Single-Event Upset (SEU)

A sudden, unintended change in the state of a computer memory bit or electronic circuit, caused when a single high-energy particle — often a solar energetic particle or a galactic cosmic ray — passes through sensitive spacecraft or aircraft electronics. A single-event upset can flip a stored bit, causing anything from a harmless, correctable glitch to a serious spacecraft malfunction, which is why radiation-hardened electronics and error-correcting memory are standard on satellites operating outside Earth's protective atmosphere.