Lisa Gambicorti

Photochemical Synthesis of Citric Acid Cycle Intermediates Based on Titanium Dioxide

The emergence of the citric acid cycle is one of the most remarkable occurrences with regard to understanding the origin and evolution of metabolic pathways. Although the chemical steps of the cycle are preserved intact throughout nature, diverse organisms make wide use of its chemistry, and in some cases organisms use only a selected portion of the cycle. However, the origins of this cycle would have arisen in the more primitive anaerobic organism or even back in the proto-metabolism, which likely arose spontaneously under favorable prebiotic chemical conditions. In this context, we report that UV irradiation of formamide in the presence of titanium dioxide afforded 6 of the 11 carboxylic acid intermediates of the reductive version of the citric acid cycle. Since this cycle is the central metabolic pathway of contemporary biology, this report highlights the role of photochemical processes in the origin of the metabolic apparatus.

LARGE APERTURE AND WIDE FIELD OF VIEW SPACE TELESCOPE FOR THE DETECTION OF ULTRA HIGH ENERGY COSMIC RAYS AND NEUTRINOS

New technologies are proposed for large aperture and wide Field of View (FOV) space telescopes dedicated to detection of Ultra High Energy Cosmic Rays and Neutrinos flux, through observation of fluorescence traces in atmosphere and diffused Cerenkov signals. The presented advanced detection system is a spaceborne LEO telescope, with better performance than ground-based observatories, detecting up to 103 - 104 events/year. Different design approaches are implemented, all with very large FOV and focal surface detectors with sufficient segmentation and time resolution to allow precise reconstructions of the arrival direction. In particular, two Schmidt cameras are suggested as an appropriate solution to match most of the optical and technical requirements: large FOV, low f/#, reduction of stray light, optionally flat focal surface, already proven low-cost construction technologies. Finally, a preliminary proposal of a wideFOV retrofocus catadioptric telescope is explained.

PLATO: detailed design of the telescope optical units

The project PLAnetary Transits and Oscillations of stars (PLATO) is one of the three medium class (M class) missions selected in 2010 for definition study in the framework of the ESA Cosmic Vision 2015-2025 program. The main scientific goals of PLATO are the i) discovery and study of extra-solar planetary systems, (including those hosting Earth-like planets in their habitable zone) by means of planetary transits detection from space and radial velocity follow-up from ground, and ii) the characterization of the hosting stars through seismic analysis, in order to determine with high accuracy planetary masses and ages. According to the study made by the PLATO Payload Consortium (PPLC) during the PLATO assessment phase, the scientific payload consists of 34 all refractive telescopes having small aperture (120 mm) and wide field of view (greater than 1000 degree2) observing over 0.5-1 micron wavelength band. The telescopes are mounted on a common optical bench and are divided in four families with an overlapping line-of-sight in order to maximize the science return. In this paper, we will describe the detailed design of the Telescope Optical Units (TOUs) focusing on the selected optical configuration and the expected performances.

A technology demonstrator for development of ultra-lightweight, large aperture, deployable telescope for space applications

This work presents the latest results of new technological concepts for large aperture, lightweight telescopes using thin deployable active mirrors. The study is originally addressed to a spaceborne DIAL (Differential Absorption Lidar) at 935.5 nm for the measurement of water vapour profile in atmosphere, as an output of an ESA contract (whose preliminary results were presented at ICSO 2006). The high versatility of these concepts allows to exploit the presented technology for any project willing to consider large aperture, segmented lightweight telescopes. A possible scientific application is for Ultra High Energy Cosmic Rays detection through the fluorescence traces in atmosphere and diffused Cerenkov signals observation via a Schmidt-like spaceborne LEO telescope with large aperture, wide Field of View (FOV) and low f/#. A technology demonstrator has been manufactured and tested in order to investigate two project critical areas identified during the preliminary design: the performances of the long-stroke actuators used to implement the mirror active control and the mirror survivability to launch. In particular, this breadboard demonstrates at first that the mirror actuators are able to control with the adequate accuracy the surface shape and to recover a deployment error with their long stroke; secondly, the mirror survivability has been demonstrated using an electrostatic locking between mirror and backplane able to withstand without failure a vibration test representative of the launch environment.

The CaSSIS imaging system: optical performance overview

The Colour and Stereo Surface Imaging System (CaSSIS) is the high-resolution scientific imager on board the European Space Agency’s (ESA) ExoMars Trace Gas Orbiter (TGO) which was launched on 14th March 2016 to Mars. CaSSIS will observe the Martian surface from an altitude of 400 km with an optical system based on a modified TMA telescope (Three Mirrors Anastigmatic configuration) with a 4th powered folding mirror. The camera EPD (Entrance Pupil Diameter) is 135 mm, and the expected focal length is 880 mm, giving an F# 6.5 in the wavelength range of 400- 1100 nm with a distortion designed to be less than 2%. CaSSIS will operate in a “push-frame” mode with a monolithic Filter Strip Assembly (FSA) produced by Optics Balzers Jena GmbH selecting 4 colour bands and integrated on the focal plane by Leonardo-Finmeccanica SpA (under TAS-I responsibility). The detector is a spare of the Simbio-Sys detector of the Italian Space Agency (ASI), developed by Raytheon Vision Systems. It is a 2kx2k hybrid Si-PIN array with a 10 μm pixel pitch. A scale of 4.6 m/px from the nominal orbit is foreseen to produce frames of 9.4 km × 47 km on the Martian surface. The University of Bern was in charge of the full instrument integration as well as the characterization of the focal plane and calibration of the entire instrument. The paper will present an overview of the CaSSIS telescope and FPA optical performance. The preliminary results of on-ground calibration and the first commissioning campaign (April 2016) will be described.

Alignment procedure for detector integration and characterization of the CaSSIS instrument onboard the TGO mission

The Colour and Stereo Surface Imaging System (CaSSIS) is a high-resolution camera for the ESA ExoMars Trace Gas Orbiter mission launched in March 2016. CaSSIS is capable of acquiring color stereo images of features on the surface of Mars to better understand the processes related to trace gas emission. The optical configuration of CaSSIS is based on a three-mirror anastigmatic off-axis imager with a relay mirror; to attain telecentric features and to maintain compact the design, the relay mirror has power. The University of Bern had the task of detector integration and characterization of CaSSIS focal plane. An OGSE (Optical Ground Support Equipment) characterization facility was set up for this purpose. A pinhole, imaged through an off-axis paraboloidal mirror, is used to produce a collimated beam. In this work, the procedures to align the OGSE and to link together the positions of each optical element will be presented. A global Reference System (RS) has been defined using an optical cube placed on the optical bench (OB) and linked to gravity through its X component; this global RS is used to correlate the alignment of the optical components. The main steps to characterize the position of the object to that of the CaSSIS focal plane have been repeated to guide and to verify the operations performed during the alignment procedures. A calculation system has been designed to work on the optical setup and on the detector simultaneously, and to compute online the new position of the focus plane with respect to the detector. Final results will be shown and discussed.

The PLATO opto-mechanical unit prototyping and AIV phase

PLATO is the acronym of PLAnetary Transits and Oscillations of stars, and it is a mission proposed for the ESA Cosmic Vision program in the Medium size program, with the target to detect and characterize exoplanets by the means of their transit on a bright star. The instrumental overall layout proposed by the Plato Payload Consortium consists in a multitelescope concept instrument, composed by several tens of telescope units, for which we are developing an all refractive optical solution. These devices are characterized by a very large Field of View (more than 20 degrees on one side) with an optical quality that fits most of the energy into a single CCD pixel. Such a goal can be achieved in a variety of solutions, some including aspheric elements as well. A complete prototype of one telescope unit is foreseen to be built initially (during phase B1) to show the alignment feasibility and, only in a second moment (Phase B2), to perform full environmental and functional test. The aim of this article is to describe the alignment, integration and verification strategy of the opto-mechanics of the prototype. Both the approaches of testing the telescope at the target working temperature or to test it at ambient temperature around a displaced zero point, taking into account the effects of thermal deformations, are considered and briefly sketched in this work.

Overview of possible optical adapters for EUSO

The Extreme Universe Space Observatory-EUSO-is devoted to the exploration from space of the highest energy processes present and accessible in the Universe. The results will extend the knowledge of the extremes of the physical world and address unresolved issued in a number of fields such as fundamental physics, cosmology and astrophysics. Several kind of detectors have been so far proposed for EUSO, all of them requiring some sort of ancillary optics to collect the light from the image produced by the main optics on the focal surface, for an efficient coupling to the detectors. Optical adapters must be selected taking in account several inputs: feasibility, cost, mass budget. Two main options are here investigated: imaging optics (by means of small lenses) and non imaging optics (by means of compound parabolic concentrators). The first kind of focal plane optics is easy and feasible, but it does not guarantee a high concentration ratio. Non imaging optics present much higher efficiency with a concentration close to the theoretical limit, but it also pose new technological diffculties and challenges. This work aims to clarify how this focal plane optics can be made, their limits in terms of concentration of radiation according to the laws of geometrical and physical optics and finally to identify the possible solution to this problem, including available technologies to be used for the construction.

A comparison between the opto-thermo-mechanical model and lab measurements for CHEOPS

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.

Technological developments for ultra-lightweight, large aperture, deployable mirror for space telescopes

The increasing interest on space telescopes for scientific applications leads to implement the manufacturing technology of the most critical element, i.e. the primary mirror: being more suitable a large aperture, it must be lightweight and deployable. The presented topic was originally addressed to a spaceborne DIAL (Differential Absorption LIDAR) mission operating at 935.5 nm for the measurement of water vapour profile in atmosphere, whose results were presented at ICSO 2006 and 2008. Aim of this paper is to present the latest developments on the main issues related to the fabrication of a breadboard, covering two project critical areas identified during the preliminary studies: the design and performances of the long-stroke actuators used to implement the mirror active control and the mirror survivability to launch via Electrostatic Locking (EL) between mirror and backplane. The described work is developed under the ESA/ESTEC contract No. 22321/09/NL/RA. The lightweight mirror is structured as a central sector surrounded by petals, all of them actively controlled to reach the specified shape after initial deployment and then maintained within specs for the entire mission duration. The presented study concerns: a) testing the Carbon Fiber Reinforced Plastic (CFRP) backplane manufacturing and EL techniques, with production of suitable specimens; b) actuator design optimisation; c) design of the deployment mechanism including a high precision latch; d) the fabrication of thin mirrors mock-ups to validate the fabrication procedure for the large shells. The current activity aims to the construction of an optical breadboard capable of demonstrating the achievement of all these coupled critical aspects: optical quality of the thin shell mirror surface, actuators performances and back-plane - EL subsystem functionality.