uint64 timestamp		# time since system start (microseconds)
uint8 seq                       # timesync msg sequence
int64 tc1                       # time sync timestamp 1
int64 ts1                       # time sync timestamp 2

uint64 remote_timestamp		# remote system timestamp (microseconds)
int64 observed_offset		# raw time offset directly observed from this timesync packet (microseconds)
int64 estimated_offset		# smoothed time offset between companion system and PX4 (microseconds)
uint32 round_trip_time		# round trip time of this timesync packet (microseconds)