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European Stratospheric Balloon Observatory Design Study

Periodic Reporting for period 1 - ESBO DS (European Stratospheric Balloon Observatory Design Study)

Reporting period: 2018-03-01 to 2019-08-31

Without the protection by the Earth’s atmosphere, there would be no life on Earth – for most astronomical measurements, however, the atmosphere is an obstacle. Observers thus started early to move their instrument as high above the perturbing atmospheric layers as possible. Spacecraft provide access to optimal observing conditions in this endeavour. However, they are not very accessible after launch and comparably expensive. For some astronomical applications, though, particularly in the far infrared wavelength region and in some parts of the ultraviolet, it is sufficient to take a smaller step up – into the stratosphere.
The ESBO DS (European Stratospheric Balloon Observatory – Design Study) project is working to realise this step and to make the excellent observing conditions at an altitude of 30 to 40 km available to a broad scientific community. The explicit goal of the endeavour is to create a European research infrastructure featuring regular flights, exchangeable instruments, and open access to observation time. If successful, ESBO DS will eventually reduce the cost of cutting-edge astronomical observations considerably and enable new insights into the formation of stars, planetary systems, and life. In practice, the work on the 3-year pilot project is focusing on two immediate objectives:
1. On the development and construction of a prototype gondola and telescope, which shall perform technology tests as well as deliver first scientific results during its maiden flight with a newly developed UV-instrument.
2. On the development of a strategy for the long-term establishment and operation of the observatory – including the study of the technical feasibility of balloon flights with larger telescopes, particularly of the 5 m aperture class for far infrared observations.
ESBO DS follows a two-tier approach throughout the entire project: on the one side, the development and construction of a prototype astronomical balloon gondola, including a 50 cm-aperture telescope with a newly-developed UV instrument; and on the other side, the conceptual design of a long-term, balloon-based research infrastructure, prominently including a flight system suitable for carrying a next-generation, 5-m aperture class telescope for far infrared observations. On these two tiers, the following work was performed during the First Reporting Period:

Work performed on the infrastructure concept study:
- Science needs for the mid- and long-term to be addressed by the infrastructure were reviewed and defined;
- The feasibility and benefit of innovative infrastructure technologies, including super pressure balloons, novel flight trajectories, and soft landing systems were studied for the infrastructure;
- Particularly for the balloon gondola / bus, subsystems that could be scaled & built in a modular fashion were studied;
- Preliminary technical system studies of the mid- and long-term flight systems (carrying a 1.5 m aperture telescope for near infrared applications and a 5 m aperture telescope for far infrared applications, respectively) were carried out to identify critical technologies, mass and power drivers, and different infrastructure options.

Work performed on the prototype development:
- Detailed requirements for the prototype were derived from both the technology demonstration perspective as well as the perspective of a later scientific exploitation of the prototype (primarily for studying variable hot compact stars in the galactic plane);
- Performance simulators for several of the prototype components were developed, including the newly-developed UV-instrument, the secondary visible light instrument (as part of the image stabilization system), and the star tracker for guiding;
- A thermal simulation model for the prototype at float altitude (~40 km ) was developed to support the design of the thermal control system;
- A concept for the closed-loop Image Stabilization System (one of the technologies to be demonstrated) was developed;
- A concept for a modular and scalable balloon gondola (one of the technologies to be demonstrated) was developed, design of the prototype gondola started;
- Other scalable balloon service subsystems were identified and concepts for the application on the STUDIO prototype developed, particularly including the gondola pointing system and the power supply system; design of these subsystems for STUDIO started;

Results achieved:
- Necessary pre-development activities to implement the infrastructure were identified;
- Technologies and scalable subsystems to be implemented and demonstrated on the prototype were defined;
- The most attractive infrastructure option was identified and chosen for further study in the second half of the project;
- The design of the telescope and optical system for the prototype was concluded;
- The design of most other subsystems for the prototype was concluded.
ESBO DS aims at developing and establishing a dedicated, regularly flying and community-accesible astronomical observatory based on stratospheric balloons, which currently does not exist. If this effort succeeds, it will make space-like observation conditions available to a much larger part of the astronomical community than currently possible, at a significantly lower cost and on significantly shorter timeframes than what comparable space missions would require. In particular, the far infrared astronomy community would benefit from the envisioned next-generation platform with an unprecedented telescope size for this wavelength range, which would make it possible to look into processes of star formation and molecular evolution in our universe in more detail. Having such a unique facility in Europe will fost innovation in scientific findings, methods, and instrumentation and make the European research area more efficient and competitive. The required technological developments for this infrastructure, particularly with regard to high-performance balloons, astronomical balloon gondolas, optical stabilisation systems, and large, light-weight telescopes will strengthen European industry in the respective fields.
"CAD model of the current balloon gondola design for the ESBO DS prototype mission ""STUDIO"""
The ESBO DS project team during the Kick-Off meeting on 21/22 March 2018 in Stuttgart, Germany.