The growth of unmanned aerial vehicles (UAVs) and cheap satellites in recent years has prompted scientists, researchers, military and business interests to look at systems that operate in between or are a hybrid of UAVs and satellites. High altitude pseudo-satellites (HAPS) are systems or platforms that usually float or operate for long periods, sometimes for months, at about 20 km above the Earth’s surface. This puts them in the range of the stratosphere, where these heights can put them above commercial aircraft and at heights that avoid turbulence and moisture.
Benefits of High altitude pseudo-satellites
The benefit of HAPS is they can complement satellite systems, by staying somewhat stationary, but are also maneuverable and potentially easier to deploy. They can provide a longer duration of flight relative to UAVs as well. This has prompted the European Space Agency (ESA) to look at them closely as one way to complement existing Earth Observing System (EOS) satellites currently used. Benefits of these systems include improved telecommunications, intelligence gathering and scientific observation of regions that the EU wants to expand.
Powering HAPS with Solar
The most common type of platforms are forms of airplanes, airships and balloons, where these platforms could be powered by solar panels. One area where there has been great interest has been by internet companies such as Google, within their Loon program, and Facebook. These projects include stratospheric balloons that create a network of wireless stations. Such types of HAPS can provide easier internet access for regions with poorly developed communication infrastructure by relaying signals across vast distance while the balloons can stay in these altitudes for months or even longer.
The commercial aircraft company Airbus has also design the Zephyr program, which is used to provide communications and payload capabilities. The Zephyr S provides voice data and communications, while the Zephyr T provides large payloads. These systems also make flight cheaper, due to less friction at high altitudes, and can fly using solar powered charging. The Zephyr platforms are still more like UAVs, but are being increasingly transformed to longer endurance aircraft. One area of expansion of the use of these vehicles will be in military intelligence gathering, particularly in marine environments where refueling is difficult. This is one area that the United States and UK governments are likely to pursue in future use of HAPS.
Other applications of High altitude pseudo-satellites
Other applications of HAPS remain to be more fully explored. The European Maritime Agency, for instance, along with other sponsors, is looking into relevant areas HAPS could be utilized for. While telecommunications have dominated most research and focus, areas such as emergency communications, intelligent transportation, maritime monitoring and surveillance, environmental observation and land border monitoring are other key potential applications. One area that also has potential is large-scale cargo transport; the Stratobus program has been developed to provide a platform that can deliver a relatively heavy payload to great distance with the aircraft operational for extended periods. The first scheduled flight of this platform is in 2021 but other aircraft are also in development or consideration to deliver even greater payloads.
Although HAPS have been in development for more than a decade, it is now that technologies are coming together in communications, battery life and weight and small EOS equipment that has made HAPS more feasible. The rush to develop these platforms by air transport and Internet companies suggests their commercial application has great potential, while support by the ESA indicates research benefits are also likely to come.
 For more on the background and usage of HAPS, see: D’Oliveira, F. A., Melo, F. C. L. de, & Devezas, T. C. (2016). High-Altitude Platforms – Present Situation and Technology Trends. Journal of Aerospace Technology and Management, 8(3), 249–262. https://doi.org/10.5028/jatm.v8i3.699.
 For more on technical specifications of HAPS, see: Pavlidou, F.-N., Miura, R., & Farserotu, J. (2005). Special Issue on “High Altitude Platform (HAP) Systems: Technologies and Applications.” Wireless Personal Communications, 32(3–4), 189–194. https://doi.org/10.1007/s11277-005-0741-4.
 For more on HAPS capabilities in telecommunications, see: Mohammed, A., Mehmood, A., Pavlidou, F.-N., & Mohorcic, M. (2011). The Role of High-Altitude Platforms (HAPs) in the Global Wireless Connectivity. Proceedings of the IEEE, 99(11), 1939–1953. https://doi.org/10.1109/JPROC.2011.2159690.
 For more on the Straobus, see: Pelton, J. N. (2017). Commercial Space Transport, On-Orbit Servicing and Manufacturing. In J. N. Pelton, The New Gold Rush (pp. 69–90). Cham: Springer International Publishing. https://doi.org/10.1007/978-3-319-39273-8_4.