Instruments and Techniques

LUCIFER is a NIR spectrograph and imager (wavelength range 0.9 to 2.5 micron) for the Large Binocular Telescope (LBT) on Mt. Graham, Arizona, working at cryogenic temperatures of less than 70K. Two instruments are built by a consortium of five German institutes and will be mounted at the bent Gregorian foci of the two individual telescope mirrors. Three exchangable cameras are available for imaging and spectroscopy: two of them are optimized for seeing-limited conditions, a third camera for the diffraction limited case will be used with the LBT adaptive secondary mirror working. Up to 33 exchangeable masks are available for longslit or multi-object spectroscopy (MOS) over the full field of view (FOV). Both MOS-units (LUCIFER 1 and LUCIFER 2) and the auxiliary cryostats together with the control electronics have been completed. The observational software-package is in its final stage of preparation. After the total integration of LUCIFER 1 extensive tests were done for all electro-mechanical functions and the verification of the instrument started. The results of the tests are presented in detail and are compared with the specifications.

An overview of instrumentation for the Large Binocular Telescope is presented. Optical instrumentation includes the Large Binocular Camera (LBC), a pair of wide-field (27'x 27') UB/VRI optimized mosaic CCD imagers at the prime focus, and the Multi-Object Double Spectrograph (MODS), a pair of dual-beam blue-red optimized long-slit spectrographs mounted at the straight-through F/15 Gregorian focus incorporating multiple slit masks for multi-object spectroscopy over a 6\arcmin\ field and spectral resolutions of up to 8000. Infrared instrumentation includes the LBT Near-IR Spectroscopic Utility with Camera and Integral Field Unit for Extragalactic Research (LUCIFER), a modular near-infrared (0.9-2.5 μm) imager and spectrograph pair mounted at a bent interior focal station and designed for seeing-limited (FOV: 4'x 4') imaging, long-slit spectroscopy, and multi-object spectroscopy utilizing cooled slit masks and diffraction limited (FOV: 0'.5 x 0'.5) imaging and long-slit spectroscopy. Strategic instruments under development for the remaining two combined focal stations include an interferometric cryogenic beam combiner with near-infrared and thermal-infrared instruments for Fizeau imaging and nulling interferometry (LBTI) and an optical bench beam combiner with visible and near-infrared imagers utilizing multi-conjugate adaptive optics for high angular resolution and sensitivity (LINC/NIRVANA). In addition, a fiber-fed bench spectrograph (PEPSI) capable of ultra high resolution spectroscopy and spectropolarimetry (R = 40,000-300,000) will be available as a principal investigator instrument. The availability of all these instruments mounted simultaneously on the LBT permits unique science, flexible scheduling, and improved operational support.

A Cassegrain telescope with a 450 mm clear aperture was developed for use in a spaceborne optical remote-sensing instrument. Self-weight deformation and thermal distortion were considered: to this end, Zerodur was used to manufacture the primary mirror. The lightweight scheme adopted a hexagonal cell structure yielding a lightweight ratio of 50%. In general, optical testing on a lightweight mirror is a critical technique during both the manufacturing and assembly processes. To prevent unexpected measurement errors that cause erroneous judgment, this paper proposes a novel and reliable analytical method for optical testing, called the bench test. The proposed algorithm was used to distinguish the manufacturing form error from surface deformation caused by the mounting, supporter and gravity effects for the optical testing. The performance of the proposed bench test was compared with a conventional vertical setup for optical testing during the manufacturing process of the lightweight mirror.

The requirements of a lightweight primary mirror for large-aperture space telescopes include a precise mirror figure and high reliability. However, lightweight mirrors are easily affected by environmental disturbances, as they lack structural stability and rigidity. Active optics can be used to compensate for the gravity-induced deformation and correct low-order aberrations due to thermal changes and gravity relief during observing periods. Due to their complexity, active optics have been rarely used in space. To validate the technology of space active optics, an active optics system based on a passive, whiffletree-supported mirror is developed. During integration and testing on ground and under normal conditions in space, the surface accuracy is guaranteed by passive support. Within this hybrid support, the active optics system only serves to assist support. This paper focuses on the compatibility between a passive multisupporting system and active optics. We present the prototype of a 0.676m diameter passive supported lightweight mirror and active support with nine axial force actuators. The passive support includes a 9-point axial support and three A-frame lateral support. The active actuator distribution has been optimized with finite element analysis and its experimental performance characterized in representative conditions. The effectiveness of the hybrid passive-active support developed has been verified.

This study presents the results of an automated parametric synthesis of a series of orthoscopic aspheric optical systems of mirror telescopes with different focal lengths, built according to the Korsch scheme. In order to ensure compactness of the design, these systems consist of three second-order aspheric mirrors and three folded flat mirrors. The obtained optical systems have a focal length ranging from 480 mm to 960 mm, an angular field of view ranging from 1.2° to 2.4°, an aperture number ranging from 6 to 12, an entrance aperture with a diameter of 80 mm, and an axial length of no more than 170 mm, which is within the dimensions of a 2U CubeSat. The maximum linear size of the image detector's sensitive area is 20 mm in all considered systems. The mirror telescopes do not have chromatic aberrations, enabling the capture of images within the visible spectrum and multiple infrared sub-bands. The provided aberration analysis demonstrates the high image quality of the considered optical systems. Specifically, for a wavelength of 0.546 μm, thediffraction modulation transfer function values both in the meridional and sagittal planes across the entire field exceed 0.53 for a spatial frequency of 30 mm-1, and 0.3 for a spatial frequency of 50 mm-1. The maximum relative distortion in the designed systems is 0.005%, corresponding to an absolute displacement of 0.5 μm. The presented telescopes are capable of covering an observation band of Earth's surface with linear dimensions ranging from 12.6 km to 25.1 km when a satellite track height is 600 km. By applying multi-element image detectors with a pixel size of 5 μm and achieving diffraction-limited image quality in the optical systems, both the geometric and diffraction resolution limits on Earth's surface will not exceed 10 m.

This article reports an approach of light-weighted mirror design and analysis to increase the weight reduction ratio and improve optical performance based on the finite element method and opto-mechanical analysis. The approach is to represent mirror surface deformation derived from finite element analysis (FEA) by Zernike polynomials, such that the impact of deformation on optical system performance can be evaluated by the optical design and analysis program. The experimental modal analysis was also performed to validate the FEA results. The numerical result shows that the light-weighted primary mirror of Cassegrain telescope is obtained by this approach and predicted deformation fulfills the requirements of optical design.

We analyze soft x-ray images of the solar corona, obtained on the day of the solar eclipse in July 1991, and find that the deviations of our telescope mirror from the perfect surface are less than 1 Å for spatial periods between 1 μm and 1 mm. Our thin film deposition technique allows us to reduce errors over larger periods to the 1 Å level. Thus, we are able to produce large (diameter over 20 cm) x-ray mirrors with diffraction limited resolution below 0.01 arcsec.

The increasing interest on space telescopes for scientific applications leads to implement the manufacturing technology of the most critical element, i.e. the primary mirror: being more suitable a large aperture, it must be lightweight and deployable. The presented topic was originally addressed to a spaceborne DIAL (Differential Absorption LIDAR) mission operating at 935.5 nm for the measurement of water vapour profile in atmosphere, whose results were presented at ICSO 2006 and 2008. Aim of this paper is to present the latest developments on the main issues related to the fabrication of a breadboard, covering two project critical areas identified during the preliminary studies: the design and performances of the long-stroke actuators used to implement the mirror active control and the mirror survivability to launch via Electrostatic Locking (EL) between mirror and backplane. The described work is developed under the ESA/ESTEC contract No. 22321/09/NL/RA. The lightweight mirror is structured as a central sector surrounded by petals, all of them actively controlled to reach the specified shape after initial deployment and then maintained within specs for the entire mission duration. The presented study concerns: a) testing the Carbon Fiber Reinforced Plastic (CFRP) backplane manufacturing and EL techniques, with production of suitable specimens; b) actuator design optimisation; c) design of the deployment mechanism including a high precision latch; d) the fabrication of thin mirrors mock-ups to validate the fabrication procedure for the large shells. The current activity aims to the construction of an optical breadboard capable of demonstrating the achievement of all these coupled critical aspects: optical quality of the thin shell mirror surface, actuators performances and back-plane - EL subsystem functionality.

A series of developmental as well as flight mirrors have been in process over the last few years for IR cryogenic telescope applications such as the Space Infrared Telescope Facility (SIRTF) and the Next Generation Space Telescope (NGST) and for visible ambient systems such as Space Based Laser (SBL). We will discuss the performance of the 0.85-m SIRTF primary mirror (26.6 kg/m 2 areal density) and the 0.5-m Subscale Beryllium Mirror Demonstrator (SBMD) beryllium mirror (9.8 kg/m 2 areal density) as well as the current status of the 1.4-m Ball semi-rigid, beryllium Advanced Mirror System Demonstrator (AMSD). The AMSD mirror itself has an areal density of 10.4 kg/m 2 and is currently in polishing. The entire AMSD assembly including composite reaction structure, flexures, and actuators, has an areal density less than 15 kb/m 2 . Cyrogenic test results of the SIRTF and SBMD mirrors will be presented along with test data on the AMSD actuators. The SBMD mirror wsa cryofigured based on ambient and cryo testing to achieve a wavefront quality of 19 nm rms at 35 K. In addition, the effects of optically coating SBMD with a protected gold multi-layer system will be shown - demonstrating that a lightweight mirror can be coated without adverse print-through due to coating stress at ambient or cryo operating temperatures.

The James Webb Space Telescope (JWST) is the infrared successor to the Hubble Space Telescope. It is a cryogenic infrared space observatory with a 25 m2 aperture (6 m class) telescope yielding diffraction limited angular resolution at a wavelength of 2 um. The science instrument payload includes three passively cooled near-infrared instruments providing broad — and narrow-band imagery, coronagraphy, as well as multi-object and integral-field spectroscopy over the 0.6 < λ < 5.0 um spectrum. An actively cooled mid-infrared instrument provides broad-band imagery, coronagraphy, and integral-field spectroscopy over the 5.0 < λ < 29 um spectrum. The JWST is being developed by NASA, in partnership with the European and Canadian Space Agencies, as a general user facility with science observations to be proposed by the international astronomical community in a manner similar to the Hubble Space Telescope. Technology development and mission design are complete, and construction is underway in all areas of the program.

The James Webb Space Telescope (JWST) is the scientific successor to the Hubble Space Telescope. It is a cryogenic infrared space observatory with a 25 m2 aperture (6 m class) telescope that will achieve diffraction limited angular resolution at a wavelength of 2 µm. The science instrument payload includes four passively cooled near-infrared instruments providing broad- and narrow-band imagery, coronography, as well as multi-object and integral-field spectroscopy over the 0.6 < λ < 5.0 µm spectrum. An actively cooled mid-infrared instrument provides broad-band imagery, coronography, and integral-field spectroscopy over the 5.0 < λ < 29 µm spectrum. The JWST is being developed by NASA, in partnership with the European and Canadian Space Agencies, as a general user facility with science observations proposed by the international astronomical community in a manner similar to the Hubble Space Telescope. Technology development and mission design are complete. Construction, integration and verification testing is underway in all areas of the program. The JWST is on schedule for launch during 2021.

In the development of thin active mirrors for future x-ray telescopes there is a need for full field, non-null methods of rapidly characterising highly distorted surfaces without contact. Phase measuring deflectometry, due to its high dynamic range and flexibility, is a promising solution to this problem. In this paper is described a system developed by the authors at University College London, as well as the results of surface measurements using this methodology on thin sheets of actuated glass.

pool of pure, silver-white mercury A makes a flawless, natural mirror. Spin the pool, and centrifugal force shapes its flat surface into a parabola. Attach this concave to the proper electronic equipment, aim it into the sky on a cloudless night, and it becomes a powerful optical telescope. This is the theory behind the mirror telescopes that astrophysicist Ermanno F Borra has built at Universite Laval in Quebec, Canada. He has made three prototypes-two of them 1 meter in diameter and the third 1.65 meters and he is using a 1-meter model this summer to look for rapid variations in the sky. Although the concept of using spinning mercury as a telescope reflector is at least two centuries old and has been attempted many times since at least 1909, Borra claims he is the first to make it work. He says he has learned to control precisely the speed of the mirror's rotation, to keep wind-generated waves from the surface of the mercury and to keep the poisonous mercury from harming telescope operators. Laboratory tests done in 1984 and 1985 demonstrated that his parabola of spinning mercury maintains a constant shape and a stable focus, Borra says. already have proved that the concept is sound, he told SCIENCE NEWS. The only thing I have to prove now is that I can make very large liquid mirrors.

We report the results of numerical simulations of the instrumental signal in the Stokes V channel of circular polarization as observed by RATAN-600 radio telescope operating in the “Southern sector with a flat reflector” mode. Our simulations are based on an improved algorithm of the beam pattern computation that takes into account diffraction in the space between the telescope mirrors. The computations cover a wide range of wavelengths in the case of a focused antenna and in the presence of aberrations. We analyze the structure and properties of the element M41 of the Mueller matrix and of the parasite signal from the solar disk in various cases of the antenna irradiation. We estimate the differences between the left- and right-polarization power-beam patterns of the telescope. We report the computed M11 and M41 elements for the case of observation of the right- and left-polarized radiation at different points of the focal line of the secondary mirror, and analyze their variations as a function of a number of parameters, including, in particular, the shift applied to correct the displacement of scans.

We have developed an energy-saving operations system featuring remote operation of central monitoring equipment installed in a building. This system applies robotic process automation to remote operation to automatically perform energy-saving operations on behalf of the operations manager. Furthermore, as another feature, the system requires only a local area network to connect to the central monitoring equipment enabling automatic operation to be performed regardless of the specifications of the central monitoring equipment. The items targeted for energy-saving operation by this system are the optimal operation of a heat source system, setting of the supply water temperature of heat source equipment, setting of room temperature, and setting of outside-air intake volume. At present, the operations manager has the role of performing these energy-saving operations, but finding the optimal value for each of these operations is a difficult task. An operations manager, moreover, is responsible for tasks other than facility operations such as maintenance management, so changing optimal settings accurately at regular intervals on an ongoing basis can be quite a burden. This system uses robotic process automation technology, so it is capable of performing all energy-saving operations that can be executed by the central monitoring equipment. We installed this system in a large-scale shopping mall and performed energy-saving operations on outside-air processing units. In this trial, we achieved a 44% reduction in the amount of energy required for outside-air processing and a 47% reduction in CO2 emissions.