This PDF file contains the front matter associated with SPIE Proceedings Volume 10012 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.
The E-ELT dynamical modeling toolkit is used extensively to understand the effect of vibrations from observatory equipments on the final performance of the telescope. The dynamical and control modeling toolkit uses the finite element model of the telescope structure and mirror units, the optical sensitivity and knowledge of the wavefront control correction capability to estimate the transmission of vibration from potential vibrational sources to the wavefront error. In addition, it helps i) to identify the sensitive optical units and sensitive vibrational sources and the frequency intervals they might affect most the wavefront error, ii) to perform design trade-offs, and iii) to derive subsystem specification requirements. In this paper, a vibration budgeting approach for the E-ELT using the modeling toolkit is presented.
The mirror segments for the E-ELT and TLT are nearly equal in size and shape (hexagonal, 1.2 m over flat sides). They
are very thin (about 50 mm) compared to their size. Supporting these mirrors and obtaining high optical performance is a
challenge from design and manufacturing point of view. TNO has designed and build (together with VDL-ETG) three
identical prototypes for supporting the mirror segments of the E-ELT. These mirror segments vary in size. Hence the
gravity induced deformation of the mirror segments will vary from mirror to mirror segment when no measures are
taken. The paper will concentrate on the design and analysis of the design features within the support structure to
minimize the mirror deformation due to gravity. These features concern passive and active means to influence the mirror
segment shape and to compensate for deformation differences.
Science goals of telescopes are the fundament data of integrated modeling of astronomical telescopes. The differences between science goals are sources of telescope’s diversities. Solar telescopes are a very special type in astronomical telescopes. Chinese Giant Solar Telescope1 (CGST) is currently designed to be an 8-meter Ring Interferometric Telescope (RIT). Even compare with the other solar telescopes, CGST is also an unusual telescope due to its ring aperture and distinctive science goals. As the initial data of integrated modeling of CGST, the main science cases determine the basic structure of the telescope as well as its working mode. This paper will discuss the importance of the primary science case in integrated modeling of CGST.
Chinese Giant Solar Telescope, which has a 8m diameter segmented primary mirror, is a plan for the next generation ground-based large solar telescope in China. A major scientific requirement for this telescope is the high accuracy polarimetry. In this paper, the instrumental polarization of the main optics is analyzed by polarization modeling, which is caused by off-axial field of view, spider asymmetry, nonuniform segment gap and segment coating. The result shows that the net polarization is sensitive to the asymmetrical spider leg widening and the uniformity of the segment optical property. For meeting the accuracy requirement, the extinction ratio and retardence error for each segment should be less than 0.3% and 0.8 degree, respectively. Generally, the ring segmented primary mirror have advantage in controlling the instrumental polarization for large main optics.
The Radboud University Nijmegen in collaboration with the NOVA Optical Infrared Instrumentation group at ASTRON is currently leading the development and realization of the BlackGEM observing facility. The BlackGEM science team aims to be the first to catch the optical counterpart of a gravitational wave event. The BlackGEM project will put an array of three medium-sized optical telescopes at the La Silla site of the European Southern Observatory in Chile. It is uniquely equipped to achieve a combination of wide-field and high sensitivity through its array-like approach. Each BlackGEM unit telescope is a modified Dall-Kirkham-type telescope consisting of a 65cm primary mirror, a 21cm spherical secondary mirror and a triplet corrector lens. The spatial resolution on the sky will be 0.56 asec/pixel and the total field-of-view per telescope is 2.7 square degrees. The main requirement is to achieve a 5-sigma sensitivity of 23rd magnitude within a 5-minute exposure under 15 m/s wind gust conditions. This demands a very stable optical system with tight control of all the error contributions. This has been realized with a spreadsheet based integrated instrument model. The model contains all relevant telescope instrument parameters and environmental conditions. The spreadsheet is partly used for performance calculations and partly used to combine and integrate the output from several other sources. The spreadsheet model calculates the overall performance based on an Exposure Time Calculator using the Noise Equivalent Area metric (NEA). The NEA is further budgeted over 7 main High Level Requirements. The spreadsheet model is coupled to 1) a ZEMAX telescope optical model 2) a telescope FEM analysis to predict the optomechanical response under various gravity, temperature and wind load conditions, 3) a Matlab Simulink thermal model to predict the transient temperature behaviour of the most important telescope elements and 4) a Matlab Simulink control model to predict the performance of the active M2 mirror. All outputs are collected in a system performance budget that readily shows the compliance with the main High Level Requirements.
ASTRI SST-2M is an end-to-end prototype of Small Size class of Telescope proposed for the Cherenkov Telescope Array (CTA). Currently under completion at the Serra La Nave observing station (Mt. Etna, Catania, Italy), the ASTRI SST- 2M telescope is the first imaging dual-mirror telescope ever realized for Cherenkov telescopes. A mini-array of nine such telescopes will form the ASTRI mini-array proposed as a precursor and initial seed of CTA to be installed at the final CTA southern site. ASTRI SST-2M is equipped with an active optics system, controlling both the segmented primary mirror and the monolithic secondary mirror, which allows optical re-alignment during telescope slew. We describe the hardware and software solution that have been implemented for optics control and the models we developed for the system.
The GTC (Gran Telescopio Canarias), with an equivalent aperture of 10.4 m, effective focal length of 169.9 m, located at
the Observatorio del Roque de los Muchachos , in La Palma, Canary Islands, will host on its Cassegrain focus the
GRAPE polarimeter (GRAntecan PolarimEter). At such focus the plate scale is 1.21 arcsec/mm and the unvignetted
FOV 8 arcmin. The instrument will provide full Stokes polarimetry in the spectral range 380-1500 nm, feeding
simultaneously up to two spectrographs. At the moment an interface to HORS (High Optical Resolution Spectrograph) is
being defined, located on the Nasmyth platform, it has a FWHM resolving power of about 25,000 (5 pixel) within a
spectral range of 400-680 nm. The rotator and instrumental flanges for the Cassegrain focus are currently under
definition. Hereafter I present the state of art of the mechanical design of the polarimeter, whose strategy is based on an
integrated model of Zemax design into ANSYS FEM static and dynamic analyses with thermal loads applied, in order to
retrieve tip-tilt, decentering errors and other significant parameters to be looped back to the Zemax model. In such a way
it is possible to compare and refine the results achieved through the tolerance analysis.
We present the proposal for the physical instrument model of the SOXS (Son OF X-Shooter) spectroscopic facility
mainly devoted to the follow-up observation of transient sources. A dedicated suitable instrument to exploit the science
of these transients is lacking, resulting in severe science “dissipation”. SOXS will cover the optical/NIR band (0.35-1.75
μm) with a medium resolution (R~4500), down to the limiting magnitude of R~20-20.5 (1 hr at S/N~10) that is perfectly
suited to study transients from on-going imaging surveys. Imaging capabilities in the optical are also foreseen to allow
for multi-band photometry of the faintest transients with a field of view of at least 2arcmin. We propose to implement a
physical modelling approach in order to link the instrument parameters and behaviour to physical quantities, thus
providing a description of the instrument that can be connected with measurements. The method has been already
successfully applied to the X-shooter instrument. The X-shooter physical model is based on a kernel optical ray-tracing
realised by means of matrix optics representation, which can handle a large number of wavelengths. This can be
extended to the SOXS design. The foreseen applications of the SOXS physical model are broad, ranging from support to
detailed instrument design and development of the data reduction software, wavelength calibration, evaluation of
instrument performance as a function of the model parameters, instrument alignment, and support during the
commissioning phase and as a tool for quality check during operations.
In this paper, we present an algorithm and supporting simulations results showing how a single conjugated AO system
can be used to detect a scalloping error occurring in the telescope. We show that when the scalloping error modes are
entered in the reconstruction modal basis, the Deformable Mirror shape can be used to estimate the scalloping error
through a simple matrix vector multiply. Temporal averaging allows to get rid of the atmospheric noise on the scalloping
measurement assuming a perfect “scalloping actuator” and to get a measurement accuracy of about 20nm rms.
The astronomical instrumentation needs high level of image quality and stability. The quality of images processed by an optical instrument can be referred to the size of the spot and/or the point spread function (p.s.f.), while the stability is related to the displacement of the spot centroid during the observations. The importance of new design procedures for astronomical instruments through the direct design of the materials taking into account their functionalities integrating different approaches (FEM + raytracing) is then enhanced by the new upcoming requirement.
Different functional materials can be joined together exploiting each peculiar property in order to realize
an integrated structure better known as Smart Structure. They are capable of sensing and reacting to their environment in a predictable and desired manner, through the integration of various elements, such as sensors, actuators, power sources, signal processors, and communications network.
The Paper describes possible application related to two main functional materials: piezoelectric materials and Shape Memory Alloys.
In order to simulate and investigate the dynamical-optical behavior of high precision optics, integrated modeling strategies and methods are proposed within this work. For instance, this optical systems can be a telescope optic or a lithographic objective. In order to derive a simplified mechanical model for time simulations with low computational cost, the method of elastic multibody systems in combination with model order reduction methods can be used. For this, software-tools and interfaces are developed. Furthermore, mechanical and optical simulation models are derived and implemented. In order to clarify these methods, an academic mirror example is chosen and the influence of the model order reduction methods is analysed.
The design of astronomical instrument is growing in dimension and complexity following ELT class telescopes.
The availability of new structural material like composite ones is asking for more robust and reliable designing
numerical tools. This paper wants to show a new opto-mechanical optimization approach developed starting
from a previously developed integrated design framework. The Idea is to reduce number of iteration in a multi-
variable structural optimization taking advantage of the embedded sensitivity routines that are available both
in FEA software and in raytracing ones. This approach provide reduced iteration number mainly in case of high
number of structural variable parameters.