Each member of the board who is not an officer or employee of the Federal Government shall be compensated at a rate equal to the daily equivalent of the annual rate of basic pay prescribed for Executive Schedule Level IV under
section 5315 of title 5, for each day (including travel time) during which such member is engaged in the performance of the duties of the board. Members of the board who are officers or employees of the United States shall serve without compensation in addition to that received for their services as officers or employees of the United States.