The Washington Bullets welcomed back exiled free-agent guard Kevin Porter yesterday by signing him to a five-year, million-dollar contract.

The Washington Post also has learned that incumbent Bullet playmaker Tom Henderson, another free agent, will sign with the Houston Rockets, probably within a few days.

The Bullets signed Porter, 29, as a free agent and will have to compensate his old team, the Detroit Pistons. The Bullets will receive compensation from the Rockets for Henderson, 27.

Bob Ferry, Bullet general manager, said details of the compensation for Porter have not yet been worked out, "but I feel they will be, very, very shortly."

The Pistons reportedly are interested most in Bullet forward Mitch Kupchak (just coming off back surgery), forward Greg Ballard (called an "untouchable" by Ferry) and guard Larry Wright.

Ferry said yesterday, however, Wright and Ballard "will be with the Bullets next season. We've been talking to the Pistons for two months and we are very close to working this out. I feel we are going to come to an agreement soon and I also feel that it doesn't necessarily have to involve any players."

According to several team sources, the Bullets do not expect to lose any key players as compensation for Porter. Rather, a deal involving draft choices and cash most likely will be consummated. Similarly, money and picks may also be worked out between Washington and Houston for Henderson.

If an agreement cannot be worked out, NBA Commissioner Larry O'Brien must settle the issue. That is not expected to happen.

Ferry would not comment on Henderson's status, other than to say he knew Henderson "was talking to a number of teams and I have a feeling he is going to be satisfied with a better offer."

Henderson was unavailable for comment last night. but his agent, Scott Lang, said, "We're close to finalizing a deal."

He declined to name the Rockets as the team, but he said he and Henderson were "very excited."

Lang said he had been negotiating with Henderson's new team for three weeks. Other teams interested in Henderson were Utah, San Diego and Boston.

Porter's signing was not unexpected.The Bullets showed an interest in reacquiring him as soon as the season ended. Porter had said he wanted to return to the Bullets.

The Bullets traded him away after the 1975 season because they felt they couldn't win the NBA championship with him. Now they believe they can't win it without him.

"When we traded Kevin to Detroit for Dave Bing it wasn't that we were trying to get rid of him," Ferry said. "We didn't have a perimeter shooting forward so we had to get more offense from somewhere and the feeling was that Bing could both handle the offense and pick up the scoring slack from the forward spot.

"Now we have the scoring from that forward spot in Bob Dandridge and we have a whole team of good shooters. Now we just need the guy to get the ball to them.

"Not taking anything away from Tom Henderson, but Kevin is the best in the game at what he does - penetrate and get the ball to the open man.

"He's exciting, too," Ferry added, "and when you're in the entertainment business, that's a good quality to have."

The signing took place in the Federal Bar Building in the office of the Bullets' legal counsel, David M. Osnos, and was followed by a news conference.

Porter playing last season for a mediocre (30-52) Detroit team that was not blessed with strong rebounders or good shooters, still set an NBA record with 1,066 assists - an average of 13.4.

Porter said the Bullets have better perimeter shooters than the Pistons and are a much better rebounding team, but he does not expect to improve his assist record.

"I don't think I'll have the same green light here I did in Detroit," he said. "(Detroit coach) Dick Vitale just told me to go out and do what I wanted to do and play my game every night. That won't happen here because we have big guys who like to set up and we'll go to them."

Porter then paused and added, "I can't wait for those Wes Unseld outlet passes."

Porter said he has always wanted to return to Washington. He said when he came back to Capital Centre in an opposing team's uniform, the fans stood up and cheered him.

"There was always a guy who would stop me and say, 'Hey, K.P., we love you.'"All I can say is that it's nice to be back home. Bob Ferry is the one who drafted me out of college and gave me the confidence to make it in pro basketball, and I just hope I can come back here now and do whatever I can to help them win the championship again.

"My role is simple - run the ball club and get the ball to the people who can get it in the hoop."

Bullets Coach Dick Motta was at his offseason home in Idaho. But his assistant, Bernie Bickerstaff, was at the news conference and said he was elated about Porter's return.

Bickerstaff was assistant to former Bullet Coach K. C. Jones when Porter was traded to Detroit.

"He's the same-type player he was when we had him before," Bickerstaff said," but he has more experience and he has matured. He's proven he's a winner. We were 60-22 with him one year, remember"

"The one thing about Kevin that makes him so valuable as a playmaker is that he knows when to run the break and when to set up," Ferry added. "Most guys have trouble knowing where to draw the line."

Said Porter, "The Bullets really expressed how badly they wanted me and wanted my career to end here, and my contract reflects it. I'm back. I'm here and I'm ready to play." CAPTION: Picture, Kevin Porter, flanked by Abe Pollin (left) and Bob Ferry, announces that he is back with the bullets. By Ken Feil - The Washington Post