Orbital officials initially aimed for Cygnus to arrive at the space station on Sunday, Sept. 22, but a data format issue between the spacecraft and orbiting lab forced the company to abort that first rendezvous attempt. Troubleshooting efforts with that glitch and the impending arrival of a new space station crew aboard a Russian Soyuz spacecraft, which launched and docked on Wednesday (Sept. 25), pushed Cygnus’ arrival to today.

via Private Cygnus Spacecraft Makes Historic 1st Rendezvous with Space Station | Space.com.

The other firm is SpaceX of Hawthorne, Calif., which has a $1.9 billion contract for 12 supply missions using its Dragon space capsules and Falcon 9 rockets. SpaceX has flown two of those delivery missions already, and is expected to test fly an upgraded version of its Falcon 9 rocket later today in a launch from California. Unlike Cygnus, SpaceX’s Dragon capsules are equipped with a heat shield and can return science experiments and gear to Earth from the station.