Nicolas Gorceix

Nasmyth focus instrumentation of the New Solar Telescope at Big Bear Solar Observatory

The largest solar telescope, the 1.6-m New Solar Telescope (NST) has been installed and is being commissioned at Big Bear Solar Observatory (BBSO). It has an off-axis Gregorian configuration with a focal ratio of F/52. Early in 2009, first light scientific observations were successfully made at the Nasmyth focus, which is located on the east side of the telescope structure. As the first available scientific instruments for routine observation, Nasmyth focus instrumentation (NFI) consists of several filtergraphs offering high spatial resolution photometry in G-band 430 nm, Ha 656 nm, TiO 706 nm, and covering the near infrared 1083 nm, 1.6 μm, and 2.2 μm. With the assistance of a local correlation tracker system, diffraction limited images were obtained frequently over a field-of-view of 70 by 70 after processed using a post-facto speckle reconstruction algorithm. These data sets not only serve for scientific analysis with an unprecedented spatial resolution, but also provide engineering feedback to the NST operation, maintenance and optimization. This paper reports on the design and the implementation of NFI in detail. First light scientific observations are presented and discussed.

Profiles of the daytime atmospheric turbulence above Big Bear solar observatory

Context. Space weather has become acutely critical for today’s global communication networks. To understand its driving forces we need to observe the Sun with high angular-resolution, and within large fields-of-view, i.e. with multi-conjugate adaptive optics correction. Aims. The design of a multi-conjugate adaptive optical system requires the knowledge of the altitude distribution of atmospheric turbulence. We have therefore measured daytime turbulence profiles above the New Solar Telescope (NST), on Big Bear Lake. Methods. To this purpose, a wide-field wavefront sensor was installed behind the NST. The variation of the wavefront distortions with angular direction allows the reconstruction of the distribution of turbulence. Results. The turbulence is found to have three origins: 1. a ground layer (<500 m) that contains 55–65% of the turbulence, 2. a boundary layer between 1–7 km comprises 30–40% of the turbulent energy, 3. and the remaining ∼5% are generated in the tropopause, which is above 12 km in summer and between 8 and 12 km in winter. Conclusions. A multi-conjugate adaptive optical system should thus aim at correcting the ground turbulence, the center of the boundary layer at roughly 3 km altitude and, eventually, the upper boundary layer around 6 km altitude.

AO-308: the high-order adaptive optics system at Big Bear Solar Observatory

In this paper we present Big Bear Solar Observatory’s (BBSO) newest adaptive optics system – AO-308. AO-308 is a result of collaboration between BBSO and National Solar Observatory (NSO). AO-308 uses a 357 actuators deformable mirror (DM) from Xinetics and its wave front sensor (WFS) has 308 sub-apertures. The WFS uses a Phantom V7.3 camera which runs at 2000 Hz with the region of interest of 416×400 pixels. AO-308 utilizes digital signal processors (DSPs) for image processing. AO-308 has been successfully used during the 2013 observing season. The system can correct up to 310 modes providing diffraction limited images at all wavelengths of interest.

First light of the 1.6 meter off-axis New Solar Telescope at Big Bear Solar Observatory

New Jersey Institute of Technology, in collaboration with the University of Hawaii and the Korea Astronomy & Space Science Institute, has successfully developed and installed a 1.6 m clear aperture, off-axis New Solar Telescope (NST) at the Big Bear Solar Observatory. The NST will be the largest aperture solar telescope in the world until the 4 m Advanced Technology Solar Telescope (ATST) and 4 m European Solar Telescope (EST) begin operation in the next decade. Meanwhile, the NST will be the largest off-axis telescope before the 8.4 m segmented Giant Magellan Telescope (GMT) comes on-line. The NST is configured as an off-axis Gregorian system consisting of a parabolic primary, prime focus field stop and heat reflector, elliptical secondary and diagonal flats. The primary mirror is made of Zerodur from Schott and figured to a final residual error of 16 nm rms by Steward Observatory Mirror Lab. The final focal ratio is f/52. The 180 circular opening in the field stop defines the maximal square field-of-view. The working wavelength range will cover 0.4 to 1.7 μm in the Coud´e Lab two floors beneath the telescope, and all wavelengths including far infrared at the Nasmyth focus on an optical bench attached to the side of the telescope structure. First-light scientific observations have been attained at the Nasmyth focus and in the Coud´e Lab. This paper presents a detailed description of installation and alignment of the NST. First-light observational results are also shown to demonstrate the validity of the NST optical alignment.

Clear widens the field for observations of the Sun with multi-conjugate adaptive optics

The multi-conjugate adaptive optics (MCAO) pathfinder Clear on the New Solar Telescope in Big Bear Lake has provided the first-ever MCAO-corrected observations of the Sun that show a clearly and visibly widened corrected field of view compared to quasi-simultaneous observations with classical adaptive optics (CAO) correction. Clear simultaneously uses three deformable mirrors, each conjugated to a different altitude, to compensate for atmospheric turbulence. While the MCAO correction was most effective over an angle that is approximately three times wider than the angle that was corrected by CAO, the full 53′′ field of view did benefit from MCAO correction. We further demonstrate that ground-layer-only correction is attractive for solar observations as a complementary flavor of adaptive optics for observational programs that require homogenous seeing improvement over a wide field rather than diffraction-limited resolution. We show illustrative images of solar granulation and of a sunspot obtained on different days in July 2016, and present a brief quantitative analysis of the generalized Fried parameters of the images.

The multi-conjugate adaptive optics system of the New Solar Telescope at Big Bear Solar Observatory

We report on the multi-conjugate adaptive optics (MCAO) system of the New Solar Telescope (NST) at Big Bear Solar Observatory which has been integrated in October 2013 and is now available for MCAO experiments. The NST MCAO system features three deformable mirrors (DM), and it is purposely flexible in order to offer a valuable facility for development of solar MCAO. Two of the deformable mirrors are dedicated to compensation of field dependent aberrations due to high-altitude turbulence, whereas the other deformable mirror compensates field independent aberrations in a pupil image. The opto-mechanical design allows for changing the conjugate plane of the two high-altitude DMs independently between two and nine kilometers. The pupil plane DM can be placed either in a pupil image upstream of the high-altitude DMs or downstream. This capability allows for performing experimental studies on the impact of the geometrical order of the deformable mirrors and the conjugate position. The control system is flexible, too, which allows for real-world analysis of various control approaches. This paper gives an overview of the NST MCAO system and reveals the first MCAO corrected image taken at Big Bear Solar Observatory.

Progress in multi-conjugate adaptive optics at Big Bear Solar Observatory

The multi-conjugate adaptive optics (MCAO) system for solar observations at the 1.6-meter clear aperture New Solar Telescope (NST) of the Big Bear Solar Observatory (BBSO) in Big Bear Lake, California, enables us to study fundamental design questions in solar MCAO experimentally. It is the pathfinder for MCAO of the upcoming Daniel K. Inoyue Solar Telescope (DKIST). This system is very flexible and offers various optical configurations such as different sequencings of deformable mirrors (DMs) and wavefront sensors (WFS), which are hard to simulate conclusively. We show preliminary results and summarize the design, and 2016 updates to the MCAO system. The system utilizes three DMs. One of which is conjugate to the telescope pupil, and the other two to distinct higher altitudes. The pupil DM can be either placed into a pupil image up- or downstream of the high-altitude DMs. The high-altitude DMs can be separately and quickly conjugated to various altitudes between 2 and 8 km. Three Shack-Hartmann WFS units are available, one for low-order, multi-directional sensing and two high-order on-axis sensing.

Control and operation of the 1.6 m New Solar Telescope in Big Bear

The 1.6m New Solar Telescope (NST) has developed a modern and comprehensive suite of instruments which allow high resolution observations of the Sun. The current instrument package comprises diffraction limited imaging, spectroscopic and polarimetric instruments covering the wavelength range from 0.4 to 5.0 microns. The instruments include broadband imaging, visible and near-infrared scanning Fabry-Perot interferometers, an imaging spectropolarimeter, a fast visible-light imaging spectrograph, and a unique new scanning cryogenic infrared spectrometer/spectropolarimeter that is nearing completion. Most instruments are operated with a 308 subaperture adaptive optics system, while the thermal-IR spectrometer has a correlation tracker. This paper reports on the current observational programs and operational performance of the telescope and instrumentation. The current control, data processing, and archiving systems are also briefly discussed.

Optical design of the Big Bear Solar Observatory's multi-conjugate adaptive optics system

A multi-conjugate adaptive optics (MCAO) system is being built for the worlds largest aperture 1.6m solar telescope, New Solar Telescope, at the Big Bear Solar Observatory (BBSO). The BBSO MCAO system employs three deformable mirrors to enlarge the corrected field of view. In order to characterize the MCAO performance with different optical configurations and DM conjugated altitudes, the BBSO MCAO setup also needs to be flexible. In this paper, we present the optical design of the BBSO MCAO system.

Repackaging and characterizing of a HgCdTe CMOS infrared camera for the New Solar Telescope

The 1.6-meter New Solar Telescope (NST) is currently the worlds largest aperture solar telescope. The NST is newly built at Big Bear Solar Observatory (BBSO). Among other instruments, the NST is equipped with several focal plane instruments operating in the near infrared (NIR). In order to satisfy the diverse observational requirements of these scientific instruments, a 1024 × 1024 HgCdTe TCM8600 CMOS camera manufactured by Rockwell Scientific Company has been repackaged and upgraded at Infrared Laboratories Inc. A new ND-5 dewar was designed to house the TCM8600 array with a low background filter wheel, inverted operation and at least 12 hours of hold time between fills. The repackaged camera will be used for high-resolution NIR photometry at the NST Nasmyth focus on the telescope and high-precision NIR spectro-polarimetry in the NST Coud´e Lab below. In March 2010, this repackaged camera was characterized in the Coud´e Lab at BBSO. This paper presents the design of new dewar, the detailed process of repackaging and characterizing the camera, and a series of test results.