In-orbit spares
Spare satellites are usually held in a 667 kilometres (410 mi) storage orbit.[24] These will be boosted to the correct altitude and put into service in case of a satellite failure. Many satellites have failed over the years, the most recent being Iridium 28, which failed in July 2008.[25] Currently there appear to be seven spares in orbit, along with several partially failed satellites that are not in active service.[26] Five non-functional satellites have also reentered the Earth's atmosphere.[26]