Release of SuitSat, an all-volunteer, educational project organised by an international group of ham radio enthusiasts, was the first task scheduled for space station commander Bill McArthur, a US astronaut, and flight engineer Valery Tokarev, a Russian cosmonaut.
Outfitted in identical Russian Orlan spacesuits, the men opened the airlock of the Pirs docking module at 5:44 pm (2244 GMT) on Friday to begin the second spacewalk of their planned six-month mission.
As they floated into open space, McArthur and Tokarev were accompanied by a third figure, SuitSat.
Stuffed in the decommissioned Russian spacesuit were a donated radio, transmitter, electronics boxes, batteries and old clothes to hold the gear in place.
Its helmet was adorned with an antenna.
Once tossed into space by Tokarev, SuitSat was to begin a short but notable life as the world's newest satellite.
Before its batteries die in a few days, SuitSat will transmit a series of digital audio messages in five languages that can be picked up by police scanners and ham radios on FM 145.990 Mhz.
Radio operators with more advanced equipment will be able to decode a digital image transmitted by SuitSat.
Julie Robinson, Nasa's deputy space station programme scientist, said during a pre-spacewalk briefing that "a lot of students are really excited and awaiting the SuitSat signal".
Eventually, the low-budget satellite will fall into Earth's atmosphere and burn up.
Laboratory in space
After SuitSat's release, McArthur and Tokarev were to turn to the more mundane, but critical tasks of maintaining a laboratory in space.
Highest on Nasa's priority list was to lock a cable cutter on the station's mobile transporter rail car.
The mechanism inadvertently triggered in December and snipped one of two cables used to relay power, data and video signals.
"A lot of students are really excited and awaiting the SuitSat signal"
Julie Robinson, Nasa's deputy space station programme scientist
Kirk Shireman, the deputy station programme manager, said: "It's essentially a guillotine. It's really important that we fix this before we can use the mobile transporter."
The device is supposed to trigger only if the cable snags and traps the mobile platform car between work sites.
The mobile transporter serves as a base for the station's construction crane.
To prevent the cutter from slicing the transporter's backup cable, Nasa wants McArthur and Tokarev to install a safety bolt.
The entire device is scheduled to be replaced during a spacewalk during the next shuttle mission to the outpost, planned for May.
The spacewalkers also planned to relocate a Russian grapple fixture, make a photographic survey of the Russian service module and retrieve a science experiment to study how micro-organisms are affected by the extreme temperatures and harsh conditions of space.
More information about SuitSat and links to further resources are available at this article about the project on Nasa's website.