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Solar Hot Air Balloons for Terrestrial and Planetary Atmospheres

Bowman, Daniel B.; Albert, Sarah A.; Dexheimer, Darielle D.

The first solar hot air balloon was constructed in the early 1970s (Besset, 2016). Over the following decades the Centre National d'Etudes Spatiales (CNES) developed the Montgolfiere Infrarouge (MIR) balloon, which flew on solar power during the day and infrared radiation from the Earth's surface at night (Fommerau and Rougeron, 2011). The balloons were capable of flying for over 60 days and apparently reached altitudes of 30 km at least once (Malaterre, 1993). Solar balloons were the subject of a Jet Propulsion Laboratory study that performed test flights on Earth (Jones and Wu 1999) and discussed their mission potential for Mars, Jupiter, and Venus (Jones and Heun, 1997). The solar balloons were deployed from the ground and dropped from hot air balloons; some were altitude controlled by means of a remotely-commanded air valve at the top of the envelope. More recently, solar balloons have been employed for infrasound studies in the lower stratosphere (see Table 1). The program began in 2015, when a prototype balloon reached an altitude of 22 kilometers before terminating just prior to float (Bowman et al., 2015). An infrasound sensor was successfully deployed on a solar balloon during the 2016 SISE/USIE experiment, in which an acoustic signal from a ground explosion was captured at a range of 330 km (Anderson et al. 2018; Young et al. 2018). This led to the launch of a 5-balloon infrasound network during the Heliotrope experiment (Bowman and Albert, 2018). The balloons were constructed by the researchers themselves at a materials of less than $50 per envelope.

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TYPE Other Report YEAR 2018
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Acoustic event location and background noise characterization on a free flying infrasound sensor network in the stratosphere

Geophysical Journal International

Bowman, Daniel B.; Albert, Sarah A.

A variety of Earth surface and atmospheric sources generate low-frequency sound waves that can travel great distances. Despite a rich history of ground-based sensor studies, very few experiments have investigated the prospects of free floating microphone arrays at high altitudes. However, recent initiatives have shown that such networks have very low background noise and may sample an acoustic wave field that is fundamentally different than that at Earth's surface. The experiments have been limited to at most two stations at altitude, making acoustic event detection and localization difficult.We describe the deployment of four drifting microphone stations at altitudes between 21 and 24 km above sea level. The stations detected one of two regional ground-based chemical explosions as well as the ocean microbarom while travelling almost 500 km across the American Southwest. The explosion signal consisted of multiple arrivals; signal amplitudes did not correlate with sensor elevation or source range. The waveforms and propagation patterns suggest interactions with gravity waves at 35-45 km altitude. A sparse network method that employed curved wave front corrections was able to determine the backazimuth from the free flying network to the acoustic source. Episodic signals similar to those seen on previous flights in the same region were noted, but their source remains unclear. Background noise levels were commensurate with those on infrasound stations in the International Monitoring System below 2 s.

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TYPE Journal Article YEAR 2018
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Results 26–42 of 42
Results 26–42 of 42