Mobile Suit Gundam SEED: Astray

After having finished a job at Research Colony Mendel, a mysterious mobile suit approaches the colony--likely with hostile intent. When Lowe Gear intercepts in the Red Frame, the pilot opens fire... and thus begins another exciting adventure set in the popular Gundam Seed universe! Mobile Suit Gundam SEED X Astray continues where Gundam Seed Astray R left off!
(Source: Tokyopop)

A rebuild of "Gundam SEED Astray" and "Gundam SEED X Astray," reshuffling chapters in the chronological story order, as well as including new Re:Master chapters.Note: Includes 3 extra chapters.

The story takes place in unnamed timeline, where humanity has highly advanced technology. However, the human population is decreasing and it seems that they're on their way to extinction.
The protagonists are Leos Alloy, Sthesia Awar and their Haro. They work on a Jupiter base called "Jupiter X", using "General Answer" (or "GA") which contains a massive repository of data about the alternate history of Humanity, Leos travels to the Earths' of the alternate timelines in an effort to collect data that might give them a hint for the evolution of mankind. 
(Source: Gundam Wikia)