Floating Bare Tether as Upper Atmosphere Probe

Use of a (bare) conductive tape electrically floating in LEO as an effective e-beam source that produces artificial auroras, and is free of problems that have marred standard beams, is considered. Ambient ions impacting the tape with KeV energies over most of its length liberate secondary electrons, which race down the magnetic field and excite neutrals in the E-layer, resulting in auroral emissions. The tether would operate at night-time with both a power supply and a plasma contactor off; power and contactor would be on at daytime for reboost. The optimal tape thickness yielding a minimum mass for an autonomous system is determined; the alternative use of an electric thruster for day reboost, depending on mission duration, is discussed. Measurements of emission brightness from the spacecraft could allow determination of the (neutral) density vertical profile in the critical E-layer; the flux and energy in the beam, varying along the tether, allow imaging line-of-sight integrated emissions that mix effects with altitude-dependent neutral density and lead to a brightness peak in the beam footprint at the E-layer. Difficulties in tomographic inversion, to determine the density profile, result from beam broadening, due to elastic collisions, which flattens the peak, and to the highly nonlinear functional dependency of line-of-sight brightness. Some dynamical issues are discussed.

Heated fiber optic distributed temperature sensing for measuring soil volumetric heat capacity and water content: A dual probe heat-pulse approach

The first feasibility study of using dual-probe heated fiber optics with distributed temperature sensing to measure soil volumetric heat capacity and soil water content is presented. Although results using different combinations of cables demonstrate feasibility, further work is needed to gain accuracy, including a model to account for the finite dimension and the thermal influence of the probes. Implementation of the dual-probe heat-pulse (DPHP) approach for measurement of volumetric heat capacity (C) and water content (θ) with distributed temperature sensing heated fiber optic (FO) systems presents an unprecedented opportunity for environmental monitoring (e.g., simultaneous measurement at thousands of points). We applied uniform heat pulses along a FO cable and monitored the thermal response at adjacent cables. We tested the DPHP method in the laboratory using multiple FO cables at a range of spacings. The amplitude and phase shift in the heat signal with distance was found to be a function of the soil volumetric heat capacity. Estimations of C at a range of moisture contents (θ = 0.09– 0.34 m3 m−3) suggest the feasibility of measurement via responsiveness to the changes in θ, although we observed error with decreasing soil water contents (up to 26% at θ = 0.09 m3 m−3). Optimization will require further models to account for the finite radius and thermal influence of the FO cables. Although the results indicate that the method shows great promise, further study is needed to quantify the effects of soil type, cable spacing, and jacket configurations on accuracy.

Prospectives of monitoring biological activity in a red-legged partridge incubator with a carbon dioxide probe

This study focuses on the relationship between CO2 production and the ultimate hatchability of the incubation. A total amount of 43316 eggs of red-legged partridge (Alectoris rufa) were supervised during five actual incubations: three in 2012 and two in 2013. The CO2 concentration inside the incubator was monitored over a 20-day period, showing sigmoidal growth from ambient level (428 ppm) up to 1700 ppm in the incubation with the highest hatchability. Two sigmoid growth models (logistic and Gompertz) were used to describe the CO2 production by the eggs, with the result that the logistic model was a slightly better fit (r2=0.976 compared to r2=0.9746 for Gompertz). A coefficient of determination of 0.997 between the final CO2 estimation (ppm) using the logistic model and hatchability (%) was found.