Callista 'Calli' Chase is a security expert for NASA.
She is several more things than that, although that is impressive enough, but when we first meet her and for most of the time we have to follow her adventures, that is what she is focused on. Chase is an Air Force captain stationed at Langley Air Base in Hampton, Virginia, working under the auspices of both NASA and the newly formed Space Force.
Chase has a twin sister named Carme who will become vitally important to the adventures that we follow Calli Chase on as she will become one of those that Calli will be on the search for. This will cause considerable trouble because since they are identical in appearance, they easily get mistaken for the other and doubt will naturally creep into people's minds wondering if they aren't engaged in trading place scenarios.
The names of both sisters come from two of Jupiters's moons, given them by parents who each had worked for NASA for most of their lives. Calli points out that while her namesake is the 2nd largest moon around that planet, Carme is "actually considered more of an irregular satellite" - sibling rivalry, obviously.
Of the two Chase women, we are told by Calli, "The two of us may look and sound the same but we couldn't be more opposite in the way we spin. Until last spring, I'd place her on the low end of the spectrum when it comes to subjectivity and emotionality, which probably is a good thing when flying helicopters tricked out with missiles and mini-Gatling guns. In Carme's world, there's no option for error. But in mine it's inevitable when the focus is aviation risk-threat analysis combined with the chaotic human factor.
"It was no surprise our freshman year at Rice University that she latched on to information systems and algorithms, with segues into military science, game programming, cybercrime and other weapons necessary to fight fire with fire. While I set my heading bug on aerospace engineering and quantum mechanics, taking time out to explore the exoplanets of literature, music, religion, criminal justice and philosophy. Along with extended stays in the computer security lab, where I steeped myself in the dirtiest data-tampering tricks of the trade and the people who try them. Gearing up to slingshot through the ether on a tether of extreme technology, like a nerdy Spider-Man or ninja, as my sister likes to say. Except I'm not her, not the superhero type."
Chase is just shy of 30 years old when we join her in her missions.