FA-0447: a fifty-three-year carrier we cannot place

On this date in 1971, days after the Calder Ridge array came online, the station logged a narrow-band carrier near 18.633 kilohertz. It has returned intermittently since, across receivers, maintenance cycles, staff changes, and several generations of recording practice.

The recurrence summary collects fifty-three years of returns into one public record. It finds no periodicity matching a catalogued transmitter, satellite pass, maintenance schedule, or celestial cycle. It finds, instead, a pattern the Laboratories can describe and cannot yet explain.

What the public summary contains

• The 1971 commissioning context and first retained observation.
• The major source-elimination categories reviewed since accession.
• The rationale for keeping FA-0447 in Class III.
• A pointer to the full recurrence-table request path for qualified researchers.

FAL is not publishing the restricted timing tables in full. Those records include instrument-change details, third-party comparisons, and site-security information that require records-office handling. The public summary is designed to explain the status without pretending the entire archive can be placed on a web page.

FA-0447 remains Class III and unresolved. That classification is a promise of restraint, not an invitation to guess.