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NASA's Earth science missions have continued to demonstrate remarkable adaptability and innovation, balancing the legacy of long-standing satellites with the momentum of cutting-edge new technologies. The Terra platform, the first of three Earth Observing System flagship missions, has been in orbit since December 1999. Over a quarter-century later, four of its five instruments continue to deliver valuable data, despite recent power challenges. As of this writing, Terra's Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) - Visible-Near Infrared (VNIR) and Thermal Infrared (TIR) bands, Multi-angle Imaging SpectroRadiometer (MISR), Moderate Resolution Imaging Spectroradiometer (MODIS), and one of the two Clouds and the Earth's Radiant Energy Systems (CERES) instruments onboard, are all still producing science data. For reasons explained below, only the Measurement of Pollution in the Troposphere (MOPITT) instrument has been shut down completely, after 25 years of successful operations. The longevity of the Terra instruments is credited to Terra's instrument team members, who have skillfully adjusted operations to compensate for the reduction in power and extend Terra's scientific contributions for as long as possible.
Terra has been experiencing power-based limitations caused by platform orbital changes and solar array impacts. On November 28, 2024, one of Terra's power-transmitting shunt units failed. A response team reviewed Terra's status, and discussed potential impacts and options. Consequently, the team changed the battery charge rate and reduced spacecraft power demands by placing the ASTER instrument into safe mode.
In order to maintain power margins, the Terra team also moved the MOPITT instrument from science mode into safe mode on February 4, 2025, ceasing data collection. On April 9, 2025, the Terra project determined that additional power was needed for the platform and MOPITT was moved from safe mode and fully turned off, ending the instrument's carbon monoxide data record of near-global coverage every three days.
MOPITT was the Canadian Space Agency's (CSA) contribution to the Earth Observing System. Launched as part of Terra's payload in 1999, it became the longest-running air quality monitor in space, and the longest continuously operating Canadian space mission in history. MOPITT's specific focus was on the distribution, transport, sources, and sinks of carbon monoxide (CO) in the troposphere - see Figure. The spectrometer's marquee Earthdata products have included MOPITT Near Real-Time Datasets and offerings from the MOPITT Science Investigator-led Processing System (MOPITT SIPS). From tracking pollution from wildfires to providing data that informs international climate agreements, MOPITT served as a powerful tool for gathering data about pollution in the lowest portion of Earth's atmosphere, informing research, policies, and even helping to advance forecasting models used by scientists worldwide. Congratulations to the MOPITT team for more than 25 years of groundbreaking science and international collaboration!
As chance would have it, the MOPITT Team had planned a 25th anniversary celebration in April, 10-11, 2025, at CSA headquarters in Longueuil, Quebec and online - which began one day after the instrument was shut down. The celebration was a fitting closeout to the MOPITT mission and a celebration of its accomplishments. Over the two days, more than 45 speakers shared memories and presented findings from MOPITT's quarter-century record of atmospheric carbon monoxide monitoring. Its data showed a global decline in carbon monoxide emissions over two decades and could also track the atmospheric transport of the gas from fires and industry from individual regions. MOPITT is a testament to remarkable international collaboration and achievement. As it is officially decommissioned, its data record will continue to drive research for years to come.
The Director General of the Canadian Space Agency-a key MOPITT partner-delivered remarks, and both Ken Jucks [NASA HQ- Program Manager for the Upper Atmosphere Research Program (UARP)] and Helen Worden [National Center for Atmospheric Research- MOPITT U.S. Principal Investigator] attended representing the U.S.
