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|Authors: ||Riva, Alberto|
|Internal Tutor: ||TREVES, ALDO|
ZERBI, FILIPPO MARIA
|Title: ||Infrared cameras for small telescopes: from requirements to device.|
|Abstract: ||This thesis work concerns the study, the procurement and the commissioning of small infrared cameras for imaging with small sized ground-based telescopes.
Observations at infrared wavelengths are of great importance in astronomy. One of the most known advantages concerns the observation of the distant universe. Due to red-shift, distant objects have their spectral features moved toward higher wavelengths. If one wants to compare the restspectrum of a nearby galaxy in the V band (500-600 nanometers) with a galaxy at z=3, he will have to observe the latter between 2000 and 2400 nanometers, i.e. in the infrared region. Furthermore if the Lyman break (912 Ångstroms) is redshifted to the upper limit of the visible region (z~7-8), the object is detectable only in the infrared.
Further advantage of the infrared band with respect to the visible is the reduced absorption of the radiation by the interstellar medium. Indeed the absorption in the classical V band is about one order of magnitude greater than the absorption in the K band. Hence any observation of sources in dusty areas such as galactic centers, clouds, etc. benefits of being carried out in infrared instead of isible.
There is another class of objects the study of which that benefits from infrared observations. Every astronomical source for which the thermal blackbody emission is relevant, if cold, will be bright in the infrared band. These objects are typically brown dwarfs, planets, protostars, low mass stars.
During the past few decades, infrared astronomy has become a major field in astronomy due to the rapid advances in infrared detector technology. One of the most important breakthroughs coincided with the introduction of new detectors imported from other applications (mainly military), like the Rockwell Hawaii (1024x1024 pixels, pitch 18.5 μm) with a pixel size comparable to that of existing visible detectors. The Hawaii allowed, with the known differences in detector handling and reading, to collect images and spectra of the same kind and quality of images and spectra in the Visible wavelength domain.
The cost of these detectors and their extreme cryogenic requirements (77 K operating temperature instead of 150-200 K of a typical CCD) limited their application to large instruments for large (VLT) or dedicated (UKIRT) telescopes. Progresses in cryo-vacuum technologies, such as Stirling cryo-coolers and cooling-flow cooling systems, as well as progresses in detector technology leading to a higher reliability and a reduction of cost, allowed to think about Infrared imaging systems for small telescopes. This timely coincided with the new scientific requirement for very fast pointing IR imaging devices for the follow-up of fast transient sources such as Gamma Ray Bursts (GRBs) afterglows.
Fast pointing robotic telescopes for transient detections have decades of tradition in astronomy. However the first successful attempt to extend their coverage to the IR band is REM (Rapid Eye Mount) installed in 2003 at La Silla Observatory and currently in operation. REM was conceived as the ground-based complement of the satellite SWIFT, the optical monitor of which (UVOT) is limited at 650 nm toward the red, hence missing most of the potential high redshift GRBs detected by the Gamma Ray detector BAT.
Well beyond its original purposes REM is today serving the Italian Community as a long-term monitoring facility for variable stars, AGNs, Supernovae and many other types of programs that need IR observations. Moreover it invalidated the equation "IR equal to large telescope" and opened to a number of projects such as BOOTES-IR and AMICA-IRAIT that are described in details in this thesis.
The new frontier of infrared astronomy is in Antarctica. This continent offers features and advantages unique on the Earth. Bases like DOME-C show promising atmospheric transparency, wider and newer transmission bands, lower background emission, reduced water vapour atmospheric content, large isoplanatic angle, promising seeing and the possibility to observe for very long periods like the entire winter night of six months. AMICA-IRAIT is an Italian project to install a pathfinder telescope and infrared camera at DOME-C.
Nowadays thinking of IR imaging at small robotic telescopes is no longer a taboo. Pathfinders had their way and the pioneering technology is consolidating. I had the chance to be part of this consolidation process through the work done in three projects: INCA (INfrared CAmera), BIRCAM (Bootes InfraRed CAMera) and AMICA (Antarctic Multi-band Infrared Camera).
INCA is the study and the development of a fully functional prototype of an infrared camera implementing innovative materials and solutions.
BIRCAM is an astronomical infrared camera followed up end-to-end by gOlem group (INAF Osservatorio Astronomico di Brera-Merate, Italy), installed on the Spanish BOOTES-IR telescope (Observatorio de Sierra Nevada, Granada, Spain) and is designed for the Gamma Ray Burst afterglow observations.
AMICA is an infrared multi-channel camera specialized for Antarctica.|
|Issue Date: ||2008|
|Doctoral course: ||Fisica|
|Academic cycle: ||20|
|Publisher: ||Università degli Studi dell'Insubria|
|Citation: ||Riva, A.Infrared cameras for small telescopes: from requirements to device. (Doctoral Thesis, Università degli Studi dell'Insubria, 2008).|
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