March 16, 2021

Keeping Time on CASSIOPE


Keeping Time

Time on CASSIOPE is measured in Mission Elapsed Time (MET), the number of seconds since the epoch date of 1968-05-24 00:00:00 UTC. Most data products mentioned in this document have been converted to UTC and are self described in their specific text, CDF, or HDF5 file (CDF Products will sometimes be described in CDF_EPOCH time). Regarding UTC leap seconds, the spacecraft clock is adjusted over the leap second while no instruments are taking data, so no adjustments to the data are required.

Due to operational timing constraints, the Bus clock is run ever-so-slightly slow, kept within 25ms/day of GPS time. GAP receives transmission from GPS satellites and syncs its pulse per second with other e-POP instruments.