14 C.F.R. § 101.37 – Notice requirements.

(a) Prelaunch notice: Except as provided in paragraph (b) of this section, no person may operate an unmanned free balloon unless, within 6 to 24 hours before beginning the operation, he gives the following information to the FAA ATC facility that is nearest to the place of intended operation:
1. (1) The balloon identification.
2. (2) The estimated date and time of launching, amended as necessary to remain within plus or minus 30 minutes.
3. (3) The location of the launching site.
4. (4) The cruising altitude.
5. (5) The forecast trajectory and estimated time to cruising altitude or 60,000 feet standard pressure altitude, whichever is lower.
6. (6) The length and diameter of the balloon, length of the suspension device, weight of the payload, and length of the trailing antenna.
7. (7) The duration of flight.
8. (8) The forecast time and location of impact with the surface of the earth.
(b) For solar or cosmic disturbance investigations involving a critical time element, the information in paragraph (a) of this section shall be given within 30 minutes to 24 hours before beginning the operation.
(c) Cancellation notice: If the operation is canceled, the person who intended to conduct the operation shall immediately notify the nearest FAA ATC facility.
(d) Launch notice: Each person operating an unmanned free balloon shall notify the nearest FAA or military ATC facility of the launch time immediately after the balloon is launched.