CAPE CANAVERAL, Fla. -- NASA's "Silver Team" of spacewalking grandfathers completed a laundry list of chores Tuesday working outside the International Space Station, the last major mission event before shuttle Atlantis is to undock Wednesday and begin a two-day trip home to Florida.

STS-110

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Conducting the fourth and final extravehicular activity (EVA) of STS-110, astronauts Jerry Ross and Lee Morin spent six hours and 37 minutes crawling around the frontier outpost to finish a variety of tasks Tuesday.

Most were incomplete jobs leftover from the mission's three earlier spacewalks.

Tuesday's exercise was the second on this flight for Morin and Ross, who extended his record for the most spacewalking time of any NASA astronaut to 58 hours and 18 minutes on nine EVAs.

The other two spacewalks were accomplished by Rex Walheim and Steven Smith. Smith holds second place in the American EVA record book with 49 hours and 48 minutes of total time outside.

Before their work began, Ross -- who is the first human to make seven spaceflights and is likely making his last trip into orbit -- reminisced with his fellow astronauts about his first ever spacewalk.

"It was a little over 16 years ago that I had another buddy out here doing a spacewalk in Atlantis' payload bay, doing experiments for working at assembly techniques for an international space station, or some kind of a space station," Ross said to Moran. "Yup. At the end of the second (spacewalk) I said, 'Woody (Springer, his then crewmate), let's go build a space station. Sixteen years later here you and I are doing it."

"Pretty amazing," Morin agreed.

Among the chores completed Tuesday:

• Tested "ready to latch" indicators on the end of the S-Zero truss, which was firmly bolted to the Destiny science module during the mission's first two spacewalks. Those microswitches will tell Mission Control when a future truss segment is securely in place at the end of the S-Zero truss.

• Installed a 14-foot (4.3-meter) long "ladder" connecting the station's Quest airlock with the S-Zero truss. The metal beam will serve as a direct pathway for future spacewalkers to follow to get between the two points.

• Moved a work platform to a more convenient spot outside the station for use by spacewalkers on the next shuttle mission, now targeted to launch in late May.

• Connected a pair of superbright work lamps, one each on the Destiny laboratory and the Unity module. The light fixtures will help illuminate some areas on the S-Zero truss for future spacewalkers and robotic arm operations.

• Added what amounts to shock absorbers on the Mobile Transporter so future assembly work by spacewalking astronauts won't disturb the system. The transporter is a "rail car" that eventually will carry the station's Candarm2 along the length of the truss.

• Removed plates that cover a set of bolts that will be used to connect the Mobile Base System to the Mobile Transporter during a future shuttle mission. The base system is what the Canadarm2 will connect to, and all of that will ride up and down the truss on the transporter.

• Deployed a sensor to detect any hazardous gases leaking from the station, a radiation monitoring device as well as several new handrails on the S-Zero truss.

• Adjusted a thermal insulation blanket that was inadvertently covering part of a Global Positioning System navigation antenna on the S-Zero truss.

One thing that didn't get done was the removal of a sticky bolt on a cable cutting system on the Mobile Transporter. The bolt prevented an emergency cutting device from accidentally firing during launch but is no longer needed. It would not come loose as planned during the first spacewalk and still couldn't be removed on Tuesday.

Officials said it was one of those things that would be nice to have done, but isn't going to be a problem.

Sounding more relaxed than during their first spacewalk on Saturday the space agency's first pair of grandfathers to make a spacewalk together took time to enjoy the spectacle of floating 240 miles (386 kilometers) above the Earth.

"This is what I call a room with a view," said Ross passed above the Pacific Ocean.

"Yes indeed," mission specialist Rex Walheim answered from inside Atlantis. Walheim was the spacewalk manager Tuesday, making sure Ross and Morin knew what to do at every step.

Having staged four spacewalks in six days and successfully completed all of the major mission goals -- including installing the S-Zero truss, hooking it up to the space station and testing the attached Mobile Transporter -- Atlantis and its seven-member crew will concentrate on packing up and saying good bye to the Expedition Four crew of Yuri Onufrienko, Carl Walz and Dan Bursch.

That effort is scheduled to begin in earnest at 7:19 a.m. EDT (1119 GMT) Wednesday, followed by shuttle and station hatches closing at 11:44 a.m. EDT (1544 GMT) and undocking at 2:31 p.m. EDT (1831 GMT).

Shuttle Atlantis pilot Stephen Frick will be at the controls for the maneuver, which will include at least a partial fly-around of the station by the spaceplane.

At 4:15 p.m. EDT (2015 GMT) the shuttle's steering jets will be fired to clear Atlantis from the area and set up a two-day trip home to a Kennedy Space Center landing Friday afternoon.

The early weather outlook appears generally favorable for a 12:37 p.m. EDT (1637 GMT) touchdown in Florida.