Abstract
Sounding balloons, available at very low cost from commercial vendors and operable with minimal training, have an excellent potential as testing platforms in the near-space environment. The work reported here was motivated by the need to perform an experimental assessment of the radio frequency (RF) background present in the ISM (Industrial, Scientific and Medical) bands, namely 868 MHz (Ultra High Frequency—UHF) and 2.4 GHz (S-Band), simulating the operational environment of a Low Earth Orbit (LEO) constellation forInternet of Things (IoT) telecommunications. To this end, five balloons were flown with a dedicated RF payload. Along with the radio measurements, the flights provided a convenient opportunity to collect data on the dynamic behavior of the payload gondola. We report on the system design and the operational phase of the mission, and discuss the data collected throughout the successful flight campaign. As a result, a preliminary understanding of the gondola dynamics has been gained, including both linear accelerations and attitude oscillations. It is also concluded that the two ISM bands considered are actually suitable for IoT ground-to-LEO links.
Highlights
Aerospace 2021, 8, 21. https://doi.org/Industrial, Scientific and Medical (ISM) bands are those portions of the electromagnetic spectrum that are made available for non-telecommunication applications
The use of ISM bands is especially appealing for Internet of Things (IoT) applications [2], where interference issues are limited by the low power, short burst nature of messages and by the use of spread-spectrum techniques
Ground tests revealed that the radio frequency (RF) components dissipate a considerable amount of heat, so that no internal heater was needed for the other subsystems
Summary
Industrial, Scientific and Medical (ISM) bands are those portions of the electromagnetic spectrum that are made available for non-telecommunication applications. Thanks to the ease of operation and cost effectiveness of sounding balloons, it was possible to perform a total of 5 flights up to the altitude of 32 km to collect radio frequency (RF) power measurements in the ISM bands At such altitude, the signal was collected from sources scattered over a quite large portion of terrain, mimicking what would be experienced by a LEO satellite. While studies exist on the motion of payload gondolas of large, zero-pressure balloons capable of lifting several tons (e.g., References [12,13,14]), the oscillatory motion of sounding balloon HABs gondolas has received much less attention Knowledge of such motion is especially important in view of the possible future use of such systems as low-cost, near-space carriers for spacecraft hardware testing and, in general, for scientific instrumentation.
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