NOAA's Use of the Radio Frequency Spectrum for Coastal Ocean Monitoring
Since the 1970s, NOAA has been active in the use of high frequency radar (HFR) for ocean remote sensing research and operations. The first system, built at NOAA in Boulder, Colorado in 1974 was named the Coastal Ocean Dynamics Applications Radar (CODAR). Operating near 25 MHz, it had a bandwidth of 125 kHz. Technology developed within NOAA is typically transitioned to the private sector and, in the case of HFR, a company called CODAR Ocean Sensors, Ltd was formed in 1984.
As research and collaboration on HFR evolved, the need to acquire surface currents to longer ranges from shore demanded lower transmit frequencies, in the 12 to 14 MHz band with 50 to 100 kHz bandwidth. Later, as ever longer ranges were desired in order to monitor larger portions of the Exclusive Economic Zone, transmit frequencies in the 4 to 5 MHz band with bandwidths of 25 kHz were needed. In order to get high spatial resolution for enclosed waters, such as bays, frequencies in the 40 to 50 MHz band were needed as well. All HFR systems radiate 40 watts of power or less.
Since NOAA is an agency of the Federal government, it is required to seek radio frequency usage through the Interdepartment Radio Advisory Committee (IRAC), which is chaired by the National Telecommunications and Information Administration, and is made up of representatives from agencies throughout the Federal government. All Federal Government requests for radio frequency usage must be approved by this committee.
Presently, more than 90 HFRs are deployed throughout the coastal United States. Nearly all of these systems are owned and operated by university research departments, with funding for the equipment obtained from Federal, State, and/or municipal governments. These radars are now part of a developing network supported by IOOS (Integrated Ocean Observing System) and the Regional Associations. In order to support the continued operation and expansion of this network, some of the radars use frequencies provided by NOAA, although the vast majority of the licenses currently in use were approved by the Federal Communications Commission (FCC).
All HFR licenses in the U.S. and most if not all worldwide bear the stipulation that they are on a "not to interfere" basis. This means that a transmitting radio station with a "primary" license for that frequency can ask that the HFR operator to change frequency or shut down. Because of the historical popularity of HF for communications prior to the advent of satellites, every 3 kHz slot in the HF band is occupied by a primary license holder somewhere in the world, most of which only transmit less than an hour a day or not at all. The FCC and IRAC therefore search for HFR slots as far away as possible from other "primary" station transmitters. In addition, an invention based on GPS timing synchronization allows many HFRs to operate on the same frequency, eliminating the need for a separate frequency or each. This is an attempt to minimize the HFR spectral footprint for other users of the HF bands.
As part of the transition of the national HFR network to a fully operational status -- and with a goal of further minimizing HFR spectral occupancy -- NOAA is seeking primary frequency allocations in the 3 to 50 MHz range for HFR ocean monitoring. This process occurs through the World Radio communication Conference (WRC) which is the final arbiter of worldwide radio spectrum usage at the international level. The NOAA Office of Radio Frequency Management is leading this effort and developed a U.S proposal that was submitted to the 2007 WRC (WRC-07). The proposal was added to the agenda, as agenda item 1.15, of the next WRC to be held in 2011 (WRC-11). The period between WRC-07 and WRC-11 will be used to conduct technical studies to determine the impact of a new allocation to radio operators with existing allocations and to identify the most suitable frequency bands for the allocations.
Private entities as well as state and local governments are required to obtain frequency licenses from the Federal Communications Commission (FCC).