Satellites allow us to put different sensors into orbit around the earth. These satellites carry the sensors, which are the most important part for those of us wishing to analyze the Earth. The applicability of the sensor depends on from which part of the electromagnetic spectrum data are being collected.

Sensors can be designed to observe many different things: the weather, the oceans, urban areas, and vegetation are some of them. The most popular satellites and sensors for vegetation and land management are:

• NOAA's Polar Orbiting Environmental Satellites with the Advanced Very High Resolution Radiometer (AVHRR) sensor
• NASA, USGS, and NOAA's Landsat satellite program with the following sensors:
  • Multispectral Scanner (MSS)
  • Thematic Mapper (TM) and Enhanced Thematic Mapper (ETM+)
• Ikonos
• Terra Moderate Resolution Imaging Spectroradiometer (MODIS)