The MCAO Assisted Visible Imager and Spectrograph (MAVIS) is currently in preliminary design for the ESO VLT. The instrument will provide multi-conjugate adaptive optics correction over a wide field of 30”x30”, feeding the visible part of the spectrum (from 370 to 1000nm) to an imager and a spectrograph. The Adaptive Optics Module (AOM) of MAVIS implements two deformable mirrors, composed by more than 2000 actuators each, and includes a Laser Guide Star (LGS) and a Natural Guide Star (NGS) wavefront sensor for the tomographic reconstruction and correction of the atmospheric turbulence. Moreover, it provides other key functionalities like atmospheric dispersion compensation and field de-rotation, delivering a corrected diffraction-limited 30”x30” focal plane to three output ports: one for the imager, one for the spectrograph and one for visiting instruments. In this paper we describe the current optical configuration of the AOM, and we report the results of the analyses conducted to evaluate the expected optical performance of the system. The analyses include simulations for the manufacturing and alignment tolerances, sensitivity to mid-spatial frequency figure errors and their impact to astrometry.
MAVIS will be part of the next generation of VLT instrumentation and it will include a visible imager and a spectrograph, both fed by a common Adaptive Optics Module. The AOM consists in a MCAO system, whose challenge is to provide a 30” AO-corrected FoV in the visible domain, with good performance in a 50% sky coverage at the Galactic Pole. To reach the required performance, the current AOM scheme includes the use of up to 11 reference sources at the same time (8 LGSs + 3 NGSs) to drive more than 5000 actuators, divided into 3 deformable mirrors (one of them being UT4 secondary mirror). The system also includes some auxiliary loops, that are meant to compensate for internal instabilities (including WFSs focus signal, LGS tip-tilt signal and pupil position) so to push the stability of the main AO loop and the overall performance. Here we present the Preliminary Design of the AOM, which evolved, since the previous phase, as the result of further trade-offs and optimizations. We also introduce the main calibration strategy for the loops and sub-systems, including NCPA calibration approach. Finally, we present a summary of the main results of the performance and stability analyses performed for the current design phase, in order to show compliance to the performance requirements.
MAVIS is a Multi-Conjugate Adaptive Optics for the UT4 of VLT designed to deliver a corrected FoV to a spectrograph, an imager, and a visiting instrument. An optical bench is used to support the post focal relay optics, which include the ADC, a K-mirror, the DM, and the selector. Said bench also rigidly supports the calibration, the LGS module, the NGS module and the imager providing the maximum stability and repeatability during maintenance operations. The Adaptive Optics Module structure (AOMS) was rigidly connected to the Nasmyth platform structure via the Overall Mechanical Structure (OMS). The OMS also provides structural integrity for the Spectrograph sub-system while isolating it from the main enclosure. At this level the AOMS and the OMS have been merged in a single structure; the decision about keeping them together or separated will be taken in the future depending on mechanical and integration considerations. The preliminary design choices adopted while designing these subsystems are presented considering the actual mechanical and thermal requirements. Particular attention is given to the derotation system design (K-mirror) and the analyses done to choose the materials and the adhesives.
An indium-gallium-arsenide (InGaAs) detector is tested for use on the new Dynamic REd All-sky Monitoring Survey (DREAMS) 0.5-m telescope. DREAMS is novel for its use of InGaAs as a higher-noise and lower-cost alternative to mercury-cadmium-telluride. The Princeton Infrared Technologies 1280SCICAM, which has one of the smallest pitches and largest focal planes of any commercially available InGaAs detector, is extensively characterized to determine the viability of InGaAs detectors for astronomy. We find the 1280SCICAM to have the one of the lowest dark currents (67e − / s) of any commercially available InGaAs focal plane array, and also confirm no fringing or non-linearity is present. Given its low noise, we conclude that DREAMS will be sufficiently background limited with InGaAs, and by extension, InGaAs is well-suited for application on low-angular-resolution NIR instruments.
The DREAMS telescope is currently under construction at the Siding Spring Observatory. Once completed, the 0.5m telescope will be the fastest infrared surveyor in the southern hemisphere and one of the best tool available for transient astronomy. The Opto-mechnical design is fully custom and consists of two distinct sections: The telescope tube assembly and the instrument optical relay that feeds the light into six InGaAs cameras. We present here, the details of the mechanical design of the telescope.
Discussion of a optical design for an Eight Channel Imager/Polarimeter is presented. The design will cover the optical and Near Infrared(NIR) wavelengths from 330nm to 2400nm in a simultaneous acquisition mode for eight distinct broad bands. The simultaneous acquisition provides capabilities to study unique events such as supernovae, Gamma Ray Bursts(GRBs), and occultations. It also increases the efficiency of long term monitoring programs such as the study of blazars. The selection of the wavelength bands were specifically chosen to match the Sloan Digital Sky Survey(u0, g0, r0, i0,z0) and the 2MASS(J,H,K) catalogs.
We present an updated optical and mechanical design of NEWS: the Near-infrared Echelle for Wide-band Spectroscopy (formerly called HiJaK: the High-resolution J, H and K spectrometer), a compact, high-resolution, near-infrared spectrometer for 5-meter class telescopes. NEWS provides a spectral resolution of 60,000 and covers the full 0.8-2.5 μm range in 5 modes. We adopt a compact, lightweight, monolithic design and have developed NEWS to be mounted to the instrument cube at the Cassegrain focus of the new 4.3-meter Discovery Channel Telescope.
HIPO is a special purpose science instrument for SOFIA that was also designed to be used for Observatory test work. It
was used in a series of flights from June to December 2011 as part of the SOFIA Characterization and Integration
(SCAI) flight test program. Partial commissioning of HIPO and the co-mounted HIPO-FLITECAM (FLIPO)
configuration were included within the scope of the SCAI work. The commissioning measurements included such
things as optical throughput, image size and shape as a function of wavelength and exposure time, image motion
assessment over a wide frequency range, scintillation noise, photometric stability assessment, twilight sky brightness,
cosmic ray rate as a function of altitude, telescope pointing control, secondary mirror control, and GPS time and position
performance. As part of this work we successfully observed a stellar occultation by Pluto, our first SOFIA science data.
We report here on the observed in-flight performance of HIPO both when mounted alone and when used in the FLIPO
configuration.
KEYWORDS: Charge-coupled devices, Digital signal processing, Telescopes, Camera shutters, Image storage, Clocks, Mirrors, Stars, Wavefront sensors, Global Positioning System
HIPO is a special purpose instrument for SOFIA, the Stratospheric Observatory For Infrared Astronomy. It is a high-speed,
imaging photometer that will be used for a variety of time-resolved precise photometry observations, including
stellar occultations by solar system objects and transits by extrasolar planets. HIPO will also be used during the test
program for the SOFIA telescope, a process that began with a series of ground-based tests in 2004. The HIPO
requirements, optical design, overall description, and an early look at performance and planned data acquisition modes
have appeared in earlier papers (e.g. Dunham, et al., Proc. SPIE 5492, 592-603 (2004)). This paper provides an update
to the instrument description, final lab measurements of instrument performance, and a discussion of the data produced
by the various observing modes.
HIPO is a special purpose instrument for SOFIA, the Stratospheric Observatory For Infrared Astronomy. It is a high-speed, imaging photometer that will be used for a variety of time-resolved precise photometry observations, including stellar occultations by solar system objects and transits by extrasolar planets. HIPO has two independent CCD detectors and can also co-mount with FLITECAM, an
InSb imager and spectrometer, making simultaneous photometry at three wavelengths possible. HIPO's flexible design and high-speed imaging capability make it well suited to carry out initial test observations on the completed SOFIA system, and to this end a number of additional
features have been incorporated. Earlier papers have discussed the design requirements and optical design of HIPO. This paper provides an overview of the instrument, describes the instrument's features, and reviews the actual performance, in most areas, of the completed instrument.
The Lowell Observatory Instrumentation System (LOIS) is an instrument control software system with a common interface that can control a variety of instruments. Its user interface includes GUI-based, scripted, and remote program control interfaces, and supports operational paradigms ranging from traditional direct observer interaction to fully automated operation. Currently LOIS controls a total of ten instruments built at Lowell Observatory (including one for SOFIA), NASA Ames Research Center, MIT (for Magellan), and Boston University. Together, these instruments include optical and near-IR imaging, spectroscopic, and polarimetric capability. This paper reviews the actual design of LOIS in comparison to its original design requirements and implementation approaches, and evaluates its strengths and weaknesses relative to operational performance, user interaction and feedback, and extensibility to new instruments.
HOPI is a special-purpose science instrument for SOFIA that is designed to provide simultaneous high-speed time resolved imaging photometry at two optical wavelengths. We intend to make it possible to mount HOPI and FLITECAM on the SOFIA telescope simultaneously to allow data acquisition at two optical wavelengths and one near-IR wavelength. HOPI will have a flexible optical system and numerous readout modes, allowing many specialized observations to be made. The instrument characteristics required for our proposed scientific pursuits are closely aligned to those needed for critical tests of the completed SOFIA Observatory, and HOPI will be used heavily for these tests.
The Lowell Observatory Instrumentation System is the control system for a series of new instruments at Lowell, including the SOFIA first light instrument, HOPI. Sine these instruments will incorporate various detector systems and will be used with several telescopes, the concept of a loadable modulator based design was developed. The fundamental idea is to view the telescope, camera, and other instrument components as separate, interchangeable entities.
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