The mm-wavelength sky reveals the initial phase of structure formation, at all spatial scales, over the entire observable history of the Universe. Over the past 20 years, advances in mm-wavelength detectors and camera systems have allowed the field to take enormous strides forward – particularly in the study of the Cosmic Microwave Background – but limitations in mapping speeds, sensitivity and resolution have plagued studies of astrophysical phenomena. In fact, limitations due to inherent biases in the ground-based mm-wavelength surveys conducted over the last 2 decades continue to motivate the need for deeper and wider-area maps made with increased angular resolution. TolTEC is a new camera that will fill the focal plane of the 50m diameter Large Millimeter Telescope (LMT) and provide simultaneous, polarization-sensitive imaging at 2.0, 1.4, and 1.1mm wavelengths. The instrument, now under construction, is a cryogenically cooled receiver housing three separate kilo-pixel arrays of Kinetic Inductance Detectors (KIDs) that are coupled to the telescope through a series of silicon lenses and dichroic splitters. TolTEC will be installed and commissioned on the LMT in early 2019 where it will become both a facility instrument and also perform a series of 100 hour “Legacy Surveys” whose data will be publicly available. The initial four surveys in this series: the Clouds to Cores Legacy Survey, the Fields in Filaments Legacy Survey, the Ultra-Deep Legacy Survey and the Large Scale Structure Survey are currently being defined in public working groups of astronomers coordinated by TolTEC Science Team members. Data collection for these surveys will begin in late 2019 with data releases planned for late 2020 and 2021. Herein we describe the instrument concept, provide performance data for key subsystems, and provide an overview of the science, schedule and plans for the initial four Legacy Survey concepts.
The Large Millimeter Telescope observatory is extending its night time operation to the day time. A sun avoidance strategy was therefore implemented in the control system in real-time to avoid excessive heating and damage to the secondary mirror and the prime focus.
The LMT uses an ”on-the-fly” trajectory generator that receives as input the target location of the telescope and in turn outputs a commanded position to the servo system. The sun avoidance strategy is also implemented ”on-the-fly” where it intercepts the input to the trajectory generator and alters that input to avoid the sun. Two sun avoidance strategies were explored. The first strategy uses a potential field approach where the sun is represented as a high-potential obstacle in the telescope’s workspace and the target location is represented as a low-potential goal. The potential field is repeatedly calculated as the sun and the telescope move and the telescope follows the induced force by this field. The second strategy is based on path planning using visibility graphs where the sun is represented as a polygonal obstacle and the telescope follows the shortest path from its actual position to the target location via the vertices of the sun’s polygon.
The visibility graph approach was chosen as the favorable strategy due to the efficiency of its algorithm and the simplicity of its computation.
One of the fundamental design principles of the LMT is that its segmented primary surface must be active: the position and orientation of each of the segments must be moved in order to maintain the precise parabolic surface that is required by the specifications. Consequently, a system of actuators, one at the corner of each segment, is used to move the segments to counteract surface deformations attributed to gravity or thermal effects.
A new control system was designed and built within the project to implement an active surface at the LMT. The technical concept for the active surface control system is to provide a set of bus boxes with built-in control and I/O capabilities to run four actuators each. Bus boxes read the LVDT sensor position and limit switch status for each actuator and use this information to drive the actuator’s DC motor, closing the position loop. Each bus box contains a DC power supply for the electronics, a second DC power supply for the motors, an embedded controller with I/O to close the position loop, and a custom printed circuit board to condition the LVDT signals and drive the motors. An interface printed circuit board resides in each actuator providing a single connector access to the LVDT, the motor, and the limit switches. During the fall of 2013, 84 bus boxes were commissioned to control the 336 actuators of the inner three rings of the telescope. The surface correction model was determined using holography measurements and the active surface system has been in regular use during the scientific observation at the LMT.
The infrared optical telescope array (IOTA), one of the most productive interferometers in term of science and
new technologies was decommissioned in summer 2006. We discuss the testing of a low-resolution spectrograph
coupled with the IOTA-3T integrated-optics beam combiner and some of the scientific results obtained from this
We present a brief review of recent scientific and technical advances at the Infrared Optical Telescope Array (IOTA). IOTA is a long-baseline interferometer located atop Mount Hopkins, Arizona. Recent work has emphasized the use of the three-telescope interferometer completed in 2002. We report on results obtained on a range of scientific targets, including AGB stars, Herbig AeBe Stars, binary stars, and the recent outburst of the recurrent nova RS Oph. We report the completion of a new spectrometer which allows visibility measurements at several high spectral resolution channels simultaneously. Finally, it is our sad duty to report that IOTA will be closed this year.
Closure-phase science and technology are dominant features of the recent activity at IOTA.
Our science projects include imaging several spectroscopic binary stars, imaging YSOs including Herbig AeBe stars, detecting asymmetries in a large sample of Mira stars, and measuring water shells around Miras.
Many technology projects were pursued in order to make these science observations possible. These include installation of a third-generation integrated-optics 3-beam combiner (IONIC), completion of the real-time control system software, installation of fringe-packet tracking software, use of narrow sub-H band filters, validation of
the phase-closure operation, development of CPLD control of the science camera (PICNIC) and star-tracker camera (LLiST), installation of a new star-tracker camera, expansion of the observing facility, and installation of new semi-automated optical alignment tools.
Remote access to telescope monitor and control capabilities
necessitates strict security mechanisms to protect the telescope and
instruments from malicious or unauthorized use, and to prevent data
from being stolen, altered, or corrupted. The Large Millimeter
Telescope (LMT) monitor and control system (LMTMC) utilizes the Common
Object Request Broker Architecture (CORBA) middleware technology to
connect remote software components.
The LMTMC provides reliable and secure remote observing by
automatically generating SSLIOP enabled CORBA objects. TAO, the ACE
open source Object Request Broker (ORB), now supports secure
communications by implementing the Secure Socket Layer Inter-ORB
Protocol (SSLIOP) as a pluggable protocol. This capability supplies
the LMTMC with client and server authentication, data integrity, and
encryption. Our system takes advantage of the hooks provided by TAO
SSLIOP to implement X.509 certificate based authorization. This
access control scheme includes multiple authorization levels to enable
granular access control.
The Large Millimeter Telescope monitor and control system is
automatically generated from a set of XML configuration files. This
insures that all inter-system communications and user interfaces
adhere to a common standard. The system was originally designed to
control the electro-mechanical components of the telescope but it maps
well to the control of instruments. Properties of the instruments are
defined in XML and subsequent control and communication code and user
interfaces are generated. This approach works well in theory, however,
when it comes to installing the system on the actual instruments,
several problems arise: the goals of instrument developers, software support for instrument developers, hardware compatibility issues, and choice of computer architecture and development environment.
In this paper, we present a discussion of the above issues and suggest tried solutions.
The Large Millimeter Telescope monitor and control system (LMTMC) is an automatically generated software system that is implemented using XML and Java. One of the requirements of the system is catalog support. Rather than developing new catalog navigation techniques and building them into the automatically generated code, we chose to use JSky. JSky is a set of Java components providing catalog and image support for Astronomy. The JSky classes are extended to form new classes with additional capabilities that tighten the integration with the LMTMC system. Not only can users navigate local and web hosted catalogs, they can also direct output from catalogs into the control panels of the system eliminating error-prone typing or cut and paste operations. In addition, users can retrieve digital sky survey images from the catalogs, and superimpose scientific data on them to verify correct operation.
The monitor and control system of a telescope must provide users with a way to control certain values in the system and view other constantly changing values. Users may also want to log system values to a database and chart changes to numerical values in real time. The components of a telescope system may change and instruments may be added and removed. The set of values that the monitor and control system must provide access to may therefore change. The challenge is to provide a flexible monitor and control system to accommodate changes to the system. The Large Millimeter Telescope monitor and control system is automatically generated from a set of XML configuration files. Because the code for the system's software objects is generated automatically it is easy to include in the generated code sufficient information about the objects to inform the display. This paper will present monitor, control, logging and charting tools that automatically change to reflect changes in the components and properties of the system. These tools depend on generating software objects that include information about their own fields.
A telescope system is composed of a set of real-world objects that are mapped onto software objects whose properties are described in XML configuration files. These XML files are processed to automatically generate user interfaces, underlying communication mechanisms, and extendible source code. Developers need not write user interfaces or communication methods but can focus on the production of scientific results. Any modifications or additions of objects can be easily achieved by editing or generating corresponding XML files and compiling them into the system.
This framework can be utilized to implement servo controllers, device drivers, observing algorithms and instrument controllers; and is applicable to any problem domain that requires a user-based interaction with the inputs and outputs of a particular resource or program. This includes telescope systems, instruments, data reduction methods, and database interfaces. The system is implemented using Java, C++, and CORBA.