Astronaut Sunita Williams voted through absentee ballot

Sunita, along with flight engineer Kevin Ford, exercised her franchise in July while stationed in Russia even before heading up to the station aboard Soyuz ships launched from the Baikonur cosmodrome.

The other four members of the station's current Expedition 33 crew are all non-Americans -- three Russian cosmonauts and one Japanese space ace.

For several years now, adventurers aboard the International Space Station have been able to cast their votes via encrypted e-mail.

Voting facility is available to those in the ISS with the help of to a digital ballot provided by Mission Control at NASA's Johnson Space Center in Houston.

The provision was envisaged by a 1997 Bill passed in the state of Texas, home to most of the NASA astronauts.

The Bill allowed registered voters to digitally beam their ballots back down to Houston.

After filling out the form, "they send it back to Mission Control," says NASA spokesman Jay Bolden.

"It's a secure ballot that is then sent directly to the voting authorities," says Bolden.

Various US astronauts have cast their ballots from orbit in various past elections, and NASA has a procedure for such cases, brought in at the behest of Texan politicians keen to capitalise on publicity around space-going voters likely to be resident in the Houston area.

When the bill was passed, David Wolf, then aboard Russia's Mir space station became the first astronaut to file his vote from space via encrypted email.

Wolf, however, was voting in a local election.

In October 2004 that Leroy Chiao, then stuck aboard the ISS, became the first far-flung astronaut to vote for a president.

Meanwhile, one former US astronaut will also be participating in the US elections.

Former space shuttle mission specialist Jose Hernandez is hoping to be elected as a Democrat congressman for California's 10th district.

Hernandez had made one spaceflight in 2009 aboard shuttle Discovery, a routine support mission to the ISS.