Roused at 3:07 a.m. by an alarm and warning signal from the guidance system, the crew members decided to stay awake after determining that the warning was a false alarm. That morning Slayton observed a grass fire in Africa, and Stafford saw a forest fire atop a mountain in the USSR. Slayton commented that things looked just the same as in an airplane at 12,000 meters. At 7:56, 5 minutes after completing another manoeuvre to bring the craft into better attitude for rendezvous, the Apollo crew attempted radio contact with Soyuz. Brand reported at 8:00 that he had sighted Soyuz in his sextant. "He's just a speck right now."
Voice contact between the two ships was established 5 minutes later. Speaking in Russian, Slayton called, "Soyuz, Apollo. How do you read me?" Kubasov answered in English, "Very well. Hello everybody."
Slayton: Hello, Valeriy. How are you. Good day, Valeriy.
Kubasov: How are you? Good day.
Slayton: Excellent. . . . I'm very happy. Good morning.
Leonov: Apollo, Soyuz. How do you read me?
Slayton: Alexey, I hear you excellently. How do you read me?
Leonov: I read you loud and clear.
Thirty-two minutes later at Slayton's signal, Kubasov turned on the range tone transfer assembly to establish ranging between the ships. The gap had been reduced to 222 kilometres. At 9:12, Apollo had changed its path again when the crew executed a co-elliptic manoeuvre that sent the craft into a 210- by 209-kilometre orbit. Apollo was spiralling outward relative to the earth to overtake the Soviet ship.
A 0.9-second terminal phase engine burn at 10:17 brought Apollo within 35 kilometres, and the crew began to slow the spacecraft as it continued on the circular orbit that would intersect that of the Soyuz. CapCom Truly advised Stafford at 10:46, "I've got two messages for you: Moscow is go for docking; Houston is go for docking, it's up to you guys. Have fun." Immediately, Stafford called out to Leonov, "Half a mile, Alexey." Leonov replied. "Roger, 800 meters." In accordance with the flight plan, the Soyuz crew had moved back into the descent vehicle and closed the hatch between them and the orbital module. Inside Apollo, the men had closed the CSM and DM hatches preparatory to docking. At a command from Stafford, Leonov performed a 60° roll manoeuvre to give Soyuz the proper orientation relative to Apollo for the final approach. On the television monitors in Houston and Moscow, Soyuz was seen as a brilliant green against the deep black of space as the onboard camera recorded the final approach.
Visitors in the MOCR viewing room for the docking included Captain Jacques Cousteau and Ambassador Anatoliy Fedorovich Dobrynin.
Leonov called out as the two ships came together. "Tom, please don't forget about your engine." This reference to the -X thrusters made Stafford and many of those on the ground who knew the story chuckle. Stafford called out the range, "less than five meters distance. Three meters. One meter. Contact." The hydraulic attenuators absorbed the force of the impact, and Leonov called out, "We have capture, . . . okay, Soyuz and Apollo are shaking hands now." It was 11:10 in Houston. Stafford retracted the guide ring, actuated the structural latches, and compressed the seals. In Russian he said, "Tell Professor Bushuyev it was a soft docking." "Well done, Tom," congratulated Leonov, "It was a good show. We're looking forward now to shaking hands with you on . . . board Soyuz."
The chase of Soyuz by Apollo had ended in a flawless docking. Stafford later recalled, "Later that night, we checked the alignment and noticed that the centre of the COAS was sitting right on the centre of a bolt that held the centre of the target in for Soyuz." That is dead centre.
Stafford and Slayton entered the docking module and closed behind them the hatch (no. 2) leading to the CSM. They raised the pressure from 255 to 490 millimetres by adding nitrogen to the previously 78 percent oxygen atmosphere. In Soyuz, the crew had reduced the cabin pressure to 500 millimetres before the docking. The pressure in the tunnel between the docking module hatch (no. 3) and the Soyuz hatch (no. 4) had been raised from zero to equal that of the docking module. Leonov and Kubasov were the first to open the hatch leading to the international greeting. During the transfer that was to follow, the pressure in the DM and Soyuz would be the same - 510 millimetres.
Then at 2:17:26 p.m. on the 17th of July, Stafford opened hatch number no. 3, which led into the Soyuz orbital module. With applause from the control centres in the background, Stafford looked into the Soviet craft and, seeing all their umbilicals and communications cables floating about, said, "Looks like they['ve] got a few snakes in there, too." Then he called out, "Alexey. Our viewers are here. Come over here, please." High above the French city of Metz, the two commanders shook hands. In the background was a hand-lettered sign in English - "Welcome aboard Soyuz."
When they talked later with President Ford, the crews were taken by surprise when the President talked for 9 minutes instead of the scheduled 5. He asked a barrage of questions that sent the crews scrambling to trade off their three flight helmets to they could respond to him.
Next Stafford, Slayton, Leonov, and Kubasov made a symbolic exchange of gifts, while Brand remained in the command module monitoring the American craft and waiting for his turn to visit Soyuz. The four men settled down to their first joint space banquet.
Stafford and Slayton said good-bye to Leonov and Kubasov at 5:47 and floated back through the tunnel into the docking module. Stafford returned to the command module, while Slayton closed the DM hatch. In Soyuz, the Soviets were securing their hatch, also. During the ensuing pressure integrity check, a possible leak through hatch nos. 3 or 4 was detected by the Soyuz monitoring equipment. This apparent flow of gas between the two hatches, while not serious, caused the crews to get to sleep a little later than planned. Finally, by 7:36, the Apollo crewmen had bid the ground good night and were beginning to settle down.