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JUICE (JUpiter ICy moons Explorer) is the first Large Mission in the frame of ESA Cosmic Vision 2015-2025 program. JANUS (Jovis, Amorum ac Natorum Undique Scrutator) is the camera system selected to fulfill the mission optical imaging scientific requirements. It is being developed by a team involving Institutes and Industries in Italy, Germany, Spain and UK, supported by respective Space Agencies. The science team includes Co-Investigators also from USA, France, Japan and Israel.Resources limitations, S/C characteristics, mission design, environment and the great variability of observing conditions for several objects put stringent constraints on optical head characteristics. High radiation environment in terms of irradiation dose and flux in specific mission phases has to be considered.The wide range of targets, that includes Jupiter atmosphere, to solid satellite surfaces, exosphere, rings, and lightning, all to be observed in several color and narrow-band filters, have all to be considered in instrument development.The many science objectives of JANUS are described together with the technical solution adopted for the optical head. © 2019 IEEE.

The present spectroscopic study of the ultraviolet coronal emission in a polar hole, detected on April 6-9, 1996 with the Ultraviolet Coronagraph Spectrometer aboard the SOHO spacecraft, identifies the inter-plume lanes and background coronal hole regions as the channels where the fast solar wind is preferentially accelerated. In inter-plume lanes, at heliocentric distance 1.7 \rsun, the corona expands at a rate between 105 km/s and 150 km/s, that is, much faster than in plumes where the outflow velocity is between 0 km/s and 65 km/s. The wind velocity is inferred from the Doppler dimming of the O VI $\lambda\lambda$ 1032, 1037 \AA lines, within a range of values, whose lower and upper limit corresponds to anisotropic and isotropic velocity distribution of the oxygen coronal ions, respectively., Comment: 14 pages, 4 figures, 3 tables, Accepted by ApJ Letters

The present spectroscopic study of the ultraviolet coronal emission in a polar hole, detected on April 6-9, 1996 with the Ultraviolet Coronagraph Spectrometer aboard the SOHO spacecraft, identifies the inter-plume lanes and background coronal hole regions as the channels where the fast solar wind is preferentially accelerated. In inter-plume lanes, at heliocentric distance 1.7 \rsun, the corona expands at a rate between 105 km/s and 150 km/s, that is, much faster than in plumes where the outflow velocity is between 0 km/s and 65 km/s. The wind velocity is inferred from the Doppler dimming of the O VI $\lambda\lambda$ 1032, 1037 \AA lines, within a range of values, whose lower and upper limit corresponds to anisotropic and isotropic velocity distribution of the oxygen coronal ions, respectively., Comment: 14 pages, 4 figures, 3 tables, Accepted by ApJ Letters

We present in this Letter the first coordinated radio occultation measurements and ultraviolet observations of the inner corona below 5.5 Rs, obtained during the Galileo solar conjunction in January 1997, to establish the origin of the slow solar wind. Limits on the flow speed are derived from the Doppler dimming of the resonantly scattered componentof the oxygen 1032 A and 1037 A lines as measured with the UltraViolet Coronagraph Spectrometer (UVCS) on the Solar and Heliospheric Observatory (SOHO). White light images of the corona from the Large Angle Spectroscopic Coronagraph (LASCO) on SOHO taken simultaneously are used to place the Doppler radio scintillation and ultraviolet measurements in the context ofcoronal structures. These combined observations provide the first direct confirmation of the view recently proposed by Woo and Martin (1997) that the slow solar wind is associated with the axes, also known as stalks, of streamers. Furthermore, the ultraviolet observations also show how the fast solar wind is ubiquitous in the inner corona, and that a velocity shear between the fast and slow solar wind develops along the streamer stalks., Comment: 15 pages, LaTex, 6 jpg figures, accepted Aug. 28, 1997 for publication in the ApJ Letters

We present in this Letter the first coordinated radio occultation measurements and ultraviolet observations of the inner corona below 5.5 Rs, obtained during the Galileo solar conjunction in January 1997, to establish the origin of the slow solar wind. Limits on the flow speed are derived from the Doppler dimming of the resonantly scattered componentof the oxygen 1032 A and 1037 A lines as measured with the UltraViolet Coronagraph Spectrometer (UVCS) on the Solar and Heliospheric Observatory (SOHO). White light images of the corona from the Large Angle Spectroscopic Coronagraph (LASCO) on SOHO taken simultaneously are used to place the Doppler radio scintillation and ultraviolet measurements in the context ofcoronal structures. These combined observations provide the first direct confirmation of the view recently proposed by Woo and Martin (1997) that the slow solar wind is associated with the axes, also known as stalks, of streamers. Furthermore, the ultraviolet observations also show how the fast solar wind is ubiquitous in the inner corona, and that a velocity shear between the fast and slow solar wind develops along the streamer stalks., Comment: 15 pages, LaTex, 6 jpg figures, accepted Aug. 28, 1997 for publication in the ApJ Letters

Static models of coronal loops are investigated. For loops that are low-flying, heights above the chromosphere somewhat < 5000 km, it is shown that a new type of solution appears to the static equations, in addition to the well known coronal loop solution. The new solution is characterized by a maximum plasma temperature somewhat < 100000 K. The structure and properties of these cool solutions are discussed. We calculate the differential emission measure Q(T) expected for a magnetic arcade, which we argue must naturally contain both hot and cool loops. It is shown that the cool loops have a dramatic effect on the form of Q(T) in the lower transition region. In particular, they can account for the observed rise in Q at low T, which has long been thought to be incomparable with the static-loop model. Finally, we dicuss the implications of the cool loops on other observations of both solar and stellar coronae and transition regions.