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从NASA到USGS：Landsat 8的神秘合作故事！
On February 11, 2013, Landsat 8 was successfully launched with a mission of hope and innovation, becoming the eighth satellite in the U.S. Earth Observation Program. This inter-agency collaboration revealed the close cooperation between NASA and the U.S. Geological Survey (USGS), marking an important milestone in the Landsat program and laying the foundation for future Earth observation.
Since Landsat 5 was retired in early 2013, only Landsat 7 has been in orbit. Landsat 8 ensures the continued acquisition and availability of Landsat data, providing essential support for the study of global land cover and land use change.
Mission Overview
Landsat 8's mission is not only to capture image data of the Earth's surface, it also aims to achieve three key scientific goals. First, Landsat 8 needs to collect and archive multispectral image data to provide quarterly coverage of the global land surface. Secondly, ensure that Landsat 8 data is consistent with earlier Landsat missions in terms of acquisition geometry, calibration and output product quality to enable long-term land change research. Finally, it is very important that Landsat 8 data products will be freely available to all users to ensure unimpeded access.
“The success of Landsat 8 is not only a scientific achievement, but also a practice of the concept of open data sharing.”
Technical details
Landsat 8 has an image resolution ranging from 15 meters to 100 meters, providing medium-resolution images including visible light, near-infrared and thermal infrared spectrum. The satellite can capture more than 700 scenes per day, a significant increase from Landsat 7's 250. All this is due to its improved signal-to-noise performance and 12-bit quantization data processing capabilities, which makes the description of land cover characteristics more accurate.
Satellite Design and Construction
Landsat 8, built by Orbital Sciences Corporation, uses the standard LEOStar-3 satellite bus, which means it uses a reliable technology architecture for power supply, orbit and attitude control, communications and data storage. A single deployable solar array powers the satellite and charges its 125 amp-hour nickel-metal hydride battery.
Sensor Configuration
Operational Land Imager (OLI)
OLI, as Landsat 8's main sensor, uses a push-broom sensor design to replace the swing-broom sensors used in earlier Landsats, which greatly improves its sensitivity and image quality. OLI is able to collect data in nine spectral bands, seven of which are compatible with earlier Landsat data, providing a stable foundation for long-term research. At the same time, the newly added bands can be used for water quality measurements and thin cloud detection.
Thermal Infrared Sensor (TIRS)
TIRS provides thermal imaging for increasingly important water resource management applications such as evapotranspiration measurement. The sensor uses a relatively new detection technology that can operate in two different long-wave infrared bands. Although TIRS is designed to have a lifespan of three years, it provides important continuity with the thermal infrared data from Landsat 6 and 7.
Ground Systems and Operations
Landsat 8's ground systems are responsible for command and control of the satellite and for managing the mission data sent from the satellite. NASA's Goddard Mission Operations Center sends commands to the satellite, and the mission data received by the satellite is stored and processed for subsequent analysis and sharing with the public.
History
The original Landsat 8 program relied on purchasing data from commercial satellite systems, but as a result of a technology evaluation, NASA changed its strategy and decided to build an independent satellite platform, which eventually became the Landsat 8 we know today.
"From the initial conception to today's data sharing, every step of Landsat 8 demonstrates the charm of technology and the power of cooperation."
Problems and solutions in orbit
In 2014, the scientific and technological team responded quickly and made multiple adjustments to the abnormal situation related to the thermal infrared sensor (TIRS). In the end, they not only restored the normal data collection capability, but also developed algorithms to compensate for some minor problems with the sensor. These experiences show how to meet challenges through cooperation and innovation in a complex and changing space environment.
Future Outlook
Since its launch in 1972, the Landsat program has always provided valuable data for scientific research in a changing global environment. Landsat 8 is not only a continuation of technology, but also an effort for human observation and understanding of the earth. As concerns about the impact of climate change grow, Landsat 8 will continue to support scientists, policymakers and the public to promote global information sharing and communication.
While we enjoy the convenience brought by technology, how will Landsat 8 continue to influence future earth observation and environmental management?
