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

Last results of technological developments for ultra-lightweight, large aperture, deployable mirror for space telescopes

The aim of this work is to describe the latest results of new technological concepts for Large Aperture Telescopes Technology (LATT) using thin deployable lightweight active mirrors. This technology is developed under the European Space Agency (ESA) Technology Research Program and can be exploited in all the applications based on the use of primary mirrors of space telescopes with large aperture, segmented lightweight telescopes with wide Field of View (FOV) and low f/#, and LIDAR telescopes. The reference mission application is a potential future ESA mission, related to a space borne DIAL (Differential Absorption Lidar) instrument operating around 935.5 nm with the goal to measure water vapor profiles in atmosphere. An Optical BreadBoard (OBB) for LATT has been designed for investigating and testing two critical aspects of the technology: 1) control accuracy in the mirror surface shaping. 2) mirror survivability to launch. The aim is to evaluate the effective performances of the long stroke smart-actuators used for the mirror control and to demonstrate the effectiveness and the reliability of the electrostatic locking (EL) system to restraint the thin shell on the mirror backup structure during launch. The paper presents a comprehensive vision of the breadboard focusing on how the requirements have driven the design of the whole system and of the various subsystems. The manufacturing process of the thin shell is also presented

The LATT way towards large active primaries for space telescopes

The Large Aperture Telescope Technology (LATT) goes beyond the current paradigm of future space telescopes, based on a deformable mirror in the pupil relay. Through the LATT project we demonstrated the concept of a low-weight active primary mirror, whose working principle and control strategy benefit from two decades of advances in adaptive optics for ground-based telescopes. We developed a forty centimeter spherical mirror prototype, with an areal density lower than 17 kg/m2, controlled through contactless voice coil actuators with co-located capacitive position sensors. The prototype was subjected to thermo-vacuum, vibration and optical tests, to push its technical readiness toward level 5. In this paper we present the background and the outcomes of the LATT activities under ESA contract (TRP programme), exploring the concept of a lightweight active primary mirror for space telescopes. Active primaries will open the way to very large segmented apertures, actively shaped, which can be lightweight, deployable and accurately phased once in flight

Laboratory demonstration of a primary active mirror for space with the LATT: large aperture telescope technology

The LATT project is an ESA contract under TRP programme to demonstrate the scalability of the technology from ground-based adaptive mirrors to space active primary mirrors. A prototype spherical mirror based on a 40 cm diameter 1 mm thin glass shell with 19 contactless, voice-coil actuators and co-located position sensors have been manufactured and integrated into a final unit with an areal density lower than 20 kg/m2. Laboratory tests demonstrated the controllability with very low power budget and the survival of the fragile glass shell exposed to launch accelerations, thanks to an electrostatic locking mechanism; such achievements pushes the technology readiness level toward 5. With this prototype, the LATT project explored the feasibility of using an active and lightweight primary for space telescopes. The concept is attractive for large segmented telescopes, with surface active control to shape and co-phase them once in flight. In this paper we will describe the findings of the technological advances and the results of the environmental and optical tests

Creativity: The Critical Element for Mission Success

Can creativity be the critical element for the success of a Space Mission? Problem solving methodologies, as brainstorming, are familiar for finding solutions to technical problems. The analytical skills to solve problems and the creativity required to invent new products may appear similar, but they are profoundly different. Creativity requires a different mindset than problem solving. In sectors where the engineering process depends on creative thinkers new ways of technology development need to be defined. The objective of the mission Rosetta to land on a comet is well defined. For most of cubesat missions, the problem is posed the other way around: to find an interesting application achievable with the strict resources of a cubesat. Creativity, more that problem solving, is the ‘rule of the game’ of cubesat. This paper presents how conventional approaches to problem solving can lead, for cubesat missions, to deadlock situations. Creativity, coupled with high tech engineering process, becomes a critical piece for finding new uses of cubesats, and therefore critical for securing the new missions. Moving from problem solving to a creative process has been experimented on the Hypercube, a hyperspectral instrument in a cubesat. The paper presents how to bring a mentality shift to evolve from problem solving to a creative environment, instrumental to face the challenges of the evolution of the small satellites

Thinking Inside the Cube

Инциденца тешке каротидне болести у пацијената који се подвргавају операцији реваскуларизације срца је у распону од 6-12%. У ових пацијената постоји три пута већи ризик од неуролошких компликација након миокардне реваскуларизације, чак и у случајевима асимптоматске каротидне болести. И поред присутних доказа о комплексности и озбиљности комбиноване каротидне и коронарне болести, оптималан третман је и даље контроверзан. Два протокола се најчешће користе: каротидно стентирање или ендартеректомија која претходи реваскуларизацији срца 2-4 недеље или, симултана интервенција. Ниједна од ових опција није показала супериорност, а, за сада, не постоје ни рандомизоване студије који би дале одговор на то питање. Код временски раздвојених интервенција где се примарно лечи каротидна болест, ризик од акутног инфаркта миокарда пре срчане операције је висок, уколико је у питању каротидна ендартеректомија, док у стентирању постоји већи ризик од неуролошких компликација. С друге стране, симултана операција је повезана са повишеним периоперативним морбидитетом и морталитетом. Код симултане хируршке реваскуларизације, и поред елиминисања међу-процедуралног ризика, резултати су слични хируршкој интервенцији у два времена, а у многим студијама су инфериорнији у односу на резултате каротидног стентирања и коронарног премошћавања када се изводи одвојено, углавном, због високог ризика од периоперативног шлога. Однедавно, доступни су подаци о четвртој опцији- симултано каротидно стентирање и миокардна реваскуларизација. Све серије су нерандомизоване, већина је ретроспективна, а све су лимитиране малим бројем пацијената и имају различите пери и постпроцедуралне протоколе. Ова студија је проспективна, рандомизована, а њен циљ је поређење раних и средњорочних резултата симултане хибридне реваскуларизације (каротидно стентирање и миокардна реваскуларизација) са хируршком комбинованом каротидном ендартеректомијом и коронарном операцијом...The prevalence of severe carotid artery disease among patients undergoing coronary artery bypass surgery (CABG) is estimated to be 6-12%. These patients have three-fold higher risk for neurological complications after CABG, even if the carotid artery disease is asymptomatic. Despite the acknowledgment of its significance, treatment options for the significant carotid artery disease in the patient undergoing CABG remain controversial. Overall, two protocols are widely used: staged procedure, with carotid artery stenting (CAS) or carotid eversion endarterectomy (CEA) followed by CABG (2-4 weeks later), and simultaneous CAS/CEA with CABG. However, either of these proved not to be superior. Moreover, there have been no randomized trials aiming to assess properly which strategy is more appropriate. In the staged surgical approach that addresses the carotid artery lesion first, the risk of acute myocardial infarction prior to CABG is rather high when performing CEA while the risk of stroke is increased in patients undergoing CAS. On the other hand, the combined surgical approach is associated with an increased risk of both cerebral and cardiac mortality and morbidity. With combined CEA/CABG, despite eliminating inter-stage risk, outcomes have been similar to staged CEA/CABG and in many studies inferior to the staged CAS/CABG, mainly due to higher operative stroke risk. Recently, more data are available for the fourth option - the simultaneous, combined approach of CAS and CABG. All published series were nonrandomized, most were retrospective, and all with limited number of patients, as well as with different periand postprocedural protocols. We performed prospective, randomized study with an aim to compare the early postprocedural results of simultaneous hybrid CAS and coronary bypass surgery vs. concomitant CEA – CABG procedure..

Freeform Grating-Based Hyperspectral Instruments: When SmallSat Solutions Benefit to Big Missions

Hyperspectral Earth Observation is a fast-growing field requiring high performing imaging spectrometers. Since 2010, the European Space Agency has initiated a series of developments demonstrating the feasibility of miniaturized hyperspectral instruments on mini-and nano-satellites[1]. Among them, ELOIS and CHIMA are two innovative full Aluminum instruments based on diffraction gratings ruled on a freeform surface (FFG : Free-Form Grating). That solution offers a reduction of about a factor of 4 in volume with respect to a Offner-Chrisp spectrometers with equivalent performances. The Spectrometers combines three promising new technologies for future hyperspectral instruments: complex blazed grating, freeform optics and backside-illuminated hyperspectral CMOS sensor. With an image space F-number of 2.1, ELOIS is also one of the fastest instrument of this type. The ratio between Swath and Ground Sampling Distance is about twice as big as currently planned hyperspectral missions. Breadboards of these spectro-imagers, limited to the visible and NIR spectra, has been manufactured and tested. This breadboard program confirmed the achievement of the challenging design specifications. Based on these demonstrations, a complete payload is now developed to cover the VNIR and SWIR spectral ranges (400nm to 2450 nm) with a spectral resolution of 10 nm. The proposed technologies are now studied in the context of the “Copernicus Space Component Expansion” program. Six candidate missions have been identified by the European Commission (EC) as priorities for implementation in the coming years. Among them, the CHIME mission (Copernicus Hyperspectral Imaging Mission for Environment) aims to provide precise spectroscopic measurements in the VNIR/SWIR spectral range. Those data will be used to derive quantitative surface characteristics supporting the monitoring, implementation and improvement of a range of policies in the domain of raw materials, agriculture, soils, food security, biodiversity, environmental degradation and hazards, inland and coastal waters, snow, forestry and the urban environment

Vernal keratoconjunctivitis revisited: a case series of 195 patients with long-term followup

This study aimed at revisiting vernal keratoconjunctivitis (VKC) on the basis of anamnestic, clinical, immunologic, histopathologic, and followup data of 195 patients

Optical compressive sensing technologies for space applications: instrumental concepts and performance analysis

This paper presents the results of a study aimed at investigating the potential of Compressive Sensing (CS) technologies for optical space instruments. Besides assessing the pros and cons for a wide set of proposed instrumental concepts for space applications, the study analyzed in further detail two CS-based instrument concepts, each targeting a specific application: an UV-VIS hyperspectral imager on orbiter for stellar spectro-photometry and a MIR camera for sky observation and real-time detection of Near Earth Objects (NEO). The proposed UV-VIS hyperspectral imager relies on a classical CS approach and addresses the CS reconstruction of the full image in order to implement slitless spectro-photometry of stars. The CS-based MIR camera for NEO detection instead explores a novel approach aiming at information extraction without a prior full reconstruction of the image. Besides outlining the optical design of the instruments, its key elements and a pros and cons analysis of the architecture, this paper presents the performance assessment of these instruments for typical application scenarios by means of simulated data. The results showed that, from the point of view of data reconstruction quality, a good performance can be achieved by the designed instruments in terms of compression ratio (CR) and image reconstruction. In terms of system budgets, the CS architecture offered only some marginal benefits with respect to their traditional counterparts, mainly due to the lack of a compression board. Most advantages are instead provided in terms of downlink requirements and memory buffer