Astronaut Mike Massimino, currently in orbit on space shuttle Atlantis, is better known in the Twitterverse as Astro_Mike. More than 300,000 Twitter users follow his updates, which began last month as chronicles of his preparations for liftoff.

A true Twitter diehard, Massimino hasn't let a mere space launch stand in the way of blasting miniature missives to his faithful.

Since Atlantis lifted off a week ago, Massimino has continuously tweeted about the beautiful views from space and, most recently, how difficult it was to sleep after an epic spacewalk.

But how does he access Twitter 350 miles (550 kilometers) above Earth?

NASA spokesperson James Hartsfield of the Johnson Space Center in Houston says that support staff on the ground post updates on Twitter that Massimino sends them from a laptop aboard the shuttle. He notes that all Atlantis crewmembers have e-mail access but that they generally only have time to use it just after waking and right before bed.

"However, the e-mail is not immediate," Hartsfield says. "It basically sits in the onboard laptop until Mission Control has the appropriate communications available to synchronize" with the laptop and relay e-mails to their intended recipients. That process usually happens just a few times a day. As a result, he adds, "unfortunately, some of the immediacy of Twitter is lost." But judging by Astro_Mike's popularity in the Twitterverse, it seems his tweets are worth the wait.

Massimino's astronaut portrait courtesy of NASA