A study is presented of the impact on science data from extremely large telescopes of a transformation of wavelength
base for optimization of actuator architecture from 2 200 to 1 250 nm. From the optical path difference (OPD) data for
Euro50, we transform to E-ELT OPDs. We compute the corresponding power spectrum, in which we simulate a higher
actuator density via high-pass filtering to convert from K to J band actuator-pitch optimization. From the modified
power spectrum we derive the correspondingly modified OPDs, PSFs and Strehl ratios. A massive improvement is
demonstrated resulting from converting from AO@K to AO@J. This result is followed up by model-based E-ELT
imaging in a field in a galactic disc at a distance of 4 Mpc. The improvements in image quality, background and limiting
magnitude are very large as are the increases in photometric precision derived from the field imaging. Further, the great
science benefit and large opportunities provided by partial AO is demonstrated. In conclusion, while admittedly
challenging, pushing AO optimization to wavelengths as short as possible is of prime concern for the science output of
Integrated models including optics, structures, control systems, and disturbances are important design tools
for Extremely Large Telescopes (ELTs). An integrated model has been formulated for the European ELT
and it includes telescope structure, main servos, primary mirror segment control system, wind, optics, wavefront
sensors, deformable mirror, and an AO reconstructor and controller. There are three model phases: Initialization,
execution of a solver to determine time responses, and post-processing. In near future, the model will be applied
for performance studies and design trade-offs for the European ELT.
Observational High Time Resolution Astrophysics differs from conventional astrophysics in regard to the detectors
employed which have a time resolution less than that obtainable through CCD with a normal readout τ < a few
minutes. This paper looks at the implications for HTRA from extremely large telescopes and specifically, as an
exemplar its possible impact on pulsar astrophysics. We demonstrate, by using the derived point-spread-function
from models of the Euro50 telescope, the possible effects active and adaptive mirrors have on observing rapidly
varying astronomical objects.
A number of Extremely Large Telescopes for visual-infrared and adjacent wavelengths are in various degrees
of progress. All have primary mirrors with equivalent diameters larger than 20 m and are intended for operation with
adaptive optics systems. We discuss several ELT observing parameters as functions of wavelength. Stellar energy
distributions and atomic line spectra are inspected as are the transmission of the Earth's atmosphere, the emissivity of the
sky and telescope and instruments as well as detector sensitivity, resolution and signal-to-noise ratio. The spatial
resolution depending on the size of the diffraction limited adaptive optics point spread function is discussed. We have
evaluated the ELT efficiency in terms of Johnson V to N band photometry, simulating diffraction-limited ELT images of
a stellar field at 4 Mpc and 4 kpc, respectively. We conclude that the information content at shorter wavelengths is of
dominant nature and that there is every reason to do the utmost to include shorter wavelengths in the AO regime. We
propose to adopt a short-wavelength goal of 1 000 nm for first light AO with later updates reaching down to visual
The formation, shaping and evolution of galaxies are processes of high interest but poorly known. This is true also for our closest galactic neighbours. Of key importance is a representative sample of all major types of galaxies with solid evolutionary parameters. Stellar clusters are excellent probes of galactic evolution, albeit so far useful at smaller distances only, mainly due to the limiting effects of image crowding. With Extremely Large Telescopes (ELTs) with full adaptive optics (AO) and near diffraction limited performance, the effects of image crowding will be drastically reduced. Thus, the excellence of clusters of stars as evolutionary probes can be extended out to cosmological distances. We have studied this extension. With data on the Strömgren uvby system, based on direct measurements taken from the literature, we synthesised an open test cluster as well as a galactic background field. The cluster was embedded in the background and located at distances between one and 500 Mpc. y and b data were measured with a 50 m ELT, reduced and analysed, out to 20 Mpc for individual cluster members and between 10 and 500 Mpc for the properties of the integrated cluster. Based on individual stellar data, colour-magnitude diagrams (CMDs) and luminosity functions (LFs) were constructed and studied for age
parameters. For the integral cluster data, we studied the cluster colour index (b-y). We conclude that with a 50 m AO ELT, turn-off point (TOP) determination in CMDs provide ages of excellent quality out to 8 Mpc, of high quality out to 16 Mpc and of reasonable quality to 20 Mpc. At this distance level, the luminosity function provides good support. The integral colour, (b-y), as an age parameter for the clusters, can be determined with high precision out to at least 300 Mpc and with somewhat reduced accuracy to 500 Mpc. Thus, using a 50 m ELT and observing stellar clusters, we can study evolutionary parameters of galaxies out to 20 Mpc and obtain age parameters out to around 500 Mpc from the Sun.
Stellar clusters are highly useful as tools for determination of distances, ages and abundances of heavy elements of galaxies, also at larger distances. Their utility for these purposes has, so far, been severely limited, mainly due to image crowding. The introduction of Extremely Large Telescopes (ELTs) with full adaptive optics (AO) and near diffraction limited performance should imply a drastic improvement concerning the usefulness of clusters and the limiting distances of high quality data. We have made a study of stellar clusters as probes of distance, evolution and chemistry of galaxies at distances from one to twenty Mpc. From data on the Stromgren uvby system, partly from direct measurements taken from the literature, we have synthesized test clusters, one open and one globular, as well as galactic backgrounds. The clusters have been embedded in the backgrounds and located at distances between one and twenty Mpc. Here, vby data have been measured, reduced and analyzed. Color-magnitude diagrams (CMDs), metallicity diagrams (MDs) and luminosity functions (LFs) have been constructed. They have been evaluated absolutely and compared to the corresponding template data. We conclude that with a 50 m AO ELT, for open as well as globular clusters, MDs are of high quality for clusters out to and beyond 5 Mpc and useful out to 10 Mpc. CMDs are of very high quality well beyond 5 Mpc. They are of high scientific value out to and beyond 10 Mpc and valuable for clusters even out to 20 Mpc. LFs are highly informative well beyond 10 Mpc and still rather valuable at 20 Mpc. With sufficient measurement data available, LFs are useful for clusters in galaxies even beyond 20 Mpc.
The REMOT (Remote Experiment Monitoring and conTrol) project was financed by 1996 by the European Community in order to investigate the possibility of generalizing the remote access to scientific instruments. After the feasibility of this idea was demonstrated, the DYNACORE (DYNAmically, COnfigurable Remote Experiment monitoring and control) project was initiated as a REMOT follow-up. Its purpose is to develop software technology to support scientists in two different domains, astronomy and plasma physics. The resulting system allows (1) simultaneous multiple user access to different experimental facilities, (2) dynamic adaptability to different kinds of real instruments, (3) exploitation of the communication infrastructures features, (4) ease of use through intuitive graphical interfaces, and (5) additional inter-user communication using off-the-shelf projects such as video-conference tools, chat programs and shared blackboards.
We discuss a device for real time compensation of image quality deterioration induced by atmospheric turbulence. The device will permit ground based observations with very high image resolution. We propose an instrument with two channels. One is an ordinary image detection channel, while the other uses a Hartmann-Shack wavefront detector to measure image degradation. This information is obtained in the form of a set of lenslet focus shifts, each corresponding to the local tilt of the wavefront. Through modeling, the entire wavefront is reconstructed. Consequently, we can estimate the optical transfer function and its corresponding point spread function. Through convolution techniques, the distorted image can subsequently be restored. Thus, image correction is performed in software, eliminating the need for expensive live optics designs. Due to the nature of atmospheric turbulence, detection and correction have to be made with 50 - 100 frames per second. This implies a need for very high computing capacity. A study of the mathematical operations involved has been made with special emphasis on implementation in the hardware architecture known as radar video image processor (RVIP). This hardware utilizes a high degree of parallelism. Results available show that RVIP together with complementary units provide the necessary high-speed computing capacity. The detection system in both channels must meet very high demands. We mention high quantum efficiency, fast readout at low noise levels and a wide spectral range. A preliminary investigation evaluates suitable detectors. ICCDs are so far the most promising candidates.