Farmers shifting stubble-burning time to dodge satellite tracking: ISRO study

A new study by scientists at the Indian Space Research Organisation (ISRO) has revealed a significant shift in the timing of stubble burning in Punjab and Haryana, as farmers increasingly set crop residue afire later in the afternoon to avoid detection by polar-orbiting satellites traditionally used for monitoring such events.

The declining trend

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Active fire locations in Haryana have sharply declined over the past four years — from 6,987 incidents in 2021 to 662 this year.

The research, published as a communication in Current Science by ISRO scientists Nimisha Singh, Rohit Pradhan, Bipasha Paul Shukla and Mehul R. Pandya of the Space Applications Centre, Ahmedabad, highlights a major monitoring gap that results in underestimation of fire incidents during the October-November burning season.

“Our analysis shows a gradual shift in peak fire activity from 13:30 IST (1.30 pm) in 2020 to 17:00 IST (5 pm) in 2024, to avoid detection by polar-orbiting satellites,” the study notes. “These findings demonstrate the importance of geostationary satellites for monitoring diurnal fire dynamics and highlight the implications of altered burning practices for emission inventories, air quality assessments, and mitigation strategies in the region.”

The researchers warn that this temporal shift could lead to a major undercount of fires and associated emissions when monitoring depends solely on polar-orbiting sensors like MODIS and VIIRS, which typically pass over North India between late morning and early afternoon.

To bridge this gap, the team analysed high-frequency data from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) onboard the Meteosat Second Generation (MSG) geostationary satellite. The 2020-2024 analysis shows a consistent shift in peak burning time from 1:30 pm to nearly 5:00 pm.

While VIIRS data indicates a decline in detectable fires, SEVIRI observations suggest otherwise. “Over the more extended period of 2012-2024, VIIRS data indicate a decreasing trend of 3,743 fire counts per year. However, when the analysis is restricted to 2020-2024, the decline becomes much steeper with a trend of -18,883 counts per year. In contrast, SEVIRI observation shows a slight positive slope of 43 counts per year, indicating that overall fire activity has not reduced,” the communication states.

The mismatch suggests that many fires are now escaping detection because they occur outside the overpass window of polar-orbiting satellites. This discrepancy has serious implications for air-quality forecasting and emission assessments across the Indo-Gangetic Plain.

The authors recommend that “future efforts should prioritise the combined use of fire data from both LEO and geostationary satellites, treating them as complementary rather than stand-alone sources.”

Chetan Agarwal, an expert active on air-pollution issues in Haryana and NCR, said the study has “apparently detected the shift of timings of stubble burning by the farmers.” He added that both geostationary thermal satellites and orbiting satellites should be used together to provide more accurate monitoring.