Terra has consistently orbited Earth from pole to pole for over twenty years, collecting important data about Earth’s systems. Crossing the equator at 10:30 am mean local time allowed Terra’s five instruments to collect consistent, simultaneous data, important to Earth’s systems research and applications. In 2020, Terra completed its final inclination maneuver, using some of its limited fuel supply, to maintain that crossing time.
Since that final inclination maneuver, Terra has continuously drifted to an earlier equatorial crossing time. By the Fall of 2022, Terra’s crossing time will be earlier than 10:15 am. To ensure Terra, with limited fuel supplies, is a safe distance from other missions in the Earth Observing Satellite constellation orbit, Terra will be lowered to a new orbit, where it will be able to collect valuable data at an even earlier crossing time.
As Terra’s crossing time creeps earlier, small changes will be noticeable in the data and imagery collected by the instruments aboard Terra. Evidence in imagery of the earlier crossing time will be visible as longer shadows, especially in mountain landscapes. Meanwhile as Terra moves closer to Earth, the sensors’ views will become narrower leading to slightly smaller swath widths (less than 1% smaller). The effect will be most noticeable in ASTER imagery, but each of Terra’s sensors will be affected. However, the impact on science is expected to be minimal. In fact, some impacts could prove beneficial to some areas of research, like land morphology, surface temperature, and climate research.
Terra’s lengthy legacy of more than two decades of data will continue to contribute to meaningful research of Earth’s Systems science for years to come.
Final Editing: Scientific Frontline