The Hessdalen lights and Project Hessdalen
Hessdalen is a valley in central Norway, about 12 km long, with about 150 inhabitants. From December 1981 residents reported unexplained lights, sometimes several a week. Most were white or yellow-white. Some hovered for over an hour, others moved fast, and many stayed below the surrounding mountain tops. Volunteers founded Project Hessdalen in 1983, with help from the Norwegian Defence Research Establishment (NDRE) and the universities of Oslo and Bergen. Its instrumented field campaign in early 1984 used cameras with spectral gratings, radar, a magnetometer, a seismograph, a spectrum analyser, a Geiger counter, an infrared viewer and a laser. Erling Strand's final technical report concluded that "the phenomenon, whatever it is, can be measured", by radar and laser as well as by eye and camera. In 1998 the project installed the "Blue Box", which it calls the world's first automated anomaly-detection station; it was re-equipped in 2024. Bjørn Gitle Hauge published an investigation of the lights in Acta Astronautica (2010). Østfold University College, where Strand taught, still holds events in the valley. Several authors have proposed natural mechanisms, chiefly a dusty plasma (Paiva & Taft 2010, 2012). The lights have not been explained.
Evidence, in date order (4)
- 1984Project Hessdalen radarsensor data36 radar recordings in 1984, three probably also seen as lights Strand, Project Hessdalen 1984 - Final Technical Report
- 1984Project Hessdalen camerassensor dataphotographs and spectra of the lights, one showing a 7 Hz oscillation Strand, Project Hessdalen 1984 - Final Technical Report
- 1984Hessdalen residentswitness188 light reports during the field campaign, 53 rated as possible phenomena Strand, Project Hessdalen 1984 - Final Technical Report
- 2010Bjørn Gitle Haugedocumentpeer-reviewed investigation of the lights Hauge 2010, Acta Astronautica 67, 1443
How plausible · High
Named researchers measured the lights with radar and cameras over decades.
- ●●Access Direct observation or instruments.
- ●●No gain sought Nothing to gain.
- ●●Restraint Reported plainly.
- ●●Character record Trained professionals.
- ●●Independent convergence Independent sources agree.
- ●●Checkable details check out Released official records.
Plausibility weighs how well an account fits where secrecy hides the documents by design, so missing records never count against it. Strength measures what is documented. Assessed 2026-10-23.
On the record
- Background in the 1984 report — firsthand (project report) — Strand 1985: the project "was born on 3 June 1983"; it was presented at BUFORA's congress on 27 August 1983; report forms went to 3,300 households in January 1984; fieldwork ran from 21 January to 26 February 1984.
- 188 light reports came in during the field period. 135 were rated "a known light" (F1-F4). 53 were rated F5 or higher, meaning "might be the Hessdals-phenomenon". Of these, about 68% moved along a north-south axis and 39% flickered. One photographed light showed an oscillation of 7 ± 2 Hz — analysis — Strand 1985.
- There were 36 radar recordings, 3 of them probably also seen as lights. On nine occasions a return travelled in a nearly straight line. Two returns photographed on the screen were as strong as returns from the mountains — firsthand (instrument record) — Strand 1985.
- On those radar returns, an NDRE radar expert said: "If this isn't a reflection of a solid object, but only gas in the air, the gas has to be locally and strongly ionised. Otherwise, it wouldn't give such a strong reflection" — analysis — unnamed NDRE radar expert, quoted by Strand 1985.
- On 12 February 1984 a laser was pointed at regularly flashing lights 9 times. There was a reaction 8 times: the light changed from a single to a double flash pattern and back when the laser was removed — firsthand (field team) — Strand 1985.
- The Geiger counter, seismograph and IR viewer recorded nothing. Cameras and other instruments often failed, "mostly when we needed them most" — firsthand — Strand 1985.