SpaceX's unmanned Dragon capsule successfully rendezvoused with the International Space Station (ISS) early Thursday morning (May 24), becoming the first commercial spacecraft to come within the vicinity of the orbiting outpost and advancing an important step closer to its capture and berthing.
The Dragon, which was visible to the station's crew, passed directly below the complex at a distance of 1.5 miles (2.5 kilometers) at 6:24 a.m. CDT (1124 GMT).
[i][b]Above[/b]: SpaceX's Dragon capsule as seen from the International Space Station during the spacecraft's fly-under demonstration.[/i]
The fly-under marked the completion of the tests that were laid out for Thursday, which also included demonstrating that the station's crew could send commands to the Dragon.
A strobe light on the exterior of the capsule was successfully turned on by the station's crew in a test of the Dragon's UHF radio system.
"Dragon showed its Absolute Global Positioning System (GPS) is in good working order. The vehicle demonstrated both a pulsed and a full abort. It also demonstrated free drift, floating freely in orbit as it will when grappled by the space station's robotic arm," SpaceX said in a statement released on Thursday. "And its proximity operations sensors and SpaceX's COTS UHF Communication Unit (CUCU) are up and running."
Earlier on Thursday, the Dragon completed two critical rendezvous thruster burns to place itself in position to perform the fly-under. The tests were designed to verify communication and navigation systems on the spacecraft before it re-approaches the station for its grapple and berthing on Friday.
Early morning on Friday, NASA will decide if Dragon is "go" to move into the approach ellipsoid 0.9 miles (1.4 kilometers) around the space station. If Dragon is "go," after approximately one hour it will move to a location 820 feet (250 meters) directly below the station.
Dragon will then perform a series of maneuvers to show systems are operating as expected. If NASA is satisfied with the results of these tests, then the Dragon will be allowed to perform the final approach to the station.
Sometime around 8 a.m. CDT (1300 GMT), astronauts on the station will grapple Dragon with the station's robotic arm and the spacecraft will be attached to the Earth-facing port on the Harmony node.