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An Overview of ASTER

The first Earth Observing System (EOS) satellite called Terra (previously AM-1) was launched on December 18, 1999 from the Vandenberg Air Force Base in California. Terra will fly in a sun-synchronous polar orbit, crossing the equator in the morning at 10:30. ASTER is one of the five state-of-the-art instrument sensor systems on-board Terra with a unique combination of wide spectral coverage and high spatial resolution in the visible near-infrared through shortwave infrared to the thermal infrared regions. It was built by a consortium of Japanese government, industry, and research groups. ASTER data are expected to contribute to a wide array of global change-related application areas including vegetation and ecosystem dynamics, hazard monitoring, geology and soils, land surface climatology, hydrology, and land cover change.

What makes ASTER unique?

• The Visible Near Infra-Red (VNIR) telescope's backward viewing band for high-resolution along-track stereoscopic observation.
• Multispectral thermal infrared data of high spatial resolution (8 to 12 µ window region, globally).
• Highest spatial resolution surface spectral reflectance, temperature, and emissivity data within the Terra instrument suite.
• Capability to schedule on-demand data acquisition requests.

History of ASTER

• 1981: NASA commissioned an in-house study to determine requirements for a polar-orbiting platform to provide Earth science observations - Resulted in System Z, now the EOS. Among the early EOS designs, one of the strawman instruments was JPL's Thermal Infrared Multispectral Scanner (TIMS) as a follow-on to the Airborne TIMS.
• 1988: TIMS' instrument design was refined and proposed as the Thermal Infrared Ground Emission Radiometer (TIGER) with Anne Kahle as PI. TIGER had 2 components: TIMS (14 channels in the 3 - 5 µ & 8 - 15 µ regions) & Thermal Infrared Profiling System (TIPS).
• Around the same time, Japan's MITI (Ministry of International Trade & Industry) offered to provide the Intermediate Thermal Infrared Radiometer (ITIR) which measured radiances in 11 bands in NIR, SWIR, & TIR regions. NASA accepted this design & asked the TIGER team to implement TIGER's design advances by influencing the Japanese design of ITIR. ITIR was later re-designed to include 14 channels in the Visible Near Infra-Red, ShortWave Infra-Red, and Thermal Infra-Red regions, and renamed ASTER (JPL, 1994).

Organizational Framework of ASTER

There are a number of entities, both in the US and Japan, which are involved in the development and production of ASTER data and data products. These include for instance, the satellite sensor systems and its operations, data reception, processing, management, and data product development, quality assurance, distribution, archival, and storage. The following Table outlines these entities.

Organizational Framework of ASTER

ASTER Sensor Systems: Baseline Performance Requirements

Subsystem	Band No.	Spectral Range (µm)	Radiometric Resolution	Absolute Accuracy ()	Spatial Resolution	Signal Quantization Levels
VNIR	1 2 3N 3B	0.52 - 0.60 0.63 - 0.69 0.78 - 0.86 0.78 - 0.86			15 m	8 bits
SWIR	4 5 6 7 8 9	1.600 - 1.700 2.145 - 2.185 2.185 - 2.225 2.235 - 2.285 2.295 - 2.365 2.360 - 2.430			30 m	8 bits
TIR	10 11 12 13 14	8.125 - 8.475 8.475 - 8.825 8.925 - 9.275 10.25 - 10.95 10.95 - 11.65			90 m	12 bits

ASTER System Baseline Performance Requirements

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