The Giant Magellan Telescope (GMT) will be a 25-meter optical telescope with a maximum weight of about 2300 t, located on Cerro Las Campanas in Chile. To fulfill the challenging pointing and tracking accuracy requirements, as well as the functionality requirements of the auxiliary subsystems, complex design solutions needed to be developed. To support and validate the design of those subsystems and to provide reliable data and parameter for performance analysis, a variety of prototyping tests have been performed during the design phase. The telescope support consists of a radial spring system that allows thermal decoupling to the concrete foundation, an earthquake damping system as well as frictionless hydrostatic bearings and a high-performance direct drives and control system. Highly accurate and precise mechanical components need to be consistent to gravity-caused structural deformations. This requires special supports to avoid structural overload. These unique supports, especially developed for the GMT have been prototyped. Self-induced vibrations are one of the most disturbing influences on such complex control systems as well as the adaptive optics of the telescope and need to be suppressed or at least reduced wherever possible. Tests have been performed to measure and optimize vibration sources like cable wraps and electronic cabinets. The covers of the primary mirrors with a diameter of more than eight meters were developed and tested in full scale to ensure proper function even in tilted position when the telescope rotates in elevation. Falling object tests have been made to demonstrate the protection of the mirrors. An inflatable wash seal around each mirror has been tested to ensure reliable functionality. The presentation will provide an overview on the subsystem development test activities and show test setups and results of main component tests supporting the subsystems design and analyses.
The Hydrostatic Bearing System (HBS) is one of the core assemblies of the Giant Magellan Telescope mount. It supports the high dead loads of the moving parts of the entire telescope while providing a stick slip free rotation in the main axes. It is capable of compensating for structural deformations while maintaining a thin oil film layer between the moving parts. Hydraulic groups have been designed to provide the kinematic compliance required to keep the bearing loads almost constant, even under geometrical deviations. The complete development of the bearing was supported by Finite Element Analysis (FEA) for various aspects. FEA was used to predict the deformation of the bearings and tracks under hydraulic loading down to the micrometer level in order to verify one of the major contributors to the oil film budget. On the other hand, FEA was taken to perform quasi static deformation analyses of the entire telescope for gravity load cases and verify alignment of optical elements and provide the basis for the levelling and tilting feature sizing of the HBS. Furthermore, a comprehensive seismic analysis was performed with various loads. The results were a driver for the hydraulic schematic. In addition to the FEA, a dynamic simulation was carried out to analyze the dynamic effects of wind loads and the effects of load variations when bearing pads pass geometrical deviations of the tracks. In the end, a good balance was found between stiffness and limited disturbances. Careful leakage analyses were performes and taken into account in the design optimization to minimize the risk of oil contamination. This was achieved by a combination of oil suction, active scrapers, seals and by guiding measures to lead back the remaining oil to the main oil return system.
Self-induced vibrations along with wind-induced jitter are considered as most limiting factors for the performance of the Giant Magellan Telescope (GMT). The status of dynamic analysis in context of the latest GMT mount design activities is reported. Particular attention is paid to the vibration error budget, which is used to manage active disturbances to meet demanding tracking performance requirements. The vibration budget is based on tracking simulation results combined with contributions from different jitter and vibration sources such as drives, utility wraps, cabinets, and many other subsystems. The Mount Transfer Function (MTF) concept as an important tool for analysis of vibration paths from the source to the image motion is introduced and its application in several use cases with both modeled and measured disturbances is illustrated.
The Giant Magellan Telescope (GMT) will be a 25 meter optical telescope with a maximum weight of about 2300t, located on Cerro Las Campanas in Chile. The telescope will be equipped with a complex adaptive optical system as well as highly sensitive instrumentation and high performance drive and control components like direct drives and high resolution band encoders. For protection of this sensitive equipment from extreme earthquake excitations, a seismic isolation system implemented at the base of the concrete telescope pier will reduce horizontal accelerations. A second earthquake damping system, currently under development at OHB, will be installed on the GMT Mount to suppress vertical accelerations. In addition to the damping system itself, adaptations need to be made to the drive and control components to allow the damping system movements without having an impact on their functionality. A prototype of the vertical damping system will be built and dynamic testing will be performed. The presentation will provide an overview on the system development status.
The goal of the RAEGE (Red Atlantica Estaciones Geodinamicas Espaciales) project is the establishment of a Spanish-Portuguese network of geodynamical and spatial geodesy stations by the installation and operation of four fundamental geodetic / astronomical stations provided with radio telescopes located at
- Yebes, close to Madrid / Spain
- Tenerife, Canary Islands / Spain
- Santa Maria, Azores Islands / Portugal.
VLBI 2010 radiotelescopes are belonging to a new generation of radiotelescopes suitable for high precision geodetical earth observation and measurements, that shall allow to built up a high precision global reference system. The design of the radiotelescopes has been finished by MT Mechatronics in summer 2011 and currently three radiotelescopes are being manufactured. The first one is scheduled for installation in summer 2012 at Yebes Observatory close to Madrid.
The performance of single dish radio antennas or telescopes is depending on the surface accuracy of the reflectors in the
beam path and the focus/pointing errors induced by deviations/misalignment of the reflectors from a desired direction.
For multiple dish VLBI arrays an additional mechanical effect, the path length stability, is a further source of performance
degradation. For application at higher frequencies environmental influences as wind and temperature have to be
considered additionally to the usually required manufacturing and alignment accuracies. Active measurement ("metrology")
of the antenna deformations and their compensation by "active optics" (AO) respectively "flexible body compensation"
(FBC) are established methods. For the path length errors AO or FBC are up to now not established methods. The
paper describes how to handle the path length errors and the related metrology analogues to the established methods used
for surface and focus/pointing error corrections.
The Suspension Assembly is the most complex mechanical subsystem of the SOFIA telescope, responsible for suspending and positioning the telescope in the aircraft on the sky. It is a highly integrated system comprising of a vibration isolating system, a spherical hydraulic bearing, a spherical torque motor, a coarse drive and airworthiness relevant components like brakes, hard-stops etc. The components were manufactured under airworthiness standards by dedicated suppliers and integrated and commissioned in 2001/2002 at MAN Technologie in Augsburg. The paper describes the experience gotten during the manufacturing and integration process.
KEYWORDS: Telescopes, Space telescopes, System integration, Gyroscopes, Observatories, Mirrors, Sensors, Control systems, Spherical lenses, Process control
System integration and testing of an airborne telescope like SOFIA is a complex process and needs to be done in three phases: 1. pre-assembling the telescope on ground; 2. integration of the telescope into the aircraft on ground; 3. in-flight commissioning and testing. Due to practical reasons (available time resources, costs) not every item can be fi-nally commissioned and tested under all environmental conditions before flight, and cooperation and joint activities between the aircraft people, the telescope people and the later users is necessary. The paper describes, how the work is shared in the three phases, what experience has been gotten so far and what is planned for the remaining activities.
One of the main requirements for the SOFIA Telescope Assembly is the achievement of a pointing stability of 0.2 arcsec. For ground based telescopes, this does not appear to be a major problem, caused by the use of heavy foundation to stabilize the telescopes to the ground. But since the SOFIA telescope is mounted into an aircraft, a high technology Suspension Assembly is required.
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