'Blinded' Satellite Gains Ground in Radio Interference Battle
A beleaguered European satellite that has been beset by patchy "blindness" from radio interference appears to be recovering after painstaking efforts to reduce signal contamination.
The radio interference is plaguing the European Space Agency's Soil Moisture and Ocean Salinity satellite, which launched in November 2009 to study Earth's water cycle. But shortly after it began transmitting, project scientists noticed that over certain areas, radio-frequency interference was badly contaminating the data.
"At times, this interference was effectively blinding the instrument, rendering the data over certain areas unusable," ESA officials said in a Wednesday (Oct. 6) statement.
The unwanted signals have mainly come from TV transmitters, radio links and networks such as security systems. Terrestrial radars appear to also cause some problems, ESA officials said.
Despite the unwanted signals, the SMOS satellite has managed to meet its scientific goals in areas free of the interference, but in order to maximize the mission's success, the issues must be resolved, ESA officials said. [Gallery - Spotting Satellites From Earth]
The interference problems experienced by the SMOS satellite are unrelated to Intelsat's wayward Galaxy 15 satellite, which lost contact with ground controllers in April, and has spent months adrift in orbit with an active payload.
Satellite's radio interference
SMOS is equipped with a passive radiometer that operates in the L-band of the electromagnetic spectrum. Regulations set by the International Telecommunications Union reserve this frequency band for space research, radio astronomy and a radio communication service between Earth stations and space, known as the Earth Exploration Satellite Service.
Yet, data from SMOS revealed that there were many incidences of other signals within this protected band, particularly in southern Europe, Asia, the Middle East and some coastal zones.
"The transmissions contaminating the data were due to two main reasons: either emissions in adjacent bands that were leaking into the protected region owing to excessive power levels, or illegal transmissions within 1400-1427 MHz," ESA officials said in a statement.
Space interference battle
In an international effort between the space agency and various governments, ESA sought to have the illegal transmissions shut down, and excessive out-of-band emissions reduced.
"The SMOS data are able to show, within a few kilometers, where the interference comes from," officials said. "Knowing the rough locations, ESA has been contacting National Spectrum Management Authorities to request that they take steps to resolve the issue."
Over the last few months, ESA officials have reported "significant improvement" in the SMOS data.
"While the cooperation between ESA and government authorities continues to be fruitful, the hope is that these cases will lead to tighter regulation enforcement," they said.
SMOS is the second Earth Explorer Opportunity mission that was developed as part of ESA's Living Planet Program. The satellite is designed to observe ocean salinity and soil moisture. SMOS data will contribute to hydrological studies that will improve our understanding of the planet's ocean circulation patterns.
