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Italian P.I.: Cesare Barbieri, Dept. of Astronomy and CISAS, University of Padova
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The WAC will obtain images of the cometary nucleus and gases over the wide FoV of 12x12 sq. deg, in optical and UV, with the aim to reconstruct the 3D-shape of comet Wirtanen, aid in the identification of the Lander descent area, and closely follow the time evolution of the large scale phenomena. During the cruise phases, images will be obtained of the Earth-Moon system, of Mars and of two asteroids, Otawara and Siwa. CISAS has provided also the shutter and front door mechanism for the Narrow Angle Camera of OSIRIS.
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OSIRIS is the visible instrument on board ROSETTA. It is composed of a Wide Angle and of a Narrow Angle Camera. The WAC has been provided by CISAS UPd, the NAC by LAS Marseille, under the overall PI-ship of the MPAe.
The WAC consists of a light-weight, thermostated telescope. The optics is capable of providing a 12x12 sq. deg Field of View. It is perfectly baffled for stray light from out of FoV (e.g. the Sun) and inside FoV (e.g. the cometary nucleus) stray light. A 3-stage baffle is implemented to guarantee a contrast ratio of 10-4 inside the field of view. The outer element is made of glass fiber composite to be thermally decoupled from the telescope. A front door mechanism protects from contamination, during the cruise phase the optics, while during the scientific operations will be used for flat-fielding too.
The exposure times are controlled by a novel shutter device capable of achieving exposure times as short as 10 msec, with a uniformity better 1/500. The shutter software contains a fairly sophisticated self-calibrating routine to optimise in flight the waveform.
The optical bench supports a 2048x2048 CCD, shielded against protons by a Suprasil plate and several mechanical stops, and a dual filter wheel holding 14 filters. In addition, CISAS, under responsibility of prof. Francesco Angrilli, has provided Front Door and Shutter mechanisms for the Narrow Angle Camera. CISAS has also been responsible for thermal and structural aspects of OSIRIS.
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CCD Detector: 2048x2048 pixels, pixel-size 13.5 ?m
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Spatial resolution: 140x140 µrad per pixels
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Spectral range: 0.25?1.0 m;
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14 filters
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Shutter Min. Exposure time 10 ms, uniformity better than 1/500
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Shutter Life time greater than 500000 cylces, Front Door greater than 5000 cylces
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Front Door for telescope protection for contamination and for in-flight calibration, with dedicated fail-safe device
General:
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Mass: 9.9 kg
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Overall dimension WxLxH [mm] 410x750x260
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Op. Temperature 285 ± 5[K], Non op. Temperature 233-323[K]
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Power consumption: 20 W, including all electronics (nominal operational mode)
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High performance and high uniform shutter mechanism (up to 10 ms with uniformity 1/500), with in-flight self tuning software and with dedicated fail safe device
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Other news
- home page WAC
- Attivitą scientifica per il programma Rosetta
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