What are the Different Types of Satellite Remote Sensors?

Remote sensing is one of the primary applications of satcom equipment. It helps professionals in environmental monitoring, climate change analysis, disaster management, and urban planning & development. However, to enable remote sensing, there are certain types of sensors attached on Low Earth Orbit (LEO), Medium Earth Orbit (MEO) and Geostationary satellites. These sensors emit or reflect light to detect and monitor environmental characteristics of the earth’s atmosphere.

Let’s have a look at the different types of remote sensing methods and the sensors used to enable them.

Types of Remote Sensing

Active Remote Sensing






 

Active remote sensing has its own source of energy which it uses to emit light signals. Once these signals are reflected back from the earth’s surface, special cameras or sensors capture the remotely sensed images that are then processed by their respective professionals. As the majority of active sensors operate in microwave frequency, they are easily able to penetrate clouds. Some advantages of using active remote sensing are:




- Can be used in tropical climates and rainy seasons as well

- Emit their own light thus can be used at all 24 hours of the day

- Suitable for continuous and precise monitoring of small scale features

- Provide control over the emitted energy, providing better data acquisition and consistency in measurements

- Helps in more precise identification and classification of the target object

 

Different Types of Active Remote Sensors

1. Radar: Transmits signals to detect objects and reflects back their distance by measuring the amount and time required to touch the object
2. Lidar: Transmits light to detect objects and reflect their positioning and distance
3. Ranging Instruments: Measure the range between different satellites or between stations and satellites
4. Sounder: Helps in studying weather conditions
5. Scatterometer: Used to measure the bounced light reflected after hitting a surface



Passive Remote Sensing






 

Unlike active remote sensors, passive remote sensors do not emit their own light. Instead, they rely on the sunlight reflected from the earth surface to detect objects and give measurements. By depending on solar energy, passive remote sensors become highly efficient and constitute the majority of high and medium-resolution satellites. However, as passive sensors work on visible and infrared frequencies, they are not able to penetrate clouds but are highly efficient in measuring sea surface, land surface, vegetation, etc. Some benefits of using passive remote sensing are:




- As passive sensing does not penetrate clouds, it can be used to detect cloud and aerosol properties

- Can be used for monitoring the planet for a long time. For example, the Landsat 1 satellite monitored Earth surface for 40 years

- Suitable for day-to-day monitoring of vegetation and crops

- Also suitable for marine sciences

 

Different Types of Passive Remote Sensors

1. Radiometer: Detects the power of radiation in visible, IR and microwave frequencies
2. Spectro-radiometer: Detects the power of radiation in multiple frequencies
3. Accelerometer: Checks linear or rotational changes in speed in comparison to time
4. Magnetometer: Detects and measures the strength of Earth’s magnetic field
5. Radio Receivers: User for communication between stations and satellites

Conclusion

Both active and passive remote sensors have some overlapping and distinctive applications. While the former emits its own light to detect objects, the latter relies on solar energy. For penetrating the heavy clouds in rainy seasons or tropical climates, active sensing is utilized and for measuring cloud characteristics or large surfaces, scientists rely on passive sensing. Also, it is possible for a satellite to have a combination of both active and passive sensors to support the applications and functionalities of both.

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