OSIRIS – The scientific camera system onboard Rosetta

The Optical, Spectroscopic, and Infrared Remote Imaging System OSIRIS is the scientific camera system onboard the Rosetta spacecraft (Figure 1). The advanced high performance imaging system will be pivotal for the success of the Rosetta mission. OSIRIS will detect 67P/Churyumov-Gerasimenko from a distance of more than 106 km, characterise the comet shape and volume, its rotational state and find a suitable landing spot for Philae, the Rosetta lander. OSIRIS will observe the nucleus, its activity and surroundings down to a scale of ~2 cm px−1. The observations will begin well before the onset of cometary activity and will extend over months until the comet reaches perihelion. During the rendezvous episode of the Rosetta mission, OSIRIS will provide key information about the nature of cometary nuclei and reveal the physics of cometary activity that leads to the gas and dust coma. OSIRIS comprises a high resolution Narrow Angle Camera (NAC) unit and a Wide Angle Camera (WAC) unit accompanied by three electronics boxes. The NAC is designed to obtain high resolution images of the surface of comet 7P/Churyumov-Gerasimenko through 12 discrete filters over the wavelength range 250–1000 nm at an angular resolution of 18.6 μrad px−1. The WAC is optimised to provide images of the near-nucleus environment in 14 discrete filters at an angular resolution of 101 μrad px−1. The two units use identical shutter, filter wheel, front door, and detector systems. They are operated by a common Data Processing Unit. The OSIRIS instrument has a total mass of 35 kg and is provided by institutes from six European countrie

Microstructural modification during isothermal ageing of a low nickel duplex stainless steel.

In order to reduce the cost of duplex stainless steel (DSS), the Ni could be partially substituted by Mn and N, to maintain the alpha/gamma microstructure, the corrosion resistance and mechanical strength similar to the common Ni-Cr-Mo DSS. In this paper the microstructure stability, impact strength and the general corrosion behaviour of a low Ni grade, 22Cr-4Mn-0,2N DSS, were examined. In the solution annealing condition the corrosion resistance is quite similar to the austenitic grade. A moderate precipitation of nitrides and carbides was evidenced after isothermal treatment in the range 600-900°C, while no dangerous topologically close packed phases (TCP-phases) were detected. The precipitation affects the impact strength, which decreases to about 50 J, while the corrosion resistance is less markedly affected

Microstructural stability of isothermally aged 2510 duplex stainless steel.

The isothermally aged 2510 duplex stainless steel is very prone to sigma nad chi precipitationn for short times of ageing in the range 800-1000C

Il trattamento di solubilizzazione degli acciai inossidabili duplex

Sono state esaminate le condizioni per il trattamento termico finale di alcuni fra gli acciai duplex di più largo impiego. Dopo il mantenimento a temperature comprese fra 1050 e 1100°C, necessario per ripristinare il corretto rapporto fra austenite e ferrite e solubilizzare le eventuali fasi dannose, deve essere eseguito un raffreddamento sufficientemente rapido, per evitare che queste possano riprecipitare. I tempi di precipitazione delle fasi ? e ? nell’intervallo critico di 750-950°C sono stati determinati con trattamenti isotermici e raffreddamenti a velocità controllata, che hanno consentito di determinare le velocità di raffreddamento minime necessarie per evitare la formazione di queste fasi