How Do Remote Sensing Satellites View the World?

Satellite remote sensing technology plays a critical role in disaster prevention and relief, emergency monitoring, urban planning, agricultural condition monitoring, and many other areas. It has become a significant driving force in advancing human technological progress and sustainable development. This article will take you into the world of remote sensing technology, showing you the marvels of remote sensing satellite technology.

Remote Sensing Satellites Are Extensions of Human Senses

Remote sensing satellites are satellites that carry cameras to sense the Earth's surface from distant space orbits. It's akin to moving our eyes to the sky, patrolling the Earth, with instruments that can extend the boundaries of human senses, helping us see electromagnetic wave information that the average human eye cannot perceive.

Depending on how data is received, remote sensing is divided into active remote sensing and passive remote sensing. The principle of active remote sensing involves the remote sensing platform emitting a certain form of electromagnetic wave to a target, and then sensors receiving and recording the reflected electromagnetic wave information from the target object. In passive remote sensing, the remote sensing system only uses detection instruments to obtain and record the electromagnetic wave information emitted or reflected by the target object from natural radiation sources (like the sun).

The Four Elements of Remote Sensing Satellite Resolution

People often consider "resolution" a key factor in evaluating a camera's quality. In other words, describing the core resolution capability of a spatial remote sensing satellite typically follows these four elements:

Spatial Resolution

Spatial resolution refers to the camera's ability to distinguish the geometric features of ground objects. Generally, this is proportional to the camera's aperture and inversely proportional to the imaging distance. Just as a DSLR camera usually has better image quality than a mobile phone, a large-aperture lens can see finer details. Today's remote sensing satellites can observe the clothing and posture of pedestrians on the ground from hundreds of kilometers away in space.

Temporal Resolution

Temporal resolution refers to the time interval at which a satellite revisits a specific location. The quicker the revisit, the higher the temporal resolution. To achieve this, one can increase the camera's swath width or use a constellation of dozens or even hundreds of satellites for joint observation, which significantly reduces the ground revisit waiting time.

Spectral Resolution

Spectral resolution is the camera's ability to distinguish different colors of light. The higher the spectral resolution, the stronger the ability to identify the spectral fingerprints of ground objects, making it easier to accurately identify objects. High-performance satellites can even detect the presence of harmful gases such as formaldehyde, sulfur dioxide, and nitrogen dioxide, which are invisible on the ground.

Radiometric Resolution

Radiometric resolution refers to the ability to discern the smallest energy levels of received light or radiation. Like a cat's vision in dim light, a camera with high radiometric resolution can clearly see lights at night, the snow and ice under the moonlight in the Arctic winter, or a 0.2℃ temperature difference on the ground.

Of course, it's challenging for a single camera to achieve the highest standards in all four types of resolution. As science and technology progress, the super visual capabilities of remote sensing satellites will continue to evolve, providing technological support for sustainable human development.