How do you cast your ballot when you are floating over 200 miles above your polling place? Thanks to a special electronic absentee ballot, astronauts are able to vote from space.

This voting process began in 1997—necessitated by the beginning of long-duration spaceflight for American astronauts--when Rule 81.35 passed in the Texas state legislature. This law states that “A person who meets the eligibility requirements of a voter under the Texas Election Code, Chapter 101, but who will be on a space flight during the early-voting period and on Election Day, may vote.” (Why Texas? That’s where NASA’s Johnson Space Center (JSC) is located, so most astronauts live in Houston.)

Here’s how that law comes into practice before Election Day: Before the mission, an astronaut identifies which elections he or she will be in orbit for. Then, before Election Day, an encrypted electronic ballot is uplinked to the astronauts by JSC’s Mission Control. Using a set of unique credentials sent to each of them by e-mail, astronauts can access their ballots, cast their votes, and downlink them back down to Earth to the County Clerk’s office.

The first astronaut to cast a vote in space was NASA’s David Wolf, while he was aboard the Russian Space Station Mir in 1997. The process hasn’t changed much, though now ballots are sent to the International Space Station instead, where astronauts’ missions generally last about six months.

All in all, not too different from voting absentee—the only big difference is that when astronauts fill out their ballots, they list their address as “low-Earth orbit.”