"It's another sealed door ... This is very important," said an excited Zahi Hawass, the director of Egypt's Supreme Council of Antiquities, as the robot broadcast its first images.
The robot - dubbed the Pyramid Rover - took two hours to crawl through a narrow shaft, drilling through a door at the end of which before pushing in a camera connected to a thin cable so to see what lay behind.
The footage showed a small, uncluttered space backed by a vertical, sheer stone surface. Hawass said the next job for researchers was to study the footage and plan for further inspections, which could take up to 12 months.
Hawass's SCA, along with engineers from the Boston firm iRobot and researchers from National Geographic, had spent a year planning for Tuesday's event.
"I enjoyed the moment of discovery. We were not disappointed ... we were successful in our mission," Tim Kelly, president of National Geographic's television and film division, told The Associated Press following the program.
Fox TV and the National Geographic Channel went live with footage of the robot inching along the 200 feet long shaft toward the door, giving TV viewers and scientists a simultaneous look at what was billed as the "Secret Chamber."
During the broadcast, Hawass made another find by lifting the lid on a stone sarcophagus found in a tomb built near the Great Pyramid, revealing the intact skeleton apparently of a man dating back to the period of the pyramid's construction some 4,500 years ago.
But this served merely as a prelude to the program's finale, the televised buildup to which was filled with reenactments of the pyramid's building and analysis over other pharaonic-era discoveries made on the world famous Giza plateau.
As the robot began inching along the rough-surfaced shaft toward a limestone door adorned with two brass handles, its path was illuminated by a blue-tinged light and broadcast live to the world.
"Those grooves you see (on the shaft walls) are the fingerprints of the (pyramid's) workers," Hawass told a National Geographic television crew member as he watched a TV screen showing the robot's progression.
From a chamber inside the pyramid, engineers controlled the robot's movement by sending instructions via cables. The tons of stone all around made radio controls impracticable.
The Great Pyramid, built 4,500 years ago by Khufu, a ruler also known as Cheops, has four narrow shafts. It is the most magnificent of all Egypt's pyramids, formed by 2.3 million stone blocks, and has lost little of its original height of 481 feet and width of 756 feet meters.
For more than a century, archaeologists have been wondering why such shafts were built and what secrets they might hold.
Hawass said the shafts may have played symbolic roles in Khufu's religious philosophy. Khufu proclaimed himself Sun God during his life - pharaohs before him believed they became sun gods only after death - and he may have tried to reflect his ideas in the design of his pyramid.
The shafts - measuring 8-inch-square - were not designed for human passage. Engineers from iRobot, benefiting from the experience of a German team that sent a robot as far as the door in 1993, have spent the last six months designing their $250,000 Pyramid Rover.
Khufu's pyramid has never yielded the treasures usually associated with pharaohs, perhaps because tomb robbers plundered it thousands of years ago.
By Nadia Abou El-Magd