The July Galileo outage was caused by multiple simultaneous failures: backup system unavailable, mishandling of new equipment during an upgrade, an anomaly in the system reference time, and a non-normal configuration.
Communication during the outage was poor, with the European Commission being the sole communicator and far removed from operations.
Galileo's operational complexity involves many organizations, leading to slow resolution of ground-based software problems and a culture of secrecy.
Despite the outage, the constellation could restart in a few days, but 5% of satellites are often unavailable due to software issues.
The SDD allows for up to 6.9 days of outage in a 30-day period, so the outage technically met minimum performance levels.
Leap seconds are controversial due to Earth's variable rotation, affecting timekeeping.
Navigation satellites like GPS, Galileo, and BeiDou use monotonic clocks unaffected by leap seconds, broadcasting offset to UTC.
Leap seconds are pre-announced months in advance, transmitted with truncated week number and day to save bandwidth.
The last leap second was in December 2016; since then, no new leap seconds have occurred, leading to a 256-week gap.
Bugs emerge when systems misinterpret leap second data, e.g., U-Blox receivers reporting a false imminent leap second, and a gpsd bug causing a 1024-week time jump.
Negative leap seconds may be needed in the future due to Earth's rotation speeding up, posing potential software issues.
GLONASS handles time differently by incorporating leap seconds directly, which can cause glitches during leap second events.