An Improved Piezoelectric Balance for Aerodynamic Force

A method for measuring model forces in the shock tunnel by means of an acceleration-compensated balance has been reported by the authors.1 Since that time, a continuing program of research and development on advanced shock-tunnel instrumentation at Cornell Aeronautical Laboratory, Inc. has led to a promising new balance configuration. This balance is inherently more compact than previous designs, and allows testing of higher lift/drag (L/D) configurations than before. The increased high-pressure capability of the shock tunnel, and the growing recognition of the importance of the shock tunnel as a means of generating large Reynolds number flow, have thus added to the importance of this new higher load, more compact balance concept. An experimental balance has been built and calibrated. The performance of this balance is presented in this paper.     

The Aouda.X space suit simulator and its applications to astrobiology

We have developed the space suit simulator Aouda.X, which is capable of reproducing the physical and sensory limitations a flight-worthy suit would have on Mars. Based upon a Hard-Upper-Torso design, it has an advanced human-machine interface and a sensory network connected to an On-Board Data Handling system to increase the situational awareness in the field. Although the suit simulator is not pressurized, the physical forces that lead to a reduced working envelope and physical performance are reproduced with a calibrated exoskeleton. This allows us to simulate various pressure regimes from 0.3-1 bar. Aouda.X has been tested in several laboratory and field settings, including sterile sampling at 2800 m altitude inside a glacial ice cave and a cryochamber at -110°C, and subsurface tests in connection with geophysical instrumentation relevant to astrobiology, including ground-penetrating radar, geoacoustics, and drilling. The communication subsystem allows for a direct interaction with remote science teams via telemetry from a mission control center. Aouda.X as such is a versatile experimental platform for studying Mars exploration activities in a high-fidelity Mars analog environment with a focus on astrobiology and operations research that has been optimized to reduce the amount of biological cross contamination. We report on the performance envelope of the Aouda.X system and its operational limitations.     

Olivine-respiring bacteria isolated from the rock-ice interface in a lava-tube cave, a Mars analog environment

The boundary between ice and basalt on Earth is an analogue for some near-surface environments of Mars. We investigated neutrophilic iron-oxidizing microorganisms from the basalt-ice interface in a lava tube from the Oregon Cascades with perennial ice. One of the isolates (Pseudomonas sp. HerB) can use ferrous iron Fe(II) from the igneous mineral olivine as an electron donor and O(2) as an electron acceptor. The optimum growth temperature is ～12-14°C, but growth also occurs at 5°C. Bicarbonate is a facultative source of carbon. Growth of Pseudomonas sp. HerB as a chemolithotrophic iron oxidizer with olivine as the source of energy is favored in low O(2) conditions (e.g., 1.6% O(2)). Most likely, microbial oxidation of olivine near pH 7 requires low O(2) to offset the abiotic oxidation of iron. The metabolic capabilities of this bacterium would allow it to live in near-surface, icy, volcanic environments of Mars in the present or recent geological past and make this type of physiology a prime candidate in the search for life on Mars.     

R3DE: Radiation Risk Radiometer-Dosimeter on the International Space Station--optical radiation data recorded during 18 months of EXPOSE-E exposure to open space

Radiation Risk Radiometer-Dosimeter E (R3DE) served as a device for measuring ionizing and non-ionizing radiation as well as cosmic radiation reaching biological samples located on the EXPOSE platform EXPOSE-E. The duration of the mission was almost 1.5 years (2008-2009). With four channels, R3DE detected the wavelength ranges of photosynthetically active radiation (PAR, 400-700?nm), UVA (315-400?nm), UVB (280-315?nm), and UVC (<280?nm). In addition, the temperature was recorded. Cosmic ionizing radiation was assessed with a 256-channel spectrometer dosimeter (see separate report in this issue). The light and UV sensors of the device were calibrated with spectral measurement data obtained by the Solar Radiation and Climate Experiment (SORCE) satellite as standard. The data were corrected with respect to the cosine error of the diodes. Measurement frequency was 0.1?Hz. Due to errors in data transmission or temporary termination of EXPOSE power, not all data could be acquired. Radiation was not constant during the mission. At regular intervals of about 2 months, low or almost no radiation was encountered. The radiation dose during the mission was 1823.98 MJ m(-2) for PAR, 269.03 MJ m(-2) for UVA, 45.73 MJ m(-2) for UVB, or 18.28 MJ m(-2) for UVC. Registered sunshine duration during the mission was about 152 days (about 27% of mission time).The surface of EXPOSE was most likely turned away from the Sun for considerably longer. R3DE played a crucial role on EXPOSE-EuTEF (EuTEF, European Technology Exposure Facility), because evaluation of the astrobiology experiments depended on reliability of the data collected by the device. Observed effects in the samples were weighted by radiation doses measured by R3DE.     

Atmospheric Science with InSight

In November 2018, for the first time a dedicated geophysical station, the InSight lander, will be deployed on the surface of Mars. Along with the two main geophysical packages, the Seismic Experiment for Interior Structure (SEIS) and the Heat-Flow and Physical Properties Package (HP³), the InSight lander holds a highly sensitive pressure sensor (PS) and the Temperature and Winds for InSight (TWINS) instrument, both of which (along with the InSight FluxGate (IFG) Magnetometer) form the Auxiliary Sensor Payload Suite (APSS). Associated with the RADiometer (RAD) instrument which will measure the surface brightness temperature, and the Instrument Deployment Camera (IDC) which will be used to quantify atmospheric opacity, this will make InSight capable to act as a meteorological station at the surface of Mars. While probing the internal structure of Mars is the primary scientific goal of the mission, atmospheric science remains a key science objective for InSight. InSight has the potential to provide a more continuous and higher-frequency record of pressure, air temperature and winds at the surface of Mars than previous in situ missions. In the paper, key results from multiscale meteorological modeling, from Global Climate Models to Large-Eddy Simulations, are described as a reference for future studies based on the InSight measurements during operations. We summarize the capabilities of InSight for atmospheric observations, from profiling during Entry, Descent and Landing to surface measurements (pressure, temperature, winds, angular momentum), and the plans for how InSight’s sensors will be used during operations, as well as possible synergies with orbital observations. In a dedicated section, we describe the seismic impact of atmospheric phenomena (from the point of view of both “noise” to be decorrelated from the seismic signal and “signal” to provide information on atmospheric processes). We discuss in this framework Planetary Boundary Layer turbulence, with a focus on convective vortices and dust devils, gravity waves (with idealized modeling), and large-scale circulations. Our paper also presents possible new, exploratory, studies with the InSight instrumentation: surface layer scaling and exploration of the Monin-Obukhov model, aeolian surface changes and saltation / lifing studies, and monitoring of secular pressure changes. The InSight mission will be instrumental in broadening the knowledge of the Martian atmosphere, with a unique set of measurements from the surface of Mars.     

Crustal S-Wave Velocity from Apparent Incidence Angles: A Case Study in Preparation for InSight

Retrieval of crustal structure and thickness of Mars is among the main goals of InSight. Here we investigate which constraints on the crust at the landing site can be provided by apparent P-wave incidence angles derived from P-receiver functions. We consider receiver functions for six different Mars models, calculated from synthetic seismograms generated via Instaseis from the Green’s function databases of the Marsquake Service, in detail. To allow for a larger range of crustal thicknesses and structures, we additionally analyze data from five broad-band stations across Central Europe. We find that the likely usable epicentral distance range for P-wave receiver functions on Mars lies between \(35^{\circ}\) and the core shadow, and can be extended to more than \(150^{\circ}\) by also using the PP-phase. Comparison to models for the spatial distribution of Martian seismicity indicates that sufficient seismicity should occur within the P-wave distance range around InSight within the nominal mission duration to allow for the application of our method. Apparent P-wave incidence angles are derived from the amplitudes of vertical and radial receiver functions at the P-wave onset within a range of period bands, up to 120 s. The apparent incidence angles are directly related to apparent S-wave velocities, which are inverted for the subsurface S-wave velocity structure via a grid search. The veracity of the forward calculated receiver functions and apparent S-wave velocities is ensured by benchmarking various algorithms against the Instaseis synthetics. Results indicate that apparent S-wave velocity curves provide valuable constraints on crustal thickness and structure, even without any additional constraints, and considering the location uncertainty and limited data quantity of InSight. S-wave velocities in the upper half of the crust are constrained best, but if reliable measurements at long periods are available, the curves also provide constraints down to the uppermost mantle. Besides, it is demonstrated that the apparent velocity curves can differentiate between crustal velocity models that are indistinguishable by other methods.     

Towards a Global Unified Model of Europa’s Tenuous Atmosphere

Despite the numerous modeling efforts of the past, our knowledge on the radiation-induced physical and chemical processes in Europa’s tenuous atmosphere and on the exchange of material between the moon’s surface and Jupiter’s magnetosphere remains limited. In lack of an adequate number of in situ observations, the existence of a wide variety of models based on different scenarios and considerations has resulted in a fragmentary understanding of the interactions of the magnetospheric ion population with both the moon’s icy surface and neutral gas envelope. Models show large discrepancy in the source and loss rates of the different constituents as well as in the determination of the spatial distribution of the atmosphere and its variation with time. The existence of several models based on very different approaches highlights the need of a detailed comparison among them with the final goal of developing a unified model of Europa’s tenuous atmosphere. The availability to the science community of such a model could be of particular interest in view of the planning of the future mission observations (e.g., ESA’s JUpiter ICy moons Explorer (JUICE) mission, and NASA’s Europa Clipper mission). We review the existing models of Europa’s tenuous atmosphere and discuss each of their derived characteristics of the neutral environment. We also discuss discrepancies among different models and the assumptions of the plasma environment in the vicinity of Europa. A summary of the existing observations of both the neutral and the plasma environments at Europa is also presented. The characteristics of a global unified model of the tenuous atmosphere are, then, discussed. Finally, we identify needed future experimental work in laboratories and propose some suitable observation strategies for upcoming missions.     

Radiance calibration of CRISTA-NF

The CRISTA-NF instrument is the airborne version of the CRISTA satellite infrared limb sounder. It has been successfully flown on the Geophysica research airplane during a test campaign in July 2005, during the SCOUT-O3 Tropical Aircraft Campaign in November/December 2005 and during the AMMA campaign in August 2006. Radiance calibrations of the airborne instrument are more complex compared to the satellite instrument because the vacuum shell of CRISTA-NF is confined by a ZnSe (zinc–selenide) window and the detectors can thermally drift during measurement flights. By comprehensive radiance calibrations with a blackbody source the window’s emissivity and transmissivity are determined and the dependence of the instrument sensitivity on the detector temperature is characterized. Taking these effects into account, the remaining radiance error of the calibration is smaller than 3%.     

火星等离子体环境探测

萤火一号(YH-1)探测器将对火星空间环境进行独立而深入的探测研究,探测各空间区域的等离子体特性及其对太阳风扰动的响应,以及火星离子逃逸过程,研究太阳风对火星水体损失的影响。为了实现这一目标,萤火一号搭载了等离子体探测包,包括2个离子分析器和1个电子分析器,具有较高的时间分辨率、能量分辨率,可以探测0.02～10 keV的离子、电子,同时能够对粒子的入射方向及1～44 au(1 au=9.1095×10~(-31)kg)质量范围内的离子成分进行分辨。本文阐述了萤火一号等离子体探测的科学意义,并对等离子体包的工作原理,仪器设计进行了介绍。     

Spectral signatures of photosynthesis. II. Coevolution with other stars and the atmosphere on extrasolar worlds

As photosynthesis on Earth produces the primary signatures of life that can be detected astronomically at the global scale, a strong focus of the search for extrasolar life will be photosynthesis, particularly photosynthesis that has evolved with a different parent star. We take previously simulated planetary atmospheric compositions for Earth-like planets around observed F2V and K2V, modeled M1V and M5V stars, and around the active M4.5V star AD Leo; our scenarios use Earth's atmospheric composition as well as very low O2 content in case anoxygenic photosynthesis dominates. With a line-by-line radiative transfer model, we calculate the incident spectral photon flux densities at the surface of the planet and under water. We identify bands of available photosynthetically relevant radiation and find that photosynthetic pigments on planets around F2V stars may peak in absorbance in the blue, K2V in the red-orange, and M stars in the near-infrared, in bands at 0.93-1.1 microm, 1.1-1.4 microm, 1.5-1.8 microm, and 1.8-2.5 microm. However, underwater organisms will be restricted to wavelengths shorter than 1.4 microm and more likely below 1.1 microm. M star planets without oxygenic photosynthesis will have photon fluxes above 1.6 microm curtailed by methane. Longer-wavelength, multi-photo-system series would reduce the quantum yield but could allow for oxygenic photosystems at longer wavelengths. A wavelength of 1.1 microm is a possible upper cutoff for electronic transitions versus only vibrational energy; however, this cutoff is not strict, since such energetics depend on molecular configuration. M star planets could be a half to a tenth as productive as Earth in the visible, but exceed Earth if useful photons extend to 1.1 microm for anoxygenic photosynthesis. Under water, organisms would still be able to survive ultraviolet flares from young M stars and acquire adequate light for growth.