Oct 7
Satellite Observation and Remote Sensing Systems in Turkey
- Gökçe Bal
- Oct 7
- 7 min read
Satellites silently orbiting in space, like vast "observation towers," constantly take photographs from a distance. Farmlands, forests, cities, and disaster areas around the world are becoming visible thanks to these devices, the eyes of space, even if they don't always utilize light. So, is this bold Sentinel or Landsat ? Or why are other satellite systems like SPOT , Pleiades , Göktürk , and WorldView preferred? In the rest of this article, we'll answer these questions and discuss the perfect satellite for every situation with concrete examples.
Contents
Satellite Observation and Remote Sensing with Sentinel and Landsat: Which System for Which Task?
When capturing images, technical terms like resolution, number of bands, and revisit time come into play. We can think of these concepts simply as "pixel size" (in meters) and "color channels. " Sentinel-2 consists of a twin satellite constellation (2A and 2B) operated by the European Space Agency (ESA). Color images (optical images) have a resolution between 10 and 60 meters. For example, the primary color channels (red, green, blue, and near-infrared) have a resolution of 10 meters, while some infrared and atmospheric correction bands have a resolution of 20 and 60 meters. Capable of covering an area of 290 km in a single frame, Sentinel-2 is ideal for a variety of tasks, including agricultural monitoring , forest and water resource monitoring, and land use mapping.
On the other hand, Landsat satellites (e.g., Landsat 8 and 9) provide 30-meter multispectral imagery. Landsat 8 has a 185×185 km window, and these images are supplemented by a sharper 15-meter panchromatic channel. While it can only re-image a region every 16 days, Landsat's greatest strength is its archive, which has been running since 1972. Landsat data is invaluable for change analyses (e.g., forest cover change from 1990 to 2020). In summary, Sentinel-2 provides more frequent (every five days) and slightly higher-detail (10 m) color imagery, while Landsat offers a lower-resolution (30 m) but extensive archive, free of charge.
On the other hand, Sentinel-1 is a radar satellite. It can receive data even in cloudy weather and at night. Operating in the C-band, Sentinel-1's imagery has a resolution of 5–25 meters (varies depending on the different modes). This allows, for example, ships on the sea surface to appear bright to the radar: even in the Sentinel-1 image of the Bosphorus, ships in the water can be distinguished as bright lines. This prevents blind spots, especially in situations like floods or ammunition transport . In short, if optical imagery and vegetation index are required, Sentinel-2/Landsat is preferred; if events occur in cloud cover or darkness, radar satellites (like Sentinel-1) take over.
Türkiye's Eyes in Space: Domestic Observation Force with Göktürk-1 and Göktürk-2
Our own satellite , Göktürk-1 , is a high-resolution surveillance satellite developed through domestic collaboration. Launched in 2016, this satellite provides windows (in black-and-white mode) with a clarity of up to 0.5 meters (50 cm) below the ground. For example, it provides fine enough detail to distinguish individual buildings or field patterns in a city. This resolution provides a significant advantage in applications such as satellite-based mapping, planning, and terrain detection . (Göktürk-1's 50 cm resolution is achieved through "triple overlap" image processing methods.)
Göktürk-2, Turkey's first high-resolution reconnaissance satellite (launched in 2012), has a resolution of 2.5 meters in black and white and 5 meters in color. Göktürk satellites are particularly used for "local and critical" surveillance operations, such as defense and security , urban planning for intensive production , and detailed agricultural analysis . For example, Göktürk-1 can map the crop pattern of an agricultural basin in Turkey; while Göktürk-2, by providing flexibility in observation angles, can be used for mapping large areas. According to information provided by TÜBİTAK and TAI, these satellite observation technologies "can provide real-time imagery from Turkey and its surrounding areas, even from any point on Earth." Furthermore, the high-resolution Göktürk-1 imagery is actively used for monitoring agricultural lands, distributing cultivated areas, and estimating crop yields. In summary, Göktürk-1 (50 cm) and Göktürk-2 (2.5 m) are Turkey’s eye in space and are ideal domestic options, especially for small-scale and detailed works.
Millimetric Views: High-Resolution Observation with SPOT, Pleiades, and WorldView
Another global satellite family frequently used in Turkey is the SPOT (French origin) satellites. SPOT-6 and SPOT-7 (twin satellites launched in 2012-2014) offer 1.5 m panchromatic and 6–8 m multispectral resolution. These satellites capture imagery across a wide 60x60 km bandwidth (horizontal strip) and are particularly preferred for mapping and land classification . For example, SPOT can be used to examine city zoning boundaries or agricultural land blocks in detail. Furthermore, SPOT 6/7 data operates simultaneously with the high-resolution Pleiades satellites in the same orbit.
Pleiades , a French-Italian partnership, is a very high-resolution satellite set consisting of two satellites (Pleiades 1A and 1B). These satellites can see everywhere every other day (twins in 180° phase-shifted orbits) and provide natural-color imagery with a pixel resolution of 0.5–0.7 m. While the official bandwidth is 0.7 m, commercial products are enhanced with pansharpen (high-resolution color image production) up to 50 cm. Therefore, Pleiades allows us to distinguish vehicles and buildings in cities, or ships at sea, with the naked eye. Pleiades data could be used for infrastructure planning, coastline management, or agricultural border delineation in large cities like Arnavutköy in Turkey.
When even higher resolution is required, satellites like WorldView (Maxar/USA) come into play. For example, WorldView offers approximately 3.31 cm panchromatic and 1.24 m multispectral resolution. It also includes multiple bands (8 color, 8 SWIR, etc.). Such small pixels provide clarity comparable to aerial photography. WorldView is preferred for treasure hunting, precision urban planning, and similar tasks. In short, SPOT offers various magnification levels, such as ~1–8 m, Pleiades ~0.5–2 m, and WorldView ~0.3–1 m; you make your choice based on the task at hand.
The Right Satellite, the Right Mission: Selection Guide Based on Usage Scenarios
Choosing satellite data is like correctly fitting a magnifying glass with different lenses. The question is: What do you need? Think about it this way:
Agriculture and Land Monitoring: Optical multispectral data is generally used for plant health and cropland analysis. For example, Sentinel-2 (10m, frequent pass) or Landsat-8 (30m, archive of past periods) are ideal for calculating vegetation indices such as NDVI. For more detailed analysis or specialized studies, higher-resolution imagery such as Göktürk-1 or Pleiades can be preferred. With Göktürk-1, monitoring periodic changes in vegetation in Turkey becomes rapid and reliable.
Forest Fires and Disaster Detection: Events such as fires, floods, or earthquakes must be monitored immediately. If the weather is clear, Sentinel-2 and Landsat-8 can perform damage analysis with pre- and post-fire imagery (example: the 2021 Muğla fire was investigated with Sentinel-2 and Landsat-8). In cloudy or dusty weather, radar satellites (Sentinel-1, COSMO-SkyMed, etc.) come into play. For example, in flooded areas, radar can detect standing water. Even under fire smoke, Sentinel-1's C-band scans the forest.
Urban Planning and Urbanism: High resolution is essential for urban analysis. WorldView and Pleiades provide surveillance of city streets, buildings, and infrastructure. For example, if you need to see detailed buildings in a zoning application, submeter-resolution satellites (Göktürk-1/Pleiades) are ideal. For larger-scale mapping, medium-resolution data such as SPOT or Sentinel-2 are sufficient.
Water Resources and Coastal Management: A pool of optical satellites is used for lake and sea monitoring
(Such as Sentinel-2's water spectral bands), but radar is the primary choice for vessel tracking. For environmental monitoring, Landsat archive data is used for long-term trends, while Sentinel-2 is active for real-time data. For coastal erosion or water quality, the red, green, and infrared bands are essential.
Regional and Global Analysis: Large-scale studies, such as land cover change and climate monitoring, require data volume and continuity. Landsat (50 years of continuous recording) and Sentinel-2 (regular and free) are used together. Because the bands of both systems are cross-calibrated, interoperability is easy. For example, for agricultural crop monitoring, both NASA and ESA engineers have aligned their sensors.
There must be a balance between these scenarios and the satellite you choose. Which satellite should you choose? Do you need timing (repetition rate), detail (resolution), or continuity ? Often, multiple satellite data is used together. For example , while Sentinel-2 provides data at frequent intervals for plant health monitoring, the clearest records at the beginning of the season may come from Göktürk-1 . If colored bands fail, radar comes to the rescue.
The Power of Observation: Problems Solved and Gains from Satellite Technology
These celestial eyes offer solutions to real-world problems. For example, like a film reel, remote-sensed images increase agricultural productivity, help prevent forest fires, monitor water shortages, and instantly detect damage during earthquakes. Even Göktürk-1 imagery is used to determine crop distribution and estimate yields in agriculture. As natural events change, real-time data is used to plan emergency responses. With high-resolution satellite data, urban planners can foresee the landscape of growing cities; air pollution can be mapped; and mining and ecosystem monitoring can be conducted. Moreover, most satellite data is free : Sentinel and Landsat are openly available, allowing even junior researchers to make global observations.
The inspiring aspect of these solutions is that they enhance the quality of life through technology that transmits the big data provided by space back to Earth. Nesting bird flocks can be identified by the trails of wastewater they leave behind, which night vision cameras cannot detect; wetlands are protected. Greenhouse coverings that change according to plant species or season can be monitored in real time. These are just a few examples; each satellite operates in a different wavelength (color, infrared, radar), providing a wealth of information.
In conclusion, satellite observation technology touches human life by making the invisible visible. Data-driven planning is achieved. Each of the systems we examine in this article, such as Sentinel, Landsat, Göktürk, SPOT, Pleiades, and WorldView, serves as an assistant in various observational tasks. Every photo sent from space means a safer, more planned, and more productive world.
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