"We appreciate the work Brett and Dave have done for us over the past seven seasons, and wish them well," Astros president and CEO George Postolos said in a statement. "We are excited to begin the search for the new radio broadcast team of the Astros, and look forward to finding a great talent to succeed Milo."
Dolan joined the Astros prior to the 2006 season from the Triple-A Tucson Sidewinders of the Pacific Coast League, where he called games from 2000 to 2005. He also has experience calling games for the Iowa Cubs, Class A Beloit Snappers and Arizona Fall League.
Dolan -- who, like Hamilton, is a graduate of the University of Iowa -- has called select University of Houston and Rice University basketball games while in Houston. While at Iowa he called baseball games in which incoming Astros manager Bo Porter played.
"I'm really disappointed," Dolan said. "Broadcasting baseball is all I've done my adult life, 19 straight years, and the last seven years [in Houston]. It's a difficult change to digest. I guess the disappointing aspect of it is [that] I bypassed pursuing some other opportunity in recent years because I wanted to be here long-term. We'll see what happens next."
Raymond, who couldn't be reached for comment, came to the Astros in 2006, having served as a part-time member of the Giants (2003) and Orioles (2005) broadcast teams. His experience includes Minor League stops with the independent Brockton Rox, Iowa Cubs, Class A Charleston River Dogs and independent Sonoma County Crushers.
He has also called games for the Longhorn Network.
One new member of the radio team for 2013 is already in place. Crawford Jones, a football player at the University of Houston, won the Astros' "You Make the Call" radio apprentice contest last month and will have a paid role on broadcasts next year, doing pre- and postgame interviews, covering news conferences and serving as a roving reporter during home games.
Former Astros player, manager and broadcaster Larry Dierker, currently a community outreach executive with the club, said on Thursday that he might have some interest in returning to the booth. Dierker broadcast Astros games for 18 years before taking over as manager.
Hamilton will continue to have a significant role with the club, handling special assignments, including serving as an emcee at special events, taking part in the Caravan and Fanfest, and making appearances for the club.