Satellites were artificial objects placed into Earth's orbit. They were often used to provide images or GPS coverage of the regions below them. They were also used to relay calls made from satellite phones. Many government agencies, private corporations, and even terrorist organizations have employed the use of satellites for a variety of uses.
At a warehouse, Jack Bauer and Jonathan Wallace were pinned down by henchmen sent by Peter Kingsley. Jack reached out to Michelle Dessler at CTU, who provided him with satellite images of the area. Bauer and Wallace used these images to plan their escape. ("Day 2: 1:00am-2:00am")
Jack Bauer was in the process of tailing terrorist Kalil Hasan, but was about to head into an area where he would be easy to spot. Jack asked Chloe O'Brian to provide a live satellite feed of the area, but she needed time to reposition one of CTU's satellites. With Hasan currently stopped at a convenience store in Somis, Jack staged a robbery of the store to buy time. ("Day 4: 10:00am-11:00am")
A conspiracy in the U.S. government provided the Dawn Brigade with twenty canisters of Sentox VX1 nerve gas. However, the conspirators planned to betray the separatists by activating the remote detonators to the canisters by satellite, thereby gassing the terrorists. ("Day 5: 12:00pm-1:00pm")
The CIA backdoored into a British-owned satellite and used it to track down a fugitive Jack Bauer. ("Day 9: 11:00am-12:00pm") During a heated confrontation with the U.S., China took out two American satellites to cripple their surveillance capabilities. ("Day 9: 9:00pm-10:00pm")