Rosetta is one of the cornerstone missions of the European Space Agency for having a rendezvous with the comet 67P/Churyumov-Gerasimenko in 2014. The imaging instrument on board the satellite is OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System), a cooperation among several European institutes, which consists of two cameras: a Narrow (NAC) and a Wide Angle Camera (WAC).
The WAC optical design is an innovative one: it adopts an all reflecting, unvignetted and unobstructed two mirror configuration which allows to cover a 12° × 12° field of view with an F/5.6 aperture and gives a nominal contrast ratio of about 10–4.
The flight model of this camera has been successfully integrated and tested in our laboratories, and finally has been integrated on the satellite which is now waiting to be launched in February 2004.
In this paper we are going to describe the optical characteristics of the camera, and to summarize the results so far obtained with the preliminary calibration data. The analysis of the optical performance of this model shows a good agreement between theoretical performance and experimental results.
We have carried out a conceptual study for an instrument (QuantEYE) capable to detect and measure photon-stream statistics, e.g. power spectra or autocorrelation functions. Such functions increase with the square of the detected signal, implying an enormously increased sensitivity at the future Extremely Large Telescopes, such as the OverWhelmingly Large (OWL) telescope of the European Southern Observatory (ESO). Furthermore, QuantEYE will have the capability of exploring astrophysical variability on microsecond and nanosecond scales, down to the quantum-optical limit. Expected observable phenomena include instabilities of photon-gas bubbles in accretion flows, p-mode oscillations in neutron stars, and quantum-optical photon bunching in time. This paper describes QuantEYE, an instrument aimed to realize the just described science, proposed for installation at the ESO OWL telescope focal plane. The adopted optical solution is relatively simple and possible with actual technologies, the main constraint essentially being the present limited availability of very fast photon counting detector arrays. Also some possible alternative designs are described, assuming a future technology development of fast photon counting detector arrays.
Rosetta is one of the cornerstone missions of the European Space Agency for having a roundez-vous with the periodic comet P/Wirtanen in 2011. One of the imaging instruments on board the satellite is the Wide Angle Camera, a cooperation among several European institutes. This camera adopts an all reflecting, unvignetted unobstructed two mirror configuration which allows to cover a 12° X 12° Field of View with an F/5.6 aperture and an optical quality better than 80% geometrical ensquared energy inside approximately 20 arcsec. The flight model of this camera has been successfully integrated and tested in our laboratories and finally has been integrated on the satellite. In this paper we are going to describe the optical characteristics of the camera, and to summarize the results so far obtained with the preliminary calibration data. The analysis of the optical performance of this model shows a good agreement between theoretical performance and experimental results.
PLEXISS (Planetary Exospheres from the International Space Station) is a proposed small instrument dedicated to the coronagraphic imaging in the Na yellow doublet (5890 and 5896 A) and in the K red doublet (7665 and 7699) A of the transient lunar atmosphere from the International Space Station (ISS). The scientific return of PLEXISS can give important information for the understanding of the transient atmospheres of several other bodies of the Solar System; in particular, the European cornerstone mission Bepi-Colombo to planet Mercury can greatly benefit from PLEXISS.
This paper describes the two concepts of coronagraphic telescope design (one totally reflecting and one totally refractive) we have developed for this very challenging application, that requires occulting the lunar disk and providing a clear field of approximately ± 2° around it, with a resolution of about 30 arcsec per pixel.
Rosetta is the cornerstone mission of ESA devoted to the study of minor bodies of Solar System. The mission will be launched on January 2003 and has the rendez-vous with P/Wirtanen comet (on November 2011) as primary target. The final aim of the mission will be a better understanding of the formation and composition of early Solar System and of its evolution over the last 4.5 billion years. Rosetta has a complex instrumentation devoted both to remote sensing and to in situ investigation. The authors were involved in the design and manufacturing of the Wide Angle Camera (WAC) of the OSIRIS imaging system. The WAC has a very peculiar optical system based on two aspherical mirrors in an off axis configuration, and will be principally devoted to the study of the very faint gas and dust cometary features. To reach this goal an innovative baffling system was designed and constructed in order to reach the stray-light suppression requirements both for source inside and outside the field of view of the camera. In particular a contrast ratio of 10-4 inside the field of view is needed in order to detect gaseous and dusty features close to the nucleus of the comet. In this paper the process of baffling design and manufacturing is described: the behavior of the baffle, previously calculated by numerical simulations from the mechanical and optical points of view, was assessed both for the single elements and for the complete assembly as described in this paper.
After the experience of GIOTTO fly-by to comet Halley in 1986, the European Space Agency planned to improve the scientific knowledge of these astronomical objects by means of an even more ambitious rendezvous mission with another comet (P/Wirtanen). This mission, named ROSETTA, will go on from 2003 to 2013, ending after the comet perihelion phase and including also the fly-by with two asteroids of the main belt (140 Siwa and 4979 Otawara). Scientific priority of the mission is the in situ investigation of the cometary nucleus, with the aim of better understanding the formation and the composition of planetesimals and their evolution over the last 4.5 billions of years. In this context, the Authors were involved in the design of the baffling for the Wide Angle Camera (WAC) of the imaging system (OSIRIS) carried on board of the spacecraft. Scientific requirements for the WAC are : a large field of view (FOV) of 12° x 12° with a resolution of 100 (mu) rad per pixel, UV response, and a contrast ratio of 10-4 in order to detect gaseous and dusty features close to the nucleus of the comet. TO achieve these performances, a fairly novel class of optical solutions employing off-axis sections of concentric mirrors was explored. Regarding baffling, the peculiar demand was the rejection of stray-light generated by the optics for sources within the FOV, since the optical entrance aperture is located at the level of the secondary mirror (instead of the primary as usual). This paper describes the baffle design and analyzes its performances, calculated by numerical simulation with ray tracing methods, at different angles of incidence of the light, for sources both outside and inside the field of view.
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