Two NASA astronaut commanders have perspectives like no others on Twitter -- the views of twin brothers preparing on opposite sides of the world to command both the space shuttle and the International Space Station.

The tweeting twins are astronauts Mark and Scott Kelly. Mark is the commander of space shuttle mission STS-134, set to launch in late 2010. Scott is the commander of station Expedition 26, also set to fly in late 2010. If schedules hold, the two may meet in space during their respective commands.

To follow the Kelly twins as they give insights to the world, and to each other, visit their respective Twitter accounts.

For Mark:

The brothers are natives of West Orange, N.J., and both are Navy captains. NASA selected them as astronauts in 1996.

Mark is a veteran of three space shuttle flights. He served as the pilot on missions STS-108 in 2001 and STS-121 in 2006 and commanded STS-124 in 2008. He has logged 38 days in space on his three flights.

Scott is a veteran of two space shuttle flights. He served as the pilot on mission STS-103 in 1999 and commanded STS-118 in 2007. He has logged almost 21 days in space and is currently preparing for a six-month stay aboard the station.

To follow all NASA astronauts currently on Twitter, visit: