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Optical Infrared Co-ordination Network for Astronomy

Final Report Summary - OPTICON (Optical Infrared Co-ordination Network for Astronomy)

Executive Summary:
OPTICON continues to deliver high quality products to the optical/IR astronomy community and prepare for future developments in the field. It is a particular strength that national Funding Agencies and ESO are partners in OPTICON since this provides direct links to national technical developments and embeds pan-European technical progress in the national plans. Relatively modest EC funding has triggered substantial external funds. In addition, this close connection is clearly beneficial when strategic choices of technology have to be made.

OPTICON is playing a major role in cohering the community through support of science and technical meetings. It is also playing a major role in training new members of the community (young and old) through schools and workshops. The interferferometry and photonics Schools held so far are innovative and of high impact.

OPTICON is providing a focus for the highest priority engineering developments in European optical/IR astronomy; investigating disruptive technologies and road-mapping. EC funding is critical in allowing the community to build networks that can take on high risk, potentially disruptive instrumental developments. It is therefore a valuable resource in the scientific and instrumental preparation for E-ELT, and is increasing the sense of ownership of the E-ELT project by the community.

The results of studies in adaptive optics technologies represent advances which are all globally unique, frequently with a high profile, and sometimes with critical significance for the E-ELT. Each study has led to the mitigation of important technical risk for the E-ELT, and will aid currently ongoing design studies to ensure the scientific productivity of the facility.

Both theoretical development, experimental and on-sky adaptive optics tests have been carried out during the 5 years of the OPTICON program. In particular, with the access to unique world-wide facilities such as the CANARY demonstrator on WHT, the Gems MCAO system on Gemini and the AOF on the ASSIST test bench, OPTICON participants have been able to conduct cutting-edge research activities with world firsts obtained on CANARY in the field of tomographic wide field AO.

All of the studies will have extensions in some form in the future, and, in many cases, have leveraged significant resources from elsewhere. They have also fostered cross-European collaboration and communication which will be of lasting benefit to the community.

An interesting spin-off development has been the development of fibre optic-based 3D bend sensors for use in chemistry, lifescience, medicine, geo-science, environmental monitoring, and materials research. The system is sensitive enough to detect the changing shape of the torso resulting from the human heartbeat, as well as detailed shape changes from breathing and torso movements.

Project Context and Objectives:
It is a truism that optical-infrared astronomy is in a “golden age”. Public interest, manifested through such criteria as downloads of Hubble images and media interest in continuing discoveries of exo-planets is higher than for almost any other subject. This follows naturally from scientific progress – there are new stories, new results, new discoveries to celebrate – and the intrinsic interest of the questions addressed by astronomy, which range from the origin of the Universe, through the nature of matter and existence, to exo-planets and life elsewhere. This story of scientific success has however not happened by chance – considerable planning and organisation, and continuing technical research and development, is required to develop the highly-skilled scientists and engineers trained to operate and exploit the state of the art facilities which deliver the scientific advances.

A decade ago planning assumptions for next-generation astronomical infrastructures took for granted that older facilities would become obsolete, would be closed, and their operational budgets would contribute to newer facilities. The scientific case for new large facilities is simply so overwhelming that they must be delivered. However, the number of new large expensive facilities is small – the number of extant facilities is large.

The change from an assumption of obsolescence to an assumption of future opportunity came to be made by the development of a European-scale astronomical community. This community was able to make the case that facilities should be enhanced and shared, not closed, that technology developments were both achievable and affordable, that astronomers could deliver cutting edge science with those enhanced facilities and crucially that the talent, expertise and financial resources to deliver all this would be available if efforts were coordinated on trans-national scales. European astronomy, largely through the excellence of the European Southern Observatory, but also through the coordination, planning, development and technical R&D work supported by the EC via ASTRONET (Strategy) and OPTICON (implementation) has made that case. In consequence, Europe has become the international leader in optical-infrared astronomy.

The exceptional strength of the European system has recently been summarised, as a model to which they might aspire, in the 2015 US National Academy of Sciences Review “Optimizing the U.S. Ground-Based Optical and Infrared Astronomy System”: Its relatively stable funding line over several years enables ESO to plan efficiently for future instruments, such as the SPHERE spectropolarimeter with high contrast Adaptive Optics [...] its instruments are developed in a coordinated way, with most built by consortia of institutes. The ESO community has thus maximized its combined resources by having a strong support network of partnerships for instrument development and small and medium telescope operations, with ESO concentrating on operating and upgrading the largest facilities. The E-ELT, a planned 39-meter telescope, is expected to have first light in the early 2020s.

OPTICON is the EC-funded coordination network which supports the multi-national partnerships on which the success of this model rests. OPTICON support in previous FP programmes prototyped and raised to operational level the critical Adaptive Optics (AO) systems in the SPHERE instrument mentioned above. OPTICON’s Trans National Access (TNA) system underlies the “support network for small and medium telescope operations” noted. OPTICON’s networking provides the community coherence which leads to coordinated instrument development, future planning, and builds the key consortia of institutes. ESO, nationally funded, complemented by the international technology development, community building and trans-national access enabled by EC funding has created this balanced excellent system.

OPTICON works with and for the community through Networks, JRA Technology R&D developments and through TNA access. Networking activities link people and communities and motivate future developments. To appreciate this context, it is perhaps helpful to imagine an (oversimplified!) story of how people are trained and motivated and how this maps onto the OPTICON programme. It begins with training and motivation (via schools, exchange visits, outreach), and progresses via experience, often on existing medium sized facilities (TNA activity) whose operations are being rationalised to ensure viability and efficiency (Telescope Directors Forum, ASTRONET implementation activities, common time application system) and whose individual capabilities are being enhanced by new software and hardware (JRAs + exchange visits). These users may require experience of specialist skills (High Time Resolution astronomy, Time Domain astronomy, Interferometry). With time they achieve merit-based access to ESO’s VLT telescopes, with their community-provided instrumentation. All this leads toward the E-ELT, for which the science case was developed, evangelised and co-ordinated with other projects (ELT network and workshops) and for which the community is developing new hardware (JRAs, including photonics, VPH, AO). Some of this is being prototyped (JRAs), while a watching brief is maintained on far future technology (Innovation Network), some of which is already being considered now and for future JRA effort, in the light of science-industry developments in the next decade or more. The service enhancement aspect of the networks is related to the efforts to deliver coordination and optimisation of the available telescopes, through the Telescope Directors’ Forum (an OPTICON initiative), through the common Call for Proposal system, with standard web interfaces and through the activities of several networks, especially the Key Technology Network and all the JRA activities, which ensure potentially viable new technologies are brought into consideration at the earliest possible opportunity.

The beginning of rationalisation and optimisation of 2-4m telescopes has taken place in recent years and more is expected. The telescope suite thus includes all the major (non-ESO) medium sized telescopes which will offer general user access during the contract period. This allows individual astronomers, especially those whose national facilities have been specialised in favour of campaign mode operations, access to a suite of resources which can support a wide range of projects. Crucially, it allows follow up and exploitation of interesting objects discovered in campaigns and surveys using the best possible tools for the job. The successful establishment of an OPTICON common time allocation process has made it easier and simpler to apply for time on non-national facilities and crucially, to develop projects which require access to multiple facilities. By developing a process which is clearly not nationally based and applies a common process to all applications, it also encourages proposals from outside the traditional national user groups.

The several JRAs in OPTICON cover a wide range of challenges related to development of future astronomical instrumentation – the community contribution to E-ELT and next generation facilities, with complementary approaches including the range from technically challenging developments of systems, which are known to be on the critical path for next generation instrumentation, through investigations of new technologies of high potential impact but as-yet less certain practicality. The balance between these activities has been set in part by the development of the OPTICON astronomical technology Roadmap, and in part by critical analysis of the very wide range of possible activities by the national funding agency scientific directors who make up the OPTICON Executive Board. For clarity, we briefly consider each JRA area in turn.

Adaptive optics (AO) systems, using both natural and laser guide stars, are the key technologies for the next major advances in ground-based optical-IR astronomy in the next 20 years. Significant progress made over the past ten years in the field of AO has brought this observational technique to the maturity level where outstanding astronomical results can be obtained routinely. Astronomers are now looking toward the next generation of AO systems, which will allow them to extend this powerful technique to new observing modes. Previous OPTICON activity aimed to design and develop Laser Guide Star Adaptive Optics systems for the existing large telescopes and to upgrade the Very Large Telescope Planet Finder instrument (SPHERE) to maintain its competitiveness in the period 2012-2014. The primary goal of this contract is to develop the technologies and the knowledge required to improve the performance and operational efficiency of these existing AO facilities in Europe, as well as to develop the state-of-the-art second generation instrumentation required for the 40m European Extremely Large Telescope (E-ELT).

Fast Detectors
OPTICON activity defines the state-of-the-art in this field. Outstanding performance was obtained from the OPTICON developed camera Ocam and its dedicated detector, the CCD220 (which has led to commercial spinoffs). Ocam technology is currently used by the second generation of VLT Adaptive Optics (AO) instruments. Third generation AO instruments will be still more demanding in terms of frame rate and readout noise, and the detector controllers will be developed in this activity. This performance update is the baseline for the E-ELT AO systems.

Developing smarter, smaller, instruments
The global telecommunications industry has invested massively in photonic systems, with many applications available in biomedicine and sensing applications. There are as yet only preliminary investigations of astronomical capabilities. Given the tiny size and mass and relatively low cost of photonic systems, they could revolutionise astronomical spectrographs, if they prove compliant with astronomical requirements. The aim of WP3 is to develop and test possible systems built on integrated photonic technologies. This activity builds on the Astrophotonica Europa Network started in FP6 as an outcome of the OPTICON Key Technologies Network and further developed in FP7, including development there of the first integrated waveguide based Photonic Couplers for astronomy. This illustrates the intimate connection between networking and JRA activity in OPTICON.

Instruments based on current optical designs tend to get bigger and more complex, leading to increasingly tight requirements on the overall performance [cf. the OPTICON technology roadmap]. The goal of WP5 is to reduce the complexity of future instruments by combining two innovative technologies namely: freeform mirrors and active optics. This could significantly simplify next generation instruments for the E-ELT and VLT.

The proposed programme of WP6 for novel optical materials is again possible only because of the successful results of the previous OPTICON activities. It involves unanticipated discoveries made during those activities, and a successful OPTICON-supported effort to recover knowledge and materials following collapse of the sole European industrial supplier. It is focused on enabling technologies (holographic and traditional gratings, innovative fibres, general holographic Optical Elements) that can potentially improve the performance and/or reduce the cost of future instrumentation.

Making optical interferometry a practical astronomical tool
OPTICON activity in recent years initiated the development of software tools for end-to-end processing of interferometric observations and data from calibration to model fitting. Since then, these tools have been continuously improved by the community and have encouraged more astronomers to make use of interferometry observations. The goal now is to go a step further, as the ability to reconstruct images is essential to exploit the very high angular resolution provided by the next generation multi-telescope instruments such as Matisse, Gravity and Pionier at Europe’s Very Large Telescope Interferometer (VLTI), LINC-Nirvana at the Large Binocular Telescope (LBT) or Vega at the Chara interferometer.

Project Results:
A strong astronomical community requires access to state of the art infrastructures (telescopes), equipped with the best possible instrumentation, and with that access being open to all on a basis of competitive excellence. Further, the community needs training in optimal use of those facilities to be available to all, Critically, it needs a viable operational model, with long-term support from the national agencies, to operate those infrastructures. The most important need for most astronomers is to have open access to a viable set of medium aperture telescopes, with excellent facilities, complemented by superb instrumentation on the extant large telescopes, while working towards next generation instrumentation on the future flagship, the European Extremely Large Telescope. OPTICON has made a substantial contribution to preparing the realisation of that ambition. OPTICON supported R&D has, and is developing critical next-generation technology, to enhance future instrumentation on all telescopes. The big immediate challenge is to retain a viable set of well-equipped medium aperture telescopes. The present project
is to make the proof of principle that such a situation is possible - a situation developed by OPTICON under its previous contracts, in collaboration with the EC supported strategy network ASTRONET - and set the stage for the step to full implementation.

The 26 partners who make up OPTICON implement this ambition through a set of 14 Working Groups, covering technology Research and Development, provision of Trans national Access, and networks to develop the community, and plan for the future. The project objectives were to continue work to complete the anticipated milestone reviews (all met - table blow), deliverables – all complete, tables below) and disseminate the project foreground through publications (table below).

Adaptive Optics – the largest challenge, biggest long-term focus, most success. Laggards to leaders.

Adaptive Optics. The significant progress made over the past 20 years in the field of adaptive optics has brought this observational technique to the maturity level where outstanding astronomical results can be obtained routinely. All the large telescopes (6 to 10-meter class) are equipped with one or more adaptive optics systems these days. These systems can be either multi-purpose instruments allowing to conduct astrophysical programmes in various fields of astrophysics with good performances, or more specialized instruments dedicated to specific goals. For instance, SPHERE at the ESO Very Large Telescope or GPI at The Gemini Southern telescope are optimized for the systematic search of extrasolar planets and circumstellar disks and provide an extremely high level of correction in a relatively small field of view, typically a few arc seconds. On the other hand, the GeMS multiconjugate adaptive optics system also on Gemini South delivers a uniform, diffraction limited image quality at near-infrared wavelengths over an extended field of view of more than 1 arcminute. Other systems are using laser generated artificial guide stars to allow the observations of very faint objects which could otherwise not be accessible to adaptive optics correction.

Astronomers are now looking toward the next generation of adaptive optics systems, especially those under development for the 40-m European Extremely Large Telescope (E-ELT), approved by the ESO member states for full deployment by end of 2024. Such ambitious scientific objectives clearly increase the complexity of future instruments, which in turn will require further development of critical technologies (larger and more stable deformable mirrors, low-noise detectors for wave front sensing in either the visible or the infrared, faster real time calculators, etc.), and also elaboration of new system concepts, new control strategies, new calibration
approaches, new data reconstruction methods, etc.

The present activities undertaken in the framework of the OPTICON FP7 Phase 2 programme contribute directly to such objectives.

Particular achievements include parallel experimental studies of two adaptive optics technologies requiring significant technology development for deployment on the next generation of extremely large telescopes (ELTs). In this context, the forthcoming 40-metre European Extremely Large Telescope is the principal driver. The two technology areas are corrective mirrors and the use of laser artificial guide stars, both on such an unprecedented telescope diameter. Additional exceptional results have been achieved in natural Guide Star Experiments.

In the case of corrective optics, the ELT-specific issues are the scale and density and control methods required for such a large telescope, and also the requirement for cryogenic operation in some circumstances. Correcting a contiguous and relatively extended field of view (10 arc minutes or even larger) on such a large diameter telescope involves a physically large corrective relay. This is an inevitable consequence of the invariance of the product of area and solid angle in any contiguous field optical relay. Where the science does not require a contiguous field,
such as where many isolated distant galaxies must be surveyed in parallel, an alternative approach may be used: multi-object adaptive optics. In this case, the invariance problem is simplified and the requirement is for large actuator count deformable mirrors, often with a high density of actuators, but which can be controlled with openloop technology (as the light transmitted to wavefront sensors is not relayed via the high-density deformable mirrors). This last requirement entails highly repeatable calibration of the deformable mirror response to control signals, as any errors may not be corrected conventionally by closed-loop control techniques. These issues of large actuation scale, high actuation density and open-loop control are the subjects of the first and second corrective optics studies. The additional thermal emissivity generated by operating deformable mirrors at ambient temperature becomes a performance limiting issue for some important ELT observational studies at wavelengths longer than 3 microns, and the possibility of operating at lower temperatures is the subject of the third corrective optics study.
All three corrective optics studies have made significant progress and have led to developments of direct relevance to the E-ELT and active input into ESO studies or studies for the E-ELT METIS instrument.

The other two studies in this report are concerned with the extrapolation of the use of laser artificial guide stars to ELT scales. The most common method for generating such a guide star is to induce a fluorescent return from the layer of atomic sodium present in the mesosphere, typically with a varying non-uniform density distribution from roughly 80 to 90km above sea level. On the current generation of large telescopes, the finite thickness of this “sodium layer”, generates a small, but not insignificant, elongation (at the The current work seeks to test current ELT design modelling using both a deterministic, repeatable laboratory study and an on-sky study, which involved adaption of the CANARY on-sky demonstrator.
Both studies emulate the effects of an ELT-scale telescope diameter (which is not, of course, currently available). The laboratory bench and on-sky laser guide star elongation studies have been fully successful. In the case of the bench system, an extensive set of results has been used to develop and verify end-to-end simulation code that is being used to develop E-ELT adaptive optics instrumentation, and, in particular, the design code for its MAORY multi-conjugate AO system (which relies on sodium laser guide stars). The on-sky study has, in collaboration with ESO, IAC and Rome University, developed an operational on-sky demonstrator at the William Herschel telescope.
This has been operated successfully and has generated datasets comparing elongated laser and natural stars.

Both theoretical development, experimental and on-sky tests have been carried out during the 5 years of the OPTICON program. In particular, with the access to unique world-wide facilities such as the CANARY demonstrator on WHT, the Gems MCAO system on Gemini and the AOF on the ASSIST test bench, OPTICON participants have been able to conduct cutting-edge research activities with world firsts obtained on CANARY in the field of tomographic wide field AO.

The work undertaken address all the links in the AO system optimisation chain.
- This starts with the best possible knowledge of the perturbation statistics and the telescope environment.
Thanks to OPTICON-FP7 a new turbulence characterisation instrument has been developed, commissioned and tested on-sky. It is now scientifically exploited and it will be a key tool for future optimisation of tomographic AO systems and for the validation of numerical turbulence forecasts.
- Before any scientific operation, any AO system must be calibrated. The new generation of adaptive telescopes in which deformable optics are included impose new constraints on calibration schemes. OPTICON-FP7 has triggered the development and test of new efficient approaches allowing to gain both in accuracy and in calibration time. Thanks to the OPTICON network, these approaches have been tested in labs and on sky using the some of the most advanced AO system in the words. In the future, they will be the new baseline of any AO instrument on the new generation of 40-m class adaptive telescope. They will ensure smooth and efficient operations for such incredibly complex telescope and its associated instrumentations.
- During the operation and because of the constant increase of performance imposed by the astronomers and their observing programs, calibration data have to be adapted and adjusted continuously to reflect the exact state of the system and the most up-to-date information on the turbulence statistics. New online optimisation approaches have been proposed to deal with this specific problem and to ensure that the AO is always working in its most efficient operation way. These new methods have been fully validated and tested using the unique on-sky demonstrator of wide-filed AO concepts: CANARY. That represents a critical milestone toward the final development of the next generation of AO system on the VLT and the ELT.
- On a longer-term basis, new control approaches based on state-of-the-art signal and automatic theories have been developed and again tested on-sky thanks to the OPTICON networking and the availability of the CANARY platform. For the very first time a full LQG controller has been applied and tested onsky.
The efficiency and the robustness of such an approach have been demonstrated and a clear gain with respect to more classical approaches has been highlighted.
- At the very end of the AO chain the post-processing aspects and more specifically the PSF reconstruction processes are critical for a good exploitation of the AO data. Scientific data coming from the camera or the spectrograph are not sufficient; they must be coupled with contextual data describing the system performance during the acquisition. Deriving this information from internal AO data is far from being easy. It requires a very good understanding of the AO process itself as well as the use of signal processing and numerical tools. Thanks to OPTICON, new approaches have been developed, numerically tested and applied on real astronomical data. This has demonstrated the efficiency of the approach. The algorithm should be soon fully included in the data pipeline of the MUSE instrument and routinely used by the astronomers in their favourite data reduction tools.

In a nutshell, the OPTICON-FP7 activities have allowed to improve each step of the full AO operation, from the AO design and observation scheduling to the final image processing. New calibration approaches have been proposed and fully validated on-sky. New control algorithms have been implemented and successfully tested.
New PSF reconstruction packages have been developed and will be soon fully implemented in operational instruments.
The developments proposed hereafter will lead to a significant gain on existing facilities and will pave the way to efficient, not to say optimized, design solutions for the future AO systems on the ELT.

The ―Natural Guide Star experimental aspects cover two very distinctive topics:
• The problematic of low order modes measurements (mainly tip-tilt and focus) using very faint natural guide star to complement the measurement coming from Laser Guide. This requires the development of brand new wavefront sensing concepts and strategies in order to optimally use the few available photons during each frame of the AO loop process. In particular, it calls for WaveFront Sensors (WFS) using the so-called ―full aperture gain‖ that is fully exploiting the very narrow diffraction limited core of a Near Infra-Red (NIR) AO corrected image. The unique combination of new fast and low noise Avalanche Photo-Diode IR detector and extremely sensitive WFS techniques is the corner stone of the development of future Laser assisted AO systems for the E-ELT which will give access to a significant part of the sky and thus which will provide unprecedented data to the astronomers, especially concerning the birth and evolution of the very first galaxies in the universe.
• The problematic of very accurate and very high order wavefront sensors for eXtreme adaptive optics systems and high contrast imaging instruments. In the OPTICON-FP7 activity, most of the developments related to this problematic have been conducted in the framework of the SPHERE project. A comprehensive analysis of the SPHERE results has been conducted, the optimisation of the AO system has been proposed to deal with unexpected input perturbations and the lesson-learned from almost 2 years of operations have been studied in order to propose a new wavefront sensor concept allowing to outperform existing devices. These studies are critical for the next generation of planet finder instruments which should be able to detect earth-like planet on the ELT in twenty years from now.

Thanks to the OPTICON-FP7 project, three kind of researches have been conducted
• The proposal of four brand new WFS concepts (LIFT, Lifted SH, Flat Pyramid, COFFEE). From theoretical developments to experimental validations (from most of them), the OPTICON program has allowed us to make major steps in terms of maturity levels and thus to make possible the integration of these WFS in the next generations of AO systems for both the VLT and the E-ELT (see Sections 2.1 2.1.3 3.3 and 3.1.3)
• The test of state-of-the art NIR detectors and their possible implementation in future wavefront sensors (see Section 2.2)
• The characterisation, optimisation and comprehensive analysis of the SPHERE AO system. Without any doubt, SPHERE is the most complex and the most powerful AO system in the world. It routinely provides the sharpest images ever obtained (both from ground or space) outperforming the Hubble space telescope even at visible wavelengths and its US competitors (GPI, SCExAO, etc.). Thanks to a direct access to SPHERE data, the OPTICON-FP7 program has allowed to fully understand the performance and the current limitations of the instrument but also to propose new WFS strategies to improve its ultimate performance. These researches have paved the way for the next generation of planet finder instruments on both VLT and ELT and for the direct detection of rocky planets in the habitable zone in the next decades.

All of the studies described in the report have been successful, and have led to results of direct relevance to design of E-ELT adaptive optics and associated instrumentation and scientific capabilities. The following examples highlight the significance of the studies:
• Based on the large corrective optics results obtained during these activities, ALPAO was selected by ESO to develop a prototype of a 3200-actuators compact deformable mirror, as part of the technology roadmap of the E-ELT.
• The first functional tests performed on the newly designed control electronics look very promising. Further tests will be performed early 2017 to characterise the performance in terms on bandwidth and to validate the sFPDP interface with ESO. Once these two remaining steps are validated, a proven solution will be available to drive high density deformable mirrors for the next generation of adaptive optics systems requiring several thousands of degrees of freedom.
• A full characterisation of the steering mirror prototype from the cryogenic correction study has been performed and a test report delivered. The steering mirror unit fulfils all of its the specifications.
• The laser guide star laboratory bench has supported the development of an end-to-end numerical simulation code for modelling the MAORY instrument for the E-ELT, it has provided experimental support to the study of centroid algorithms, supported the definition of the architecture of the MAORY instrument, and supporting the definition of mitigation strategies for spot truncation / under-sampling which affect the performance of LGS WFS on ELTs.
• The on-sky experiment has produced unique data sets comparing wavefronts measurements conducted with natural guide stars to ones made with a sodium laser guide star with the same perspective elongation as the worst case on the E-ELT. Together with the laboratory bench, this system also represents a significant resource for further studies related to the E-ELT AO systems in the future. The on-sky project has been the basis of a wider collaboration, which has harnessed resources from ESO, IAC and Roma, and has allowed further development of the CANARY ELT AO demonstrator on the 4.2-metre telescope, which will support further collaboration in the forthcoming H2020 network. The CANARY system has
benefitted from support from previous OPTICON frameworks, and a list of resulting publications has been appended to the reference section.
The results of these studies represent advances which are all globally unique, frequently with a high profile, and sometimes with critical significance for the E-ELT. Each study has led to the mitigation of important technical risk for the E-ELT, and will aid currently ongoing design studies to ensure the scientific productivity of the facility.
All of the studies will have extensions in some form in the future, and, in many cases, have leveraged significant resources from elsewhere. They have also fostered cross-European collaboration and communication which will be of lasting benefit to the community.

Fast and Efficient Sensors for Adaptive Optices and wider use.

Adaptive optics systems depend critically on extreme-sensitivity and fast detectors. OPTICON effort is dedicated to the development of detectors for future Adaptive Optics (AO) systems using laser guide stars (LGS). The detector control systems are prototypes, which allow testing of the detector in our laboratories, but do not allow development of the production camera which will be used on the telescope itself. During our previous contract, outstanding performance was obtained from the prototype, OCam, and its dedicated detector, the CCD220 by the company e2v. This technology is currently used by the second generation of VLT AO instruments. The third generation of AO instruments will be still more demanding in terms of frame rate and readout noise, and are the basis for the AO systems of the future European Extremely Large Telescope (E-ELT). This WP developed the final design of the Natural Guide Star Detector (NGSD) imaging system.
Significantly, during our development programme new partners from outside astronomy contacted us to investigate the use of this technology for monitoring civilian airport runways from the control tower, taking advantage of OCam’s ability to observe at low light levels and freeze the atmospheric turbulence at high frame rates.
The goal of the next proposal is to build an industrial product, ready to market, that can be used on any large telescope environment like the E-ELT for laser guide star wavefront sensing. Large telescopes require artificial guide stars for wavefront control. These guide stars are induced by laser stimulation of the 80-90km dust layer in the upper atmosphere. For control use, the images must be sampled at one kilo-frame/sec, and must cover a wide area, sufficient to sample the complex pattern of spot elongations induced by perspective effects. This provides an extremely demanding technical specification. A large Visible Adaptive Optics WFS Detector is needed to sample the spot elongation. To achieve this goal, it is necessary to finish the LGS Detector industrial collaboration started during previous work. A new detector foundry run offers an optimized design taking into account the results of the previous detector foundry runs, and increases its raw performance. Opticon will develop an integral Peltier package for this device, fully related to the camera development which is the main goal of this work. This new LGS detector will then be integrated in an industrial camera prototype developed by the First Light Imaging Company which will be a partner of the project. Linking the LGS camera to a Real Time Computer (RTC) solution with the required frame rate, latency and data throughput, an integral aspect, is a critical step on the path toward a system demonstration of what is needed on the E-ELT. In addition to the astronomical applications, market studies will also demonstrate that this future camera and this detector can also be used in biomedical applications.

AstroPhotonics applications from Industry

The overall vision of astrophotonics is to optimally utilise the massive global investment in Photonics for telecom, biomedical and sensing applications to provide enabling technologies for the next generation of astronomical instruments. By developing key components of a new Photonic Spectroscopic System based on optical fibre and integrated photonic technologies the project aims to provide novel photonic devices that dramatically reduce the size and cost whilst increasing the sensitivity of ground based optical spectroscopic instruments. The project initially concentrated on two main components of the Photonic Spectroscopic System (PSS): (a) the photonic filter based on multicore fibre (MCF) and (b) Photonic Coupler based on integrated waveguides. The former is a low-cost, compact, robust and highly efficient for OH-Suppression that improves the sensitivity of ground-based near infrared observations, and the later transforms a two-dimensional seeing or partially AO-corrected telescope image into a diffraction-limited entrance slit of a spectrograph. However, delays with the photonic filter enabled the development of a low mode noise scrambling fibre based on the multicore fibre technology.
The two technologies underpinning the developments, the multicore fibre photonic lantern and 3D waveguide reformatting structure fabricated by ultrafast laser inscription (ULI), increase the stability and sensitivity of precision spectrographs and can enable the spectrograph design to be independent of the telescope's focal plane
parameters. In doing so they can greatly benefit science cases requiring high precision and high throughput visible/NIR spectroscopy from ground-based telescopes, such as extra-solar planet detection, galactic archaeology, galactic evolution and real time cosmology.

Bend Sensors: An interesting spin-off development enabled by activities for photonic filters has been the development of fibre optic-based 3D bend sensors for use in chemistry, life science, medicine, geo-science, environmental monitoring, and materials research The device, using the original 120 core MCF combined with a long period fibre grating was developed for 3D bend sensing. This device has been shown to be much more sensitive to shape changes than previous generations of this type of device. This development, with medical applications such as real time torso sensing, was in collaboration with the University of Aston. The system is sensitive enough to detect the changing shape of the torso resulting from the human heartbeat, as well as detailed shapechanges from breathing and torso movements.

Optical-InfraRed Interferometry
Optical interferometry is another technique to deliver high-resolution data. Except perhaps for the most simple objects, interferometric data are hard to interpret
directly and image reconstruction is required to analyze the observations. Restoring a correct image from optical interferometric data is challenging because of the sparsity of the measurements and of missing information. Several image reconstruction algorithms have been developed to cope with optical interferometric data and most of them are freely available. These algorithms are however not black boxes which could produce reliable images without any human interaction. A set of cookbooks has been developed to introduce the algorithms. The objective of these cookbooks is to introduce the reader to the use of a number of algorithms.

Modern Manufacturing-aspherical surfaces

Just like the telescopes on which they are mounted, astronomical instruments are becoming increasingly larger and more complex. Looking at the next generation of instruments for (future) telescopes we see: increased size, increased number of components, increased complexity and more demanding requirements. The construction of the next generation 40 m-class astronomical telescopes poses an enormous challenge for the design and manufacturing of associated instruments and their optics. In order to profit the most from the potential provided by the large telescopes there is a strong need to simplify system complexity and/or boost performance. This challenge can be met by making use of the (almost) unexplored world of options that lay ahead by application of freeform optics1; non-symmetric complex surface shapes.
In general the adoption of freeforms is held back by the difficulty of optimizing the freeform based optical designs, as well as the issues around production and positioning of these components up to the required accuracies. The objective of the FAME project was to study optical and opto-mechanical design strategies that combine (extreme) freeforms with standard optics for stable integrated systems, regardless of working wavelength range and environment (cryogenics or otherwise).
With its demonstrator FAME aims to show reduction in complexity, mass, volume and cost, while improving the performance of the overall system when compared to classical optical designs with the potential to be used in future instrumentation.
First a pre-polished substrate is permanently deformed in its near required shape by pushing the substrate against a mould by means of fluid under high pressure. This way hard contact with the mould is avoided and after pressure removal a smooth surface shape can be obtained. Further refining of the surface shape is done through stress polishing. The mirror face sheet is put under stress by pushing the substrate into a pre-defined shape in a dedicated warping harness. When still under stress in the harness, the substrate is further grinded and polished. When the mirror face sheet is released from its harness it “springs” into its final shape.
The early adopted modular design approach allowed for each individual building block to find innovative design solutions. Combined they offer a whole new approach towards freeform and/or active mirror design and use.
The demonstrator shows the practical use of active freeform in an optically demanding, but on the other hand surprisingly clean and simple set-up. Besides the one special freeform component the rest of the set-up is built with commercially available units.
In addition each individual building block show potential to be used in other (instrumental) applications. To summarise, this project contributed the following:
- Freeform based optical modelling tool
- Novel approach for intrinsically stiff and stable but actively adjustable mirrors
- Novel high quality shaped mirror production
- Innovative miniature actuator developments for harsh environments
- Active mirror behaviour modelling and optimization
The research and early results show the enormous potential of this particular approach in dealing with the expected instrumental complexities of large astronomical observatories. Allowing the reduction of future instrumental complexity, volume, number of components and thus costs, the FAME concept provides the tools to enter the un(der)explored design space of freeform systems. It is now also more accessible due to the availability of freeform based optical design optimization tools made possible by this research.
The actuation of the freeform mirror even allows fine tuning of the optical performance of entire the instrument after it is fully assembled and stabilized at its operating temperature. Furthermore, drift during operation can be corrected. Due to all these benefits, and the gain in performance, the requirements on complex optical components like dispersion elements for spectrometers or (polarization) modulators for polarization instruments can be relaxed, reducing risks and costs.
A next step will be the investigation of compatibility with operation in vacuum and cryogenic environments. The demonstrator is already built against the requirements of these extreme conditions.

Novel Dispersive and Holographic Optical Elements for Astronomy

This deals with the study of new materials for making Novel Dispersive and Holographic Optical Elements for Astronomy. The research started with the design and testing of new materials and ended up with the manufacturing of the working devices. This was possible thanks to the different expertise of the WP team that goes from chemistry to materials engineering and astronomy.
Two main research lines were carried out in this WP:
1. Development and testing of photopolymers for Volume Phase Holographic Gratings (VPHGs);
2. Development of photochromic materials for Computer Generated Holograms (CGHs) to be written by means of the DMD (Digital Micromirror Device) technology.
In both cases, we succeeded in obtaining the expected results, namely a device that works properly based on the new developed materials.
In particular, for the first time some VPHGs with innovative photopolymers (produced by Covestro®, Germany) have been manufactured and installed in existing spectrographs mounted at the NOT (Nordic Optical Telescope, La Palma, Spain) and at the Copernico Telescope (Asiago, Italy). They provided a remarkable gain in the spectroscopic performances in comparison to the old installed elements and they are now available for the astronomical community.
As for CGHs, we demonstrate the production of grayscale holograms with a very good reconstruction quality by using a projection technique based on DMD and exploiting the conversion kinetics of photochromic materials.

Computer Generated Holograms (CGHs) are devices capable to reconstruct an image or to generate a well-defined wavefront on the base of a calculated hologram impressed in a suitable material. Such holographic elements play an important role in the metrology of complex optical elements, such as aspheric mirrors and lenses and freeform optics. Indeed, it is possible to design the CGH that reproduces the “perfect” optics under test; therefore, the quality of the element can be evaluated by interferometry.
Conventionally, CGHs are produced exploiting the lithographic techniques, namely, the pattern in transferred to the photosensitive substrate and then a developing/etching process is necessary to permanently write the holographic pattern. Such process is well-established, but intrinsically complex and does not allows to produce rewritable holograms. Moreover, the established technology could provide grayscale holograms, which give better image qualities, only by a very complex procedure.
The use of photochromic materials was proposed to overcome all these limitations by exploiting their unique properties. Indeed, photochromic materials are able to change, in a reversible fashion, the color in the visible spectral range upon illumination with light of defined wavelength. A change in color means a change in transparency that makes the materials suitable for producing amplitude CGHs, namely CGHs based on a modulated transparency pattern. Since the photochromic reaction is reversible the CGH can be written, used and then rewritten with a different pattern.

Perspectives
The important results we achieved open the way to different step forward in the developing of the holographic devices.
In the case of VPHGs, the first goal is to increase the size of the produced VPHGs in the range of 100–250 mm in diameter in order to fit the astronomical instrumentation mounted on large telescopes in the world. Moreover, we will take advantage of the simple production process and easy handling for designing innovative dispersing elements with new functionalities, which are not accessible with the standard holographic materials. The stack of different grating on the same elements or the realization of many identical copies of the same VPHG in one shot is just an example of these new opportunities.
Focusing on the photochromic CGHs, the idea to have in a single set-up both the writing step and the CGH imaging in-situ and in real time is attractive: we open to a unique reconfigurable device for making any CGH according to the requests. By exploiting the tunable properties of the photochromic materials by changing their chemical structure, it will be interesting to make multiplexed CGHs, namely more than one hologram will be stored on the same photochromic substrate and addressed independently.

Industry connections, foreground

OPTICON networking covers development of the community and of its interactions with industry and society.
Optical and Infrared Astronomy has both fed off new technologies coming from industry and acted as a stimulus for industrial innovation. An example of this ‘cycle of innovation’ is the adoption of infrared detectors developed for military applications for the first array-based IR cameras and spectrometers in the 1980’s. The strong push for higher performance in astronomical applications, particularly for wavefront sensing in adaptive optics, has stimulated Selex ES to improve the performance of these detectors, thereby improving their competitiveness for other markets. Within the OPTICON programme, there is an excellent example of the application of the OCam high-speed camera, developed for adaptive optics, but now finding wide industrial and scientific applications though the French start-up company First Light Imaging. The Innovation Network has also promoted novel optical manufacturing processes, having a part in the success of the UK spin-out company Optoscribe, which is using an ultrafast laser inscription process developed for the OPTICON Astrophotonics programme in high-speed optical telecommunication devices. Optoscribe were recently successful in generating £1.2M of venture capital investment.

Community networking

We investigated the expected photometric performance of the adaptive optics (AO) assisted European Extremely Large Telescope (E-ELT). The main problems affecting photometry with such systems include the following: angular anisoplanatism, variations of the Point Spread Function (PSF) as a function of time due to changes in the seeing and the wavefront sensor noise, residual features/speckles in the PSF, and the halo surrounding the core of the PSF. To examine the photometric accuracy, we simulated star fields using various Adaptive Optics PSFs generated by the Octopus and Cibola software tools, and performed PSF-fitting photometry on the fields, with particular attention to the crowded fields. We present the results of a preliminary investigation into the efficiency of current data reduction techniques for reducing E-ELT simulated data and discuss the merits and disadvantages of the StarFinder software and IRAF (DAOPHOT) based functions. These packages are investigated with the use of simulated images.
Some network effort empowers scientists with access only to small and old facilities to become part of cutting-edge research in TimeDomainAstronomy by having their data processed, calibrated and archived for analysis by themselves and larger groups. The facility is the Cambridge Photometric Calibration Server (CPCS), a system designed and developed by Sergey Koposov and Łukasz Wyrzykowski. The Server is the central point where the photometric data from various telescopes for multiple targets are being stored. The system performs homogenous zero-point calibrations for heterogenous data sets, using stars found in the field around the target of interest. The zero-point is derived by comparison between the measured magnitudes of many stars with these in the archival catalogue. A linear relation between the magnitudes is assumed and the relation with the lowest scatter is selected (when in automatic mode). Once the transformation is known, the magnitude of the target of interest is computed. A users manual is available, community adoption is underway.

The community training schools remain popular and heavily in demand, with typically 40 students from 20 countries taking part in each. Annual hands-on schools were held, supplemented by dedicated archive access schools, teaching access to the wealth of available data. to reinforce the practical aspects, besides the traditional data reduction exercises (with archival data), emphasis was also put on how to write a good observing time proposal (an aspect which is often discouraging for young, new-comers) and how these proposals are evaluated: the participants were invited to play themselves the role of referees, as in a real Observing Program Committee, to evaluate real (but old...) proposals and to grant (or not...) observing time. The best way to understand a process is often to do it directly...This school has therefore covered all the aspects of the tasks of an observing astronomer, followed with great interest and enthusiasm by the participants, which also discovered its complexity.

The European Interferometry Initiative developed a 100+pp White paper outlining the subject’s future. The report presents a synthesis of the topics discussed by the working group Future of interferometry in Europe (FIE) of the EC-FP7-2 OPTICON Network, work-package 14.4 funded by the European Commission. We describe the current momentum in the field driven by an exciting range of new instruments, and by improved interferometric facilities becoming available to the larger astronomical community right now. The central theme of this report is to discuss which steps are necessary to benefit from this current momentum and to focus it into an even brighter future, making eventually the 2030s the decade of optical interferometry, as the natural next revolutionary step of astronomical instrumentation after the construction of the 30+m class of so-called extremely large telescopes (ELTs), which is currently under way.

Potential Impact:
The EC Mid Term review, held March 2015, concluded:
OPTICON is a well-oiled machine!
It continues to deliver high quality products to the optical/IR astronomy community and prepare for future developments in the field. It is a particular strength that national Funding Agencies and ESO are partners in OPTICON since this provides direct links to national technical developments and embeds pan-European technical progress in the national plans. Relatively modest EC funding has triggered substantial external funds. In addition, this close connection is clearly beneficial when strategic choices of technology have to be made.
OPTICON is playing a major role in cohering the community through support of science and technical meetings. It is also playing a major role in training new members of the community (young and old) through schools and workshops. The interferferometry and photonics Schools held so far are models of organisation, focus, and impact.
OPTICON is providing a focus for the highest priority engineering developments in European optical/IR astronomy; investigating disruptive technologies and road-mapping. EC funding is critical in allowing the community to build networks that can take on high risk, potentially disruptive instrumental developments. It is therefore a valuable resource in the scientific and instrumental preparation for E-ELT, and is increasing the sense of ownership of the E-ELT project by the community.

Expected final results and potential impacts

The OPTICON technology R&D program, across its several broad fronts has been impressively successful. The technology development teams have worked together long enough for the individuals to develop mutual respect and understanding, and for the teams to develop the range of expertise and experience needed to make progress in difficult challenges.

A priority for OPTICON is the optimisation of potential impact. This we ensure through a dedicated Work Package (WP9), whose task is to develop and maintain a watching brief on future Key technologies (we do this in collaboration with ESA), and to build close industry-research partnerships to ensure potential exploitation of IPR and foregrounds. This work package covers activities to reinforce the partnership with industry, e.g. transfer of knowledge and other dissemination activities, activities to foster the use of research infrastructures by industrial researchers and involvement of industrial associations in consortia or in advisory bodies.
One of the key deliverables from this work package is an industry showcase event where the work of OPTICON would be advertised to an audience of potential industrial partners and the opportunities for collaboration between OPTICON members and industrial organisations would be highlighted.
OPTICON is specifically aimed at ground based astronomical instrumentation and for this reason it was decided to hold the event at the world’s largest astronomical instrumentation exhibition which is the SPIE conference on astronomical instrumentation and telescopes. The conference takes place every two years. For this reason, the event was held back to the last year of the contract so that it would coincide with the SPIE conference. The main aim of the event was defined as “highlighting the OPTICON developments, and providing an opportunity for further connections to take place.” The industry showcase event was very focussed on the companies that were looking to gain access to the astronomy market. The stand and networking event were well attended, at a level that exceeded the expectation and the end result was a surge of new members to the OPTICON LinkedIn group. (Deliverable D9.2 provides details.)
Optical and Infrared Astronomy has both fed off new technologies coming from industry and acted as a stimulus for industrial innovation. An example of this ‘cycle of innovation’ is the adoption of infrared detectors developed for military applications for the first array-based IR cameras and spectrometers in the 1980’s. The strong push for higher performance in astronomical applications, particularly for wavefront sensing in adaptive optics, has stimulated Selex ES to improve the performance of these detectors, thereby improving their competitiveness for other markets. Within the OPTICON programme, there is an excellent example of the application of the OCam high-speed camera, developed for adaptive optics, but now finding wide industrial and scientific applications though the French start-up company First Light Imaging. The Innovation Network has also promoted novel optical manufacturing processes, having a part in the success of the UK spin-out company Optoscribe, which is using an ultrafast laser inscription process developed for the OPTICON Astrophotonics programme in high-speed optical telecommunication devices. Optoscribe were recently successful in generating £1.2M of venture capital investment.

OPTICON is playing a major role in cohering the community through support of science and technical meetings. It is also playing a major role in training new members of the community (young and old) through schools and workshops. The interferometry and photonics Schools held so far are models of organisation, focus, and impact.
OPTICON is providing a focus for the highest priority engineering developments in European optical/IR astronomy; investigating disruptive technologies and road-mapping. EC funding is critical in allowing the community to build networks that can take on high risk, potentially disruptive instrumental developments. It is therefore a valuable resource in the scientific and instrumental preparation for E-ELT, and is increasing the sense of ownership of the E-ELT project by the community.
Adaptive Optics: Thanks to the OPTICON-FP7 programs, new components and new wave front sensor concepts have been proposed, simulated, experimentally tested and even applied on sky for some of them. They all have been designed to improve the performance of AdaptiveOptics (AO)-assisted instruments and thus to give access to new astrophysical objects. The sky coverage improvement of the Laser assisted AO system and the gain in contrast for eXtreme AO and the planet finder instrument will trigger new discovery in both the cosmological domain (earliest galaxy in the Universe) and exoplanet hunt (toward the direct imaging of earth-like planets).
AstroPhotonics: The overall vision of astrophotonics is to optimally utilise the massive global investment in Photonics for telecom, biomedical and sensing applications to provide enabling technologies for the next generation of astronomical instruments. By developing key components of a new Photonic Spectroscopic System based on optical fibre and integrated photonic technologies the project aims to provide novel photonic devices that dramatically reduce the size and cost whilst increasing the sensitivity of ground based optical spectroscopic instruments.
Optical interferometry is another technique to deliver high-resolution data. Interferometric data are hard to interpret directly and image reconstruction is required to analyze the observations. Restoring a correct image from optical interferometric data is challenging because of the sparsity of the measurements and of missing information. A set of cookbooks has been developed to introduce the algorithms. The objective of these cookbooks is to introduce the reader to the use of a number of algorithms for practical application. The working group Future of interferometry in Europe (FIE) of describes the current momentum in the field driven by an exciting range of new instruments, and by improved interferometric facilities becoming available to the larger astronomical community right now. The central theme of this report is to discuss which steps are necessary to benefit from this current momentum and to focus it into an even brighter future, making eventually the 2030s the decade of optical interferometry, as the natural next revolutionary step of astronomical instrumentation after the construction of the 30+m class extremely large telescopes (ELTs), which is currently under way.

Innovative manufacturing: Just like the telescopes on which they are mounted, astronomical instruments are becoming increasingly larger and more complex. Looking at the next generation of instruments for (future) telescopes we see: increased size, increased number of components, increased complexity and more demanding requirements. The construction of the next generation 40 m-class astronomical telescopes poses an enormous challenge for the design and manufacturing of associated instruments and their optics. In order to profit the most from the potential provided by the large telescopes there is a strong need to simplify system complexity and/or boost performance. This challenge can be met by making use of the (almost) unexplored world of options that lay ahead by application of freeform optics; non-symmetric complex surface shapes. The objective of the FAME project was to study optical and opto-mechanical design strategies that combine (extreme) freeforms with standard optics for stable integrated systems, regardless of working wavelength range and environment (cryogenics or otherwise). With its demonstrator FAME aimed to show reduction in complexity, mass, volume and cost, while improving the performance of the overall system when compared to classical optical designs with the potential to be used in future instrumentation.

Innovative Optical Materials: includes the study of new materials for making Novel Dispersive and Holographic Optical Elements for Astronomy. The research covered the design and testing of new materials and ended up with the manufacturing of working devices. This was possible thanks to the expertise of the WP team that includes chemistry to materials engineering and astronomy.
Two main research lines were carried out:
1. Development and testing of photopolymers for Volume Phase Holographic Gratings (VPHGs);
2. Development of photochromic materials for Computer Generated Holograms (CGHs) to be written by means of the DMD (Digital Micromirror Device) technology.
In both cases, we succeeded in obtaining the expected results, namely a device that works properly based on the new developed materials. In particular, for the first time some VPHGs with innovative photopolymers (produced by Covestro®, Germany) have been manufactured and installed in existing spectrographs mounted at the NOT (Nordic Optical Telescope, La Palma, Spain) and at the Copernico Telescope (Asiago, Italy). They provided a remarkable gain in the spectroscopic performances in comparison to the old installed elements and they are now available for the astronomical community. As for CGHs, we demonstrated the production of grayscale holograms with a very good reconstruction quality by using a projection technique based on DMD and exploiting the conversion kinetics of photochromic materials.

Networking empowered scientists with access only to small and old facilities to become part of cutting-edge research in Time Domain Astronomy by having their data processed, calibrated and archived for analysis by themselves, and allowing their participation in larger groups. This initiated a major expansion of this activity, matched to a burgeoning of time-domain astronomy more generally driven by exo-planet interests. Building on this small-scale start, time-domain astronomy has become a major feature of OPTICON activity in H2020, and is bringing into the modern research community large numbers of scientists from small and non-traditional research communities across central Europe. Interestingly there is substantial and growing interest among amateur astronomers, many of whom own (private or club) facilities able to contribute usefully to this research field.
As part of the dissemination activity associated with this wide public interest we have develop a free smartphone app (described in D11.2) which is popular, and attracts children more widely to realise that the Universe is a vibrant and changing place, worthy of their interest. The app (iOS and Android) is available at the usual places, and at http://gaia.ac.uk/alerts.

Community training schools, remain popular and heavily in demand, with typically 40 students from 20 countries taking part in each classical observing school. The interferometry and photonics Schools held are the first of their kind worldwide, and of extremely high impact for training young scientists in at the industry-research interface.

An extension of the interferometry schools was production of short explanatory “educational worksheets” explain the science and technology of adaptive optics. These are being translated into each of the EU local languages for educational use. (www.european-interferometry.eu/training ).
# Title Minimum
Level of Audience Methodology
1 Adaptive optics: introduction (4 pages) All levels Internet search for information
2 Measuring aberrations with a Shack-Hartmann wave-front sensor: simulations (9 pages) College level Simulation with YAO software package
3 Measuring aberrations with a Shack-Hartmann wave-front sensor: laboratory (5 pages) College level Experimental use of the demonstration bench
4 Adaptive optics correction of aberrations: simulations (8 pages) College level Simulation with YAO software package
5 Adaptive optics correction of aberrations: laboratory (4 pages) College level Experimental use of the demonstration bench

List of Websites:
http://www.astro-opticon.org/