Telescope technologies for the infrared, optical and uv bands, from the ground and space
Historically, Italian astronomy has always had a leading role in the development and construction of both large, ground based, optical/UV and near-infrared (NIR) telescopes, and the associated focal plane instruments. There is also a strong tradition in the development of space instruments, especially in the UV band, but now there are also interesting prospects in the NIR.
As far as ground based telescopes are concerned, of the principal collaborations we mention especially that with the European Southern Observatory (ESO), that has led to Italian participation in the development of various instruments. Italy has also developed and built the TNG on the island of La Palma (Canaries) and its entire suite of instruments (SARG, NICS, DOLORES, AdOPT, and finally GIANO). Italy is also playing an important role in the construction of the Large Binocular Telescope (LBT) in Arizona (USA) as wellas some of its instruments (LBC, LINC-NIRVANA).
Ground based telescopes, and therefore optical/UV and near infrared observations, are ever more competitive with respect to the costs of space based projects in the same bands, thanks to the construction of 10 metre-class telescopes equipped with active and adaptive optics which allow resolutions approaching those obtained from space. The use of adaptive optics developed by INAF for the Large Binocular Telescope has made it the largest optical telescope in the world, with a resolving power three times greater than that of the most famous space telescope, Hubble. The use of efficient detectors and the development of innovative focal plane instruments has extended our observing capabilities. With the aim of making ground based instruments even more competitive, in recent years, there has been a move towards instrument specialisation for specific scientific targets, requiring the development of new technologies. Amongst the more interesting ideas in which the Italian community will certainly be involved in the coming years is the E-ELT. In order to take a significant step forward from 10 metre-class telescopes, work on the conception and development of telescopes with diameters over 30 metres has now been ongoing for a few years. The European proposals have converged to form the E-ELT (European Extremely Large Telescope) project, directed by ESO, that will have a diameter of 42 metres. The diameter of the telescope requires the solution of numerous problems, including:
- the need to produce an enormous number of hexagonal mirror segments to cover the collecting area of around 1400 square metres. Their relative positions will need to be controlled;
- the active correction of the mirrors to compensate for the mechanical deformation caused by the enormous weight;
- necessary infrastructure;
- adaptive correction to obtain a real gain in terms of spatial resolution;
- the dimensions of the instruments that start to take on enormous proportions, especially given the current limits on the maximum possible dimensions of optical elements such as lenses, mirrors, reticules and prisms;
- the increase in the detecting area with consequent construction of ever larger detector mosaics.
Italy has at its disposal a scientific and industrial capability sufficient to meet international competition in proposing innovative solutions for the construction of E-ELT. Techniques are being investigated for the mass production of light "moulded" mirrors, in particular in collaboration with the USA and Media Lario as part of the CTA/AGIS (Cherenkov Telescope Array / Advanced Gamma-ray Imaging System) project, of adaptive optics systems, with collaboration between some INAF observatories and the Microgate and ADS companies, and of metrological apparatus for their characterisation.
As far as technology for future space missions is concerned the efforts of the Italian community in the design and development phases of ESA's cosmological mission Euclid should be highlighted. This mission, for the study of dark energy and dark matter, has been selected for a Phase A study under the Cosmic Vision programme.