Launch from Cape Canaveral; landing 130 km southeast of the Midway Islands in the Pacific Ocean.

This final mission of the Mercury program should last more than all the other NASA spaceflights before. The primary objectives of this mission were to evaluate the effects of a longer stay in space on man and to verify man as the primary spacecraft system. All in all Gordon Cooper performed 11 experiments including deploying of a mini satellite (4,5 kg) for reflection experiments and testing radiation measurements. It was the first time, a satellite was deployed by a manned spacecraft. During the mission Gordon Cooper became the first American astronaut to sleep in orbit. He made several photos and was able to see roads, rivers, small villages, and even individual houses if the lighting and background conditions were right. High over the highest plateau on Earth, the Tibetan highlands, where the air is thin and visibility is seldom obscured by haze, Gordon Cooper thought he could even judge speed and direction of ground winds by the smoke from the house chimneys. He also broadcasted slow scan black and white television pictures to the ground. The picture showed a ghostly image of the astronaut.

But during the 19th orbit things got more and more wrong. Gordon Cooper quote: Well, things are beginning to stack up a little. ASCS inverter is acting up. And my CO2 is building up in the suit. Partial pressure of 02 is decreasing in the cabin. Standby inverter won't come on the line. Other than that things are fine. That shows how cool Gordon Cooper acted. It started with a faulty indicator and ended short time later with the lost of all attitude readings. The 21st orbit saw a short-circuit occur in the bus bar serving the 250 volt main inverter. This left the automatic stabilization and control system without electric power. Then Gordon Cooper noted that the carbon dioxide level was rising in the cabin and in his spacesuit, but still Gordon Cooper remained cool, calm and collected.

So, the reentry could not be made automatically, but the astronaut was able to manually guide the spacecraft to a pinpoint landing near the recovery ship USS Kearsarge. It was the first complete manual reentry in space history.