Each GPS satellite (there are 24 of them) orbits the earth twice a day and, powered by solar power, travels at a speed of about 7,000 miles an hour.
Of those 24 satellites, 22 work full time and the other two are back-up satellites in case anything goes wrong with any of the others. It costs a lot to get satellites into orbit, so it’s better to put up a couple extra than wait for one to fail.
