THE SOURCE
DOW-UAP-D017, “UAP Reported at Sandia Base, 1948-1950”, a 116-page document file from the U.S. Department of War’s PURSUE Release 02, published at war.gov/ufo on 22 May 2026. It collects records from the Armed Forces Special Weapons Program and the U.S. Air Force covering a series of sightings and investigations at Sandia, New Mexico.
What this briefing is
In late 1948, something began crossing the sky over the one patch of ground the United States could least afford to be casual about. Sandia Base, New Mexico, was where the country’s nuclear weapons were engineered, assembled and stored, and the people watching its airspace, many of them military and technical personnel, started reporting green fireballs. Often enough, and credibly enough, that the weapons programme and the Air Force spent the next two years building a file. DOW-UAP-D017 is that file, all 116 pages of it, surfacing now through PURSUE Release 02.
This is the episode the UAP literature calls the green fireballs, and it sits at the root of one of the most emotionally powerful ideas in the field: that the phenomenon shows an interest in nuclear weapons. That idea is also one of the most loosely sourced, which is exactly why this file matters. It is the closest thing the PURSUE releases have so far produced to a primary-document foundation for the claim, and it deserves a careful reading rather than an excited one. With this file, for once, the careful reading is the exciting one.
This briefing sets out what the file contains, places it in its historical setting, and works through the one technical thread inside it that points towards an answer: the copper powder.
TL;DR
Between 1948 and 1950, observers in and around Sandia Base, New Mexico, reported a wave of strange objects in the sky. DOW-UAP-D017 logs 209 such sightings: “green orbs”, “discs” and “fireballs”. Witnesses described the objects manoeuvring, flying out of sight, vanishing, or exploding. The records come from the Armed Forces Special Weapons Program, the post-war successor organisation to the Manhattan Project, and from the U.S. Air Force.
Two things make this file matter. The first is location. Sandia Base sat at the centre of the early American nuclear weapons enterprise. A sustained wave of unexplained aerial sightings over that exact ground, taken seriously enough to generate a 116-page investigative file, is a documented fact, not a rumour. The second is that the file includes investigations into residual copper powder found in some areas where sightings occurred, and notes that a few of these investigations fed into Project Grudge, an early U.S. Air Force effort to collect UFO reports from military installations.
Taken together, this is tier 2 primary material. It documents the early atomic state’s anxiety in detail; what it documents about the sightings themselves is the record of the investigation, not a resolution of it. The green fireballs have long-standing conventional explanations, debated for decades, and the copper-powder thread sits inside that debate. The file documents that the worry was real; it does not by itself settle whether the worry was correct. Seventy-five years on, the case remains open.
The setting, and why Sandia
To read this file you have to picture the place. In 1948 the United States had a tiny number of sites that mattered more than any others to its survival as a nuclear power, and they were clustered in New Mexico: Los Alamos, where the weapons were designed; Sandia Base near Albuquerque, where they were engineered, assembled and stored; Kirtland Air Field alongside it. This was the most sensitive airspace in the country.
So when observers, many of them military and technical personnel, began reporting green fireballs over that airspace in late 1948, the reaction was not amusement. It was concern. The records in DOW-UAP-D017 are the paperwork of that concern: an organised attempt by the weapons programme and the Air Force to work out what was crossing the sky above the nation’s bomb factory, and whether it was a threat.
That is the first and most reliable thing the file establishes. Not that the objects were anomalous, but that the people responsible for nuclear security found the sightings credible enough, and frequent enough, to investigate them for two years.
What 209 sightings actually is
The number is worth pausing on. Two hundred and nine logged sightings over roughly two years is a sustained pattern, not a one-off scare. The descriptive language is consistent: green, the recurring colour; orbs, discs and fireballs, the recurring shapes; and behaviours that include manoeuvring, disappearing, and in some cases exploding.
A sceptical reader and a curious reader can both take something real from that. The sceptic notes that a wave of similar reports, in a jittery population primed to watch the sky over a nuclear site, is exactly what a single natural phenomenon plus heightened attention would produce. The curious reader notes that the witnesses were not a jittery public but largely trained personnel, and that “exploding” and “manoeuvring” are not the usual vocabulary of ordinary meteors. Both observations are fair. The file supports holding them at once.
The copper-powder thread
The single most analytically interesting detail in DOW-UAP-D017 is easy to miss. The file includes investigations into residual copper powder found in some areas where sightings were reported.
That detail connects to the green. Copper and copper compounds burn with a strong green flame; it is the standard chemistry-class demonstration of a green emission line. A fireball that burns green is, to a meteoricist or a chemist, a fireball with copper in it. So the copper-powder investigations are not a side note. They are an attempt to test a specific hypothesis: that the green fireballs were a meteoric or atmospheric phenomenon involving copper, rather than craft.
This is where the file rewards a slow reader. It does not simply log sightings; it shows the investigators reaching for a physical, testable explanation, and gathering residue to check it. Whether that residue analysis was conclusive is the kind of thing the 116 pages themselves will settle, and a future briefing may take the residue question on its own once the full file has been read closely. But the presence of the thread tells you something important about the era: the investigators were not credulous. They were doing chemistry.
The Project Grudge connection
The file also notes that a few of these Sandia investigations became part of the basis for Project Grudge. Grudge was an early U.S. Air Force programme that collected unidentified flying object reports from military installations, and the collection DOW-UAP-D017 sits in includes Grudge material from other bases.
Grudge’s background is worth setting out. It was not a neutral scientific study; the early Air Force UFO projects of this period are widely understood to have leaned towards explaining sightings away. The Sandia file feeding into Grudge has two sides: the sightings were significant enough to shape national UFO policy, and that policy was being shaped by an organisation with a known disposition to find conventional answers.
What the file says
It establishes that between 1948 and 1950 there was a sustained wave of unexplained aerial sightings, 209 of them, in and around Sandia Base, one of the most sensitive nuclear sites in the United States. It establishes that the Armed Forces Special Weapons Program and the U.S. Air Force treated this wave as a real security question and investigated it across two years and 116 pages. It establishes that the investigation included physical evidence gathering, the copper-powder residue work, aimed at a testable explanation. And it establishes a documented, primary-source link between the Sandia episode and Project Grudge. For the nukes-and-UFOs question, this file is the kind of grounding the topic has usually lacked: an official archive, not a retelling.
What the file does not say
It does not establish that the green fireballs were anomalous. The episode has serious conventional explanations, principally an unusual run of meteoric or atmospheric activity, and these have been argued over by credible people for decades. The copper-powder thread inside the file is part of the conventional case, not a refutation of it.
It does not establish that the phenomenon was “interested in” nuclear weapons. Sightings clustered over New Mexico in 1948 partly because New Mexico in 1948 was full of trained observers who were watching the sky, under orders, around the clock. Concentrated observers produce concentrated reports. That is a real confound, and a careful reader keeps it in mind before reading intent into the geography.
It does not deliver a verdict, because a 116-page file summarised in a catalogue blurb has not yet been read page by page in public. This briefing introduces the file. It does not pretend to have exhausted it.
And it does not rise above tier 2. DOW-UAP-D017 is authentic, official, primary documentation of a genuine historical episode. That is a strong place to stand. It is the proof that the worry existed. It is not the proof that the worry was right.
What to watch
The case is more than seventy-five years old and was never resolved; the conventional explanation, an unusual run of meteoric or atmospheric activity, was argued over for decades and never settled, and a catalogue release does not change that. What it changes is access, along three threads. The 116 pages have not been read closely in public, and somewhere in them is the most decidable question the episode left, whether the copper-powder residue analysis reached a conclusion. DOW-UAP-D017 sits among Project Grudge material from other bases, which may hold the records to test whether other installations saw the same pattern. And a primary file of this size is the kind of thing that can move a long-stuck argument.
Read the file. Decide for yourself.
References and further reading
- DOW-UAP-D017, “UAP Reported at Sandia Base, 1948-1950”, PURSUE Release 02, U.S. Department of War, hosted at war.gov/ufo
- Presidential Unsealing and Reporting System for UAP Encounters, U.S. Department of War, war.gov/ufo
- AARO UAP Records, All-domain Anomaly Resolution Office, aaro.mil/UAP-Records
- Background on the green fireball episode of 1948 to 1951 and the early U.S. Air Force UFO projects, standard historical accounts
- Signals from the Periphery, Release 01 Briefing 1, on how to read a PURSUE primary document