NASA ASTER L1B Data Dictionary

 

Acquisition Date

 

• Field Definition:  The year, month and day the image was acquired.

               Format:

               YYYY/MM/DD

 

Acquisition Time

• Field Definition:  The time of day or night the image was acquired.

               Example:

               16:28:23.443

               Valid Format: HH:MM:SS:TTT

               HH - hours (00-23)

               MM - minutes (00-59)

               SS - second (00-59)

               TTT - fractional seconds

 

Band Availability (1-14)

• Field Definition:  The Level-1B product offers the same number of bands at the same resolution as the Level-1A product. Level-1B data are required as the input for generating higher level-2 geophysical products. Bands are incorporated in each mode as follows:
  
  
  
  Values:

 

Coordinates - Decimal Degrees

• Field Definition:  The latitude and longitude are provided in decimal degrees for the following fields:

                 Values:      

                 Scene Center Latitude and Longitude

                 Northeast (NE) Corner Latitude and Longitude

                 Northwest (NW) Corner Latitude and Longitude

                 Southeast (SE) Corner Latitude and Longitude

                 Southwest (SW) Corner Latitude and Longitude

                 Latitude Format Decimal Degrees: -90.000 through 90.000

                 Longitude Format Decimal Degrees: -180.000 through 180.000

                 Number of decimal places will vary by dataset – check collection in EE.

 

Coordinates - Degrees, Minutes, Seconds

• Field Definition:  The latitude and longitude are provided in degrees, minutes, and seconds for the following fields:

                 Values:

                 Scene Center Latitude and Longitude

                 Northeast (NE) Corner Latitude and Longitude

                 Northwest (NW) Corner Latitude and Longitude

                 Southeast (SE) Corner Latitude and Longitude

                 Southwest (SW) Corner Latitude and Longitude

                Longitude Format:

                DDDMMSS.SSH

                DDD = Degree(s) with a range of 0 through 180

                MM = Minute(s) with a range of 0 through 59

                SS.SS = Second(s) with a range of 0 through 59.99

                H = Hemisphere with E for east and W for west

                Latitude Format:

                DDMMSS.SSH

                DD = Degree(s) with a range of 0 through 90

                MM = Minutes(s) with a range of 0 through 59

                SS.SS = Second(s) with a range of 0 through 59.99

                H = Hemisphere with N for north and S for south

 

Date Entered

• Field Definition:  Reference image capture date.
  
   

Date Updated

• Field Definition:  The Date of Update refers to the date the inventory record was added to the inventory, or the date the record was last updated.
  
   

Day/Night

• Field Definition:  Indicates when image was captured as follows

              Values:

              Day = Images acquired during the day

              Night = Images acquired during the night

              Both = Images acquired day/night

              ALL = Images acquired at any time

 

Entity ID

• Field Definition:  Unique identification for this product.

               Example:

               1085259

 

Full Scene Cloud Cover

• Field Definition:  Full Scene Cloud Cover is the percentage of a scene that is obscured by clouds and is the average of all four quadrant cloud cover values.

               Values:

               0 - 100

 

Lower Left Quadrant Cloud Cover

• Field Definition:  Indicates the percent of cloud cover in the lower left quadrant of the scene. Users are encouraged to preview browses prior to ordering data products to confirm acceptable cloud cover impacts.

              Values:

              0 - 100

 

Lower Right Quadrant Cloud Cover

• Field Definition:  Indicates the percent of cloud cover in the lower right quadrant of the scene. Users are encouraged to preview browses prior to ordering data products to confirm acceptable cloud cover impacts.
  
   

Orbit Direction

• Field Definition:  The code used to indicate the satellite's orbital direction that applied when this data was acquired.

               Values:

               D = Descending

               A = Ascending

 

Processing Level

• Field Definition:  These are the product descriptions for the various formats of ASTER Level 1B data. They are also referred to as the "short name".

              Values:

              Processing Levels:

              AST L1B = Registered Radiance at the Sensor: The ASTER Level-1B Registered Radiance at the Sensor product contains radiometrically calibrated and geometrically co-registered data for the acquired channels of the three different telescopes of level-1A data.

              AST L1BE = Routine Registered Radiance at the Sensor - Expedited: The ASTER Expedited L1B Registered Radiance at the Sensor data set is produced with the express purpose of providing the ASTER Science Team members data of their particular interest in quick turn-around time from the moment the data are acquired.

 

Sun Azimuth

• Field Definition:  Sun azimuth angle (degrees) at the WRS scene c enter. A positive value (+) indicates angles to the East or clockwise from North. Zero indicates North. A negative value (-) indicates angles to the West or counterclockwise from North.

              Values:

              -180.0000000 through +180.0000000 degrees

 

Sun Elevation

• Field Definition:  Sun elevation angle (degrees) at the WRS scene center. A positive value (+) indicates a daytime scene. Zero indicates a night time scene. A negative value (-) indicates a nighttime scene.

              Values:

              - 90.0000000 through + 90.0000000 degrees

 

SWIR Mode

• Field Definition:  The Short Wave Infrared Radiometer (SWIR) is an advanced high resolution multispectral radiometer which detects reflected solar radiation from the earth surface in the wavelength region of 1.6 - 2.43 um. SWIR also has the capability to change the boresight in the cross-track direction by +/-8.55 degrees from nadir, by using a pointing mechanism.
  
   

TIR Mode

• Field Definition:  The Thermal Infrared Radiometer (TIR) s an advanced spaceborne radiometer with five spectral bands in the thermal infrared (8-12 um). Its ability to measure thermal emission properties is useful for locating mineral resources, characterizing the land and sea surface and observing the atmosphere.
  
   

TIR P Angle

• Field Definition:  The Thermal Infrared Radiometer (TIR) P Angle refers to the "pointing" angle of the TIR subsystem. The scanning mirror functions both for scanning and cross-track pointing (to +/- 8.55 degrees). In the scanning mode, the mirror oscillates at about 7 Hz and, during oscillation, data are collected in one direction only. During calibration, the scanning mirror rotates 90 degrees from the nadir position to view an internal black body. Because of the instrument's high data rate, restrictions have been imposed so that the average data rate is manageable by the spacecraft data management system. This restriction is a one-orbit maximum average rate of 16.6 Mbps and a two-orbit maximum average rate of 8.3 Mbps, which results in approximately a 9.3% duty cycle.
  
   

Upper Left Quadrant Cloud Cover

• Field Definition:  Indicates the percent of cloud cover in the upper left quadrant of the scene.

              Values:

              0 - 100

 

Upper Right Quadrant Cloud Cover

• Field Definition:  Indicates the percent of cloud cover in the lower right quadrant of the scene.

               Values:

               0 - 100

 

VNIR1 Mode

• Field Definition:  This VNIR subsystem backward looking telescope is of the same design as the nadir telescope and contains only a single silicon charge coupled detector line array and no calibration lamps as it is only used to acquire a stereo pair image.
  
   

VNIR2 Mode

• Field Definition:  This VNIR subsystem nadir looking telescope is a reflecting-refracting improved Schmidt design. The focal plane of this telescope contains three 5000 silicon charge coupled detector line arrays.
  
   

VNIR P Angle

• Field Definition:  The Visible and Near-Infrared Radiometer (VNIR) P Angle refer s to the "pointing" angle of the VNIR subsystem. The nadir and backward looking telescope pair are used for same orbit stereo imaging and can be rotated as a unit +/- 24 degrees to provide extensive cross-track pointing capability. Light from either of two halogen lamps are used periodically for subsystem calibration.
  
   

VNIR Skew Amount

• Field Definition:  This VNIR subsystem skew amount refers to the degrees off nadir. The system signal-to-noise is controlled by specifying the NE delta rho to be < 0.5% referenced to a diffuse target with a 70% albedo at the equator during equinox. The absolute radiometric accuracy is to be + 4% or better.
  
   

VNIR Skew Angle

• Field Definition:  VNIR high-resolution radiometer observes targets using solar radiation reflected from the earth surface in three visible and near-infrared bands. With all four bands operating (3 nadir and 1 backward) the data rate including image data, supplemental information and subsystem engineering data is 62 Mbps.
  
   

WRS Path

• Field Definition:  WRS - defined nominal Landsat satellite track (path).

               Values:

               001 - 251

 

WRS Row

• Field Definition:  WRS latitudinal center line of a Landsat image.

               Values:

               001-059 = Northern Hemisphere (Descending)

               060 = Equator (Descending)

               061-119 = Southern Hemisphere (Descending)

               120-122 = Southern Polar Zone (Descending)

               123-183 = Southern Hemisphere (Ascending)

               184 = Equator (Ascending)

               185-246 = Northern Hemisphere (Ascending)

               247-248 = Northern Polar Zone (Descending)