46 CFR 15.815: Radar Observers.

(a) Each person in the required complement of deck officers, including the Master, on inspected vessels of 300 GRT or over which are radar equipped, must hold an endorsement as Radar Observer.

(b) Each person who is employed or serves as Pilot in accordance with Federal law onboard radar-equipped vessels of 300 GRT or over must hold an endorsement as Radar Observer.

(c) Each person having to hold an MMC officer endorsement under 46 U.S.C. 8904(a) for employment or service as Master or Mate onboard a towing vessel of 8 meters (26 feet) or more in length must, if the vessel is equipped with radar, hold an endorsement as Radar Observer.

(d) Until July 22, 2024, a person may satisfy the requirements in paragraph (a), (b), or (c) by having immediately available a valid course completion certificate from an appropriate Coast Guard-approved or accepted radar course that was issued within the previous 5 years.