ITU Radio Regulations
High-altitude platform station or high-altitude pseudo-satellite (short: HAPS) or high-altitude platform (short: HAP or HAPs[plural]) is – according to "Article 1.66A" of the International Telecommunication Union's (ITU) ITU Radio Regulations (RR) – defined as "a station on an object at an altitude of 20 to 50 km and at a specified, nominal, fixed point relative to the Earth".