KEYWORDS: Process control, Mirrors, Software frameworks, Data acquisition, Human-machine interfaces, Databases, Data modeling, Aluminum, Observatories, Data storage
Details of the software framework for the upcoming in-situ re-aluminization of the 6.5m MMT Observatory (MMTO) primary mirror are presented. This framework includes: 1) a centralized key-value store and data structure server for data exchange between software modules, 2) a newly developed hardware-software interface for faster data sampling and better hardware control, 3) automated control algorithms that are based upon empirical testing, modeling, and simulation of the aluminization process, 4) re-engineered graphical user interfaces (GUI’s) that use state-of-the-art web technologies, and 5) redundant relational databases for data logging. Redesign of the software framework has several objectives: 1) automated process control to provide more consistent and uniform mirror coatings, 2) optional manual control of the aluminization process, 3) modular design to allow flexibility in process control and software implementation, 4) faster data sampling and logging rates to better characterize the approximately 100-second aluminization event, and 5) synchronized “real-time” web application GUI’s to provide all users with exactly the same data. The framework has been implemented as four modules interconnected by a data store/server. The four modules are integrated into two Linux system services that start automatically at boot-time and remain running at all times. Performance of the software framework is assessed through extensive testing within 2.0 meter and smaller coating chambers at the Sunnyside Test Facility. The redesigned software framework helps ensure that a better performing and longer lasting coating will be achieved during the re-aluminization of the MMTO primary mirror.
The MMT Observatory (MMTO) uses a complex system of pneumatic actuators to support the telescope's 6.5m primary
mirror. For operational checkout after repair and to collect calibration data for use in the primary mirror support control software, the Steward Observatory Mirror Lab (SOML) built a test stand that accurately measures the output forces and moments from the actuator using a 6-DOF (degree of freedom) work plate. The electronics and software provided by SOML are outdated and needed replacing. In this report, we discuss the selection of EtherCAT as the data-acquisition hardware, the software development required, and the some aspects of using the test stand in the lab.
Over the past few years, the MMT Observatory has developed a number of web browser front ends for operation
interfaces and staff access to internal databases. Among these is a facility for viewed reduced tracking logs in both time
series and FFTs for convenient examination of tracking performance. Part of the back-end software also keeps the
tracking data in a searchable database, allowing data over long periods of time to be collected and analyzed to look for
trends, the influence of environmental factors on tracking, and help detect tracking degradation in a timely manner.
Starting in 2009, MMTO began design and installation of a new set of electronics to measure a set of radiallydistributed
type T thermocouples installed after the primary mirror polishing was completed. These thermocouples
are arranged in both single measurement points and as thermopiles for differential temperature sensing. Since the
goal of the primary mirror temperature control system is to minimize mirror seeing and mirror figure errors induced
by temperature variation across the primary mirror, it depends on excellent accuracy from the temperature sensing
system. The new electronics encompass on-board cold-junction compensation, real-time ITS-90 curve fitting, and
Ethernet connectivity to the data servers running in the MMTO software infrastructure. We describe the hardware
design, system wiring, and software used in this system.
The Multiple Mirror Telescope (MMT), upgraded in 2000 to a monolithic 6.5m primary mirror from its original array of six 1.8m primary mirrors, was commissioned with axis controllers designed early in the upgrade process without regard to structural resonances or the possibility of the need for digital filtering of the control axis signal path. Post-commissioning performance issues led us to investigate replacement of the original control system with a more modern digital controller with full control over the system filters and gain paths. This work, from system identification through
controller design iteration by simulation, and pre-deployment hardware-in-the-loop testing, was performed using latest-generation
tools with Matlab® and Simulink®. Using Simulink's Real Time Workshop toolbox to automatically generate C source code for the controller from the Simulink diagram and a custom target build script, we were able to deploy the new controller into our existing software infrastructure running Wind River's VxWorks™real-time operating system. This paper describes the process of the controller design, including system identification data collection, with discussion of implementation of non-linear control modes and disturbance decoupling, which became necessary to obtain acceptable wind buffeting rejection.
In May, 2000 the MMT Conversion was dedicated. Space limitations on the summit of Mt. Hopkins, AZ and limited financial resources dictated in-situ aluminization of the φ 6.5m primary mirror. Some of the attendant challenges successfully addressed in the course of accomplishing that task are described. For example: a 22 metric ton, φ7m vacuum head had to be lifted 25m before being lowered through the horizon-pointing telescope truss (clearing by 16 mm), then secured to the mirror cell that serves as a vacuum vessel; dirty mirror-support hardware integral to the cell required isolation of the process volume operating at 10-6mbar; extensive modeling of source geometry was needed to achieve uniformity goals at very short source-substrate distances; and a cost-effective 75kW DC filament voltage source using commercially-available arc welders was developed that allowed simultaneous firing of 200 evaporation sources. Details of design and construction of the evaporation system are given along with techniques and results of the successful coating in November 2001 and September 2005.
Dan Blanco, Michael Alegria, Shawn Callahan, Dusty Clark, Brian Comisso, Craig Foltz, J. Gibson, Carol Heller, Ron James, Bill Kindred, Steve King, Cory Knop, Howard Lester, John McAfee, Alejandra Milone, Ricardo Ortiz, Timothy Pickering, Phil Ritz, Barbara Russ, Gary Schmidt, Dennis Smith, Peter Spencer, Tom Trebisky, Ken Van Horn, Steven West, Court Wainwright, Grant Williams, J. Williams
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.
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