AGENDA ITEM 1.12: 37-38 GHZ

To protect the primary services in the band 37-38 GHz from interference resulting from aeronautical mobile service operations, taking into account the results of ITU R studies, in accordance with Resolution 754 (WRC 07).

The primary concern is the continued protection of the 36-37 GHz EESS (passive) allocation used by microwave radiometers from the U.S. Air Force, Navy, NOAA, and NASA, which have been making space-borne observations near 37 GHz since Scanning Multichannel Microwave Radiometer was launch in 1978. The passive EESS sensors shown in Table 2.7 are currently on orbit, measuring at frequencies either in or directly adjacent to the 37-38 GHz band. In addition to the current sensors, two missions currently in development will operate in this frequency band: NASA’s Global Precipitation Measurement’s (GPM) Microwave Imager (GMI) and the Joint Polar Satellite System (JPSS) Microwave Imager Sounder (MIS).

Based upon scientific requirements expected to be achieved in 2008-2013, to protect EESS satellite observations from interference, ITU-R RS.1029 (2003) recommended a maximum interference level in the 36.0-37.0 GHz band of -246 dBW/Hz, with this interference level not to be exceeded for more than 0.1% of the sensor viewing area or measurement time. In the specific part of the band from 36.43-36.5 GHz, ITU Radio Regulations Footnote 5.149 states that “administrations are urged to take all practicable steps to protect the radio astronomy service from harmful interference. Emissions from spaceborne or airborne stations can be particularly serious sources of interference to the radio astronomy service.”

This band is needed to distinguish between water vapor content and liquid cloud content and also constitutes an essential part of measurements of ocean wind speed, snow cover depth on land, as well as sea ice type, age and temperature. Measurement of these geophysical parameters is critically important to weather prediction, climate monitoring and understanding changes in the global water cycle. Performing such passive microwave measurements at a suite of frequencies is essential to separate the effect of water vapor, clouds, and/or precipitation from changes in the radiance of the land, ocean or ice below. The suite of frequencies most often used for this includes a subset of 18.7, 19.35, 22.2, 23.8, 31.4, 36.5, 37.0, 85.5 and 89 GHz.1

TABLE 2.7 EESS Passive Sensors Using the Spectrum Between 36 and 38 GHz

Sensor Satellites Agencies Minimum Frequency (GHz) Maximum Frequency (GHz)
SSMIS DMSP F16 U. S. Air Force 36.25 37.75
SSM/I DMSP F13 and F15 U.S. Air Force 36.5 37.5
WindSat Coriolis U.S. Navy 36.0 38.0
AMSR-E2 EOS Aqua NASA and JAXA 36.0 37.0
GMI GPM NASA 36.0 37.0
MIS JPSS DOD 36.0 37.0
TMI TRMM NASA 36 38

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1 National Research Council, Spectrum Management for Science in the 21st Century, The National Academies Press, Washington, D.C., 2010, p. 29.

2 AMSR-2 on GCOM-W1, set for launch in early 2012, is a follow-on to AMSR-E and is planned to operate at a center frequency of 36.5 GHz. SOURCE: http://sharaku.eorc.jaxa.jp/AMSR/AMSR2_RA/documents/GCOM_RA1_E.pdf; last accessed on June 18, 2010.



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