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OCR for page 29
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Agenda Item 1.15: 350 MHz, Oceanographic radar
Agenda item 1.15 is to consider possible allocations in the range 3‐50 MHz to the radiolocation service
for oceanographic radar applications, taking into account the results of ITU R studies, in accordance with
Resolution 612 (WRC 07).
EESS
Agenda item 1.15 seeks to provide a formal allocation for oceanographic radars which have operated on
an experimental basis between 3 and 50 MHz in the past. A number of systems are deployed along the
U.S. coast that support oceanographic observations of winds and currents.30 The frequencies and power
levels of these WavE RAdar (WERA) systems vary. Bandwidths of WERA systems depend on resolution
and typically are 50 kHz or 125 kHz, though 500 kHz is desired for high resolution applications.31 The
systems could potentially be used for tsunami warnings and sea ice motion. They are also used for
monitoring oil spills, ship movements and search and rescue applications and have become essential for
both safety and meteorological applications. A formal allocation is sought to continue to support these
uses.
Table 1.15‐1 Example systems with center frequencies, and where available, transmit power levels
OSCR U.S. 24.5 MHz
NASA U.S. 50.0 MHz
NiCT Japan 9.25 MHz
WERA Germany 29.85 MHz, 27.65 MHz, 16.045
MHz, 12.50 MHz (30W)
WERA Florida 12 MHz 16 MHz (30W)
WERA South Carolina 8.3 MHz (30W)
Conclusion: Oceanographic radars operating in 3‐50 MHz do not adversely affect any other known EESS
bands and are thus not of concern for EESS(passive), so long as out‐of‐band RFI is maintained at levels
compatible with Recommendation ITU‐R RS.1029.
RAS
The primary concern for Radio Astronomy is the RAS bands in the 3‐50 MHz range (which include 13.36‐
13.41, 25.56‐25.67 and 37.50‐38.25 MHz) should be protected from unwanted emissions due to new
allocations.
Use of 10‐50 MHz is important to current and future radio astronomy. Features essential to
understanding the earliest cosmic structures (redshifted hydrogen from the “Dark Ages” before the first
generation of quasars) are expected to appear in the lowest frequencies accessible through the
ionosphere. Signals in this frequency range propagate on continental to global scales due to ionospheric
refraction and other mechanisms. Every effort should be made to ensure that the oceanographic radars
do not impact the radio telescopes operating between 3‐50 MHz.
30
See http://sampit.geol.sc.edu/radar.html.
31
See URL http://ifmaxp1.ifm.uni‐hamburg.de/WERA_Guide/WERA_Guide.shtml.
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Scientific frontiers in this frequency range include: (1) The periodic or transient universe such as the
emission from extra‐solar planets, gamma‐ray bursts, ultra‐high energy cosmic rays, and new sources of
unknown origin; (2) The high‐redshift (z) universe, including distant black‐hole‐powered radio galaxies
and clusters – tools for understanding proto‐galaxy collapse in the early Universe and the cosmological
evolution of Dark Matter and Dark Energy, respectively – and path‐finding studies of the Dark Ages at z >
30 (ν < 50 MHz), before stars turned on or galaxies formed; and (3) Acceleration, propagation, and
turbulence in the interstellar medium, including the space distribution of galactic cosmic rays and
supernova remnants together with scattering‐ and absorption‐based probes of the magnetized
interstellar plasma.
Meteor scatter and sporadic E can have path loss as low 160 dB (for distances in the 800‐2000 km range)
at 30‐50 MHz so that an EIRP of about ‐30 dBW will be at the interference (approx. ‐190 dBW sensitivity
of the LWA) threshold levels of the LWA. If the radars radiate +20 dBW EIRP (100 watts) out to sea they
will need to be sure their antenna backlobe is down by 50 dB to avoid interfering with the LWA in New
Mexico.
Recommendation: Unwanted emissions due to new radar allocations the 3‐50 MHz range should be
low enough to meet the levels of Recommendation ITU‐R RA.769 in the RAS bands at 13.36‐–13.41,
25.56‐25.67 and 37.50‐38.25 MHz.
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