— Completing a tradition that dates back more than 30 space shuttle missions, the four astronauts flying on NASA's final shuttle flight added their insignia to several of the walls aboard the International Space Station before leaving the orbiting laboratory Tuesday for the final time.

"This is the last shuttle. This is the last time we are going to do this," shuttle Atlantis' STS-135 mission commander Chris Ferguson said Monday (July 18) before applying a decal showing their insignia to a long panel in the station's Unity Node 1 module.

The addition of the emblem to the near-bottom of Unity's space shuttle patches-covered panel not only marked the successful end to the astronauts' work transferring cargo between the space station and Atlantis, but perhaps more poignantly, offered an on-orbit showcase for the 135th and last space shuttle mission patch.

"Even though it is [at] the bottom, it's really the capstone of the space station construction," Ferguson said.

Even before the first space shuttle left the launch pad in April 1981, astronaut crews had been designing emblems to represent their missions' goals and themselves. They wore the patches on their spacesuits and on their in-flight apparel, as well as carried spares to space as souvenirs. NASA used the crews' insignia to adorn everything from the astronauts' checklists to the packing foam used to protect equipment being launched to orbit.

When the shuttle began lofting the large components that today make up the complete space station, the astronauts accompanying the modules began leaving their emblems — either in sticker or embroidered form — on the walls of the orbiting research facility as a sign that they had been there. Today, there are full wall panels covered by mission patches.

"They do have a place where we leave the patches and our stickers," STS-135 mission specialist Rex Walheim told collectSPACE.com on Friday (July 15) from on board the space station.

"We're going to leave our patch in Node 1," Walheim said, referencing the first U.S.-launched piece of the station, called Unity, where a panel displays the emblems of all 37 — including now STS-135 — shuttle missions to visit and help build the International Space Station.

Omega on Alpha

Most mission patches are rich in symbolism and the STS-135 insignia that Ferguson and his crewmates left on the International Space Station "Alpha" is no different.

According to NASA, Atlantis is centered over elements of the NASA logo on the STS-135 patch to depict how the space shuttle has been "at the heart of NASA" for the last 30 years.

"One of the main things we wanted to show with our patch was that it is an incredible team that makes the space shuttle program possible," said Walheim in a pre-flight interview. "That's why we incorporated part of the NASA emblem. We wanted to show [that] it's the contractors and the NASA civil servants and the whole team that makes it possible, so that's what that symbolizes."

"And then of course, the shuttle kind of reminisces almost of the STS-1 patch a little bit," Walheim said, referring to the first space shuttle mission patch, which also featured the shuttle launching.

The shuttle and the elements from the NASA emblem are framed on the patch by omega, the last letter in the Greek alphabet, recognizing STS-135 as the last mission of the space shuttle program.

"Of course we did want to commemorate the fact this is the last mission," Walheim said. "To do that we picked the Greek omega letter, which is the last letter of their alphabet, to kind of commemorate the fact that this is the last mission."

According to Ferguson, the choice of the greek letter was also an attempt to be subtle.

"We tried to — without being overt about it — insinuate that this was in fact the last flight, and hence the omega," said Ferguson. "We didn't want to be too far out there but we did want the subtlety to come through and when somebody looks at the STS-135 patch and says it's the omega; that's the last flight."

In the family

While all four STS-135 crew members have reason to be proud of their flight's insignia, Walheim has an additional reason to take pride.

"My wife is a graphics designer by trade, and so she was helping us with the patch, and she designed this patch," Walheim said. "It's a lot of work designing a patch and she always does a wonderful job so it was a pleasure to have her on our team to design our patch and also to incorporate all the ideas that we were giving her and other people were giving her also to arrive at a patch that suitably commemorated the last flight of the space shuttle program. We all think it turned out nice."

Walheim's wife, Margie, also designed patches for shuttle Atlantis' STS-110 and STS-122 flights, Walheim's earlier shuttle missions.

"Fortunately, my crews in the past have been able to let Margie work, do her magic, and come up with something beautiful," Walheim told collectSPACE before his latest launch. "And that's what we wanted to do."

"We gave her a little bit of free reign to do what she thought was nice. Because if you get four engineers to design a space shuttle patch you get a space shuttle patch that looks like it was designed by four engineers," Walheim joked.

With great pride (and a little sadness)

"With great pride we put [the patch] there and a little bit of sadness, [too]," said Ferguson of his and his crewmates' emblem being placed on the station. "I think we're all just elated to have been a part of this."

In addition to the sticker affixed in the Unity node, an embroidered STS-135 patch was hung alongside a cloth emblem for STS-1, the first shuttle mission, and a U.S. flag carried on both first and last missions that was placed on the hatch that led to where the shuttles docked.

Another decal was applied on the station's Quest airlock's bulkhead, following another tradition that called for crew members who performed station spacewalks to also leave their mark.

The four STS-135 crewmates themselves did not venture outside the station but they supported two of their station counterparts during an excursion conducted while Atlantis was berthed at the complex.

"In breaking with tradition, where each [spacewalk] has either had an expedition patch or a shuttle patch, we feel like it is really appropriate that we have both of them for this occasion," said station spacewalker Mike Fossum.

As such, both the STS-135 and Expedition 28 emblems were added to the airlock wall, one slightly overlapping the other, just like the the last of the shuttle-station crews.