PREPARING TO BRING HOME TWO AFT ROT NAUGHTS WHO HAVE BEEN STUCK IN SPACE SINCE JUNE. MARISA PARRA REPORTS. >> Reporter: SPACEX COUNTING DOWN FOR TWO CRITICAL MISSIONS. THE COMPANY TAPPED TO BRING ASTRONAUT BUTCH WILMORE AND SUNI WILLIAMS BACK DOWN TO EARTH IN FEBRUARY. >> HELLO, EVERYBODY. >> THE DUO HAVE MADE THE INTERNATIONAL SPACE STATION HOME AFTER LAUNCHING ON BOEING'S STARLINER. THAT SPACESHIP SET TO RETURN HOME WITHOUT THEM BECAUSE OF THE THRUSTERS THAT LEFT THE TWO STRANDED. THEY SAY IN PART, WE CONTINUE TO FOCUS, FIRST AND FOREMOST, ON THE SAFETY OF THE CREW AND SPACECRAFT, AND IN JUST DAYS -- >> IT'S BEEN A REALLY EXCITING JOURNEY. >> THE POLARIS DAWN MISSION SET TO MAKE HISTORY WILL INCLUDE THE FIRST ALL-CIVILIAN SPACE WALK AND A WHOPPING ORBIT 780 MILES ABOVE EARTH. >> WELCOME TO OUR SIMULATOR. >> TOGETHER, SCOTT POTEET, SARAH GILLIS AND ANNA MENON DO WHAT NO HUMAN HAS BEFORE, PREVIEW THIS ANIMATION ACROSS FIVE DAYS THEY'LL MAKE STARLINK CONTACT, THE ASTRO NEWTS GILLIS AND ISAKSON WILL STEP OUT OF THE DRAGON CAPSULE AND BE HUMAN BOUND IN SPACE. >> THEY'LL GO OUT INTO THE VACUUM OF SPACE. >> IT'S SOMETHING FORMER SHUTTLE COMMANDER EILEEN COLLINS KNOWS ALL TOO WELL. >> I THINK IT IS GOING TO BE FINE, BUT I ALSO THINK IT'S RISKY. FOR CREW LEADER ISAACMAN, THE RISK IS WORTH THE REWARD. >> WE'RE TRYING TO INSPIRE PEOPLE TO THINK ABOUT THIS EXTRAORDINARY WORLD WE COULD LIVE IN TOMORROW. >> ONE STEP AND 870 MILES CL