NASA's weather satellites could have a new use as wildfire and storm trackers as they float through the atmosphere.

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The Terra satellite, launched by NASA in 1999, has witnessed unprecedented global change. Half a degree of heat has been added to the surface. The rise in sea level is 80 millimetres. Almost the whole area of the Amazon Rainforest is now covered with plants. Terra and two additional satellites, Aqua (launched in 2002) and Aura (launched in 2004), have been operating much into their 6-year missions as the primary sentinels of a changing planet.

Currently, the three satellites are all nearing the end of their lives. They need to conserve energy to slow down for the last dive into Earth's atmosphere and avoid any lingering space debris. There isn't enough fuel to keep their exact pole-crossing orbits, which allow them to fly over the tropics at the same time every day. NASA is anticipated to make a decision on whether to cancel the missions, which cost $85 million year to operate, or whether to spend that money in its next-generation Earth System Observatory satellite programme, which would replace part of the trio's capabilities by the late 2020s.

However, experts working on the missions think that killing them off at this time would be a mistake. With their current state of health, the satellites should last until at least the middle of this decade, and they will continue to collect data that can't be matched by any other spacecraft. They won't be hindered by their orbital wandering at all, and instead will be able to see Earth from different angles and at different times of day. Physicist Norman Loeb of NASA's Langley Research Center and Ceres' chief investigator said, "These are almost like new missions." Ceres is an instrument on Terra and Aqua that detects Earth's energy imbalance.

The price is a major concern for NASA. According to a NASA statement to Science, "it would demand delays in the Earth System Observatory" if all three missions are prolonged. The scientists are now pleading with NASA to give them a chance to present their case in a "senior review" conference scheduled for next year. This meeting is held once every three years to determine the future of active missions.

The bus-sized Terra and Aqua, which were first conceived of in the 1980s, were each outfitted with a variety of instruments, including the ground-breaking Moderate Resolution Imaging Spectroradiometer (MODIS), which could distinguish between reflected light from vegetation, clouds, and sea ice across 36 separate frequency channels. The infrared sounder aboard Aqua is only one example of a device that records a wide range of environmental factors every day. Meanwhile, Aura conducts detailed research into the chemistry of the atmosphere. The equipment' close calibration and shared spaceship platform allowed them to detect patterns that would have been missed by other means. Former NASA head scientist and remote sensing expert at the University of Colorado Boulder, Waleed Abdalati, remarked, "These will be greatly missed observations."

For instance, before Aqua, scientists believed that clouds covered around half the Earth at any given time; today they know that this percentage is closer to 70%. According to Terra, the globe has become "greener" as a result of increased carbon dioxide and temperature during the past two decades. Water vapour sent into the stratosphere by volcanic eruptions is caught by Aura, where it contributes to warming the planet and depleting ozone. Increases in greenhouse gases and decreases in Sun-reflecting pollution hazes have caused the deficit of energy exiting Earth to quadruple since 2005, as measured by the Ceres sensors. In his own words, "We're the only ones in the world doing this," Loeb claims. We're it.

The principal investigator of MODIS, Miguel Román, works for Leidos, a large Washington, D.C.-based technology contractor, and notes that while the new polar-orbiting weather satellites from the National Oceanic and Atmospheric Administration (NOAA) carry similar instruments, they only have two-thirds as many channels as MODIS. Fundamentally, "you're swapping a Swiss Army knife with 36 characteristics down to 22," he argues. Few satellites are specifically designed for climate science, but the NOAA sensors are built with weather forecasting in mind. In regards to climate change, Joo Teixeira, an atmospheric scientist at NASA's Jet Propulsion Laboratory and the infrared sounder's primary investigator, believes that the general public assumes that everyone is watching the climate.

Keeping the satellites operational would also assure overlap with ISS observations beginning in early 2024. To improve upon previous sensors, the Climate Absolute Radiance and Refractivity Observatory (CLARREO) Pathfinder has been installed on the station. According to Kurtis Thome, Terra's project scientist at NASA's Goddard Space Flight Center, long-term changes in Earth's energy balance will be simpler to determine if the Ceres and MODIS results are calibrated with CLARREO Pathfinder's (GSFC). We'll have enough data to work with to know that whatever trends we observe are genuine.

Claire Parkinson, Aqua project scientist at GSFC, who has led the mission for the past 29 years, says that if the mission is allowed to continue, the satellite will eventually drift out of its current orbit, which crosses the equator more than a dozen times a day at 1:30 p.m. local time, and into one that crosses at 3:50 p.m. local time. The morning pass for Terra will move forward by 50 minutes, from 10:30 to 9:00, while the afternoon pass for Aura will move forward by 50 minutes, from 1:45 to 2:35.

Researchers believe the shifts will pave the way for vital new studies. Long shadows captured by satellites in the early morning or late afternoon can reveal the 3D structure of surface objects or clouds. By travelling across the Arctic Ocean at different times of day, scientists can learn more about the heat exchange between the ocean and the atmosphere. Aqua will be in great condition to investigate the afternoon's peak of severe storms and flames. A new fire satellite is being delivered to us via orbital drift, Román boasts. Value for money is really high.

NASA's legacy will be safe even if they decide to stop the missions. The initial plan was for three 6-year satellite missions to document 18 years of change. Although Thome's desire was granted, just one set was ever released due to its durability. Saying, "We got it. Our research yielded the results we were hoping for.