ASTER Description

GLCF provides access to a series of targeted ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) acquisitions. ASTER is a joint Japan-US imager deployed on NASA's Terra platform. Unlike Landsat, ASTER is a pointable, stereoscopic instrument which, along with its rapid revisit period, allows for dynamic monitoring of Earth surface events. Such events range from active volcanism to floods to more gradual impacts such as urban growth and forest change.
Please visit the ASTER web site for a more comprehensive overview of applications. There is also a very helpful user guide maintained by the Japanese ASTER team.

Orbit & Acquisition Characteristics

ASTER was launched in 1999 and, as of Q1 2006, remains fully operational. Flying at an altitude of 438 miles, ASTER has a 16-day revisit period and follows a sun-synchronous polar orbit. Each ASTER acquisition is approximately 60km by 60km. Although ASTER imagery is not tiled in the same fashion as Landsat data, it is still available according to the same "World Reference System" (WRS-2).

Radiometric Characteristics

The ASTER instrument acquires information across the visible and infrared spectrums. Specifically, information is acquired by three separate instruments:
  • VNIR (Visible and Near-Infrared Radiometer)
  • SWIR (ShortWave Infrared Radiometer)
  • TWIR (Thermal Infrared Radiometer)
Each of the ASTER instruments has a unique series of channels or "bands", each having its own unique radiometric characteristics. The radiometric characteristics of each band are detailed in Table 1 and Figure 1. Understanding the radiometric characteristics of the individual bands can help determine the most appropriate application for each band or combination of bands. For example, Bands 2 and 3n are often utilized in calculating vegetation indices while the thermal bands are used monitor atmospheric and thermal anomalies. Through the use of third-party software bands 3n and 3b can be utilized to create detailed elevation models.