The linear Atmospheric Dispersion Corrector has been operating at the SOuthern Astrophysical Research telescope since 2014. It was designed and built in collaboration between the University of North Carolina at Chapel Hill, and Cerro Tololo Inter-American Observatory. The device is installed in the elevation axis before the instruments mounted at the optical Nasmyth focus. It consists of two 300mm diameter sol-gel coated fused silica prisms, trombone mounted, which can be folded in or out of the beam. It is important for long slit spectroscopy, and essential for Multi-Object Slit spectroscopy. We present optical and mechanical designs, electronics and software control, and on-sky performance.
The adaptive module of the 4-m SOAR telescope (SAM) has been tested on the sky by closing the loop on
natural stars. Then it was re-configured for operation with low-altitude Rayleigh laser guide star in early 2011.
We describe the performance of the SAM LGS system and various improvements made during one year of on-sky
tests. With acceptably small LGS spots of 1.6′′ the AO loop is robust and achieves a resolution gain of almost
two times in the I band, under suitable conditions. The best FWHM resolution so far is 0.25′′ over the 3′ field
of the CCD imager.
The SOAR telescope fast tip-tilt tertiary mirror, was delivered by the Goodrich Optical and Space Systems Division,
Danbury, CT, and integrated into the SOAR optical system in 2004. It consist of a plane, light weighted 655×470 mm
elliptical mirror, controllable over a range of ±1 mrad, in two axes, with a required position loop bandwidth of 50 Hz. It
operates using the signal from a fast read-out guide camera to generate position commands, in an outer loop fashion.
The original tertiary mirror controller consisted of several analog circuit boards, incorporating the position control loop
compensation, and power amplifiers. This system was limited by the difficulty of making any modifications, to optimize
the control loop, and meet the required bandwidth. The analog controller was replaced with a digital controller based on
a National Instruments Compact RIO/FPGA device. This allows the full optimization of the control system, and also
allows closing the torque (acceleration) loop using the optical feedback of the guide signal alone, which should result in
even higher performance. This paper will describe the models, design, and performance tests, of the new digital control
An active tangent link system was developed to provide transverse support for large thin meniscus mirrors. The support
system uses six tangent links to control position and distribute compensating force to the mirror. Each of the six tangent
links utilizes an electromechanical actuator and an imbedded lever system working through a load cell and flexure. The
lever system reduces the stiffness, strength and force resolution requirements of the electromechanical actuator and
allows more compact packaging. Although all six actuators are essentially identical, three of them are operated quasi
statically, and are only used to position the optic. The other three are actively operated to produce an optimal and
repeatable distribution of the transverse load. This repeatable load distribution allows for a more effective application of
a look up table and reduces the demands on the active optics system.
A control system was developed to manage the quasi static force equilibrium servo loop using a control matrix that
computes the displacements needed to correct any force imbalance with good convergence and stability.
This system was successfully retrofitted to the 4.3 meter diameter, 100 mm thick SOAR primary mirror to allow for
more expeditious convergence of the mirror figure control system. This system is also intended for use as the transverse
support system for the LSST 3.4 meter diameter thin meniscus secondary mirror.
Development of the 4.1 meter SOuthern Astrophysical Research (SOAR) Telescope is now complete. All baseline systems are in place and extensive commissioning activities have been performed with and without the primary optics installed in the telescope. The facility and dome have been under observatory operations and TCS control for a year of testing and tuning. The altitude over azimuth telescope mount was integrated on the mountain in a rapid 3-month period due to the complete assembly and testing performed at the factory prior to delivery. Early mount testing and successful integration into the Telescope Control System (TCS) without the optical system was accomplished on the sky through use of two separate small aperture telescopes fixed to the structure. One of these, the "feed telescope" was also pivotal in early testing of the calibration wavefront sensor and SOAR optical imager by directing focused light to these separate instruments. The SOAR optical system, with its 4.1 meter clear aperture, 100 cm thick, ULEtm primary mirror, its lightweight ULEtm secondary, and its fast tip tilt ULEtm tertiary has been delivered and installed in the telescope. This system was also assembled as an electrically connected system and individually optically tested under a visible interferometer at the factory enabling rapid integration and a short commissioning period on telescope. In this paper we present the project status, a summary of the commissioning period, and the performance data for the completed telescope and its major components.
The 4.1 meter Southern Astrophysical Research (SOAR) Telescope is now entering the operations phase, after a period of construction and system commissioning. The SOAR TCS implemented in the LabVIEW software package, has kept pace throughout development with the installation of the other telescope subsystems, and has proven to be a key component for the successful deployment of SOAR. In this third article of the SOAR TCS series, we present the results achieved when operating the SOAR telescope under control of the SOAR TCS software. A review is made of the design considerations and the implementations details, followed by a presentation of the software extensions that allows a seamless integration of instruments into the system, as well as the programming techniques that permit the execution of remote observing procedures.
Development of the SOuthern Astrophysical Research (SOAR) Telescope is nearing completion atop Cerro Pachón in Chile. The facility and many accessory systems have been completed and are operational. The dome is installed and in the final stages of debugging, the telescope mount is being assembled on site after a successful trial integration and complete test at the contractor's facility, and the optical system is well on its way to completion later this year. Many instruments are under development with one in the final phases of integration and laboratory testing. This paper summarizes the status of the major subsystems, provides measured performance parameters where available, and outlines the remaining plans for the telescope development and subsequent commissioning.
To meet the needs of the SOAR 4.2-m telescope first-generation instrument suite, as well as new instruments for the Blanco 4-m telescope, we developed a new camera controller system called ArcVIEW. In order to provide a strong foundation and rapid development cycle, we decided to build the system using National Instrument's LabVIEW environment. The advantages of this approach centers on the tools available for rapid prototyping, integration and testing of components.
Over the past 2 years, we have taken ArcVIEW from a design document to the point of controlling two new instruments being built at CTIO. The IR imager, ISPI, will complete final testing this semester and go into use on the Blanco telescope in September 2002.
The second instrument, the SOAR Optical Imager, is due for completion this semester and will be the commissioning instrument for the SOAR telescope, for which first light is expected in early 2003.