05/03/2016
A recent BBC news article[1] regarding a synthetic aperture radar (SAR)
contract award for operation within the 70 centimeter band has raised some
concern within the Amateur Radio community. The contract to Airbus Space would
involve determining the density of Earth's forests using a P-band (432-438 MHz)
SAR. That band segment was allocated for use by the Earth Exploration Satellite
(Active) Service at World Radiocommunication Conference 2003 (WRC-03). ARRL
Chief Technology Officer Brennan Price, N4QX, said SAR activity has not been
found to be a significant problem to Amateur Radio activity on the 70
centimeter band. Both EESS (Active) and Amateur Radio are secondary on the band
in International Telecommunication Union (ITU[2]) Regions 2 and 3 (Amateur
Radio is co-primary with the Radiolocation Service in ITU Region 1), and Price
said SAR operation is subject to significant constraints.
"The interference potential from one orbiting SAR to one fixed Amateur Radio
station is on the order of less than 1 minute over an orbital period of more
than 10 days," Price said. "Practically speaking, nearby electrical lines and
Part 15 devices are more likely to be bothersome."
Price said news items in articles aimed at the general public are "often
notoriously short" on technical details. ITU-R Recommendation RS.1260-11 -
incorporated by reference in the ITU Radio Regulations and binding on EESS
(Active) stations - spells out the WRC-03 consensus on SARs operating at 70
centimeters. Among other things, RS.1260-1 states that EESS (Active)
instruments operation profile "shall be campaign-oriented, targeted to specific
geographical areas and shall limit the instrument active time to the minimum
required to achieve the campaign objectives. Thus, the measurements carried out
by the instrument do not require continuous operation of the instrument, and
intervals of months between successive measurements on the same area can be
expected." The Recommendation further states that the operational duty cycle of
an SAR in campaign mode will be 15 percent (typically 10 percent).
A Russian satellite, AIST-2D, launched on April 28, will conduct SAR work as a
technology demonstration and scientific research satellite developed at Samara
Aerospace University. Its 200 W SAR will operate in the 433-438 MHz band. It
will also transmit telemetry in the 70 centimeter band.
[1] http://www.bbc.co.uk/news/science-environment-36195562
[2] http://www.itu.int/
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