These definitions describe how terms are used in this archive. Institutional language changes, and different organizations sometimes use the same acronym differently. Each legal or institutional definition below identifies its source or defining body and was checked on August 6, 2026. A label describes the available record; it does not establish the origin of an observation.
Core terminology
- Anomalous
- Departing from what an observer, model, or sensor expected. An apparent anomaly may result from missing context, geometry, calibration, perception, or an unusual event; the word does not identify a cause. See the Evidence and Technology hub.
- UAP
- Unidentified anomalous phenomena. Under the current U.S. statutory framework summarized by AARO, the term covers immediately unidentifiable airborne objects, transmedium objects or devices, and certain submerged objects or devices. Other institutions may use a narrower sky-only definition. Compare the site’s UAP and UFO terminology guide.
- UFO
- Unidentified flying object. A historical and popular term for something observed in the sky but not identified at the time. The National Archives Project Blue Book guide uses the term for the Air Force case files. It describes identification status, not extraterrestrial origin.
- Unidentified
- Not confidently identified from the available data. It may reflect insufficient information rather than unusual performance.
- Resolved
- A case assigned an explanation at a stated confidence, such as balloon, aircraft, satellite, bird, sensor artifact, or atmospheric effect. Resolution quality depends on the evidence and method disclosed.
- Unresolved
- A case for which the available data does not support a confident identification. Unresolved does not mean inexplicable.
- Transmedium
- In the U.S. definition, an object or device observed to transition between space and the atmosphere, or between the atmosphere and bodies of water, and not immediately identifiable. The definition appears in ODNI’s 2022 UAP report; a report of transition is not proof that transition occurred.
- UAP event
- ODNI’s 2022 report uses this for the overall occurrence in which a pilot or aircrew witnessed or detected a UAP. One event may contain more than one incident or observation; compare dated entries in the UAP and disclosure timeline.
- UAP report
- ODNI’s 2022 report uses this for documentation of an event, including chain-of-custody information and basics such as time, date, location, and description. A report is an input to analysis, not a conclusion.
Institutions and programs
- AARO
- The All-domain Anomaly Resolution Office, the U.S. Department of Defense office tasked with synchronizing identification, attribution, and mitigation of UAP near national-security areas. Its published findings represent AARO’s assessments, which should be attributed to the office.
- Department of Defense (DoD)
- The U.S. executive department responsible for national defense. UAP programs and records may sit within different DoD components; a department-level label should not be substituted for the issuing office named on a document.
- ODNI
- The Office of the Director of National Intelligence, which heads and integrates the U.S. Intelligence Community and has issued statutory UAP reports with DoD.
- UAPTF
- The Unidentified Aerial Phenomena Task Force, a DoD effort that preceded AARO. Historical documents should retain the name used at the time rather than retroactively labeling every task-force record as AARO material.
- Project Sign
- A U.S. Air Force investigation active in the late 1940s and a predecessor to Project Grudge and Project Blue Book. Consult the National Archives record-group history for the program sequence and surviving Air Force records.
- Project Grudge
- The Air Force investigation that followed Project Sign and preceded Project Blue Book, as documented in the National Archives record-group history. Program names mark administrative periods; they do not certify the accuracy of every case file.
- Project Blue Book
- The U.S. Air Force program that investigated UFO reports from 1952 until its closure in 1969. Its records are in National Archives custody. Use the Agencies and Programs hub for broader institutional context.
- AAWSAP
- The Advanced Aerospace Weapon System Applications Program, described in AARO’s 2024 historical report as a Defense Intelligence Agency-managed contract program operated from 2009 to 2012. Attribute that account to AARO and use dated contracting records when describing scope.
- AATIP
- Advanced Aerospace Threat Identification Program. AARO’s 2024 historical report says the name appeared interchangeably with AAWSAP in some official documentation but was not itself an official DoD program, and was later used for an informal activity. Other accounts differ, so identify the source and period.
- NASA UAP Independent Study Team
- The external study team commissioned by NASA in 2022 to examine how scientific data and analysis could improve UAP study. Its final report and study materials were published in 2023; the study did not investigate individual cases.
- GEIPAN
- The French national group within CNES that collects, investigates, classifies, and publishes civilian reports of unidentified aerospace phenomena. Its official case database uses its own classification system, which should not be mapped automatically to U.S. labels. Explore comparative records through the Global Disclosure hub.
Evidence and sensor terms
- Primary source
- An original record, image, dataset, physical item, or first-hand account. Primary does not mean accurate or complete. Start with the official repository desk.
- Secondary source
- Reporting or analysis that interprets primary material and other evidence. A strong secondary source identifies its inputs and method.
- Provenance
- The documented origin and history of a record or object: who created it, where it came from, how it was handled, and whether it changed.
- Chain of custody
- The documented sequence of possession, transfer, and handling used to evaluate whether evidence remained intact. A gap does not automatically make an item false, but it limits what can be claimed.
- Corroboration
- Evidence from a genuinely independent source that supports part of an account. Multiple articles repeating one witness or document are not independent corroboration. See the site’s corroboration standards.
- Metadata
- Information about a record, such as creation time, device, location, file format, or edit history. Metadata can be absent, altered, or misread and must be compared with the file and acquisition history.
- Calibration
- Comparison of a measuring system with a known reference so its accuracy and limitations can be characterized. NASA’s UAP study materials emphasize calibrated data and complete sensor metadata.
- Sensor artifact
- A feature introduced by a camera, radar, display, compression process, stabilization system, or operating mode rather than the observed scene.
- Parallax
- Apparent displacement or motion caused by a change in viewing position or geometry. Distant objects may appear to move rapidly relative to a foreground.
- Signal-to-noise ratio
- A comparison between the desired measurement and background variation or interference. Low signal-to-noise data can support detection while remaining too weak for identification.
- Multisensor
- Observed or recorded by more than one sensor type. Multiple sensors can strengthen a case only when timing, calibration, geometry, and independence are established; two displays may derive from one underlying feed.
- Compression artifact
- A block, halo, smear, or other feature introduced when media is encoded or re-encoded. Analysis should use the earliest available file rather than a social-media copy.
Records, law, and access
- FOIA
- The U.S. Freedom of Information Act, codified at 5 U.S.C. 552, which provides a process to request existing federal agency records subject to exemptions and exclusions. It does not require an agency to answer research questions or create a new record. See FOIA.gov and the site’s request-planning guide.
- Agency record
- Recorded information maintained by or for a federal agency and subject to FOIA when the statutory conditions are met. Congressional, state, local, judicial, and private records follow different access regimes.
- Electronic reading room
- An agency area for proactively disclosed records and frequently requested material. Search it before filing; a reading-room copy may be a later release of an older original.
- FOIA exemption
- One of nine statutory categories permitting or requiring federal agencies to withhold protected information. The FOIA.gov FAQ explains the exemptions and three narrow law-enforcement or national-security exclusions.
- Redaction
- Information withheld from a released copy. Federal releases normally identify the applicable exemption unless doing so would itself harm the protected interest.
- Segregability
- The FOIA requirement to release reasonably segregable, nonexempt portions after protected material is removed. A partially redacted record is not necessarily the complete responsive file.
- Administrative appeal
- A request that an agency reconsider an adverse FOIA determination. Deadlines and procedures are agency-specific; use the instructions in the response rather than a generic timetable.
- Classified
- Designated under authorized national-security classification rules. Classification concerns protection from disclosure, not whether every statement in the material is true.
- Declassified
- Formally removed from classification. Declassification permits access subject to other restrictions; it does not validate the document’s claims. Follow declassification and records debates through the Politics of Disclosure hub.
- Archive identifier
- A catalogue, record-group, series, file, item, or document number assigned by a repository. It is usually more durable than a webpage address and should be captured in citations.
Reporting and claim labels
- Allegation
- A claim that has been asserted but not established by the evidence presented. Name the person or document making it.
- Testimony
- A person’s statement in a formal proceeding or submitted record. Testimony proves that the statement was made; its underlying claims require separate evaluation.
- Attribution
- Clear identification of who made a statement, produced an analysis, or reached a conclusion. Passive phrases such as it was confirmed should name the confirming source.
- Documented
- Supported by an accessible record that directly establishes the limited fact stated, such as a hearing occurring or an office issuing a report.
- Plausible
- Consistent with known facts and mechanisms but not established. Plausibility is weaker than verification and should identify the assumptions involved.
- Disputed
- Materially contested by relevant sources or evidence. State the disagreement and the basis on each side without turning dispute into proof.
- Contradicted
- In conflict with stronger evidence or a decisive record. Identify what contradicts the claim and whether any part remains open.
- Unresolved claim
- A claim for which public evidence is insufficient to choose confidently among live explanations. Use the claim-evaluation worksheet, then consult related editorial briefings. Send documented corrections through the Contact page.