Complex sentence: Orbit was the teams official mascot from the 1990 through the 1999 seasons until the 2000 season, where Junction Jack was introduced as the team's mascot with the move from the Astrodome to then Enron Field.
Split into simpler sentences: Orbit was the teams official mascot from the 1990 through the 1999 seasons. For the 2000 season, Junction Jack was introduced as the team's mascot with the move from the Astrodome to then Enron Field.