Porter, 40, spent the previous two seasons as the third-base coach for the Nationals and is inheriting an Astros team that has lost 213 games in the past two seasons. Luhnow said Porter will meet with the media at Minute Maid Park on Thursday.
The Astros' current coaching staff consists of bench coach Joe Pettini, hitting coach Ty Van Burkleo, pitching coach Doug Brocail, third-base coach Dave Clark, first-base coach Dan Radison and bullpen coach Craig Bjornson. Van Burkleo and Radison took over in August when manager Brad Mills, hitting coach Mike Barnett and first-base coach Bobby Meacham were let go.
Pettini, who came to the Astros after 10 years as the Cardinals' bench coach, and Brocail both said last month they would like to return next year, but their fate remains up in the air. Tony DeFrancesco, who served as interim manager for the final 41 games, could also return to the field staff in some capacity.
"It was fun with this young club," Pettini said last month. "It wasn't so much fun losing so many [games] as we have, but it's always fun working with younger guys and seeing guys develop. Some guys turn into everyday players and some guys might not make it or stay here. That's the growing pains in the organization.
"Yeah, I would [like to stay]. I'm 57 years old and have 11 years as a coach at the big league level and a few as a player, and I'm not quite ready to retire yet. I'd like to do it a few more years."
Brocail, 45, put in a full season as pitching coach in 2012 after taking over midway through the 2011 season when Brad Arnsberg was let go.
"Of course, I'd love to be back," he said last month. "I love this job, but we have a lot of work to do. I'd like to see it through. I don't know what their thoughts are. Nobody's talked about it, but if they want to sit down and talk, I'd love to be back. We all know we have a ton of work to do, we all know there's a plan in place, and that plan needs to be followed to a 'T,' and I hope I'm the guy and they have confidence in me."
Porter began the 2010 season as the third-base coach for the D-backs before being promoted to bench coach on July 1 when Kirk Gibson was named manager. Porter also served as the third-base coach for the Marlins for three seasons (2007-09) prior to joining the D-backs.
Porter also has experience as a manager, skippering the Marlins Jamestown club of the New York-Penn League for the 2006 season. He made his coaching debut as the hitting coach for Class A Greensboro of the South Atlantic League in 2005.
During his playing career, Porter played in parts of three seasons in the Major Leagues as an outfielder for the Cubs (1999), A's (2000) and Rangers (2001), appearing in a total of 89 games. He appeared in two playoff games for Oakland during the 2000 season. Porter was originally selected by the Cubs in the 1993 Draft and hit 113 home runs with 503 RBIs and 236 stolen bases in 10 Minor League seasons.