Orbital Sciences' Cygnus Craft Now Set to Dock With ISS This Weekend

Dulles, Va.-based Orbital Sciences says it has prepared a software patch to fix an issue that prevented its Cygnus resupply craft from docking with the International Space Station as originally planned.

Orbital launched its Cygnus cargo spacecraft on a resupply run to the International Space Station last week. Since then, the space mission has hit a proverbial bump in the road. It has been postponed until Saturday at the earliest, following the planned arrival tomorrow at the ISS of Michael Hopkins of NASA and Oleg Kotov and Sergey Ryazanskiy of the Russian Federal Space Agency.

Cygnus on its way to rendezvous with the space station. Source: NASA.

As reported by The Associated Press, after boosting into orbit last Wednesday, Orbital's Cygnus met up with the ISS on schedule, prepared to deliver 1,300 pounds of food and clothing to the crew there. A software mishap, however, prevented Cygnus from docking as planned on Sunday.

In an interview, Orbital's Vice President for Corporate Communications, Barron Beneski, said the software glitch was due to the ISS and the Cygnus capsule utilizing two different, but both valid, systems for translating GPS signals into time-and-date. When the two vessels met, their computers recognized the discrepancy but could not resolve it, at which point fail-safe measures instructed them to break off contact.

Orbital has prepared a software patch that will bridge the GPS data divide, and plans to test it this week before uploading to Cygnus. The company will delay making an attempt at docking with the ISS until after a new three-man crew of astronauts has arrived from Kazakhstan, and settled in later this week, then try to dock again either Saturday or Sunday.

Because this is a test flight of the Cygnus, nothing valuable or urgent is on board. If necessary, it could keep orbiting the world for weeks, even months, before pulling up at the orbiting lab.

NASA said Cygnus achieved three of its "demonstration objectives" during its first two days in orbit. It demonstrated its ability to orient itself in space, turned off its engines and operated while in free drift, and conducted a demonstration abort maneuver.

NASA gives the following breakdown of how Cygnus will approach the ISS:

The resupply craft is followed closely by mission controllers on its way to the station. When the spacecraft reaches certain points along its trajectory the flight director polls mission controllers before giving the "go/no-go" decision to proceed to its next point.

As Cygnus meets its demonstration objectives and moves closer to the space station, Expedition 37 Flight Engineers Luca Parmitano and Karen Nyberg will be watching and working in tandem with Mission Control. Parmitano will be in the cupola at the Canadarm2 controls monitoring its approach. Nyberg will be his back up at the secondary robotics workstation inside the Destiny laboratory.

When Cygnus meets its final demonstration objective of pointing a tracking laser at a reflector on the Kibo laboratory it will move to its capture point about 10 meters from the station. Cygnus will turn off its thrusters, operating in free drift, and Parmitano will maneuver the Canadarm2 to grapple and capture the new resupply craft.

After capture, Parmitano will operate the Canadarm2 to move Cygnus and attach it to the Harmony node. The hatches to Cygnus are planned to be opened following leak checks and power connections.

To date, Orbital has invested some $262 million in developing Cygnus, and a few hundreds of millions more in developing the Antares rocket that launched it, with a further $288 million in R&D money contributed by NASA. The ongoing Cygnus mission is the final stage of Orbital's COTS (Commercial Orbital Transportation Services) contract with NASA, and paves the way for the company's beginning a series of eight resupply missions to ISS under a subsequent Commercial Resupply Services contract valued at $1.9 billion. That next contract will continue through 2016.

Click here to find the latest information Orbital's Antares-Cygnus project.

-- Material from The Associated Press was used in this report.


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