No Need for Panic Regarding Synthetic Aperture Radars on 70 Centimeters, ARRL CTO Says


A recent BBC news article 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) 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.