In a move that caused some consternation in the Prince George's County Police Department, Police Chief John W. Rhoads informed his staff yesterday that Lt. Col. Joseph D. Vasco and Vincent duCellier will trade jobs on Jan. 29.

Vasco, as chief of operations, runs the department on a day-to-day basis and is Rhoads' top assistant. DuCellier, who is in charge of personnel, is currently the No. 3 man on the force.

Vasco's experience in 15 years on the force is in investigations and operations. Rhoads recently called him an "ideal man for the operations job." DuCellier has spent virtually his entire career in administrative work.

"I don't understand John's thinking on this one at all," police union president Laney Hester said. "Both of these guys will be like fish out of water in their new jobs."

Technically, the switch does not represent a demotion for Vasco or a promotion for duCellier because neither man's rank will be affected. But many officers wondered yesterday "what Vasco did wrong."

"Vasco didn't do anything wrong," Rhoads said. "He and duCellier have both done excellent jobs. The reason for this move is career development. Both of them will be better rounded police officers because of the new experience.

"Anyone who reads anything more than that into this move is just way off base."

Vasco said he was not the least upset by the switch but admitted he would be forced to make some adjustments.

"It's a radical change for both of us," he said. "But I certainly don't look on it as a demotion, even though Vince will be running the department whenever the chief is absent.

"Certainly, we'll both lean heavily on one another at first, but I had to grope a little when I first moved in here. I think we all know that no matter what we say there are going to be 841 different opinions on the force about why the move was made. Everybody will read something deep into it.

"I guess," said Vasco, "the chief wanted to be able to say that he has two men who are ideal to run operations."