Automated payload and instruments for astrobiology research developed and studied by German medium-sized space industry in cooperation with European academia

For more than a decade Kayser-Threde, a medium-sized enterprise of the German space industry, has been involved in astrobiology research in partnership with a variety of scientific institutes from all over Europe. Previous projects include exobiology research platforms in low Earth orbit on retrievable carriers and onboard the Space Station. More recently, exobiology payloads for in situ experimentation on Mars have been studied by Kayser-Threde under ESA contracts, specifically the ExoMars Pasteur Payload. These studies included work on a sample preparation and distribution systems for Martian rock/regolith samples, instrument concepts such as Raman spectroscopy and a Life Marker Chip, advanced microscope systems as well as robotic tools for astrobiology missions. The status of the funded technical studies and major results are presented. The reported industrial work was funded by ESA and the German Aerospace Center (DLR).     

The Rolis Experiment on the Rosetta Lander

ROLIS (Rosetta Lander Imaging System) is one of the two imaging systems carried by Rosetta’s Lander Philae, successfully launched to comet 67P/ Churyumov-Gerasimenko in March 2004. Consisting of a highly-miniaturized CCD camera, ROLIS will operate as a descent imager, acquiring imagery of the landing site with increasing spatial resolution. After touchdown ROLIS will focus at an object distance of 30 cm, taking pictures of the comet’s surface below the Lander. Multispectral imaging is achieved through an illumination device consisting of four arrays of monochromatic light emitting diodes working in the 470, 530, 640 and 870 nm spectral bands. The drill sample sites, as well as the Alpha X-Ray Spectrometer (APXS) target locations will be imaged to provide context for the measurements performed by the in situ analyzers. After the drilling operation, the borehole will be inspected to study its morphology and to search for stratification. Taking advantage of the Lander’s rotation capability, stereo image pairs will be acquired, which will facilitate the mapping and identification of surface structures.     

Characteristics of piezoelectric lead zirconate titanate multilayered detector bombarded with hypervelocity iron particles

A cosmic dust detector is currently being developed using a piezoelectric lead zirconate titanate (PZT) element. The characteristics of the multilayered detector (MD), which was composed of one hundred PZT disks, were investigated by bombarding it with hypervelocity iron particles supplied by a Van de Graaff accelerator. It was confirmed that there was a linear relationship between the signal amplitude observed from MD and the momentum of the particles. As compared with the single-layered detector (SD) that was composed of one PZT disk, it was found that the sensitivity of MD was ∼3 times higher than that of SD within the limits of the experimental conditions.     

Effects of UV-B radiation on photosynthesis activity of Wolffia arrhiza as probed by chlorophyll fluorescence transients

The higher plant Wolffia arrhiza is regarded to be well suited concerning the provision of photosynthetic products in the cycle of matter of a Controlled Ecological Life Support System (CELSS) to be established in the context of extraterrestrial, human-based colonization and long-term space flight. Since UV radiation is one major extraterrestrial environmental stress for growth of any plant, effects of UV-B radiation on W. arrhiza were assessed in the present study. We found that UV-B radiation significantly inhibited photosynthetic CO₂ assimilation activity, and the contents of chlorophyll a, chlorophyll b (Chl a, Chl b) and carotenoids considerably decreased when plants were exposed to UV-B radiation for 12 h. High UV-B radiation also declined the quantum yield of primary photochemistry (φ_po), the quantum yield for electron transport (φ_Eo) and the efficiency per trapped excitation (Ψ_o) in W. arrhiza simultaneously, while the amount of active PSII reaction centers per excited cross section (RC/CS) and the total number of active reaction centers per absorption (RC/ABS) had comparative changes. These results indicate that the effects of UV-B radiation on photosynthesis of W. arrhiza is due to an inhibition of the electron transport and via inactivation of reaction centers, but the inhibition may take place at more than one site in the photosynthetic apparatus.     

Elexbus — An attractive technical solution for small mission opportunities

Responding to the demand for a ‘faster, cheaper, better’ implementation of space related services. Dornier Satellitensysteme GmbH has established and exercised an approach for the development and production of satellites and the corresponding ground equipment for small missions, referred to as Flexbus. It allows to support space service customers starting from mission engineering via design, development and manufacturing of the necessary hardware, the launch service and ending with the hand-over of the operational system. Flexbus harmonises a modular component concept with a sound design and development approach, as a whole providing the means to offer high quality products in a fairly short time and for competitive pricing. This paper will outline the major features of the Flexbus approach and describe application examples.     

Survival of spores of the UV-resistant Bacillus subtilis strain MW01 after exposure to low-earth orbit and simulated martian conditions: data from the space experiment ADAPT on EXPOSE-E

In the space experiment "Molecular adaptation strategies of microorganisms to different space and planetary UV climate conditions" (ADAPT), bacterial endospores of the highly UV-resistant Bacillus subtilis strain MW01 were exposed to low-Earth orbit (LEO) and simulated martian surface conditions for 559 days on board the European Space Agency's exposure facility EXPOSE-E, mounted outside the International Space Station. The survival of B. subtilis MW01 spores from both assays (LEO and simulated martian conditions) was determined by a colony-formation assay after retrieval. It was clearly shown that solar extraterrestrial UV radiation (λ≥110?nm) as well as the martian UV spectrum (λ≥200?nm) was the most deleterious factor applied; in some samples only a few spore survivors were recovered from B. subtilis MW01 spores exposed in monolayers. However, if shielded from solar irradiation, about 8% of MW01 spores survived in LEO conditions, and 100% survived in simulated martian conditions, compared to the laboratory controls. The results demonstrate the effect of shielding against the high inactivation potential of extraterrestrial solar UV radiation, which limits the chances of survival of even the highly UV-resistant strain of B. subtilis MW01 in the harsh environments of outer space and the martian surface.     

EXPOSE-E: an ESA astrobiology mission 1.5 years in space

The multi-user facility EXPOSE-E was designed by the European Space Agency to enable astrobiology research in space (low-Earth orbit). On 7 February 2008, EXPOSE-E was carried to the International Space Station (ISS) on the European Technology Exposure Facility (EuTEF) platform in the cargo bay of Space Shuttle STS-122 Atlantis. The facility was installed at the starboard cone of the Columbus module by extravehicular activity, where it remained in space for 1.5 years. EXPOSE-E was returned to Earth with STS-128 Discovery on 12 September 2009 for subsequent sample analysis. EXPOSE-E provided accommodation in three exposure trays for a variety of astrobiological test samples that were exposed to selected space conditions: either to space vacuum, solar electromagnetic radiation at >110?nm and cosmic radiation (trays 1 and 3) or to simulated martian surface conditions (tray 2). Data on UV radiation, cosmic radiation, and temperature were measured every 10?s and downlinked by telemetry. A parallel mission ground reference (MGR) experiment was performed on ground with a parallel set of hardware and samples under simulated space conditions. EXPOSE-E performed a successful 1.5-year mission in space.     

The impact on tsunami detection from space using GNSS-reflectometry when combining GPS with GLONASS and Galileo

The devastating Sumatra tsunami in 2004 demonstrated the need for a tsunami early warning system in the Indian Ocean. Such a system has been installed within the German-Indonesian Tsunami Early Warning System (GITEWS) project. Tsunamis are a global phenomenon and for global observations satellites are predestined. Within the GITEWS project a feasibility study on a future tsunami detection system from space has therefore been carried out. The Global Navigation Satellite System Reflectometry (GNSS-R) is an innovative way of using GNSS signals for remote sensing. It uses ocean reflected GNSS signals for sea surface altimetry. With a dedicated Low Earth Orbit (LEO) constellation of satellites equipped with GNSS-R receivers, densely spaced sea surface height measurements could be established to detect tsunamis. Some general considerations on the geometry between LEO and GNSS are made in this simulation study. It exemplary analyzes the detection performance of a GNSS-R constellation at 900 km altitude and 60° inclination angle when applied to the Sumatra tsunami as it occurred in 2004. GPS is assumed as signal source and the combination with GLONASS and Galileo signals is investigated. It can be demonstrated, that the combination of GPS and Galileo is advantageous for constellations with few satellites while the combination with GLONASS is preferable for constellations with many satellites. If all three GNSS are combined, the best detection performance can be expected for all scenarios considered. In this case an 18 satellite constellation will detect the Sumatra tsunami within 17 min with certainty, while it takes 53 min if only GPS is considered.     

Modelling the Attitude Noise of the Gaia Spacecraft. A Simplified Approach

A high-precision attitude determination and control of the forthcoming European Gaia satellite is an essential task for the success of the whole mission. The requirements for the spacecraft’s attitude require exceptional efforts in the simulation of the rotations of the satellite under the influence of continuous and randomly arising effects. This paper describes the structure of a physically-motivated noise model for simulating the attitude in a closed loop configuration. It deals with the analysis of the most important disturbing forces and torques acting on the Gaia spacecraft.