a member of the command or a member under the supervision of the officer, a formal complaint alleging sexual harassment by a member of the armed forces shall, as soon as practicable after such receipt, forward the complaint to an independent investigator. (b) Commencement of investigation To the extent practicable, an independent investigator shall commence an investigation of a formal complaint of sexual harassment not later than 72 hours after— (1) receiving a formal complaint of sexual harassment forwarded by a commanding officer or officer in charge under subsection (a)