SpaceX's Dragon capsule on Thursday successfully completed a fly-under of the International Space Station, a key milestone in its groundbreaking test flight for private enterprise, NASA said.
Next, the unmanned spacecraft owned by Internet entrepreneur Elon Musk will attempt to latch onto the station Friday to unload the half ton of supplies it has brought to space and then get restocked with gear to return to Earth.
"Everything held up under the scrutiny of really flying in space with Dragon for the first time," said NASA flight director Holly Ridings of the fly-under that took the Dragon 1.5 miles from the $100 billion lab.
"To get through this piece of it obviously makes you feel positive, but in terms of the activities tomorrow there are still a lot of really new things that the teams need to perform and the vehicles frankly need to perform."
Astronauts aboard the ISS are planning to help the berthing operation by reaching out with the station's robotic arm to grab the spacecraft so it can latch on to the Harmony module of the station.
If NASA gives the final go-ahead, the robotic arm grab attempt would begin around 8:00 am with the docking itself scheduled for around 11:30 am, Ridings told reporters.
On Thursday, the Dragon completed several maneuvers to lay the groundwork for the berthing attempt, including an abort demonstration, communications tests and navigation on GPS (global positioning system) technology alone.
There was also a "free-drift demonstration," whereby the capsule's thrusters were all shut down as it will need to do prior to being grappled by the space station's robotic arm, said lead mission director John Couluris of SpaceX.
"We have proven that both Dragon can already navigate within close proximity of station and that the crew can command Dragon, so two very important mission points for today," he told reporters.
"I'd say generically speaking it is definitely a more intense day tomorrow. Fly-by today allowed us to check out a lot of systems and retire a lot of risk for tomorrow's flight," he added.
"It is a test flight. We are being cautiously optimistic."
Carrying cargo but no humans yet, SpaceX's Dragon capsule launched on Tuesday atop the company's Falcon 9 rocket, marking the first time a commercial enterprise has sent its own craft to the orbiting lab.
Currently, only the space agencies of Europe, Russia and Japan can send supply ships to the ISS. The United States lost that ability when it retired the space shuttle fleet last year.
California-based SpaceX hopes that its gumdrop-shaped Dragon capsule will be able to carry astronauts to the ISS in about three years' time.
SpaceX and a handful of other companies are being helped in their endeavors with seed money from NASA to build cargo and crew capability.
SpaceX has a $1.6 billion contract with NASA to supply the ISS with cargo in the coming years. Orbital Sciences has a $1.9 billion contract and is scheduled for its first launch attempt later this year.
Meanwhile, SpaceX's billionaire chief executive continued to celebrate the success of the mission so far, confessing on the microblogging site Twitter that he'd almost missed a key phone call from U.S. President Barack Obama.
"The President just called to say congrats. Caller ID was blocked, so at first I thought it was a telemarketer :)," Musk wrote.
Copyright Agence France-Presse, 2012