The MMT Observatory uses a suite of Shack-Hartmann wavefront sensors to maintain telescope focus, collimation, and primary mirror figure. The first of those systems were developed and commissioned in 2001–2003 and in routine operation since then. The software developed control these systems and analyze the data they produce was largely unchanged until 2017. We have since replaced that software with completely new software based on Python and the AstroPy ecosystem.
The MMT Observatory (MMTO) uses a suite of Shack-Hartmann wavefront sensors to maintain focus, collimation, and primary mirror optical figure. This first of these were fully commissioned in early 2003 and they have been an integral part of routine operations since then. The data they produce can also be used to estimate the atmospheric seeing in a consistent way that follows the same optical path as the science instruments. We have used archived Shack-Hartmann wavefront sensor data to measure seeing statistics over the course of the last 15 years of MMTO operations.
Pandeia is the exposure time calculator (ETC) system developed for the James Webb Space Telescope (JWST) that will be used for creating JWST proposals. It includes a simulation-hybrid Python engine that calculates the two-dimensional pixel-by-pixel signal and noise properties of the JWST instruments. This allows for appropriate handling of realistic point spread functions, MULTIACCUM detector readouts, correlated detector readnoise, and multiple photometric and spectral extraction strategies. Pandeia includes support for all the JWST observing modes, including imaging, slitted/slitless spectroscopy, integral field spectroscopy, and coronagraphy. Its highly modular, data-driven design makes it easily adaptable to other observatories. An implementation for use with WFIRST is also available.
Proc. SPIE. 8444, Ground-based and Airborne Telescopes IV
KEYWORDS: Observatories, Telescopes, Astronomy, Reliability, Adaptive optics, Large telescopes, Atmospheric turbulence, Infrared telescopes, Atmospheric monitoring, Global system for mobile communications
We present a comprehensive review of the first two years of a site monitoring campaign at the South African Astronomical Observatory (SAAO) located outside Sutherland, South Africa. This campaign is in support of the Southern African Large Telescope (SALT), a 11-metre, fixed-elevation, optical telescope located at SAAO . The heart of this observing campaign involves continuous monitoring of the site by a MASS-DIMM instrument. The MASS-DIMM has been in routine use since March 2010 and its operation is now fully automated. At the beginning of this campaign, simultaneous observations were also made by a SLODAR instrument, which allows high resolution observations of the lower atmosphere. In August 2011 a two week campaign was carried out with a two-channel Generalized Seeing Monitor (GSM) telescope along with a lunar limb profiler (Profileur Bord Lunaire; PBL). Combined with the MASS-DIMM data these observations provide multiple independent measurements of atmospheric turbulence as a function of height. They also help improve the calibration of our site for more direct comparison to other major astronomical observatories. Our results so far indicate that the atmospheric conditions at the SAAO Sutherland site have deteriorated compared to past measurements. The ground layer accounts for the majority of the integrated seeing, while the free atmosphere seeing is comparable with other major sites.
The Southern African Large Telescope (SALT), located at the South African Astronomical Observatory (SAAO) site near Sutherland, South Africa, is an 11-metre fixed-elevation telescope currently operating at UV-visible wavelengths (320-950 nm) with a near-infrared extension (850-1700 nm) due in the near future. SALT does not currently have an adaptive optics (AO) system and a feasibility study for adding one is under way. Using results from an on-going site monitoring campaign at the SAAO we have begun carrying out simulations to investigate how different AO systems might perform and could be optimized for SALT. We will present the parameters of an optimization study and performance results for a single on-axis natural guide star (NGS) AO system on SALT for operation at both visible (R) and near-IR (J and H) wavelengths.
PySALT is the python/PyRAF-based data reduction and analysis pipeline for the Southern African Large Telescope
(SALT), a modern 10m class telescope with a large user community consisting of 13 partner institutions. The two first
generation instruments on SALT are SALTICAM, a wide-field imager, and the Robert Stobie Spectrograph (RSS). Along
with traditional imaging and spectroscopy modes, these instruments provide a wide range of observing modes, including
Fabry-Perot imaging, polarimetric observations, and high-speed observations. Due to the large user community, resources
available, and unique observational modes of SALT, the development of reduction and analysis software is key to
maximizing the scientific return of the telescope. PySALT is developed in the Python/PyRAF environment and takes
advantage of a large library of open-source astronomical software. The goals in the development of PySALT are: (1)
Provide science quality reductions for the major operational modes of SALT, (2) Create analysis tools for the unique
modes of SALT, and (3) Create a framework for the archiving and distribution of SALT data. The data reduction software
currently provides support for the reduction and analysis of regular imaging, high-speed imaging, and long slit
spectroscopy with planned support for multi-object spectroscopy, high-speed spectroscopy, Fabry-Perot imaging, and
polarimetric data sets. We will describe the development and current status of PySALT and highlight its benefits through
early scientific results from SALT.
The 6.5m MMT telescope currently has three focal configurations. The f/5 optical configuration has a system of optical
baffles to prevent stray light from entering the focal plane. The system consists of a cone baffle supported on the
secondary (M2) structure and set of concentric rings suspended between the secondary and the primary (M1). This paper
reviews the optical configurations, mechanical design, alignment, installation, and measured performance of the system.
In using common HTML/Ajax approaches for web-based data presentation and telescope control user interfaces at the
MMT Observatory (MMTO), we rapidly were confronted with web browser performance issues. Much of the
operational data at the MMTO is highly dynamic and is constantly changing during normal operations. Status of
telescope subsystems must be displayed with minimal latency to telescope operators and other users. A major
motivation of migrating toward web-based applications at the MMTO is to provide easy access to current and past
observatory subsystem data for a wide variety of users on their favorite operating system through a familiar interface,
their web browser. Performance issues, especially for user interfaces that control telescope subsystems, led to
investigations of more efficient use of HTML/Ajax and web server technologies as well as other web-based
technologies, such as Java and Flash/Flex. The results presented here focus on techniques for optimizing HTML/Ajax
web applications with near real-time data display. This study indicates that direct modification of the contents or
"nodeValue" attribute of text nodes is the most efficient method of updating data values displayed on a web page. Other
optimization techniques are discussed for web-based applications that display highly dynamic data.
We have performed finite element thermal analysis of our 6.5 meter primary mirror in the hopes of improving
the accuracy of our open loop models and reducing the need to interrupt science observations to tune our optics.
In the analysis we apply temperature variations to the front, back, and middle of the mirror to correspond to the
locations of installed thermocouples. The input temperature variations and the predicted steady-state surface
distortions are modeled as Zernike polynomials. The most significant effect we find is the focus error generated
by a temperature gradient between the front and back of the mirror. Comparison with wavefront sensor data
shows that we can get reasonably good agreement between predicted and measured focus errors. However, we
do not yet get good agreement for other, higher order terms. There is also poorer agreement when conditions
are changing rapidly.
The MMT all-sky camera is a low-cost, wide-angle camera system that takes images of the sky every 10 seconds, day and night. It is based on an Adirondack Video Astronomy StellaCam II video camera and utilizes an auto-iris fish-eye lens to allow safe operation under all lighting conditions, even direct sunlight. This combined with the anti-blooming characteristics of the StellaCam's detector allows useful images to be obtained during sunny days as well as brightly moonlit nights. Under dark skies the system can detect stars as faint as 6th magnitude as well as very thin cirrus and low surface brightness zodiacal features such as gegenschein. The total hardware cost of the system was less than $3500 including computer and framegrabber card, a fraction of the cost of comparable systems utilizing traditional CCD cameras.
Shack-Hartmann wavefront sensors have been commissioned and are now in
routine use at both of the optical foci (f/9 and f/5) of the converted
MMT. Both units are of moderate resolution with 14x14 square
apertures across the pupil for f/5 and 13x13 hexagonal apertures for
f/9. They share a common software interface that fits a set of 19
Zernike polynomials to the wavefront errors. Zernike focus and coma
are corrected by moving the secondary mirror, third order spherical by
a combination of secondary motion and primary bending, and the rest by
primary bending alone. In this paper we will describe the two
wavefront sensor systems and how they have performed thus far.
Originally commissioned in 1979, the Multiple Mirror Telescope was a highly innovative and successful facility that pioneered many of the technologies that are used in the new generation of 8 to 10 m class telescopes. After 19 years of operations the MMT was decommissioned in March of 1998: the enclosure was modified, the optics support structure was replaced, and a single 6.5-meter primary mirror was installed and aluminized in-situ. First light for the new MMT was celebrated on May 13, 2000. Operations began with an f/9 optical configuration compatible with existing instruments. Work has continued commissioning two new optical configurations that will serve a suite of new instruments: an f/15 deformable secondary mirror and adaptive optics facility that has obtained diffraction-limited images; and an f/5.4 secondary mirror and refractive corrector that provides a one-degree diameter field of view. The wide-field instrument suite includes two fiber-fed bench spectrographs, a robotic fiber positioner, and a wide-field imaging camera.