WASHINGTON – The International Space Station and a commercial cargo ship are now locked in an electronic embrace after a series of rendezvous maneuvers brought the SpaceX Dragon spacecraft within sight of the orbiting laboratory on Thursday (May 24).
John Couluris, SpaceX mission director for the Dragon test flight to the space station, said the pioneering commercial space company is now “cautiously optimistic” about Friday’s scheduled docking with the space station. “It’s a test flight,” stressed Couluris, echoing other company and NASA officials who cautioned before Tuesday’s successful launch how difficult the first commercial cargo mission would be. “But right now the mission is looking just like our simulations.”
To achieve rendezvous about 1.5 miles from the space station, NASA and SpaceX conducted about 20 joint simulations over the last 18 months, Couluris said.
The Dragon spacecraft used less thruster fuel than anticipated to catch up with the space station, SpaceX said. “We should be good” on fuel, Couluris added.
The unmanned Dragon spacecraft as seen from the International Space Station after a successful rendezvous on Thursday (May 24). The SpaceX cargo ship is parked about 1.5 miles from the station. (Source: NASA)
So far, Dragon’s UHF communications systems also have worked better than anticipated while approaching the space station. Prior to what NASA calls the “start of integrated operations,” the phase of the mission when space station astronauts take control of the unmanned spacecraft, the crew was able use the communications link at a range of 90 km. Couluris said the station crew successfully tested the comms link by switching on Dragon’s rendezvous strobe light.
Dragon is currently flying under the space station at a distance of 1.5 miles. Holly Ridings, NASA's space station flight director, said Thursday morning that the spacecraft will remain in this “fly-under” formation for at least 20 hours while NASA and SpaceX determine the “health” of the spacecraft in advance of the attempt to dock with the space station on Friday.
Ridings said mission controllers will make a series of “go/no go” decisions over the next day as Dragon executes a series of maneuvers that will bring it within reach of the space station’s robotic arm. If the delicate maneuvers go as planned, an astronaut controlling the arm would latch on to Dragon as it drifts about 10 meters from the space station and pull it into a docking port.
A final decision on the “berthing” maneuver is expected at about 7 a.m. CDT on Friday, Ridings said.
She added that mission controllers have the option of leaving Dragon in an “overnight park configuration” on the robotic arm if space station astronauts fall behind schedule on Friday. This contingency was built into the mission because NASA officials said their prime consideration is managing the crew’s daily check list of activities.
Nevertheless, the successful rendezvous represents another major milestone in the Dragon test flight. Friday’s planned docking “is definitely a more intense day,” Couluris acknowledged during a media briefing, but “we retired a lot of risk” by catching up with the space station.