R. Kohley

FastCam: a new lucky imaging instrument for medium-sized telescopes

FastCam is an instrument jointly developed by the Spanish Instituto de Astrofísica de Canarias and the Universidad Politécnica de Cartagena designed to obtain high spatial resolution images in the optical wavelength range from ground-based telescopes. The instrument consists of a very low noise and very fast readout speed EMCCD camera capable of reaching the diffraction limit of medium-sized telescopes from 500 to 850 nm. FastCam incorporates a FPGAs-based device to save and evaluate those images minimally disturbed by atmospheric turbulence in real time. The undisturbed images represent a small fraction of the observations. Therefore, a special software package has been developed to extract, from cubes of tens of thousands of images, those with better quality than a given level. This is done in parallel with the data acquisition at the telescope. After the first tests in the laboratory, FastCam has been successfully tested in three telescopes: the 1.52-meter TCS (Teide Observatory), the 2.5-meter NOT, and the 4.2-meter WHT (Roque de los Muchachos Observatory). The theoretical diffraction limit of each telescope has been reached in the I band (850 nm) -0.15, 0.08 and 0.05 arcsec, respectively-, and similar resolutions have been also obtained in the V and R bands. Future work will include the development of a new instrument for the 10.4-meter GTC telescope on La Palma.

Gaia Data Release 1 - On-orbit performance of the Gaia CCDs at L2

The European Space Agencys Gaia satellite was launched into orbit around L2 in December 2013 with a payload containing 106 large-format scientific CCDs. The primary goal of the mission is to repeatedly obtain high-precision astrometric and photometric measurements of one thousand million stars over the course of five years. The scientific value of the down-linked data, and the operation of the onboard autonomous detection chain, relies on the high performance of the detectors. As Gaia slowly rotates and scans the sky, the CCDs are continuously operated in a mode where the line clock rate and the satellite rotation spin-rate are in synchronisation. Nominal mission operations began in July 2014 and the first data release is being prepared for release at the end of Summer 2016. In this paper we present an overview of the focal plane, the detector system, and strategies for on-orbit performance monitoring of the system. This is followed by a presentation of the performance results based on analysis of data acquired during a two-year window beginning at payload switch-on. Results for parameters such as readout noise and electronic offset behaviour are presented and we pay particular attention to the effects of the L2 radiation environment on the devices. The radiation-induced degradation in the charge transfer efficiency (CTE) in the (parallel) scan direction is clearly diagnosed; however, an extrapolation shows that charge transfer inefficiency (CTI) effects at end of mission will be approximately an order of magnitude less than predicted pre-flight. It is shown that the CTI in the serial register (horizontal direction) is still dominated by the traps inherent to the manufacturing process and that the radiation-induced degradation so far is only a few per cent. We also present results on the tracking of ionising radiation damage and hot pixel evolution. Finally, we summarise some of the detector effects discovered on-orbit which are still being investigated. (Less)

Gaia: 1,000 million stars with 100 CCD detectors

Gaia is the next space-astrometry mission of the European Space Agency, following up on the success of the Hipparcos mission. With a focal plane containing more than 100 large-area CCD detectors, Gaia will survey the sky and repeatedly observe the brightest 1,000 million (one billion) objects, down to 20th magnitude, during its 5-year nominal lifetime. Gaias science data will comprise absolute astrometry, broad-band photometry, and low-resolution spectro-photometry. Medium-resolution spectroscopic data (resolving power 11,500) will be obtained for the brightest 150 million sources, down to 17th magnitude. The extreme thermo-mechanical stability of the spacecraft, combined with the selection of the L2 Lissajous point of the Sun-Earth/Moon system for operations, allows stellar parallaxes (distances) to be measured with standard errors less than 10 micro-arcsecond (μas) for stars brighter than 13th magnitude, 20-30 μas for stars at 15th magnitude, and around 300 μas at magnitude 20. Photometric standard errors are in the milli-magnitude regime. The spectroscopic data will allow the measurement of radial velocities with errors at the level of 15 km s-1 at magnitude 17. Gaias primary science goal is to unravel the kinematical, dynamical, and chemical structure and evolution of the Milky Way. In addition, Gaias data will touch many other areas of research, for instance stellar physics, solar-system bodies, fundamental physics, and exo-planets. The Gaia spacecraft is currently undergoing its critical design review (CDR). With a launch foreseen in the second half of 2012, the final catalogue is expected in 2020. The science community in Europe, organized in the Gaia Data Processing and Analysis Consortium (DPAC), is responsible for the processing of the Gaia data. This formidable task is in full preparation. The calibration of the data presents exciting challenges, in particular in the area of radiation-damage-induced charge-transfer inefficiency (CTI).

Gaia's FPA: sampling the sky in silicon

ESA´s astrometry satellite Gaia is scheduled for launch in 2013. In a combination of outstanding hardware performance, autonomous object detection and sophisticated data processing, Gaia will chart more than a billion stars of the entire sky to unprecedented accuracy during its 5 years mission. A key element to its mission success is the focal plane assembly (FPA), the largest ever flown to space, comprising a close-butted almost Giga-pixel mosaic of 106 large area CCDs. Manufacturing and extensive testing of the individual devices and detector system units as well as integration on the single-piece, silicon-carbide support structure has been a challenge. The focal plane is now assembled and has undergone its final tests during 2012. The paper summarizes the expected in-flight performances of Gaia´s FPA and the implemented tools and procedures to monitor its operation in space. Accurate knowledge of the impact of FPA performance parameters on individual measurements and its evolution in time is critical to achieve the high accuracy needed in calibrating the science data. An example is the radiation-induced deterioration of the CCD charge transfer efficiency, which acts on distorting the detected object PSFs while observing the sky in continuous scan mode. Through dedicated calibration procedures and directly through the scientific data processing, Gaia will therefore closely track the radiation environment at L2 from the FPA output itself. Detection of transient effects and analysis of persistent damage on the CCDs mainly caused by solar protons converts Gaias FPA inherently into the largest ever radiation monitor in space.

Gaia on-board metrology: basic angle and best focus

The Gaia payload ensures maximum passive stability using a single material, SiC, for most of its elements. Dedicated metrology instruments are, however, required to carry out two functions: monitoring the basic angle and refocusing the telescope. Two interferometers fed by the same laser are used to measure the basic angle changes at the level of μas (prad, micropixel), which is the highest level ever achieved in space. Two Shack- Hartmann wavefront sensors, combined with an ad-hoc analysis of the scientific data are used to define and reach the overall best-focus. In this contribution, the systems, data analysis, procedures and performance achieved during commissioning are presented .

Status of Elmer: an instrument for the GTC 10-m telescope

Elmer is an imager and spectrograph in the visible wavelength range for the Gran Telescopio CANARIAS, GTC. Elmer is being managed directly by the GTC Project Office, who has done the whole Preliminary Design and large part of the Detailed Design. This instrument shall operate at the telescope on Day One, as a back up in case of delays of the major instruments, guaranteeing the scientific return of the GTC. A brief presentation of the instrument is here given. The expected scientific performance of the instrument is summarized. Finally, the general description of the management strategy and project parameters are described.

Getting ELMER ready for science: laboratory tests

Elmer is an imager and spectrograph in the visible range that has been designed and managed within the GTC Project Office. Elmer will be installed at the telescope at the beginning of the commissioning phase. The observing modes of the instrument are: Imaging, Long Slit, Mask and Slit-less multi-object Spectroscopy, Fast Photometry and Fast short-slit Spectroscopy. The pupil elements are a set of conventional broad band and narrow band filters as well as a set of prisms, grisms and VPHs, that allow spectroscopy with resolving powers of 200, 1000 and 2500 between 365 and 1000nm. Elmer has been exhaustively tested and each of its observing modes has been fully characterized at the laboratory. This contribution summarizes the results of this Test Plan, showing the excellent performance of Elmer in both, Imaging and Spectroscopy modes that, together with the GTC, will lead to a powerful scientific return.

Design and initial test results of a CCD fan-out board with integrated preamplifier and ESD protection for the scientific instrument ELMER at the GTC 10-m telescope

The scientific instrument ELMER for the GTC 10-m telescope integrates an E2V Technologies CCD44-82 detector and can optionally use the MIT/LL CCID-20 device. Fan-out electronics have been developed that support both detectors reusing the same PCB design and cabling. The main system component, the fan-out board, provides dual-channel input clamp and preamplification of the CCD output signal as well as filtering and active ESD protection of all the CCD lines within a 60x80mm envelope. The preamplifier stage is based on complementary bipolar operational amplifiers with dielectric isolation technology for optimum noise performance and minimum settling time. Matched, discrete JFET buffers are used for improved DC precision. Preliminary tests performed on the system yield 2.0μVrms preamplifier noise after CDS at 50kHz readout frequency. Slew rate in excess of 230V/μs and settling time well below 75ns have been obtained for a gain 4 preamplifier configuration driving non terminated coaxial cable.

CCD camera and data acquisition system of the scientific instrument ELMER for the GTC 10-m telescope

ELMER is a multi-purpose instrument for the GTC designed for both, Imaging and Spectrosopy in the visible range. The CCD camera employs a E2V Technologies CCD44-82 detector mounted in a high performance LN2 Bath Cryostat based on an ESO design and a SDSU-II CCD controller with parallel interface. The design including the low-noise fan-out electronics has been kept flexible to allow alternatively the use of MIT/LL CCID-20 detectors. We present the design of the CCD camera and data acquisition system and first performance test results.

GTC Acquisition Cameras and Wavefront Sensors

The GTC (Gran Telescopio Canarias) employs an Acquisition and Slow Guiding Sensor based on a Marconi CCD47-20. This chip is also the core sensor for the telescope Segment Figure Sensor. A third sensor, based on a Marconi CCD39-01 implements Fast Guiding and is also used for Wavefront Sensing under continuous rotation. 1 Hz full-frame readouts and 10 Hz window readouts are performed onto the slow guiding sensor, whereas 200 Hz full-frame readouts are required for the fast guiding sensor in binning modes. GTC sensors are low-profile, lightweight, individual CCD heads with integral low-noise preamplifier stages and Peltier cooling electronics. These CCD heads are liquid-cooled and include forced, dry air circulation. Besides, high noise inmunity, proper shielding and grounding and impedance matching of the cabled links have been major design concerns.