Winners of the third annual Cavallo Prize for Moral Courage in Business and Government will receive more than $30,000 in cash awards at a reception here today. The recipients -- all whistle-blowers -- are:

Roger Boisjoly, a former structural engineer for Morton Thiokol who opposed the launch of the Challenger space shuttle, which exploded in January 1986, killing the crew of seven.

Richard Cook, a former budget analyst for the National Aeronautics and Space Administration, who spoke out about technical problems prior to the Challenger launch.

Pauline Ewald, a Virginia state employee who was fired when she warned superiors about the danger of delaying a Superfund hazardous waste project.

John Shannon, a senior physicist at the Knolls Atomic Power Laboratory in New York, who was demoted after raising questions about safety problems at the Energy Department facility.

Robert Sullivan, who lost his job as a General Services Administration investigator in Boston after exposing contract violations. He later won reinstatement.

Boisjoly and Cook will share one $10,000 Cavallo award, and Ewald and Shannon will each receive $10,000. Sullivan will receive a $3,000 "special recognition award."

The 1990 awards are being sponsored by the Cavallo Foundation, established in 1987 by Cambridge, Mass., money manager Michael Cavallo, and the Fund for Constitutional Government, a nonprofit group created in 1974 to expose corruption in the federal government.