arXiv subjects

Lars Hanke

Publications and source records attributed to Lars Hanke.

6 recordsLinked to original sources

arXiv2022

Stratospheric balloons as a platform for the next large far infrared observatory

Observations that require large physical instrument dimensions and/or a considerable amount of cryogens, as it is the case for high spatial resolution far infrared (FIR) astronomy, currently still face technological limits for their execution from space. Angular resolution and available observational capabilities are particularly affected. Balloon-based platforms promise to complement the existing observational capabilities by offering means to deploy comparatively large telescopes with comparatively little effort, including other advantages such as the possibility to regularly refill cryogens and to change and/or update instruments. The planned European Stratospheric Balloon Observatory (ESBO) aims at providing these additional large aperture FIR capabilities, exceeding the spatial resolution of Herschel, in the long term. The plans focus on reusable platforms performing regular flights and an operations concept that provides researchers with proposal-based access to observations. It thereby aims at offering a complement to other airborne, ground-based and space-based observatories in terms of access to wavelength regions, spatial resolution capability, and photometric stability. While the FIR capabilities are a main long-term objective, ESBO will offer benefits in other wavelength regimes along the way. Within the ESBO Design Study (ESBO DS), a prototype platform carrying a 0.5 m telescope for ultraviolet and visible light observations is being built and a platform concept for a next-generation FIR telescope is being studied. A flight of the UV/VIS prototype platform is estimated for 2021. In this paper we will outline the scientific and technical motivation for a large aperture balloon-based FIR observatory and the ESBO DS approach towards such an infrastructure. Secondly, we will present the technical motivation, science case, and instrumentation of the 0.5 m UV/VIS platform.

astro-ph.IM↗

arXiv2022

Stratospheric Balloons as a Complement to the Next Generation of Astronomy Missions

Observations that require large physical instrument dimensions and/or a considerable amount of cryogens, as it is for example the case for high spatial resolution far infrared astronomy, currently still face technological limits for their execution from space. The high cost and finality of space missions furthermore call for a very low risk approach and entail long development times. For certain spectral regions, prominently including the mid- to far-infrared as well as parts of the ultraviolet, stratospheric balloons offer a flexible and affordable complement to space telescopes, with short development times and comparatively good observing conditions. Yet, the entry burden to use balloon-borne telescopes is high, with research groups typically having to shoulder part of the infrastructure development as well. Aiming to ease access to balloon-based observations, we present the efforts towards a community-accessible balloon-based observatory, the European Stratospheric Balloon Observatory (ESBO). ESBO aims at complementing space-based and airborne capabilities over the next 10-15 years and at adding to the current landscape of scientific ballooning activities by providing a service-centered infrastructure for broader astronomical use, performing regular flights and offering an operations concept that provides researchers with a similar proposal-based access to observation time as practiced on ground-based observatories. We present details on the activities planned towards the goal of ESBO, the current status of the STUDIO (Stratospheric UV Demonstrator of an Imaging Observatory) prototype platform and mission, as well as selected technology developments with extensibility potential to space missions undertaken for STUDIO.

astro-ph.IM↗

arXiv2021

Towards a European Stratospheric Balloon Observatory -- The ESBO Design Study

This paper presents the concept of a community-accessible stratospheric balloon-based observatory that is currently under preparation by a consortium of European research institutes and industry. The planned European Stratospheric Balloon Observatory (ESBO) aims at complementing the current landscape of scientific ballooning activities by providing a service-centered infrastructure tailored towards broad astronomical use. In particular, the concept focuses on reusable platforms with exchangeable instruments and telescopes performing regular flights and an operations concept that provides researchers with options to test and operate own instruments, but later on also a proposal-based access to observations. It thereby aims at providing a complement to ground-, space-based, and airborne observatories in terms of access to wavelength regimes - particularly the ultraviolet (UV) and far infrared (FIR) regimes -, spatial resolution capability, and photometric stability. Within the currently ongoing ESBO Design Study (ESBO DS), financed within the European Union's Horizon 2020 Programme, a prototype platform carrying a 0.5-m telescope for UV and visible light observations is being built and concepts for larger following platforms, leading up to a next-generation FIR telescope are being studied. A flight of the UV/visible prototype platform is currently foreseen for 2021. We present the technical motivation, science case, instrumentation, and a two-stage image stabilization approach of the 0.5-m UV/visible platform. In addition, we briefly describe the novel mid-sized stabilized balloon gondola under design to carry telescopes in the 0.5 to 0.6 m range as well as the currently considered flight option for this platform. Secondly, we outline the scientific and technical motivation for a large balloon-based FIR telescope and the ESBO DS approach towards such an infrastructure.

astro-ph.IM↗

arXiv2020

Microchannel-Plate Detector Development for Ultraviolet Missions

The Institute for Astronomy and Astrophysics in T\"ubingen (IAAT) has a long-term experience in developing and building space-qualified imaging and photon counting microchannel-plate (MCP) detectors, which are sensitive in the ultraviolet wavelength range. Our goal is to achieve high quantum efficiency and spatial resolution, while maintaining solar blindness and low-noise characteristics. Our flexible detector design is currently tailored to the specific needs of three missions: For the ESBO DS (European Stratospheric Balloon Observatory Design Study) we provide a sealed detector to the STUDIO instrument (Stratospheric Ultraviolet Demonstrator of an Imaging Observatory), a 50 cm telescope with a UV imager for operation at an altitude of 37-41 km. In collaboration with the Indian Institute of Astrophysics we plan a space mission with a CubeSat-sized far-ultraviolet spectroscopic imaging instrument, featuring an open version of our detector. A Chinese mission, led by the Purple Mountain Observatory, comprises a multi-channel imager using open and sealed detector versions. Our MCP detector has a cesium activated p-doped gallium-nitride photocathode. Other photocathode materials like cesium-telluride or potassium-bromide could be used as an alternative. For the sealed version, the photocathode is operated in semi-transparent mode on a MgF$_2$ window with a cut-off wavelength of about 118 nm. For missions requiring sensitivity below this cut-off, we are planning an open version. We employ a coplanar cross-strip anode and advanced low-power readout electronics with a 128-channel charge-amplifier chip. This publication focuses on the progress concerning the main development challenges: the optimization of the photocathode parameters and the sophisticated detector electronics.

astro-ph.IM↗

arXiv2020

Mapping Diffuse Emission in Lyman UV band

The CAFE (Census of warm-hot intergalactic medium, Accretion, and Feedback Explorer) and LyRIC (Lyman UV Radiation from Interstellar medium and Circum-galactic medium) have been proposed to the space agencies in China respectively. CAFE was first proposed in 2015 as a joint scientific CAS-ESA small space mission. LyRIC was proposed in 2019 as an independent external payload operating on the Chinese Space Station. Both missions are dedicated to mapping the Lyman UV emission (ionized oxygen (O VI) resonance lines at 103.2 and 103.8 nm, and Lyman series) for the diffuse sources in our Galaxy and the circum-galactic mediums of the nearby galaxies. We present the primary science objectives, mission concepts, the enabling technologies, as well as the current status.

astro-ph.IM↗

arXiv2018

MCP detector development for UV space missions

We are developing imaging and photon counting UV-MCP detectors, which are sensitive in the wavelength range from far ultraviolet to near ultraviolet. A good quantum efficiency, solar blindness and high spatial resolution is the aim of our development. The sealed detector has a Cs-activated photoactive layer of GaN (or similarly advanced photocathode), which is operated in semitransparent mode on (001)-MgF 2 . The detector comprises a stack of two long-life MCPs and a coplanar cross strip anode with advanced readout electronics. The main challenge is the flawless growth of the GaN photocathode layer as well as the requirements for the sealing of the detector, to prevent a degradation of the photocathode. We present here the detector concept and the experimental setup, examine in detail the status in the production and describe the current status of the readout electronics development.

physics.ins-det↗