Low Flyby Research Articles

Short-term noise annoyance towards drones and other transportation noise sources: A laboratory study.

Noise from unmanned aerial vehicles, commonly referred to as "drones," will likely shape our acoustic environment in the near future. Yet, reactions of the population to this new noise source are still little explored. The objective of this study was to investigate short-term noise annoyance reactions to drones in a controlled laboratory experiment. Annoyance to (i) two quadcopters of different sizes in relation to common contemporary transportation noise sources (jet aircraft, propeller aircraft, helicopters, single car passbys), and (ii) different drone maneuvers (takeoff; landing; high, medium, and low flybys) flown at different speeds and elevations was systematically assessed. The results revealed that, at the same sound exposure level, drones are perceived as substantially more annoying than other airborne vehicles and passenger cars. Furthermore, for drone maneuvers, landings, and takeoffs are more annoying than flybys, as are maneuvers flown at low speed. Different loudness metrics (LAE, LDE, effective perceived noise level, psychoacoustic loudness level) accounted for drone noise annoyance ratings to an equal degree. An analysis of psychoacoustic parameters highlighted the significant link between drone noise annoyance and tonality, sharpness, and loudness level. The results suggest a different perception and an increased annoyance potential of drones, which will likely require specifically tailored legislation.

Spacecraft Charging Simulations of Probe B1 of Comet Interceptor during the Cometary Flyby

Comet Interceptor will be the first mission to make a flyby of a long-period or interstellar comet. After launch, the spacecraft will wait at the Sun–Earth Lagrange point L2 for a yet-to-be-discovered comet to appear. The mission comprises three spacecraft: One main spacecraft, A, developed by ESA, and two subprobes, B1 and B2, developed by JAXA and ESA, respectively. All spacecraft will carry plasma instruments for a three-dimensional sampling of the cometary plasma environment. The plasma measurements will likely be affected by the spacecraft potential and by particles emitted from the spacecraft surface. In this work, we use the Spacecraft Plasma Interaction Software and the ElectroMagnetic Spacecraft Environment Simulator to make particle-in-cell simulations of the spacecraft–plasma interactions of probe B1 in different environments during the cometary flyby. This is done for two production rates of the target comet and two relative flyby velocities of the probe. At low flyby velocities, the spacecraft potential varies from 9 V in the solar wind to −5 V in the inner coma for a comet similar to comet 67P/Churyumov–Gerasimenko. For a comet similar to 1P/Halley, the potential is slightly less negative in the inner coma due to the more effective collisional cooling of the electrons in the environment. At high flyby velocities, secondary electron emissions from neutral gas impacts dominate the currents, charging the probe to positive potentials in most of the studied environments.

Interplanetary navigation along the low-thrust trajectory of BepiColombo

For BepiColombo's five-year journey into the inner solar system, a combination of low-thrust arcs and six flybys (one at Moon and Earth, two at Venus and two at Mercury) will be used to reach Mercury with low relative velocity. At arrival a gravitational capture approach is foreseen, in which the Sun perturbation is exploited to get weakly captured around Mercury for a number of orbits. This trajectory imposes severe constraints from a navigational point of view. Very precise navigation is required due to the low flyby altitudes planned for Venus (300 km) and Mercury (200 km) and the level of accuracy needed for the final arrival through the vicinity of the Sun–Mercury L1 point. Besides that, the solar plasma effect severely degrades the quality of the radiometric measurements near superior solar conjunctions, which are more frequent for missions to the inner solar system. Moreover, perturbations, as the ones introduced by momentum wheel desaturation burns, entry into safe modes or solar radiation pressure, must also be taken into account. Delta-differential one-way range measurements are found to be required in periods of poor orbit determination prior to some gravity assists. Nevertheless, if a safe mode is triggered at a critical moment that produces a change in velocity in an unfavourable direction, the mission could be jeopardised. To avoid that risk, an increase in the flyby altitude and possibly a partial or total redesign of the trajectory to avoid flybys near solar conjunctions are considered.

Temperature variations in Titan's upper atmosphere: Impact on Cassini/Huygens

Abstract. Temperature variations of Titan's upper atmosphere due to the plasma interaction of the satellite with Saturn's magnetosphere and Titan's high altitude monomer haze particles can imply an offset of up to ±30K from currently estimated model profiles. We incorporated these temperature uncertainties as an offset into the recently published Vervack et al. (2004) (Icarus, Vol. 170, 91-112) engineering model and derive extreme case (i.e. minimum and maximum profiles) temperature, pressure, and density profiles. We simulated the Huygens probe hypersonic entry trajectory and obtain, as expected, deviations of the probe trajectory for the extreme atmosphere models compared to the simulation based on the nominal one. These deviations are very similar to the ones obtained with the standard Yelle et al. (1997) (ESA SP-1177) profiles. We could confirm that the difference in aerodynamic drag is of an order of magnitude that can be measured by the probe science accelerometer. They represent an important means for the reconstruction of Titan's upper atmospheric properties. Furthermore, we simulated a Cassini low Titan flyby trajectory. No major trajectory deviations were found. The atmospheric torques due to aerodynamic drag, however, are twice as high for our high temperature profile as the ones obtained with the Yelle maximum profile and more than 5 times higher than the worst case estimations from the Cassini project. We propose to use the Cassini atmospheric torque measurements during its low flybys to derive the atmospheric drag and to reconstruct Titan's upper atmosphere density, pressure, and temperature. The results could then be compared to the reconstructed profiles obtained from Huygens probe measurements. This would help to validate the probe measurements and decrease the error bars.