Electromagnetic radiation is emitted continuously or in pulses by objects as wave radiation and does not require a propagation medium. Consequently, it can take long distances, even in space. Far-field exploration uses this characteristic. The entirety of the wavelengths occurring in electromagnetic radiation ranges from short to long wavelengths and is called the electromagnetic spectrum. Depending on the individual material properties,
- Deflection, scattering or reflection,
- Absorption and
of electromagnetic radiation occurs at the interfaces of investigated objects or materials. To measure this radiation, complex systems and individually adapted optics are required. In addition to high-quality spheres, aspheres or mirror systems, high-performance sensors (e.g. within a spectrometer) are used to detect the electromagnetic radiation. Furthermore, a carrier (satellite), a placement and control unit are required. For data transmission, a far-reaching data transmission system is required too.