Center for Earth Observation

...supporting the remote sensing needs of the University

ASTER

ASTER at Earthdata Search

The NASA Earthdata Search application provides an easy way to find ASTER scenes.  In the future you will also be able to order ASTER products from this site.  Begin by navigating to the Earthdata Search application and click on the Spatial button and select the tool you wish to use to define your area of interest; this can be a rectangle, point, polygon or file.  Once you have defined your spatial location, enter ASTER L1T into the search bo

Image Rotation

ASTER L1B full scenes and ASTER products (as of this writing) are delivered oriented along the satellite path. While these data are georeferenced, they are NOT oriented with north at the top of the image.  These data should be rotated into a map orientation with north being at the top of the image.  This step is NOT necessary for ASTER L1T full scenes. 

How to convert ASTER TIR to Brightness Temperature in Degrees Kelvin

ENVI has a multi-step process that can perform basic atmospheric correction then convert the resulting emissivity bands to a brightness-temperature image in degrees Kelvin.  When ENVI reads an ASTER AST_L1B scene it calibrates the TIR bands to proper radiance values.  If you are working with one of these datasets proceed to Step 2.  For the newer ASTER AST_L1T datasets ENVI opens these with “byte values” which must first be converted to floating-point radiance values as shown in Step 1.

How to convert ASTER VNIR Radiance to Reflectance

ENVI automatically applies the proper calibration coefficients to convert the integer digital numbers to floating-point radiance values when opening a Level 1B or 1T dataset.  You can easily convert these values to Top-Of-Atmosphere Reflectance in ENVI.  From the Toolbox select Radiometric Correction | Radiometric Calibration and select the three-band VNIR file.  Change the Calibration Type to Reflectance, enter a new filename, and click OK.

Opening ASTER files with ENVI

The following instructions describe how to open ASTER data using the ENVI 5.x Standard interface.  You can perform the same steps in ENVI Classic under the Basic Tools menu.  ASTER data sets and products are distributed in the hierarchical data format (HDF).  Use the following method to properly open and calibrate these data in ENVI. 

ASTER at GloVis

GloVis is the USGS Global Visualization Viewer site that is a primary source of data from many sensors.  This FAQ only covers ASTER data.  Connect to the site at:  http://glovis.usgs.gov/.  This will use Java to open a data visualization window (it may be behind your current browser window).  Note: You must be a registered user to place orders within GLOVIS.

What is ASTER?

The ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) sensor is an imaging instrument flown on the Terra satellite which was launched in December 1999.  ASTER has been designed to acquire land surface temperature, emisivity, reflectance, and elevation data and is a cooperative effort between NASA and the Japanese Ministry of Economy, Trade, and Industry (METI).  As of April 1, 2016 these date are being distributed free of charge. 

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