid body motions that produce a good optical wavefront across the entire field may be determined. We will describe the details of the techniques for obtaining these solutions. We will show that, for the expected mirror deformations and rigid body misalignments, the solutions that are found using these techniques produce an image quality over the field that is close to optimal. We will discuss how many wavefront sensors are needed and the tradeoffs between the number of wavefront sensors, their layout and noise sensitivity.

FRIDA (inFRrared Imager and Dissector for the Adaptive optics system of the Gran Telescopio Canarias) está siendo diseñado como un instrumento con óptica limitada por difracción con capacidades de imagen de banda ancha y angosta y espectroscopía integral de campo para operar en el intervalo de longitudes de onda de 0.9 -2.5 µm. FRIDA es un proyecto de colaboración entre los socios principales de GTC, a saber, España, México y Florida. Las principales características de diseño de FRIDA se describen en esta contribución.

We introduce the S M Nazmuz Sakib First-Null Area Product Law (FNAPL): for scalar, coherent Fraunhofer diffraction of a uniformly filled aperture that is any affine image of a disk (ellipse or sheared ellipse), the product of the pupil area A p and the focal-plane first-null enclosed area A 0 , normalized by (λ med f) 2 , is the universal constant ν 2 1 /4 ≈ 3.670531. The result follows from the Fourier-optics pupil↔PSF relation and the affine theorem of the 2-D Fourier transform, and it unifies the classical Airy case with all affine distortions. We discuss limits (apodization, aberrations, high-NA vector regimes), provide simulation guidance, and outline metrological applications.

In this paper, the performance of a cooperative Decode-and-Forward (DF) relay network with adaptive M-ary Quadrature Amplitude Modulation (M-QAM) is analyzed. A five mode adaptive M-QAM scheme is employed, and the system performance is investigated for both fixed switching levels and for optimized switching levels with a target bit error rate (BER) constraint. Expressions for average BER, spectral efficiency, and outage probability are derived to investigate the performance of the cooperative system under independently and identically distributed (i.i.d.) Nakagami-m fading wireless environments. Adaptive M-QAM with optimized switching levels maintains the target BER constraint while fixed switching levels achieves a conservative BER, which is lower than the target.

Abstract
The SERAPH-BLADE system represents a breakthrough in continental and hemispheric defense by addressing the long-standing physical limitations of ground-based Directed Energy Weapons (DEWs). Conventional DEWs are constrained by atmospheric thermal blooming, weather degradation, and horizon limits, making them inadequate against emerging threats such as hypersonic glide vehicles, hardened satellites, and maneuverable reentry systems. SERAPH-BLADE resolves these constraints through a novel vertical laser uplink architecture: a megawatt-class ground laser injects energy near-vertically into the atmosphere, minimizing distortion, before relaying the beam to a geostationary orbital platform. In orbit, precision optics, adaptive steering mirrors, and gimbaled telescopes condition and redirect the beam at speed-of-light response times to global targets.
The system is designed as a layered defense asset, integrating seamlessly with U.S. and allied missile defense networks, including THAAD, SM-6, and GMD, while adding a persistent orbital shield above midcourse and terminal defense arcs. Strategic targets include hypersonic missiles, ICBMs, anti-satellite weapons, drones, high-value terrestrial sites, and maritime threats. Engagement modeling shows that a constellation of three GEO platforms can provide near-global coverage, enabling rapid intercepts with sub-centimeter precision and one-second dwell times sufficient for burn-through effects.
Beyond performance, SERAPH-BLADE incorporates a sustainment and servicing architecture—pressurized docking enclosures, field-replaceable modules, and robotic or crewed maintenance access—ensuring a 10–20 year orbital life. Power options include high-efficiency solar arrays, thorium micro-reactors, and hybrid buffer systems, while hardened terrestrial bases are designed with bedrock anchoring, EMP shielding, and decoy deception to ensure survivability. Naval integration is also proposed, with Nimitz-class carriers repurposed as mobile uplink sites leveraging nuclear power and unlimited cooling capacity.
The program follows a phased execution plan: atmospheric/balloon prototypes and adaptive optics validation (Years 1–2), a GEO demonstrator with low-power beam handoff (Years 3–4), and full operational deployment of megawatt-class orbital relays (Years 5–7). Current technology readiness levels (TRL 7–9 for adaptive optics, HELIOS-class lasers, and satellite beam control) support an accelerated demonstration path.
Policy analysis concludes that SERAPH-BLADE can be legally advanced under the Outer Space Treaty if framed as a defensive orbital relay rather than an offensive weapon. A parallel diplomatic strategy is recommended to codify norms for defensive orbital beam systems.
In sum, SERAPH-BLADE is a scalable, modular, and survivable architecture that redefines space superiority by combining physics-driven design, near-term technical feasibility, and layered strategic integration. It provides the United States and allies with a persistent orbital shield—an unconquerable deterrent designed not for conquest, but for protection.

Since a majority of young low-mass stars are members of multiple systems, the study of their stellar and disk configurations is crucial to our understanding of both star and planet formation processes. Here we present near-infrared adaptive optics observations of the young multiple star system VW Cha. The previously known 0 ′′ • 7 binary is clearly resolved already in our raw J and K band images. We report the discovery of a new, faint companion to the secondary, at an apparent separation of only 0 ′′ • 1 or 16 AU. Our high-resolution photometric observations also make it possible to measure the J -K colors of each of the three components individually. We detect an infrared excess in the primary, consistent with theoretical models of a circumprimary disk. Analytical and numerical calculations of orbital stability show that VW Cha may be a stable triple system.

Dust from the interstellar medium (ISM) can collide with and destroy particles in the circumstellar dust disks around main-sequence stars (Vega/b Pic stars). Two current theories tying the occurrence of the Vega/b Pic phenomenon to the erosive inÑuence of the ISM are critically reconsidered here. Using the local standard of rest frame, we Ðnd little evidence for a correlated motion (streaming) of prominent disk systems, which one theory suggests would result from a passage about 107 yr ago of these stars, but not the control A-type stars, through the nearby Lupus-Centaurus interstellar cloud complex. Moreover, the prototype system of b Pic could not have retained dust produced in such a passage for much longer than 104 yr. We show theoretically that the ISM sandblasting of disks has minor importance for the structure and evolution of circumstellar disks, except perhaps in their outskirts (usually [400 AU from the stars), where under favorable conditions it may cause asymmetries in observed brightness and color. The ISM neither produces the disks (as in one theory) nor depletes and eliminates them with time (as in another theory), because typical ISM grains are subject to strong radiative repulsion from A-and F-type dwarfs (a few to 100 times stronger than gravity). Atypically large ISM grains are not repelled strongly, but are unimportant on account of their small number density. Dust production and destruction in b Pic-type disks results mainly from their collisional nature enhanced by the radiatively produced eccentricities of particle orbits, rather than from nurture in a hostile ISM. The residence times of the few-micron dust grains predominant in the densest part of the b Pic disk is only 104 yr, or a few dozen orbital periods. Submicronic debris is blown out as b meteoroids, carrying away from this system an equivalent of the solar systemÏs total mass in solids (D120 Earth masses) in only D65 Myr. This rate of collisional erosion exceeds almost 108 times that of the zodiacal light disk of our own system. A massive and relatively young Myr) planetesimal disk appears to ([102 surround b Pic, destined to decline in dust density over time comparable to its age. Other dust disks, like those around Fomalhaut and Vega, contain much less dust and may be much older than the b Pic disk, but like the b Pic disk they are also derived from and replenished many times during their lifetimes by unseen parent bodies.

We present the Young Exoplanet Transit Initiative (YETI), in which we use several 0.2 to 2.6m telescopes around the world to monitor continuously young (≤ 100 Myr), nearby (≤ 1 kpc) stellar clusters mainly to detect young transiting planets (and to study other variability phenomena on time-scales from minutes to years). The telescope network enables us to observe the targets continuously for several days in order not to miss any transit. The runs are typically one to two weeks long, about three runs per year per cluster in two or three subsequent years for about ten clusters. There are thousands of stars detectable in each field with several hundred known cluster members, e.g. in the first cluster observed, Tr-37, a typical cluster for the YETI survey, there are at least 469 known young stars detected in YETI data down to R=16.5 mag with sufficient precision of 50 milli-mag rms (5 mmag rms down to R=14.5 mag) to detect transits, so that we can expect at least about one young transiting object in this cluster. If we observe ∼ 10 similar clusters, we can expect to detect ∼ 10 young transiting planets with radius determinations. The precision given above is for a typical telescope of the YETI network, namely the 60/90-cm Jena telescope (similar brightness limit, namely within ±1 mag, for the others) so that planetary transits can be detected. For targets with a periodic transit-like light curve, we obtain spectroscopy to ensure that the star is young and that the transiting object can be sub-stellar; then, we obtain Adaptive Optics infrared images and spectra, to exclude other bright eclipsing stars in the (larger) optical PSF; we carry out other observations as needed www.an-journal.org

Searches for planets around massive stars are essential for developing general understanding of planet formation and evolution of the planetary systems. The main objective of the Pennsylvania -Torun Planet Search is detection of planets around G-K subgiants and giants through precision radial velocity (RV) measurements with iodine absorption cell using HET HRS spectrograph. However, the long period radial velocity variations of red giants may also have other than planetary nature (e.g. a non-radial pulsations or rotational modulation in presence of starspots). In this work we present bisector analysis of cross-correlation functions (CCF) constructed from the spectra used for radial velocity determination but cleaned from the iodine lines for the second red giant with planets from our survey HD 102272.

One important frontier for astronomical adaptive optics (AO) involves methods such as Multi-Object AO and Multi-Conjugate AO that have the potential to give a significantly larger field of view than conventional AO techniques. A second key emphasis over the next decade will be to push astronomical AO to visible wavelengths. We have conducted the first laboratory simulations of wide-field, laser guide star adaptive optics at visible wavelengths on a 10-meter-class telescope. These experiments, utilizing the UCO/Lick Observatory's Multi-Object / Laser Tomography Adaptive Optics (MOAO/LTAO) testbed, demonstrate new techniques in wavefront sensing and control that are crucial to future on-sky MOAO systems. We (1) test and confirm the feasibility of highly accurate atmospheric tomography with laser guide stars, (2) demonstrate key innovations allowing open-loop operation of Shack-Hartmann wavefront sensors (with errors of ∼ 30 nm) as will be needed for MOAO, and (3) build a complete error budget model describing system performance. The AO system maintains a performance of 32.4% Strehl on-axis, with 24.5% and 22.6% at 10. ′′ and 15. ′′ , respectively, at a science wavelength of 710 nm (R-band) over the equivalent of 0.8 seconds of simulation. The mean ensquared energy on-axis in a 50 milliarcsecond spaxel is 46%. The off-axis Strehls are obtained at radial separations 2-3 times the isoplanatic angle of the atmosphere at 710 nm. The MOAO-corrected field of view is ∼ 25 times larger in area than that limited by anisoplanatism at R-band. The error budget we assemble is composed almost entirely of terms verified through independent, empirical experiments, with minimal parameterization of theoretical models. We find that error terms arising from calibration inaccuracies and optical drift are comparable in magnitude to traditional terms like fitting error and tomographic error. This makes a strong case for implementing additional calibration facilities in future AO systems, including accelerometers on powered optics, 3D turbulators, telescope and LGS simulators, and external calibration ports for deformable mirrors. These laboratory demonstrations add strong credibility to the implementation of on-sky demonstrators of Laser Tomographic Adaptive Optics (LTAO) on 5-10 meter telescopes in the coming years.

The success of the next generation of instruments for ELT class telescopes will depend upon improving the image quality by exploiting sophisticated Adaptive Optics (AO) systems. One of the critical components of the AO systems for the E-ELT has been identified as the optical Laser/Natural Guide Star WFS detector. The combination of large format, 1760x1680 pixels to finely sample the wavefront and the spot elongation of laser guide stars, fast frame rate of 700 frames per second (fps), low read noise (< 3e-), and high QE (> 90%) makes the development of this device extremely challenging. Design studies concluded that a highly integrated Backside Illuminated CMOS Imager built on High Resistivity silicon as the most likely technology to succeed. Two generations of the CMOS Imager are being developed: a) the already designed and manufactured NGSD (Natural Guide Star Detector), a quarter-sized pioneering device of 880x840 pixels capable of meeting first light needs of the E-ELT; b) the LGSD (Laser Guide Star Detector), the larger full size device. As well as presenting the detailed design including the approach of using massive parallelism (70,400 ADCs) to achieve the low read noise at high pixel rates of ~3 Gpixel/s and the 88 channel LVDS 220Mbps serial interface to get the data off-chip. To enable read noise closer to the goal of 1e-to be achieved, a split wafer run has allowed the NGSD to be manufactured in the more speculative, but much lower read noise, Ultra Low Threshold Transistors in the unit cell. The NGSD has come out of production, it has been thinned to 12µm, backside processed and packaged in a custom 370pin Ceramic PGA (Pin Grid Array). First results of tests performed both at e2v and ESO are presented.

The success of the next generation of instruments for ELT class telescopes will depend upon improving the image quality by exploiting sophisticated Adaptive Optics (AO) systems. One of the critical components of the AO systems for the E-ELT has been identified as the optical Laser/Natural Guide Star WFS detector. The combination of large format, 1760x1680 pixels to finely sample the wavefront and the spot elongation of laser guide stars, fast frame rate of 700 frames per second (fps), low read noise (< 3e-), and high QE (> 90%) makes the development of this device extremely challenging. Design studies concluded that a highly integrated Backside Illuminated CMOS Imager built on High Resistivity silicon as the most likely technology to succeed. Two generations of the CMOS Imager are being developed: a) the already designed and manufactured NGSD (Natural Guide Star Detector), a quarter-sized pioneering device of 880x840 pixels capable of meeting first light needs of the E-ELT; b) the LGSD (Laser Guide Star Detector), the larger full size device. As well as presenting the detailed design including the approach of using massive parallelism (70,400 ADCs) to achieve the low read noise at high pixel rates of ~3 Gpixel/s and the 88 channel LVDS 220Mbps serial interface to get the data off-chip. To enable read noise closer to the goal of 1e-to be achieved, a split wafer run has allowed the NGSD to be manufactured in the more speculative, but much lower read noise, Ultra Low Threshold Transistors in the unit cell. The NGSD has come out of production, it has been thinned to 12µm, backside processed and packaged in a custom 370pin Ceramic PGA (Pin Grid Array). First results of tests performed both at e2v and ESO are presented.

Interest in Adaptive Coded Aperture Imaging (ACAI) continues to grow as the optical and systems engineering community becomes increasingly aware of ACAI's potential benefits in the design and performance of both imaging and non-imaging systems , such as good angular resolution (IFOV), wide distortion-free field of view (FOV), excellent image quality, and light weight construct. In this presentation we first review the accomplishments made over the past five years, then expand on previously published work to show how replacement of conventional imaging optics with coded apertures can lead to a reduction in system size and weight. We also present a trade space analysis of key design parameters of coded apertures and review potential applications as replacement for traditional imaging optics. Results will be presented, based on last year's work of our investigation into the trade space of IFOV, resolution, effective focal length, and wavelength of incident radiation for coded aperture architectures. Finally we discuss the potential application of coded apertures for replacing objective lenses of night vision goggles (NVGs).

This paper proposes a comprehensive exploration of novel theoretical frameworks in spectropolarimetry, bridging quantum and classical phenomena to enhance observational astrophysics. The outlined manuscript introduces models for noise transitions, atmospheric-instrumental interactions, polarization mixing, adaptive optics limits, non-linear detector responses, turbulence effects, and quantum state tomography. Each section integrates theoretical formulations, practical applications, and future research directions, supported by complete references to existing literature. The frameworks aim to improve the precision and interpretability of spectropolarimetric measurements in astrophysical contexts.

Optofluidics" is the marriage of optics, optoelectronics and nanophotonics with fluidics. Such integration represents a new approach for dynamic manipulation of optical properties at length scales both greater than and smaller than the wavelength of light with applications ranging from reconfigurable photonic circuits to fluidically adaptable optics to high sensitivity bio-detection currently under development. The capabilities in terms of fluidic control, mixing, miniaturization and optical property tuning afforded by micro-, nano-and electro-fluidics combined with soft lithography based fabrication provides an ideal platform upon which to build such devices. In this paper we provide a general overview of some of the important issues related to the fabrication, integration and operation of optofluidic devices and present three comprehensive application examples: nanofluidically tunable photonic crystals, optofluidic microscopy and DFB dye lasers.

We present results from infrared spectroscopic projects that aim to test the relation between the mass of a black hole MBH and the velocity dispersion of the stars in its host-galaxy bulge. We demonstrate that near-infrared, high-resolution spectroscopy assisted by adaptive optics is key in populating the high-luminosity end of the relation. We show that the velocity dispersions of mid-infrared, high-ionization lines originating from gas in the narrow-line region of the active galactic nucleus follow the same relation. This result provides a way of inferring MBH estimates for the cosmologically significant population of obscured, type 2 AGN that can be applicable to data from spectrographs on next-generation infrared telescopes.

The Telescope to Observe Planetary Systems (TOPS) is a proposed space mission to image in the visible (0.4-0.9 µm) planetary systems of nearby stars simultaneously in 16 spectral bands (resolution R≈20). For the ≈10 most favorable stars, it will have the sensitivity to discover 2R E rocky planets within habitable zones and characterize their surfaces or atmospheres through spectrophotometry. Many more massive planets and debris discs will be imaged and characterized for the first time. With a 1.2m visible telescope, the proposed mission achieves its power by exploiting the most efficient and robust coronagraphic and wavefront control techniques. The Phase-Induced Amplitude Apodization (PIAA) coronagraph used by TOPS allows planet detection at 2λ/d with nearly 100% throughput and preserves the telescope angular resolution. An efficient focal plane wavefront sensing scheme accurately measures wavefront aberrations which are fed back to the telescope active primary mirror. Fine wavefront control is also performed independently in each of 4 spectral channels, resulting in a system that is robust to wavefront chromaticity.

We propose an adaptive transmission technique for optical wireless (OW) systems, operating in atmospheric turbulence and employing subcarrier phase shift keying (S-PSK) intensity modulation. Exploiting the constant envelope characteristics of S-PSK, the proposed technique offers efficient utilization of the OW channel capacity by adapting the modulation order of S-PSK, according to the instantaneous state of turbulence induced fading and a pre-defined bit error rate (BER) requirement. Novel expressions for the spectral efficiency and average BER of the proposed adaptive OW system are presented and performance investigations under various turbulence conditions and target BER requirements are carried out. Numerical results indicate that significant spectral efficiency gains are offered without increasing the transmitted average optical power or sacrificing BER requirements in moderate-to-strong turbulence conditions.

We propose an adaptive transmission technique for free space optical (FSO) systems, operating in atmospheric turbulence and employing subcarrier phase shift keying (S-PSK) intensity modulation. Exploiting the constant envelope characteristics of S-PSK, the proposed technique offers efficient utilization of the FSO channel capacity by adapting the modulation order of S-PSK, according to the instantaneous state of turbulence induced fading and a pre-defined bit error rate (BER) requirement. Novel expressions for the spectral efficiency and average BER of the proposed adaptive FSO system are presented and performance investigations under various turbulence conditions and target BER requirements are carried out. Numerical results indicate that significant spectral efficiency gains are offered without increasing the transmitted average optical power or sacrificing BER requirements, in moderate-to-strong turbulence conditions. Furthermore, the proposed variable rate transmission technique is applied to multiple input multiple output (MIMO) FSO systems, providing additional improvement in the achieved spectral efficiency as the number of the transmit and/or receive apertures increases.

As space debris in lower Earth orbits are accumulating, techniques to lower the risk of space debris collisions must be developed. Within the context of the Space Environment Research Centre (SERC), the Australian National University (ANU) is developing an adaptive optics system for tracking and pushing space debris. The strategy is to pre-condition a laser launched from a 1.8 m telescope operated by Electro Optics Systems (EOS) on Mount Stromlo, Canberra and direct it at an object to perturb its orbit. Current progress towards implementing this experiment, which will ensure automated operation between the telescope and the adaptive optics system, will be presented.

In order to guide the adaptive optics design and aid in performance predictions, optical turbulence at the site of the future Giant Magellan Telescope (GMT) is characterized using MooSci, a lunar scintillometer, and MASS-DIMM, a combination differential image motion monitor and multiaperture scintillation sensor. As a new instrument, MooSci, is verified as a reliable ground-layer turbulence profiler. The GMT can expect an improvement of approximately 0.1″ over the site testing results as measured with a DIMM. Turbulence below 30 m is horizontally nonhomogeneous, dependent on wind speed and direction, and on average accounts for 60% of the full ground-layer (up to 500 m) turbulence.

Among the adaptive optics systems available to astronomers, the US Air Force Advanced Electro-Optical System (ABOS) is unique because it delivers very high order wave front correction. The Lyot Project includes the construction and installation of the world's first diffraction-limited, optimized coronagraph that exploits the full astronomical potential of ABOS and represents a critical step toward the long-term goal of directly imaging and studying extrasolar planets (a.k.a. "exoplanets"). We provide an update on the Project, whose coronagraph saw first light in March 2004. The coronagraph is operating at least as well as predicted by simulations, and a survey of nearby stars has begun.

For the first time in history, astronomers can image the environments of nearby stars on scales approaching that of our solar system. New classes of astrophysical objects have been discovered including circumstellar debris disks, brown dwarfs, and super-Jupiter mass planets. These discoveries have galvanized intense public interest and have led to profound new insights into the formation and evolution of planetary systems such as our own. Among the key enabling technologies are adaptive optics (AO) and coronagraphy, which deliver the high contrast necessary for the discovery and characterization of faint stellar companions and circumstellar disks in the solar neighborhood. Among the AO systems available to astronomers, AEOS is unique because it delivers very high order wave front correction. The Lyot Project includes the construction and installation of an AEOS-optimized coronagraph that exploits the full astronomical potential of AEOS and represents a critical step toward the long-term goal of directly imaging and studying extrasolar planets (a.k.a. ``exoplanets''). We provide an update on the Project, whose coronagraph will be installed at AEOS in October 2003, and whose infrared camera saw first light in April 2003.

Lightweight X-ray Wolter optics with a high angular resolution will enable the next generation of X-ray telescopes in space. The candidate mission ATHENA (Advanced Telescope for High Energy Astrophysics) required a mirror assembly of 1 m² effective area (at 1 keV) and an angular resolution of 10 arcsec or better. These specifications can only be achieved with a novel technology like Silicon Pore Optics, which is being developed by ESA together with a consortium of European industry. Silicon Pore Optics are made of commercial Si wafers using process technology adapted from the semiconductor industry. We present the recent upgrades made to the manufacturing processes and equipment, ranging from the manufacture of single mirror plates towards complete focusing mirror modules mounted in flight configuration, and results from first vibration tests. The performance of the mirror modules is tested at X-ray facilities that were recently extended to measure optics at a focal distance up to 20 m.

Bu çalışmada, Türkiye Ulusal Gözlemevleri, optik laboratuvarında bulunan Shack-Hartmann adaptif optik (SH-AO) enstrümanının mekanik kurulumu ve hassas optik hizalaması yapıldıktan sonra, optik yola statik ve dinamik aberasyon kaynakları entegre edilmesiyle, sistemin dalga cephesi düzeltme performansı ile ilgili sonuçlar paylaşılacaktır.

Özet Bu çalışmada, Türkiye Ulusal Gözlemevleri bünyesindeki Doğu Anadolu Gözlemevi (DAG) optik laboratuvarında kurulan Shack-Hartmann adaptif optik (SH-AO) sisteminin düzeltme performansı deneysel olarak incelenmiştir. Çalışmanın giriş bölümünde, adaptif optik konseptine ve astronomik uygulamalardaki önemine genel bir bakış sunulmuş, ardından farklı türdeki dalga cephesi algılama tekniklerine değinilmiştir. Shack-Hartmann dalga cephesi sensörünün çalışma prensibi ve performans parametreleri detaylandırılmıştır. Materyal ve yöntem bölümünde, deneysel düzenek ve sistem bileşenleri hakkında bilgi verilmiş; mekanik kurulum ve hassas optik hizalama süreçleri ele alınmıştır. Optik yolda faz farkı oluşturabilecek statik ve dinamik aberasyon kaynaklarının sisteme entegrasyonu açıklanmıştır. Sonuçlar bölümünde, sistemin dalga cephesi düzeltme performansı değerlendirilmiştir. Elde edilen metrikler ve sonuçlar, sistem performansını analiz etmek amacıyla kullanılmıştır. Kalibrasyon sırasında kullanılan dalga cephesinin sahip olduğu, statik dalga cephesi hatası her iki durumda da ortak olarak bulunduğundan, bozulmuş ve düzeltilmiş dalga cephelerine ait tepe çukur hata ölçümleri kullanılarak yapılan hesaplama sonucunda, SH-AO sisteminin hata düzeltme yüzdesi %63.43 olarak hesaplanmıştır.

The field of view of high-resolution ophthalmoscopes that require the use of adaptive optics (AO) wavefront correction is limited by the isoplanatic patch of the eye, which varies across individual eyes and with the portion of the pupil used for illumination and/or imaging. Therefore all current AO ophthalmoscopes have small fields of view comparable to, or smaller than, the isoplanatic patch, and the resulting images have to be stitched off-line to create larger montages. These montages are currently assembled either manually, by expert human graders, or automatically, often requiring several hours per montage. This arguably limits the applicability of AO ophthalmoscopy to studies with small cohorts and moreover, prevents the ability to review a real-time captured montage of all locations during image acquisition to further direct targeted imaging. In this work, we propose stitching the images with our novel algorithm, which uses oriented fast rotated brief (ORB) descriptors, local sensitivity hashing, and by searching for a 'good enough' transformation, rather than the best possible, to achieve processing times of 1-2 minutes per montage of 250 images. Moreover, the proposed method produces montages which are as accurate as previous methods, when considering the image similarity metrics: normalised mutual information (NMI), and normalised cross correlation (NCC).

Precise measurements of photoreceptor numerosity and spatial arrangement are promising biomarkers for the early detection of retinal pathologies and may be valuable in the evaluation of retinal therapies. Adaptive optics scanning light ophthalmoscopy (AOSLO) is a method of imaging that corrects for aberrations of the eye to acquire high-resolution images that reveal the photoreceptor mosaic. These images are typically graded manually by experienced observers, obviating the robust, large-scale use of the technology. This paper addresses unsupervised automated detection of cones in non-confocal, split-detection AOSLO images. Our algorithm leverages the appearance of split-detection images to create a cone model that is used for classification. Results show that it compares favorably to the state-of-the-art, both for images of healthy retinas and for images from patients affected by Stargardt disease. The algorithm presented also compares well to manual annotation while excelling in sp...

We have analysed a recently obtained high resolution 3 mum spectrum of Titan in order to determine the altitudes where hydrogen cyanide, acetylene, methane, and mono-deuterated methane bands are formed and to constrain the locations and chemical make-up of cloud and haze layers that affect the view of Titan in this wavelength range. We deduce that the observed emission lines from CH4 and HCN originate at stratospheric and mesospheric altitudes and that the mixing ratio of HCN at those altitudes is approximately as predicted by photochemical models. C2H2 is considerably less abundant than HCN at those high altitudes. At 3.10-3.54 mum an opaque layer of cloud and/or haze at the 100 km level, composed of organic particles reduces the strength of the CH4 absorption lines. This layer is transparent at 2.9 mum, where the CH3D band is seen in absorption largely against a cloud deck at an altitude of about 50 km. The shape of the CH3D absorption lines demonstrates that this cloud deck is ei...

A hybrid deformable x-ray mirror consisting of a mechanical bender and a bimorph deformable mirror has been developed to realize adaptive optical systems, such as zoom condenser optics, for synchrotron-radiation-based x-ray microscopy. In the developed system, both bending mechanisms comprehensively contribute to the formation of the target mirror shape and can narrow the role of piezoelectric actuators, thereby enabling a more stable operation. In this study, the behavior of the bimorph mirror under the clamped condition was investigated, and the sharing of the deformation amount for each bending mechanism was optimized to minimize the amplitude of the voltage distribution of the bimorph mirror.

The space-variant wavefront reconstruction problem inherently exists in deep tissue imaging. In this paper, we propose a framework of Shack–Hartmann wavefront space-variant sensing with extended source illumination. The space-variant wavefront is modeled as a four-dimensional function where two dimensions are in the spatial domain and two are in the Fourier domain with priors that both gently vary. Here, the affine transformation is used to characterize the wavefront space-variant function. Correspondingly, the zonal and modal methods are both escalated to adapt to four-dimensional representation and reconstruction. Experiments and simulations show double to quadruple improvements in space-variant wavefront reconstruction accuracy compared to the conventional space-invariant correlation method.

CHIME, the Copernicus Hyperspectral Imaging Mission for the Environment, is one of the six High Priority Candidate Missions (HPCM) of the evolution in the Copernicus Space Component (CSC) foreseen in the mid-2020s that is proposed for further analysis. In this paper we summarize the results as retrieved by OHB (D) as part of the Phase A/B1. The contract was kicked off in 2018 and concluded in 2020 after finalisation of the Pre-development activities. The proposed instrument is a hyperspectral imager instrument with reflective telescope and grating-based spectrometer. The selected orbit is in the range of 625 ± 30 km, LTDN 10:45 -11:15 am with a repeat cycle of 20 to 25 days for a single satellite and 10-12.5 days revisit for 2 satellites. The payload of each satellite records at a Spatial Sampling Distance (SSD) of 30m the full spectral range from 400 to 2500nm at a Spectral Sampling interval < 10nm with Low Keystone/Smile. On the front end a high performance TMA with wide-band coated optics collects the light from ground and feeds it to a highly linear almost distortion free spectrometer assembly attaining very good spectral stability. All units are integrated in an optical bench structure that offers excellent AIT access and provides a highly stable LOS. The electro-optical backend contains low-noise cold MCT detectors creating margin in the predicted NEDL performance. The instrument can be calibrated via on-board devices or using reference targets outside the spacecraft. We present the functional decomposition and the physical instrument architecture: the optical design and opto-mechanical layout, the electro-optical imaging chain ant thermal control system.

This research outlines the future perspectives of a novel optical system that concentrates sunlight into two distinct focal points using a large double-convex lens and a concave mirror. The system demonstrates the potential to produce high-frequency light energy, possibly reaching the cosmic or gamma photon range. This paper presents a forward-looking view of how such a system could evolve into a valuable scientific and technological tool for applications in energy and space research.

Modern MT (www.modernmt.eu) is a three-year Horizon 2020 innovation action (2015±2017) to develop new open-source machine translation technology for use in translation production environments, both fully automatic and as a back-end in interactive post-editing scenarios. Led by Translated srl, the project consortium also includes the Fondazione Bruno Kessler (FBK), the University of Edinburgh, and TAUS B.V. Modern MT has received funding from the (XURSHDQ 8QLRQ¶V +RUL]RQ UHVHDUFK DQG LQQRYDWLRQ SURJUDPPH under Grant Agreement No645487 (call ICT-17-2014).

The current results of our ongoing Galactic Center (GC) observations with optical long baseline interferometry (OLB-IF) are presented. We achieved first IR-IF fringes in both available IR science regimes of the VLTI (MIDI: 10 µm) and (AMBER: 2 µm), demonstrating the new capabilities provided by large aperture telescope arrays to the Galactic center research. We show that the highest angular resolution only available through interferometric techniques is necessary to observe the GC ISM production in the making and distinguish individual sources from its dusty surroundings. An overview over the currently available IF-technology is given, biased towards the GC science case. The feasibility of phase-referencing to the supergiant GCIRS 7, located only 5 away from SgrA*, to increase the sensitivity and spectral resolution of the observations, is discussed, and supported by the first real data. The presentation will conclude with an outlook to the near future about how the upcoming astrometric and off-axis phase-referencing capabilities of the Keck and VLT Interferometers, nicknamed ASTRA and PRIMA, will greatly extend the currently existing capabilities to observe astrophysical phenomena in the Galactic center at the borderline to General relativity in a yet uninvestigated regime.

The Keck Interferometer is a NASA-funded joint development between JPL and the W. M. Keck Observatory. The interferometer will combine the two 10-m Keck telescopes with four 1.8-m outrigger telescopes in several observing modes. These include: nulling interferometry at 10 um to measure the quantity of exozodiacal emission around nearby stars; nearinfrared differential-phase measurements to detect "hot Jupiters" by their direct emission; narrow-angle astrometry to search for exoplanets by their astrometric signature; and near-infrared imaging to address a variety of imaging science. Active development of the instrument subsystems and associated infrastructure is underway at JPL and CARA.

The first refereed science papers based on data with the Keck II natural guide star (NGS) and laser guide star (LGS) adaptive optics (AO) system were published in 2000 January and 2005 May, respectively. As of the end of 2012 a total of 260 refereed science papers have been published based on Keck NGS AO data and 152 with the Keck LGS AO system. This paper provides an overview of the first dozen years of scientific productivity with Keck AO and the lessons that can be drawn from this experience. The performance and limitations of the existing Keck AO systems are also discussed along with the technical developments currently underway to improve the scientific reach of these systems. The Keck AO capabilities are in high demand by a broad science community, a community that has expanded as new capabilities, especially LGS AO, have been added.

High sensitivity fringe visibility (V2) measurements -Combines the AO-corrected beams -V2 measurements in the near-IR -Nulling beam combiner to suppress central star -Measure zodiacal dust around nearby stars -Multi-color fringe measurements