Remote Sensing - a tool for environmental observation

25 spatial resolution is low ie its pixel size is

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25 spatial resolution is low (i.e. its pixel size is large: ± 1.1 k). Lillesand & Kiefer (1994), page 502 and colour plate 16, 17 and 18 show examples of NOAA-AVHRR images. It has the following five spectral bands: NOAA-AVHRR: 1. 0.58 - 0.68 μm Altitude: 830 k 2. 0.72 - 1.10 μm Orbit incl.: 98.9 ° 3. 3.55 - 3.93 μm Repeat time: 1 day 4. 10.5 - 11.5 μm IFOV: ± 1.1 k 5. 11.5 - 12.5 μm NOAA-AVHRR are used by environmentalists to monitor changes in vegetation cover at a continental scale e.g. Tucker et al. (1986) and Tucker et al. (1984). NOAA-AVHRR data are also used for the ARTEMIS project (the Africa Real Time Environmental Modelling using Imaging Systems). This project of the Food and Agricultural organization (FAO) was funded by the Netherlands and aims at supplying a continuous, real-time overview of the ecological conditions of the African continent. This enables planners to avoid famine due to bad harvests. The point of contact in the Netherlands to obtain NOAA images is the KNMI at de Bilt. NIMBUS The NIMBUS satellite, the first NIMBUS was launched in 1964 and NIMBUS-7 was put in orbit in 1978, was developed by NASA for meteorological and oceanographic research: measuring sea water temperature, to map phytoplankton concentration and suspended materials. The sensor aboard NIMBUS is the Coastal Zone Colour Scanner CZCS: NIMBUS-CZCS: 1. 0.43 - 0.45 μm Altitude: 910 k 2. 0.51 - 0.53 μm Orbit incl.: ± 98 ° 3. 0.54 - 0.56 μm IFOV: ± 800 m 4. 0.66 - 0.68 μm 5. 0.70 - 0.80 μm 6. 10.5 - 12.5 μm Meteosat This satellite is operated by the European Space Agency (ESA) and is located on a fixed position above the Greenwich Meridian over West Africa. Such an orbit is called a geostation- ary orbit: it is an orbit at an altitude of 35.786 km in the equatorial plane, which matches speed so that a satellite remains over a fixed point on the earth’s surface. Meteosat-1 was launched in November 1977. The Meteosat record images every 30 minutes in three wavelengths in visible and near-infrared, in the water vapour absorption region and in the thermal infrared:
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26 Meteosat: 1. 0.4 - 1.1 μm Altitude: 35.786 k 2. 5.7 - 7.1 μm Geostationary orbit 3. 10.5 - 12.5 μm Record image every 30 minutes Pixelsize: 2.5 - 5.0 k The meteosat images are probably very familiar to you because they are shown almost every evening during the weather forecast on television. Due to their poor spatial resolution, environ- mentalists rarely use the meteosat images. Lillesand and Kiefer (1994), page 508 show an example of a GOES image, which is the American version of the European Meteosat. 2.3 Earth Resources Satellites The large number of remote sensing satellites is for most new-comers very confusing. However, the number of satellites of interest for environmental studies is rather limited and comprise: the Landsat series: Landsat-MSS and Landsat-TM, SPOT, NOAA-AVHRR, ERS and the future satellite Envisat. Important properties to know of these satellites are their orbit (geostationary or polar, altitude and/or pixel size) and the spectral positions of their sensors.
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