SpaceX Dragon capsule buzzed the space station

Early this morning, the SpaceX Dragon capsule passed just 2.4 kilometers below the International Space Station, completing another critical step in its mission profile that'll lead to it docking with the orbiting station Friday morning.

From the station, astronauts captured video as the capsule cruised by:

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Very, very cool. You can see the Dragon capsule in this video frame grab: it's in the lower left corner, silhouetted against the Earth. The extended solar panels are obvious, and you can just make out the shape of the capsule itself.

This flyby was an important milestone, since it showed that the capsule could approach the station and also abort the approach if needed. Other key elements it demonstrated were that it could float freely (as it will have to when it docks with ISS), that its proximity sensors worked, and that its GPS was operational as well. Astronauts on the ISS were also able to command a strobe light remotely, confirming they could link to the capsule.

All this leads up to the big show on Friday: docking. At about 09:00 UTC (05:00 Eastern US time), NASA will decide if the capsule is ready to approach. If so, over the course of an hour or two it will come with 250 meters of the station. It will then perform some last maneuvers to prove it's ready to go, and then it will make its final approach.

Then, around 13:00 UTC, it will come within just a few meters of ISS, and astronauts on board will grab it with the robotic arm, bringing it in to mate. After that, there will be quite a few checks done which will take some time, leading up to the hatch being opened Saturday morning, scheduled to happen around 11:00 UTC.

All the fun stuff so far has been happening in the middle of the night for me in Boulder, but the approach tomorrow morning isn't too bad. I'll get up a little early to watch it live (06:00? We'll see). I'll live-tweet the events as they happen.

This is all very exciting! The capsule has been performing essentially flawlessly since launch, so I have high hopes for the next few days.

Image credit: NASA

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- Space X set to launch on Saturday May 19