The first Earth Observing System (EOS) satellite called Terra (previously AM-1) was launched on December 18, 1999. Terra flys 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 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.
Subsystem: VNIR | |||||
---|---|---|---|---|---|
Band No. |
Spectral Range |
Radiometric Resolution |
Absolute Accuracy |
Spatial Resolution |
Signal Quantization Levels |
1 2 3N 3B |
0.52–0.60 0.63–0.69 0.78–0.86 0.78–0.86 |
NEΔρ 0.5% NEΔρ 0.5% NEΔρ 0.5% NEΔρ 0.5% |
≤±4% ≤±4% ≤±4% ≤±4% |
15 m 15 m 15 m 15 m |
8 bits 8 bits 8 bits 8 bits |
Subsystem: SWIR | |||||
Band No. |
Spectral Range |
Radiometric Resolution |
Absolute Accuracy |
Spatial Resolution |
Signal Quantization Levels |
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 |
NEΔρ≤ 0.5% NEΔρ≤ 1.3% NEΔρ≤ 1.3% NEΔρ≤ 1.3% NEΔρ≤ 1.0% NEΔρ≤ 1.3% |
≤±4% ≤±4% ≤±4% ≤±4% ≤±4% ≤±4% |
30 m 30 m 30 m 30 m 30 m 30 m |
8 bits 8 bits 8 bits 8 bits 8 bits 8 bits |
Subsystem: TIR | |||||
Band No. |
Spectral Range |
Radiometric Resolution |
Absolute Accuracy |
Spatial Resolution |
Signal Quantization Levels |
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 |
NEΔΤ≤ 0.3% NEΔΤ≤ 0.3% NEΔΤ≤ 0.3% NEΔΤ≤ 0.3% NEΔΤ≤ 0.3% |
-- ≤3K (200–240K) ≤2K (240–270K) ≤1K (270–340) ≤2K (340–370) |
90 m 90 m 90 m 90 m 90 m |
12 bits 12 bits 12 bits 12 bits 12 bits |
Swath Width |
60 Kms |
---|---|
Total Cross-Track Coverage |
±116 to ±318 Kms |
Stereo Base-to-Height Ratio |
0.6 (along-track) |
Modulation Transfer Frequency |
0.25 (cross-track 0.20 (along-track) |
Band-to-Band Registration |
0.2 pixels (intra-telescope) 0.3 pixels (inter-telescope) |
Duty Cycle |
8% (VNIR & SWIR) 16% (TIR) |
Peak Data Rate |
89.2 Mbps |
Mass |
406 Kgs |
Peak Power |
726 W |
The ASTER Level-1 data are swath-based HDF-EOS products. The Level-1B data set provides scaled or calibrated radiance values, and is the input for most of the higher-level products. The data are contained in separate Vgroups for each of the three sensor systems. Refer to the following link, which describes the structure of an ASTER Level-1B HDF-EOS file:
The ASTER Level-1 data have two sources of metadata: the embedded HDF metadata, and the external ECS metadata. There are similarities and differences between them. For georeferencing purposes, we generally recommend using the values delineated in the embedded HDF metadata. Other product-specific and core metadata can be referred from either source.
The HDF metadata file is the information that is embedded within the header of the Level-1 HDF file. The embedded HDF metadata are written in ODL (Object Description Language), an ASCII-based Òparameter = valueÓ format, and contains a number of attributes relating to the Level-1 data set. The HDF metadata file broadly contains eight attribute groups with a number of specific attributes in each of them. These groups are listed below:
Refer to the ASTER User Handbook for details on the individual attributes contained in each of the above attribute groups.
The ECS (generated by the EOSDIS Core System) metadata file is the external .met file, which is delivered to the user along with the Level-1 data set. It contains a number of attributes relating to the Level-1 data set. The .met file provides a subset of the HDF metadata. It contains three broad groups of information:
The ASTER higher level products are also packaged similarly with embedded HDF metadata, and external ECS metadata. As an additional source of some valuable metadata, a set of attributes and their values are appended (product summary) at the end of the embedded metadata for all the higher-level products except the ASTER DEM.