JANUS is a multi-filter optical camera part of the JUICE ESA Mission, that has been launched last April from the French Guiana towards the Giovian system, where it will arrive in 2031. During the design phase of the instrument an extensive Straylight Analysys has been carried on, but after AIV the need to update the analysis on the base of the 'as built' system has become desiderable, to better interpretate the calibration data and prepare for science phase. We here report about this update, covering the rationale of the update, the used methodology and the obtained results.
There is currently a growing interest for the in-situ robotic and human exploration of the Moon’s surface and subsurface. In particular, several mission concepts foresee the exploration of lunar caves and underground structures like e.g. the lava tubes, (i.e. conduit formed by flowing lava from a volcanic vent that moves beneath the hardened surface of a lava flow) and other depressed morphologies such as permanently shadowed craters which could present in situ resources such as water ice. Given the limited onboard resources of these missions and extreme illumination conditions ranging from sunlight to complete darkness, the cameras might be capable of operating without the support of any artificial illumination system. This paper studies the radiance properties of a set of different lunar cave pits as illuminated uniquely by the sunlight for different Sun elevations above the Moon horizon and permanently shadowed craters such as Shackleton’s interior. This is as an endmember for complete darkness of extreme importance because it could be a cold trap for volatiles and a potential future human exploration target. The simulations are carried out using the OpticStudio ray tracing software and a Lambertian scattering model of the cave pit walls. The radiance maps within the caves can be used by the scientific community to estimate the typical Signal to Noise Ratio (SNR) of the required observations with optical cameras deployed on the lunar surface. This is accomplished both for directly illuminated, penumbra and umbra regions of the cave pit. We believe that the proposed investigations are of wide interest for the future missions to the Moon and its robotic and manned exploration.
HYPSOS (Hyperspectral Stereo Observing System, patented) is a novel concept for a hyperspectral-stereo camera that combines the 3D information attainable by two stereo images, with the fine spectral sampling of a spectrograph. Planetary remote sensing represents an interesting application field for the HYPSOS concept. At the basis of HYPSOS there is the merge between two different approaches for studying the surface of a planet: the morphology of any feature analyzed by the geologist through the 3D images, and the composition of the same feature, through the hyperspectral data. In general, the merging of data provided by two different instruments may have problems due to co-registration and calibration, and the resolutions may be different requiring some interpolation. HYPSOS solves this problem by hardware: the images of the stereo channels are oriented in such a way that they are both placed along the same direction. In this way it is possible to use the same spectrometer for both channels, eventually leaving some space between the two channels to avoid signal contamination. This configuration is achieved by the placement of simple field rotating prisms along the optical paths of the two stereo-channels. A further advantage of this approach is that it does not require to limit the spectral range, which is otherwise necessary to avoid the superposition of spectra obtained by using two slits separated along track. In this paper we provide details on the configuration of the instrument, the optical layout of a possible implementation, and the resulting performances.
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