Complex sentence: The spacecraft returned to Earth at 06:00:00 UTC on 20 August, the day after its launch, although telemetry revealed that one dog had suffered seizures during the fourth orbit, thus it was decided to limit the first manned flight to three orbits.
Split into simpler sentences: The spacecraft returned to Earth at 06:00:00 UTC on 20 August, the day after its launch, although telemetry revealed that one dog had suffered seizures during the fourth orbit. Thus, it was decided to limit the first manned flight to three orbits.