ASTER Overview


Introduction

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five state-of-the-art instrument sensor systems operating on the Terra spacecraft. The Terra satellite was launched on December 18, 1999. Terra flies in a sun-synchronous polar orbit, crossing the equator at 10:30 a.m. Eastern Standard Time (EST).

ASTER utilizes 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 is a partnership between NASA, Japan's Ministry of Economy, Trade and Industry (METI), the National Institute of Advanced Industrial Science and Technology (AIST) in Japan, and Japan Space Systems (J-spacesystems).

ASTER data contributes to a wide array of global change-related application areas including vegetation and ecosystem dynamics, hazard monitoring, geology and soils, hydrology, and land cover change.

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ASTER Naming Conventions

ASTER Filenames

ASTER filenames (i.e., the local granule ID) follow a naming convention which provides useful information regarding the specific product.

In this example, the filename AST_L1T_00309122019230211_20190913112425_15725 indicates:

  • AST_L1T – Product Short Name
  • 003 – Collection Version
  • 09122019 – Calendar Date of Acquisition (MMDDYYYY)
  • 230211 – Hours, Minutes, and Seconds of Acquisition (HHMMSS)
  • 20190913 – Calendar Date of Processing (YYYYMMDD)
  • 112425 – Hours, Minutes, and Seconds of Processing (HHMMSS)
  • 15725 – Unique Acquisition Identifier

ASTER Product Long Name

The ASTER Product Long Name (i.e. Collection-Level) convention provides useful information regarding the product.

In this example, ASTER L1B Registered Radiance at the Sensor V003:

  • ASTER: Instrument/Sensor
  • L1B: Processing Level
  • Registered Radiance at the Sensor: Geophysical Parameter
  • V003: Collection or Version
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ASTER Temporal and Spatial Resolution

ASTER Temporal Resolution

The ASTER products distributed from LP DAAC are produced from on-demand data acquisition requests and are not categorized by regular temporal ranges.

ASTER Spatial Resolution

The ASTER instruments acquire data in three native spatial resolutions:

  • VNIR (Visible and Near-Infrared) Bands 1, 2, 3N, 3B1: 15 meter
  • SWIR (Shortwave Infrared) Bands 4–9: 30 meter
  • TIR (Thermal Infrared) Bands 10–14: 90 meter

1Band 3 nadir (3N) and band 3 backward-looking (3B) allows capability of creating a Digital Elevation Model when both bands are acquired.

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ASTER Processing Levels

LP DAAC distributes ASTER land data processed to Level 1 through 3:

  • Level-1A: Reconstructed, unprocessed instrument data at full resolution, time-referenced, and annotated with ancillary information, including radiometric and geometric calibration coefficients and georeferencing parameters (e.g., platform ephemeris) computed and appended but not applied to Level 0 data.
  • Level-1B: Level-1A data that have been processed to sensor units (not all instruments have Level 1B source data).
  • Level-2: Derived geophysical variables at the same resolution and location as Level-1 source data (swath products).
  • Level-3: Variables mapped on uniform space-time grid scales, usually with some completeness and consistency.
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ASTER Metadata

The ASTER products have two sources of metadata: the embedded Hierarchical Data Format (HDF) metadata, and the external Earth Observing System Data and Information System (EOSDIS) metadata, otherwise known as the EOSDIS Core System (ECS) metadata. The generated ECS .met file is the external metadata file in XML format that is delivered to the user along with the ASTER product. For georeferencing purposes, use the values delineated in the embedded HDF metadata. Other product-specific and core metadata can be referred from either source.

Refer to the ASTER User Handbook for L1B products and the User Guide for higher level products regarding details on the individual core and product metadata attributes.

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ASTER Tools and Services

Data access options such as Data Pool, Earthdata Search Client, and EarthExplorer can be found under Tools.

An HDF-EOS file contains information essential for NASA data access tools and services. Most software programs that can process standard HDF files can read an HDF-EOS file. However, it is difficult for a standard HDF call to interpret HDF-EOS geolocation or temporal information without further knowledge of the file structure.

Certain open source tools and proprietary tools are available for use with ASTER HDF-EOS products:

Open Source Tools

Proprietary Tools

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