A signal at a single station can fault, drift, or reflect. The same signal at two stations, hundreds of miles apart, in the same instant, cannot do any of those things without cause. The Laboratories hold a small number of such coincident detections, most recorded in early spring, as Class III.
Every test the Laboratories apply for chance coincidence, instrument cross-talk, and shared interference has been applied to these events, and does not account for them. They are catalogued precisely as unresolved and kept under study. A coincidence is reported as what was measured; the Laboratories draw no conclusions the data does not support.
What the public record includes
First retained pair
Separated stations record a same-instant event that survives clock drift review.
Second retained window
A similar station-pair event triggers Array Calibration Working Group review.
Cross-talk review
Shared routing, network timing, and maintenance channels are removed from the explanation list.
Public timing abstract
Station names and exact offsets are withheld; separation class and method are released.
Review method
- Sub-second coincidence screen after clock correction.
- Chance-alignment estimate over retained station hours.
- Cross-talk review across network, power, and maintenance systems.
- Environmental event comparison using public and internal records.
Ordinary sources checked
- local station fault
- shared network timing artifact
- power-grid transient
- ordinary weather front
- Station pairings are not public.
- Exact timing offsets are withheld from automatic public download.
- The finding reports simultaneity, not a source location.