Joint Research Activities

With the Joint Research Activities in SOLARNET we aim on improving the services provided by the observing facilities and the virtual installations by exploring new fundamental technologies. The work on the spectrographs involved will result in higher performance instrumentation. By developing higher performance methodologies, innovative software solutions fill allow the high-resolution solar physics community benefiting from new services.

Towards a European Solar Data Centre (WP5)

Given the number of solar infrastructures operated and under development by the European institutions, WP5 focuses on activities of common interest to the Solar Physics community for the curation and dissemination of solar data, to boost its use and re-use and thus optimize its scientific exploitation in line with the spirit/essence of the European Open Science Cloud (EOSC) project. These common efforts can be understood as the first steps towards building up a European Solar Data Centre for EST. The activities of this work package respond to the demands on data management which is an essential theme throughout this SOLARNET proposal.

WP5 will pursue the following activities: data calibration, data archiving and development of advanced data search techniques, the Solar Virtual Observatory (SVO) as a frame work for data dissemination, and high-level data products and visualization tools. The work package combines the competences of 16 partner institutions, including one industrial partner. The first activity implements automatic calibration pipelines for panoramic spectrometers and investigates several new approaches to accelerate and improve post processing of high resolution observations, with a view to EST. There will be an interface to WP7 on adaptive optics development in this part of the project. The second activity focuses on applying new approaches to data archiving and data mining including Automatic Test Equipment (ATE) application of deep learning methods for data retrieval. The third activity will carry SVO from prototype to production level. The fourth activity addresses the question of co-alignment of data from various sources and the development of basic and advanced tools for data analysis, focusing on specific scientific questions.

Advanced Instrument Development (WP6)

This work package combines several instrument development projects to improve the existing solar telescopes and with a perspective to application in future large aperture solar telescopes. There are two projects pursuing solar field-integrated spectroscopy (the combination of high spectral dispersion with a diffraction-limited two-dimensional field of view), and which have already passed the prototype stage. The goal is to develop facility instruments implementing these concepts on existing telescopes, which requires substantial development. The concepts are based on image slicers for 2D spectroscopy and micro-lens based bi-dimensional spectroscopy. Both concepts have been realized for applications in night-time telescopes, so there is an inheritance which is being exploited for the purposes of solar observations. Both concepts are also relevant for application in EST.
A third project will develop design concepts for a narrow-band tunable-filter Imager for EST. The main challenge is the large optical throughput required for the key elements – the etalons – which result from the combination of a 4m aperture and a useful field size. The fourth project will develop a new method for very high precision absolute polarization measurements at the IRSOL telescope in Switzerland, with a perspective for migration to a larger telescope like GREGOR. This new capability addresses directly a key science goal of EST. This work package combines the competences of 11 partners.

Multi-Conjugate Adaptive Optics for EST (WP7)

The investigation of systems of solar magnetic field require simultaneous observations of fields approaching an arc minute (45.000 km on the solar surface) with highest resolution. European research groups have pioneered the development of solar multi-conjugate adaptive optics (MCAO), which aims at compensating arc minute sized fields of view. In comparison to conventional AO, which use a single deformable mirror at a transferred pupil of the telescope, MCAO controls several deformable mirrors which are conjugated to different altitudes in the Earth’s atmosphere. Recognizing that the development of MCAO is quite complex, the solar community joined forces in the EU and the USA to collaborate in the development of this technology for large aperture solar telescopes. Recently, solar MCAO has been demonstrated to compensate a 30 arcsec field with a total of three DMs (see figure). This proposal comprises a part of the joint effort focused on the requirements of EST.

The main goal of this work package is to carry out the research needed for a preliminary design for the EST multi-conjugate adaptive optics system to establish the point where all major design choices are resolved. In order to verify concepts and design choices, we will build a prototype MCAO system which will be tested in the laboratory and on the sky using the GREGOR telescope at the Teide Observatory on Tenerife. The prototype will be used to test several solutions for wave front sensing and for system control including neural networks. Other work packages address the performance evaluation based on on-sky test data (liaison to WP5) and measurements of the turbulence profile at intermediate altitudes which are an essential input for the design work. The parts of the prototype which are funded by KIS will eventually evolve into a standing MCAO system for the GREGOR solar telescope and become a part of the service to the solar community. The work package also includes studies for technology drivers which are specific to EST.

This work package combines the competences of nine partners, including one industrial partner. One partner (IOSB) provides the competence of the remote sensing community, which – although unrelated to solar physics – contributes valuable experience in adaptive optics technology and characterization of the Earth’s atmosphere.

Conventional (left) and multi-conjugate (right) solar adaptive optics (Schmidt et al., Astron. Astrophys. 597, L8, 2017). Conventional AO produces a sharp image only at the center of the field, limited to a single isoplanatic patch of 5 arcsec. MCAO extends the compensated field to 30 arcsec with three deformable mirrors in this case.

Solar Physics Research Integrated Network Group – SPRING (WP8)

This work package addresses the essential capabilities needed to complete the facilities for experimental solar physics from the ground. Large, high resolution telescopes admit only a small field of view. However, context data showing the big picture of the dynamics and magnetism at different heights of the solar atmosphere are equally important to understand the Sun in general. Real-time information about the variation of surface velocity, magnetic field and intensity at different solar layers is an essential input to space weather prediction and to fundamental solar physics, but still hard to come by with any degree of reliability. There is a consensus that a world-wide distributed network of a suite of small, dedicated telescopes which observe the entire solar disk will be an essential support for coordinated observations with the major infrastructures.
This work package will translate the technical concept for such a network – SPRING – which has been developed during SOLARNET FP7, into a preliminary design. The key scientific products of this facility will be arc-second resolution context images in various wavelengths, synoptic vector magnetic fields, synoptic surface velocity fields with high time cadence, and observations of transient events such as flares. The work will include designs of mounting and telescopes, design and prototyping of post focus instruments, and the definition of the data processing pipelines. The work package combines the competences of 15 partners, two of which are from the US and two are industrial.