"It was confirmed at about 8:49 am (2349 GMT Friday) that the satellite had developed some abnormality and its operation had shifted into an energy-saving mode," the Japan Aerospace Exploration Agency said in a statement.
"At about 8:55 am it became impossible to confirm telemetry data following a disruption in communications," it said, adding that the agency was trying to ascertain the cause of the trouble and bring the satellite back to normal.
The satellite, codenamed ADEOS-2, was launched in December by Japan's state-of-the-art H-2A rocket along with three other satellites including the Australian FedSat which is geared to conduct various experiments.
The ADEOS, an acronym for advanced earth observation satellite, was developed at a cost of 70 billion yen (636 million dollars) to replace its predecessor which broke down 10 months after it was launched in 1996.
Equipped with five US and French-made sensors, ADEOS has been gathering data on global weather changes for the past 10 months. It has a lifespan of three years and crosses the earth over the two poles at an altitude of about 800 kilometers (500 miles).