The KM3NeT/ARCA calibration unit is a dedicated calibration system designed to improve the accuracy of the acoustic positioning system of the detector optical modules and monitor the water column physical properties. The calibration unit is composed of a calibration base and an instrumentation unit, connected with an electrical inter-link cable. The deployment of one calibration unit for each of the two building-blocks, in which the ARCA detector is subdivided, is foreseen, with the first one to be deployed in 2024. The calibration base is made of an anchoring structure, connected for power supply and communication to a junction-box, where an acoustic beacon and a hydrophone used for the positioning system are mounted and which hosts a pressure vessel containing the required electronics. The instrumentation unit consists of an anchoring base and a 750m-long inductive line, kept vertical by a top buoy and equipped with oceanographic sensors. The base is linked to the calibration base for power and readout and hosts an absolute pressure gauge used as depth reference and a vessel containing the electronics for managing sensor communication. The line hosts two sound velocimeters and two conductivity-temperature-depth probes equipped with dissolved oxygen sensors, to measure sound velocity and allow for the determination of acoustic wave speed, and two Doppler current sensors to provide information on sea current speed and direction, further improving the accuracy of the positioning system.
This study investigates the preliminary propulsive performances of a cathode-less plasma thruster with air as its propellant. The analysis is carried out through a global model and simulates a thruster over a power range of 0 to 50 W. The developed code considers a set of 177 chemical reactions involving 8 different species and includes empirical equations to account for electronegative effects. The analysis presents the steady-state values of species densities at 10 W, 30 W, and 50 W to gain insights into the key characteristics of plasma dynamics. Moreover, the study estimates the thrust and specific impulse and compares the results to data from models that employ xenon and iodine, aiming to understand the performances of air in low-power thrusters. Lastly, the study examines the effects of varying air inflow concentration on the chemistry, analyzing three different orbit altitudes (i.e., 200, 300, and 400 km).
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