First light for the sodium laser guide star adaptive optics system on the Lijiang 1.8m telescope

A first generation sodium Laser Guide Star Adaptive Optics System(LGS-AOS) was developed and integrated into the Lijiang 1.8 m telescope in 2013. The LGS-AOS has three sub-systems:(1) a 20 W long pulsed sodium laser,(2) a 300-millimeter-diameter laser launch telescope, and(3) a 37-element compact adaptive optics system. On 2014 January 25, we obtained high resolution images of an mV8.18 star,HIP 43963, during the first light of the LGS-AOS. In this paper, the sodium laser, the laser launch telescope,the compact adaptive optics system and the first light results will be presented.     

A Shack–Hartmann wavefront sensor projected on to the sky with reduced focal anisoplanatism

A method for producing a laser guide star wavefront sensor for adaptive optics with reduced focal anisoplanatism is presented. A theoretical analysis and numerical simulations have been carried out and the results are presented. The technique, named Sky-Projected Laser Array Shack–Hartmann (SPLASH), is shown to suffer considerably less from focal anisoplanatism than a conventional laser guide star system. The method is potentially suitable for large telescope apertures (∼8 m), and possibly for extremely large telescopes.     

Achromatic interfero-coronagraph with variable rotation shearing for studying extrasolar planets

Direct observation of exoplanets will make it possible to clarify many principal questions connected both with extrasolar planets and planetary systems and to measure atmospheric spectra of the planets. Obtaining an exoplanet image not distorted by the light from a star is at the cutting edge of present-day optical technologies owing to the combination of tremendous brightness contrasts and small angular distances between the planet and star. To observe the exo-Earth, it is necessary to weaken the brightness of the parent star image by 9–10 orders of magnitude (in the optical and near-IR ranges). To compensate the influence of the atmosphere, ground-based (e.g., 8–10 m) telescopes intended for observing exoplanets are equipped with adaptive optics systems, the spatial and temporal resolutions of which are not yet sufficient. A meter-class space telescope equipped with a star coronagraph will make it possible to observe the nearest exoplanets. In this paper, an improved tool for star coronagraphy is considered, namely, the achromatic interferometric coronagraph with a variable rotational shear. It is fabricated according to the optical scheme of the common path interferometer for studying extrasolar planets by direct observations. Theoretical and experimental estimations for the main characteristics of the scheme were carried out. Laboratory experimental measurements were carried out on a coronagraph model.     

Direct imaging of extra-solar planets with stationary occultations viewed by a space telescope

The feasibility of detecting planets outside the solar system through imaging at optical wavelengths by a telescope in space is considered. The “black” limb of the moon can be used as an occulting edge to greatly reduce the background light from the planet's star. With this technique and if certain other technical requirements can be realized, a hypothetical Jupiter-Sun system could be detected at a distance of 10 pc. For this system, a signal-to-noise ratio of 9 could be achieved in less than 20 min with a 2.4-m telescope in space. For diffraction limited optics, the required integration time is inversely proportional to the fifth power of the telescope aperture. An orbit for the telescope is described that could achieve a stationary lunar occultation of any star that would last nearly two hours, providing six times more integration time than required by the hypothetical Jupiter-Sun example.     

European Solar Telescope: Progress status

In this paper, the present status of the development of the design of the European Solar Telescope is described. The telescope is devised to have the best possible angular resolution and polarimetric performance, maximizing the throughput of the whole system. To that aim, adaptive optics and multi‐conjugate adaptive optics are integrated in the optical path. The system will have the possibility to correct for the diurnal variation of the distance to the turbulence layers, by using several deformable mirrors, conjugated at different heights. The present optical design of the telescope distributes the optical elements along the optical path in such a way that the instrumental polarization induced by the telescope is minimized and independent of the solar elevation and azimuth. This property represents a large advantage for polarimetric measurements. The ensemble of instruments that are planned is also presented (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

High-contrast coronagraph for ground-based imaging of Jupiter-like planets

We propose a high-contrast coronagraph for direct imaging of young Jupiter-like planets orbiting nearby bright stars. The coronagraph employs a steptransmission filter in which the intensity is apodized with a finite number of steps with identical transmission in each step. It should be installed on a large ground-based telescope equipped with a state-of-the-art adaptive optics system. In this case, contrast ratios around 10-6 should be accessible within 0.1 arcsec of the central star. In recent progress, a...     

OSIRIS: AO-assisted integral-field spectroscopy at the Keck Observatory

OSIRIS (OH-Suppressing Infra-Red Integral-field Spectrograph) is a new facility instrument for the Keck Observatory. After seeing first light in February 2005, OSIRIS is currently undergoing commissioning. OSIRIS provides the capability of performing three-dimensional spectroscopy in the near-infrared z, J, H, and K bands at the resolution limit of the Keck II telescope, which is equipped with adaptive optics and a laser guide star. The science case for OSIRIS is summarized, and the instrument and associated data reduction software are described.     

Probing young massive clusters with laser guide star adaptive optics

We use laser guide star adaptive optics (LGS/AO) on the 10 m Keck II telescope to obtain high spatial resolution images of young massive clusters (YMCs) in NGC1569 and M82. These data probe YMC structure and the relation of the YMCs to the ambient field star population. The higher resolution of Keck LGS/AO relative to Hubble Space Telescope/NICMOS in the near-infrared enables us to examine whether YMCs are monolithic or hierarchical assemblies. The new integral-field spectrometer OSIRIS operating behind LGS/AO can trace the distribution of massive evolved stars within a cluster and reveal the nature of mass segregation.     

Comments on the next generation of ground-based solar telescopes

The development of telescope capabilities tends to go in spurts. These are triggered by the availability of new techniques in optics, mechanics and/or instrumentation. So has nighttime telescope technology developed since the construction in the nineteen-forties of the 5-m Hale telescope, first by the introduction in the sixties of high efficiency electronic detectors, followed recently by the production of large 8- to 10-m mirrors and now by the implementation of adaptive optics. In solar astronomy, major steps were the introduction of the coronagraph by Lyot in the nineteen-thirties and the vacuum telescope concept by Dunn in the sixties. In the last thirty years, telescope developments in solar astronomy have relied primarily on improved instrumental capabilities. As in nighttime astronomy, these instruments and their detectors are reaching their limits set by the quantum nature of light and the telescope diffraction. Larger telescopes are needed to increase sensitivity and angular resolution of the observations. In this paper, I will review recent efforts to increase substantially the telescope capabilities themselves. I will emphasize the concept of a large all-wavelength, coronagraphic telescope (CLEAR) which is presently being developed.Dedicated to Cornelis de Jager     

Design and development of the Advanced Technology Solar Telescope

Led by the National Solar Observatory, plans have been made to design and to develop the Advanced Technology Solar Telescope (ATST). The ATST will be a 4‐m general‐purpose solar telescope equipped with adaptive optics and versatile post‐focus instrumentation. Its main aim will be to achieve an angular resolution of 0.03 arcsec (20 km on the solar surface). The project and the telescope design are briefly described.     

Adaptive Optics Image Restoration Based on Frame Selection and Multi-frame Blind Deconvolution

Restricted by the observational condition and the hardware, adaptive optics can only make a partial correction of the optical images blurred by atmospheric turbulence. A postprocessing method based on frame selection and multi-frame blind deconvolution is proposed for the restoration of high-resolution adaptive optics images. By frame selection we mean we first make a selection of the degraded (blurred) images for participation in the iterative blind deconvolution calculation, with no need of any a priori knowledge, and with only a positivity constraint. This method has been applied to the restoration of some stellar images observed by the 61-element adaptive optics system installed on the Yunnan Observatory 1.2m telescope. The experimental results indicate that this method can effectively compensate for the residual errors of the adaptive optics system on the image, and the restored image can reach the diffraction-limited quality.     

GREGOR solar telescope: Design and status

The integration and verification phase of the GREGOR telescope reached an important milestone with the installation of the interim 1 m SolarLite primary mirror. This was the first time that the entire light path had seen sunlight. Since then extensive testing of the telescope and its subsystems has been carried out. The integration and verification phase will culminate with the delivery and installation of the final 1.5 m Zerodur primary mirror in the summer of 2010. Observatory level tests and science verification will commence in the second half of 2010 and in 2011. This phase includes testing of the main optics, adaptive optics, cooling and pointing systems. In addition, assuming the viewpoint of a typical user, various observational modes of the GREGOR Fabry‐Pérot Interferometer (GFPI), the Grating Infrared Spectrograph (GRIS), and high‐speed camera systems will be tested to evaluate if they match the expectations and science requirements. This ensures that GREGOR will provide high‐quality observations with its combination of (multi‐conjugate) adaptive optics and advanced post‐focus instruments. Routine observations are expected for 2012 (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

SciMeasure Wavefront Sensor Cameras and their Application in the Palomar Adaptive Optics System

SciMeasure, in collaboration with Emory University and the Jet Propulsion Laboratory, has developed a very versatile CCD controller for use in adaptive optics, optical interferometry, and other applications requiring high-speed readout rates and/or low read noise. The overall architecture of this controller system will be discussed and its performance using both EEV CCD39 and MIT/LL CCID-19 detectors will be presented. This controller is used in the adaptive optics system, developed by JPL, for the 200′′ Hale telescope at Palomar Mountain. Early diffraction-limited science results, recently achieved by the AO system, are presented. We gratefully acknowledge the financial support of NASA through SBIR contracts NAS8–97195 and NAS8–98081. This revised version was published online in July 2006 with corrections to the Cover Date.     

SciMeasure Wavefront Sensor Cameras and their Application in the Palomar Adaptive Optics System

SciMeasure, in collaboration with Emory University and the Jet Propulsion Laboratory, has developed a very versatile CCD controller for use in adaptive optics, optical interferometry, and other applications requiring high-speed readout rates and/or low read noise. The overall architecture of this controller system will be discussed and its performance using both EEV CCD39 and MIT/LL CCID-19 detectors will be presented. This controller is used in the adaptive optics system, developed by JPL, for the 200′′ Hale telescope at Palomar Mountain. Early diffraction-limited science results, recently achieved by the AO system, are presented. We gratefully acknowledge the financial support of NASA through SBIR contracts NAS8–97195 and NAS8–98081.     

Adaptive optics for large telescopes

The performance of large telescopes is determined both by their angular resolution and by their collection area. It is, therefore, important to achieve as high an angular resolution as possible by site selection, by avoiding image deterioration by the telescope and its environment, and by real time image restoration by adaptive optics. We summarize the principles of adaptive optics, their predicted performance and the current programs underway to implement adaptive optics for astronomical purposes.Paper presented at the Symposium on the JNLT and Related Engineering Developments, Tokyo, November 29–December 2, 1988.     

Adaptive Optics on a 3.6-Meter Telescope. The ADONIS System.

ADONIS is an adaptive optics (AO) user friendly instrument offered to the European astronomical community on the ESO 3.6-m telescope at La Silla. It is an upgraded version of COME-ON-PLUS, the VLT AO prototype, which already produced significative astrophysical results in a wide range of fields, from planetology to extragalactic astrophysics. ADONIS is now allowing the astronomer to use adaptive optics as a common user instrument thanks to the implementation of an open artificial intelligence software that handles the large number of parameters needed to optimise the AO correction. We will describe the ADONIS system, including the two dedicated infrared cameras, summarize its performances and discuss the observing procedures.     

The project of high spatial resolution near infrared imaging system at Beijing Observatory

A high spatial resolution near infrared imaging system is being developed at Beijing Observatory. It is a joint-project with Institute of Optics and Electronics, CSA, and National Astronomical Observatory, Japan. The system contains a 512 × 512 PtSi CSD near infrared camera and a 21-element adaptive optics system and will be operated at Coudé focus of the 2.16 meter telescope at Xinglong Station, Beijing Observatory. The infrared camera will be fixed at Cassegrain focus with focus reducers too.     

Single layer atmospheric turbulence demonstrated by adaptive optics observations

Carried with an astronomical adaptive optics (AO) system, this work reports the observational evidences of wave-front deformations dominated by sources of perturbation acting as phase slabs moving at a constant speed in front of the telescope aperture. Consequences for improved adaptive optics compensation are suggested.     

Super resolution for astronomical observations

In order to obtain detailed information from multiple telescope observations a general blind super-resolution (SR) reconstruction approach for astronomical images is proposed in this paper. A pixel-reliability-based SR reconstruction algorithm is described and implemented, where the developed process incorporates flat field correction, automatic star searching and centering, iterative star matching, and sub-pixel image registration. Images captured by the 1-m telescope at Yunnan Observatory are used to test the proposed technique. The results of these experiments indicate that, following SR reconstruction, faint stars are more distinct, bright stars have sharper profiles, and the backgrounds have higher details; thus these results benefit from the high-precision star centering and image registration provided by the developed method. Application of the proposed approach not only provides more opportunities for new discoveries from astronomical image sequences, but will also contribute to enhancing the capabilities of most spatial or ground-based telescopes.