The payload Terzina is one of the two payloads on board the mission NUSES. NUSES is a space mission pathfinder for the study of high and low energy radiations, enabling new sensors, tools and methodologies. The NUSES satellite hosts two payloads: • Zirè: Monitor of protons and electrons flux variations (E<250 MeV); • Terzina: Path-finder missions for high energy (E>1 PeV) detection: Astrophysical neutrinos and cosmic rays will be detected from space using the atmospheric Cherenkov radiation. Requirements frequently become challenges when they must be traded off to resolve optimization conflicts. The very large Field of View (FoV), the requested compact design and the large collection area are in contrast with need for stray light optimization. The peculiar application forbids the presence of a flattener close to the focal plane, to avoid false Cherenkov events generated in the glass bulk. This fights the request of a flat focal plane. Large spectral bandwidth crossing the spectral range of the light pollution sources band drives the coating optimization. This paper will explain the logical trade-off procedure used to determine the optimum compromise solution for Terzina success.
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.
JANUS (Jupiter Amorum ac Natorum Undique Scrutator) is a high-resolution camera to be flown on board JUICE Spacecraft, devoted to investigate the atmosphere of Jupiter and the surfaces of his icy moons (Europa, Ganymede and Callisto), in the frame of ESA “Cosmic Vision” program. The scientific objectives that JANUS will reach constrained the design of JANUS Optical Head Unit (OHU), and in particular the specific measurement of Ganymede Libration, imposes highly stringent requirement on the Line of Sight (LoS) knowledge of the instrument. The differential thermal environment conditions of the mission orbits, as well as the instrument heat dissipation timelines, induce optical elements translation and rotations that correspond to a Line of Sight variation. During the mission, the LoS can be characterized with a stellar field or single star observation but none direct measurement of its variation can be retrieved during the scientific imaging sessions. To recover the LoS knowledge, a Structural Thermal Optical and Performance Analysis (STOP) is implemented. The optics and the instrument structure are Finit Element Modeled and processed (NASTRAN) imposing the temperature distributions obtained by the OHU Thermal Model (ESATAN-TMS). The obtained thermo-elastic deformations are then considered in the OHU Optical Model (ZEMAX). The resulting LoS and the dominant OHU temperature gradients are finally entangled with a proportionality relation, as well as its direction uncertainty. The indirect estimation of the LoS variation, and its uncertainty, can be establish, thanks to STOP analysis, in real time during operations as function of installed temperature sensor measurements.
CHEOPS is the first small class mission adopted by ESA in the framework of the Cosmic Vision 2015-2025. Its launch is foreseen in early 2019. CHEOPS aims to get transits follow-up measurements of already known exo-planets, hosted by near bright stars (V<12). Thanks to its ultra-high precision photometry, CHEOPS science goal is accurately measure the radii of planets in the super-Earth to Neptune mass range (1<Mplanet/MEarth<20). The knowledge of the radius by transit measurements, combined with the determination of planet mass through radial velocity techniques, will allow the determination/refinement of the bulk density for a large number of small planets during the scheduled 3.5 years life mission. The instrument is mainly composed of a 320 mm aperture diameter Ritchey-Chretien telescope and a Back End Optics, delivering a de-focused star image onto the focal plane. In this paper we describe the opto-thermo-mechanical model of the instrument and the measurements obtained during the opto-mechanical integration and alignment phase at Leonardo company premises, highlighting the level of congruence between the predictions and measurements.
JANUS is the camera of the ESA mission JUICE, dedicated to high-resolution imaging in the extended-visible wavelength region (340 – 1080nm). The camera will observe Jupiter and its satellites providing detailed maps of their surfaces and atmospheres. During the mission, the camera will face a huge variety of observing scenarios ranging from the imaging of the surfaces of the satellites under varying illumination conditions to limb observation of the atmospheres. The stray-light performance of JANUS has been studied through non-sequential ray-tracing simulations with the aim to characterize and optimize the design. The simulations include scattering effects produced by micro-roughness and particulate contamination of the optical surfaces, the diffusion from mechanical surfaces and ghost reflections from refractive elements. The results have been used to derive the expected stray-light performance of the instrument and to validate the instrument design.
JANUS (Jovis Amorum Ac Natorum Undique Scrutator) is a high-resolution visible camera designed for the ESA space
mission JUICE (Jupiter Icy moons Explorer). The main scientific goal of JANUS is to observe the surface of the Jupiter
satellites Ganymede and Europa in order to characterize their physical and geological properties. During the design phases,
we have proposed two possible optical configurations: a Three Mirror Anastigmat (TMA) and a Ritchey-Chrétien (RC)
both matching the performance requirements. Here we describe the two optical solutions and compare their performance
both in terms of achieved optical quality, sensitivity to misalignment and stray light performances.
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