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Register a new userThe RCT 1.3-meter Robotic Telescope: Broad-band Color Transformation and Extinction Calibration
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Louis-Gregory Strolger
Publication date
2013
fields
Physics
and research's language is
English
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The RCT 1.3-meter telescope, formerly known as the Kitt Peak National Observatory (KPNO) 50-inch telescope, has been refurbished as a fully robotic telescope, using an autonomous scheduler to take full advantage of the observing site without the requirement of a human presence. Here we detail the current configuration of the RCT, and present as a demonstration of its high-priority science goals, the broadband {it UBVRI} photometric calibration of the optical facility. In summary, we find the linear color transformation and extinction corrections to be consistent with similar optical KPNO facilities, to within a photometric precision of 10% (at $1sigma$). While there were identified instrumental errors likely adding to the overall uncertainty, associated with since-resolved issues in engineering and maintenance of the robotic facility, a preliminary verification of this calibration gave good indication that the solution is robust, perhaps to a higher precision than this initial calibration implies. The RCT has been executing regular science operations since 2009, and is largely meeting the science requirements set in its acquisition and re-design.
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NIKA2 is a dual-band millimetric continuum camera of 2900 Kinetic Inductance Detectors (KID), operating at $150$ and $260,rm{GHz}$, installed at the IRAM 30-meter telescope. We present the performance assessment of NIKA2 after one year of observation using a dedicated point-source calibration method, referred to as the emph{baseline} method. Using a large data set acquired between January 2017 and February 2018 that span the whole range of observing elevations and atmospheric conditions encountered at the IRAM 30-m telescope, we test the stability of the performance parameters. We report an instantaneous field of view (FOV) of 6.5 in diameter, filled with an average fraction of $84%$ and $90%$ of valid detectors at $150$ and $260,rm{GHz}$, respectively. The beam pattern is characterized by a FWHM of $17.6 pm 0.1$ and $11.1pm 0.2$, and a beam efficiency of $77% pm 2%$ and $55% pm 3%$ at $150$ and $260,rm{GHz}$, respectively. The rms calibration uncertainties are about $3%$ at $150,rm{GHz}$ and $6%$ at $260,rm{GHz}$. The absolute calibration uncertainties are of $5%$ and the systematic calibration uncertainties evaluated at the IRAM 30-m reference Winter observing conditions are below $1%$ in both channels. The noise equivalent flux density (NEFD) at $150$ and $260,rm{GHz}$ are of $9 pm 1, rm{mJy}cdot s^{1/2}$ and $30 pm 3, rm{mJy}cdot s^{1/2}$. This state-of-the-art performance confers NIKA2 with mapping speeds of $1388 pm 174$ and $111 pm 11 ,rm{arcmin}^2cdot rm{mJy}^{-2}cdot rm{h}^{-1}$ at $150$ and $260,rm{GHz}$. With these unique capabilities of fast dual-band mapping at high (better that 18) angular resolution, NIKA2 is providing an unprecedented view of the millimetre Universe.
The calibration hardware system of the Large Synoptic Survey Telescope (LSST) is designed to measure two quantities: a telescopes instrumental response and atmospheric transmission, both as a function of wavelength. First of all, a collimated beam projector is designed to measure the instrumental response function by projecting monochromatic light through a mask and a collimating optic onto the telescope. During the measurement, the light level is monitored with a NIST-traceable photodiode. This method does not suffer from stray light effects or the reflections (known as ghosting) present when using a flat-field screen illumination, which has a systematic source of uncertainty from uncontrolled reflections. It allows for an independent measurement of the throughput of the telescopes optical train as well as each filters transmission as a function of position on the primary mirror. Second, CALSPEC stars can be used as calibrated light sources to illuminate the atmosphere and measure its transmission. To measure the atmospheres transfer function, we use the telescopes imager with a Ronchi grating in place of a filter to configure it as a low resolution slitless spectrograph. In this paper, we describe this calibration strategy, focusing on results from a prototype system at the Cerro Tololo Inter-American Observatory (CTIO) 0.9 meter telescope. We compare the instrumental throughput measurements to nominal values measured using a laboratory spectrophotometer, and we describe measurements of the atmosphere made via CALSPEC standard stars during the same run.
Context. The Neel IRAM KIDs Array (NIKA) is a fully-integrated measurement system based on kinetic inductance detectors (KIDs) currently being developed for millimeter wave astronomy. In a first technical run, NIKA was successfully tested in 2009 at the Institute for Millimetric Radio Astronomy (IRAM) 30-meter telescope at Pico Veleta, Spain. This prototype consisted of a 27-42 pixel camera imaging at 150 GHz. Subsequently, an improved system has been developed and tested in October 2010 at the Pico Veleta telescope. The instrument upgrades included dual-band optics allowing simultaneous imaging at 150 GHz and 220 GHz, faster sampling electronics enabling synchronous measurement of up to 112 pixels per measurement band, improved single-pixel sensitivity, and the fabrication of a sky simulator to replicate conditions present at the telescope. Results. The new dual-band NIKA was successfully tested in October 2010, performing in-line with sky simulator predictions. Initially the sources targeted during the 2009 run were re-imaged, verifying the improved system performance. An optical NEP was then calculated to be around 2 dot 10-16 W/Hz1/2. This improvement in comparison with the 2009 run verifies that NIKA is approaching the target sensitivity for photon-noise limited ground-based detectors. Taking advantage of the larger arrays and increased sensitivity, a number of scientifically-relevant faint and extended objects were then imaged including the Galactic Center SgrB2(FIR1), the radio galaxy Cygnus A and the NGC1068 Seyfert galaxy. These targets were all observed simultaneously in the 150 GHz and 220 GHz atmospheric windows.
Lijiang 2.4-meter Telescope(LJT), the largest common-purpose optical telescope in China, has been applied to the world-wide astronomers since 2008. It is located at Gaomeigu site, Lijiang Observatory(LJO), the southwest of China. The site has very good observational conditions. Since 10-year operation, several instruments have been equipped on the LJT. Astronomers can perform both photometric and spectral observations. The main scientific goals of LJT include photometric and spectral evolution of supernova, reverberation mapping of active galactic nucleus, physical properties of binary star and near-earth object(comet and asteroid), identification of exoplanet, and all kinds of transients. Until now, the masses of 41 high accretion rate black holes have been measured, and more than 168 supernova have been identified by the LJT. More than 190 papers related to the LJT have been published. In this paper, the general observation condition of the Gaomeigu site is introduced at first. Then, the LJT structure is described in detail, including the optical, mechanical, motion and control system. The specification of all the instruments, and some detailed parameters of the YFOSC is also presented. Finally, some important scientific results and future expectations are summarized.
The approach of Observational Astronomy is mainly aimed at the construction of larger aperture telescopes, more sensitive detectors and broader wavelength coverage. Certainly fruitful, this approach turns out to be not completely fulfilling the needs when phenomena related to the formation of black holes (BH), neutron stars (NS) and relativistic stars in general are concerned. Recently, mainly through the Vela, Beppo-SAX and Swift satellites, we reached a reasonable knowledge of the most violent events in the Universe and of some of the processes we believe are leading to the formation of black holes (BH). We plan to open a new window of opportunity to study the variegated physics of very fast astronomical transients, particularly the one related to extreme compact objects. The innovative approach is based on three cornerstones: 1) the design (the conceptual design has been already completed) of a 3m robotic telescope and related focal plane instrumentation characterized by the unique features: No telescope points faster; 2) simultaneous multi-wavelengths observations (photometry, spectroscopy o& polarimetry); 3) high time resolution observations. The conceptual design of the telescope and related instrumentation is optimized to address the following topics: High frequency a-periodic variability, Polarization, High z GRBs, Short GRBs, GRB-Supernovae association, Multi-wavelengths simultaneous photometry and rapid low dispersion spectroscopy. This experiment will turn the exception (like the optical observations of GRB 080319B) to routine.
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