The LSST project (Large Survey for Space and Time), Vera Rubin Observatory is designed to observe the deep and wide Universe addressing the questions about dark matter as well as the near Universe with the study of the Milky Way. These observations are conducted by a high-resolution camera, which is made up of 189 4k×4k CCD sensors observing from the UV to the near-infrared. Some sensors supplied by ITL (Imaging Technology Laboratory), present a layer of cleaning residue or non-stoichiometric oxidized silicon adhering the surface after etching and create some non-uniformity in backside charging and irregularities inducing a variation of counting in UV and imprecise photometry. In this paper, we will present the camera and the particularities of the ITL sensors, then, the impact of this layer on the performances of the sensors and finally on the observed astronomical object.
Scientific CMOS image sensors are a modern alternative for a typical CCD detectors, as they offer both low read-out noise, large sensitive area, and high frame rates. All these makes them promising devices for a modern wide-field sky surveys. However, the peculiarities of CMOS technology have to be properly taken into account when analyzing the data. In order to characterize these, we performed an extensive laboratory testing of Andor Marana sCMOS camera. Here we report its results, especially on the temporal stability and linearity, and compare it to the previous versions of Andor sCMOS cameras. We also present the results of an on-sky testing of this sensor connected to a wide-field lens, and discuss its applications for an astronomical sky surveys.
Tree rings are one of the sensor effects that may affect precise measurements in the Large Synoptic Survey Telescope (LSST). The effect is caused by silicon wafer manufacturing process, resulting in formation of circular patterns due to variations of the silicon dopant concentration. We have analyzed flat-field images taken at Brookhaven National Laboratory and SLAC for all production sensors used to build the LSST camera in order to measure the amplitudes and periods of the tree ring patterns as a function of the radius, illumination wavelength, and sensor back bias voltage. With nominal back bias voltage settings, the tree ring amplitudes and periods for both ITL and e2v sensors are considered to have small impact on the galaxy shear measurement in LSST.
We outline the design of a test stand for characterization of optical sensors intended for use in astronomical applications, and we report the current state of the setup. Once completed, the system will be capable of measuring the performance of charge-coupled devices, complementary metaloxidesemiconductor, and prospective new sensors or cameras equipped with such sensors. The setup vacuum chamber will provide a stable environment for the device under test and allow for cooling down to cryogenic temperatures. The optical system will provide flexibility for the illumination of the sensor—the wavelength and duration can be precisely controlled; flat-field, spot, or patterns can by applied.
We present the design of a MegaTORTORA telescope (and its prototype, mini-MegaTORTORA, presently in
construction at Special Astrophysical Observatory) - modular, multi-purpose, scalable grid of optical cameras
based on commercially available objectives and fast CCDs, able to operate with sub-second temporal resolution
in both wide-field monitoring regime with all objectives observing different regions of the sky as well as in
narrow-field follow-up mode with co-aligned channels and installed color and polarimetric filters for detailed
investigation of selected objects, and to change the regime of operation on a sub-second time scale.
The Position-Sensitive Detector (PSD) on base of GaAs photocathode and microchannel plate set has been
developed. PSD consists of thick semiconductor photocathode with quantum efficiency about 48% in the range
of 4000-8000AA, two microchannel plates, and 16-electrode collector. The detector has spatial resolution of 20-30
microns for about 5 • 105 pixels, time resolution of 1 us and effective sensitivity up to 40%.
To study short stochastic optical flares of different objects (GRBs, SNs, etc) of unknown localizations as well
as NEOs it is necessary to monitor large regions of sky with high time resolution. We developed a system
which consists of wide-field camera (FOW is 400-600 sq.deg.) using TV-CCD with time resolution of 0.13 s
to record and classify optical transients, and a fast robotic telescope aimed to perform their spectroscopic and
photometric investigation just after detection. Such two telescope complex TORTOREM combining wide-field
camera TORTORA and robotic telescope REM operated from May 2006 at La Silla ESO observatory. Some
results of its operation, including first fast time resolution study of optical transient accompanying GRB and
discovery of its fine time structure, are presented. Prospects for improving the complex efficiency are given.