Constant SIDEREAL_DAY_NANOS 

pub const SIDEREAL_DAY_NANOS: i128 = 86_164_090_500_000; // 86_164_090_500_000i128

Length of the mean sidereal day used for constellation-default GPS phasing.

The value is 23 h 56 min 4.0905 s, stored as an integer nanosecond duration so repeat_period does not depend on floating-point rounding.