The HIPAS (HIgh Power Auroral Stimulation) Observatory was a research facility, built to study the
ionosphere and its influence on
radio
Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transm ...
communications. It was located 25 miles east of
Fairbanks
Fairbanks is a home rule city and the borough seat of the Fairbanks North Star Borough in the U.S. state of Alaska. Fairbanks is the largest city in the Interior region of Alaska and the second largest in the state. The 2020 Census put the ...
,
Alaska
Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S ...
in the
Fairbanks North Star Borough
The Fairbanks North Star Borough is a borough located in the state of Alaska. As of the 2020 census, the population was 95,665, down from 97,581 in 2010.
The borough seat is Fairbanks. The borough's land area is slightly smaller than that of ...
area.
It was operated by the
UCLA
The University of California, Los Angeles (UCLA) is a public university, public Land-grant university, land-grant research university in Los Angeles, California. UCLA's academic roots were established in 1881 as a Normal school, teachers colle ...
laboratory from 1986 through 2007. A unique capability at that time, it could radiate 70 MW
ERP at either 2.85 MHz or 4.53 MHz. These frequencies are close to a multiple of 2 and 3 of the electron gyro-frequency at ionospheric altitudes. Sending a pulse of HF-radio waves upward could accelerate the electrons in the ionosphere. Somewhat like waves on the ocean, the character of the ionosphere could be inferred from the
backscatter
In physics, backscatter (or backscattering) is the reflection of waves, particles, or signals back to the direction from which they came. It is usually a diffuse reflection due to scattering, as opposed to specular reflection as from a mirror, ...
signal. Other experiments attempted to combine RF and visible excitation where the latter probed metal ions such as
sodium
Sodium is a chemical element with