Remote Sensing - a tool for environmental observation

A more advanced version of gome is sciamachy

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collect information on the gases atmosphere using absorption spectra. A more advanced version of GOME is SCIAMACHY. SCIAMACHY will be built by Dutch and German companies and is planned to be launched late 2002 (see chapter 2). Other radar satellites are the Canadian Radarsat, the Japanese JERS-1 and the Russian Almaz-1. Radarsat is launched in 1997 with aboard a SAR C-band. Its most important task is almost real- time monitoring of the glacial conditions of the shipping routes along Canada’s coasts. JERS-1 was launched on 11 February 1992 with an L-band (23.5 cm) SAR system aboard. Almaz-1 was launched on 31 March 1991 and carries an S-band (10 cm) SAR. The European Envisat satellite, see also chapter 2, is carrying an ASAR: advanced Synthetic Aperture Radar. 3.9 RADAR Interferometry Radar interferometry is a fast developing technique for measuring the topography and the deformation of the Earth surface (Hansen 2001). SAR observations are made using a monochromatic radar signal i.e. one frequency. The time that the return signal arrives at the sensor provides the travel time of the signal and hence the distance to the Earth surface. If we now have two observations from two orbits at distance B apart and we compute the shift in phase of the return signal it is possible to derive an digital elevation model or DEM from Radar images. Radar observations collected over time make it possible to detect deformations of the Earth surface caused by Earthquakes or volcanic eruptions. An example is shown in figure 3.13. Figure 3.12 SAR Interferometry configuration. Two orbits provide a baseline B to determine interferometric phase differences.
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53 3.10 Examples Many examples of radar remote sensing can be found on the internet e.g. at the Canadian Centre of Remote Sensing at or at the Delft Earth Observing Section DEOS: Figure 3.13 A) Radar intensity map of northern Turkey near Izmit and the Black Sea. B) Interferogram constructed of two radar images of 13 August 1999 and 17 September 1999 showing the deformation pattern due to the Izmit earth quake at 17 August 1999. Source: Hansen, 2001.
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54 Chapter 4 Thermal Infrared Remote Sensing 4.1 Introduction All matter radiates energy at thermal infrared wavelengths (3.0-15.0 μm). We cannot see this radiation because the human eye is only sensitive for radiation in the visible part of the spectrum (0.4-0.65 μm) and not for the thermal part. The emitted radiation can theoretically be computed using the Stefan Boltzmann equation described in chapter 1 and shown in figure 1.4. Unfortunately, this relation is only valid for black bodies in ideal situations. The real world of thermal remote sensing is a bit more complex as will be discussed in this chapter. 4.2 Temperature and Emissivity The temperature of an object is normally measured by putting a thermometer in direct contact with or even in the object. The temperature measured using this method is called kinetic or internal temperature: T kin . In fact, the kinetic energy of the particles of matter (molecules) is determined. The random motion causes particles to collide, resulting in changes of the energy state (of e.g. the electrons) and the emission of electromagnetic radiation. The amount of energy
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