Christian shares the inspiration behind 'Navigation and Star Identification for an Interstellar Mission'.

John Christian was obsessed with maps as a child. Now, the Georgia Tech associate professor owns many maps — some dating back to before the Civil War. 

But these days, Christian, a former engineer at NASA, spends his days doing a different kind of mapping, exploring navigation and travel in the far reaches of space rather than tracing state and county lines. His work in the Space Exploration Analysis Laboratory in the Daniel Guggenheim School of Aerospace Engineering focuses on algorithms that process sensory data from a spacecraft to assess its location, direction, or orientation. 

Since 2019, Christian has been working to find a universal means of navigating in space using optical observations of stars, planets, asteroids, and other celestial bodies. While his work usually focuses on exploration within our solar system, some of these ideas might also someday find a use in interstellar exploration.

Realizing this, Christian and his students began to consider how the apparent direction of stars could be used to triangulate the location of a spacecraft on an interstellar voyage. They also considered how stellar aberration, a phenomenon that causes the apparent direction to a star to change due to the observer’s motion, could be used as a direct measure of velocity. 

“Navigating through interstellar space with stars is similar to orienteering while hiking in the woods: in both cases, navigators determine their location by taking sightings to known objects. Each sighting produces a line on a map, and your location is where these lines intersect.,” said Christian, an associate professor in the AE School.

For a spacecraft flying within our solar system, the stars are so far away that they appear to be in roughly the same direction, which isn’t very useful for practical triangulation, Christian said.

“This all changes for the enormous distances traversed during interstellar flight, where the stars in our galaxy aren’t just distant dots in the sky anymore; they become a cloud of 3D points that we are potentially moving through,” Christian said. “This suggests that an interstellar mission will require us to reimagine the ways that we build star maps, recognize star patterns, and use stars for navigation.”” 

Recently, the Canopus Awards recognized Christian’s research on interstellar navigation, naming him a Finalist in the published non-fiction category of the 2023 Canopus Award for Excellence in Interstellar Writing. Named after the second-brightest star in the night sky, the Canopus Awards recognize works that enhance “the understanding, excitement, and knowledge of interstellar space exploration and travel,” according to its website

The Canopus Awards are sponsored by the 100 Year Star Ship project, a DARPA-initiated organization focused on achieving human travel to other star systems in the next 100 years, with the understanding that being technologically ready for such a feat then requires preparation now.

This mentality motivated Christian to pursue his own research outside the usual bounds of  interplanetary navigation, and the eventual publication of the finalist paper, “Navigation and Star Identification for an Interstellar Mission,” in Acta Astronautica. 

“The scenarios we consider in this paper might not happen in my lifetime or my kids’ lifetime, but if no one thinks about it, there will never be a foundation on which future generations may build,” he said. “I’m thankful for the freedom I have as a Georgia Tech professor to take a rigorous, serious, and disciplined look at these long-term engineering problems for which the return may be far into the future.”

John Christian

John Christian