Morton Thiokol Inc. will announce today that the two engineers who testified that they were punished for objecting to the launch of the Challenger space shuttle will be reinstated in their old jobs as part of a larger management shakeup aimed at mollifying congressional critics of the company, according to company sources.

The firm will also announce the retirement of Jerald Mason, the senior company official who overruled the engineers and recommended approving the launch. Mason, 59, senior vice president at Thiokol, distributed an internal memo saying he plans to retire.

The company shakeup comes after Thiokol, which makes the shuttle's solid rocket boosters, was severely criticized by Congress over its treatment of the two engineers. William P. Rogers, the chairman of the presidential commission investigating the accident, called the company's handling of engineers Allan McDonald and Roger Boisjoly "shocking," and the inspector general of the National Aeronautics and Space Administration began an investigation into the matter.

McDonald, who told the panel last month he had been stripped of his responsibilities and placed in a lesser job after he testified about his objections to the shuttle launch, will be reinstalled as director of Thiokol's solid rocket motor project, sources said.

Boisjoly, the coordinator of the company's task force in charge of the seals that bind the rocket's joints, will be once again allowed to meet directly with NASA officials on the redesign.