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Abstract. This paper describes the aerosol measurement setup and results obtained during the BEXUS18 (Balloon-borne Experiments for University Students) stratospheric balloon within the A5-Unibo (Advanced Atmospheric Aerosol Acquisition and Analysis) experiment performed on 10 October 2014 in northern Sweden (Kiruna). The experimental setup was designed and developed by the University of Bologna with the aim of collecting and analyzing vertical profiles of atmospheric ions and particles together with atmospheric parameters (temperature, relative humidity, and pressure) all along the stratospheric ascent of the BEXUS18 stratospheric balloon. Particle size distributions were measured with the MeteoModem Light Optical Aerosol Counter (LOAC) and air ion density was measured with a set of two commercial and portable ion counters. Though the experimental setup was based upon relatively low-cost and light-weight sensors, vertical profiles of all the parameters up to an altitude of about 27 km were successfully collected. The results obtained are useful for elucidating the relationships between aerosols and charged particles between ground level and the stratosphere, with great potential in collecting and adding useful information in this field, also in the stratosphere where such measurements are rare. In particular, the equipment detected coherent vertical profiles for particles and ions, with a particularly strong correlation between negative ions and fine particles, possibly resulting from proposed associations between cosmic rays and ions as previously suggested. In addition, the detection of charged aerosols in the stratosphere is in agreement with the results obtained by a previous flight and with simulations conducted with a stratospheric ion–aerosol model. However, further measurements under stratospheric balloon flights equipped with a similar setup are needed to reach general conclusions about such important issues.

Abstract. This paper describes the aerosol measurements setup and results obtained during the BEXUS18 stratospheric balloon within the A5-Unibo (Advanced Atmospheric Aerosol Acquisition and Analysis) experiment performed on October 10th, 2014 in northern Sweden (Kiruna). The experimental setup was designed and developed by the University of Bologna with the aim of collecting and analyzing vertical profiles of atmospheric ions and particles together with atmospheric parameters (temperature, relative humidity and pressure) all along the stratospheric ascent of the BEXUS18 stratospheric balloon. Particles size distributions were measured with the MeteoModem Light Optical Aerosol Counter (LOAC) and air ion density was measured with a set of two commercial and portable ion counters. Though the experimental setup was based upon relatively low-cost and light-weight sensors, vertical profiles of all the parameters up to an altitude of about 27 km were successfully collected. The results obtained are useful for elucidating the relationships between aerosols and charged particles between ground level and the stratosphere with great potential in collecting and adding useful information in this field, also in the stratosphere where such measurements are rare. In particular, the equipment detected coherent vertical profiles for particles and ions, with a particularly strong correlation between negative ions and fine particles, possibly resulting from proposed associations between cosmic rays and ions as previously suggested. In addition, the detection of charged aerosols in the stratosphere is in agreement with the results obtained by a previous flight and with simulations conducted with a stratospheric ion-aerosol model. However, further measurements under stratospheric balloon flights equipped with a similar setup are needed to reach general conclusions on such important issues.

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A collision risk mitigation strategy is proposed for DEMOS-1 and DEIMOS-2 in order to ensure mission survivability, although taking into account several constraints coming from the platform. Due to the fact that both satellites are equipped with low-thrust electric propulsion systems, the achievable delta-V is too low to be able to separate the satellite enough from the incoming object along the radial direction. The strategy consists of a single collision avoidance maneuver that has to be made several hours before the Time of Closest Approach in order to achieve the suitable in-track separation from the expected collision location. The propulsion system characterization provides a deeper insight of that. The internal procedure implements a constant monitoring of hazardous events, assessing conjunction characteristics and sharing trajectory information with the 18th SPace Control Squadron (SPCS). It provides a scheme to be followed when meeting certain conditions, mainly the time to closest approach and collision probability. In this process, the automatic generation of risk assessment reports and reception of alarms by email are essential for the Flight Dynamics Team to be warned of new important events at any time of the day. The safety of the post-maneuver trajectory must also be granted by analyzing the close approaches foreseen after any orbit control maneuver and before executing it. This paper goes through the risk mitigation procedure especially dedicated to Deimos Imaging's low-thrust satellites when maneuvering for collision avoidance or orbit control purposes. I. Nomenclature Delta-V= velocity variation PC = collision probability as computed by Deimos Imaging