Advanced Spaceborne Thermal Emission and Reflection Radiometer

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is a Japanese remote sensing instrument onboard the Terra satellite launched by NASA in 1999. It has been collecting data since February 2000.

ASTER image of Rub' al Khali (Arabia's Empty Quarter)

ASTER image draped over terrain model of Mount Etna

ASTER provides high-resolution images of Earth in 14 different bands of the electromagnetic spectrum, ranging from visible to thermal infrared light. The resolution of images ranges between 15 and 90 meters. ASTER data is used to create detailed maps of surface temperature of land, emissivity, reflectance, and elevation.[1]

In April 2008, the SWIR detectors of ASTER began malfunctioning and were publicly declared non-operational by NASA in January 2009. All SWIR data collected after 1 April 2008 has been marked as unusable.[2]

The ASTER Global Digital Elevation Model (GDEM) is available at no charge to users worldwide via electronic download.[3]

As of 2 April 2016, the entire catalogue of ASTER image data became publicly available online at no cost.[4] It can be downloaded with a free registered account from either NASA's Earth Data Search delivery system[5] or from the USGS Earth Explorer delivery system.[6]


ASTER bands
ASTER false-colour satellite image of 2010 eruption of Mount Merapi, showing evidence of a large pyroclastic flow along the Gendol River south of Mount Merapi
Band Label Wavelength
(µm)		 Resolution
(m)		 Nadir or
Backward		 Description
B1 VNIR_Band1 0.520 - 0.60 15 Nadir Visible green/yellow
B2 VNIR_Band2 0.630 - 0.690 15 Nadir Visible red
B3N VNIR_Band3N 0.760–0.860 15 Nadir Near infrared
B3B VNIR_Band3B 0.760–0.860 15 Backward
B4 SWIR_Band4 1.600–1.700 30 Nadir Short-wave infrared
B5 SWIR_Band5 2.145–2.185 30 Nadir
B6 SWIR_Band6 2.185–2.225 30 Nadir
B7 SWIR_Band7 2.235–2.285 30 Nadir
B8 SWIR_Band8 2.295–2.365 30 Nadir
B9 SWIR_Band9 2.360–2.430 30 Nadir
B10 TIR_Band10 8.125–8.475 90 Nadir Long-wave infrared
or thermal IR
B11 TIR_Band11 8.475–8.825 90 Nadir
B12 TIR_Band12 8.925–9.275 90 Nadir
B13 TIR_Band13 10.250–10.950 90 Nadir
B14 TIR_Band14 10.950–11.650 90 Nadir

[7]

ASTER Global Digital Elevation Model
SRTM3 vs. ASTER1 comparison (Île d'Yeu), inaccuracies and errors of the latter are indicated by arrows

Version 1

On 29 June 2009, the Global Digital Elevation Model (GDEM) was released to the public.[8][9] A joint operation between NASA and Japan's Ministry of Economy, Trade and Industry (METI), the Global Digital Elevation Model is the most complete mapping of the earth ever made, covering 99% of its surface.[10] The previous most comprehensive map, NASA's Shuttle Radar Topography Mission, covered approximately 80% of the Earth's surface,[11] with a global resolution of 90 meters,[12] and a resolution of 30 meters over the USA. The GDEM covers the planet from 83 degrees North to 83 degrees South (surpassing SRTM's coverage of 56 °S to 60 °N), becoming the first earth mapping system that provides comprehensive coverage of the polar regions.[11] It was created by compiling 1.3 million VNIR images taken by ASTER using single-pass[13] stereoscopic correlation techniques,[8] with terrain elevation measurements taken globally at 30-meter (98 ft) intervals.[10]

Despite the high nominal resolution, however, some reviewers have commented that the true resolution is considerably lower, and not as good as that of SRTM data, and serious artifacts are present.[14][15]

Some of these limitations have been confirmed by METI and NASA, who point out that the version 1 of the GDEM product is "research grade".[16]

Version 2
STL 3D model of Penang Island terrain based on ASTER Global DEMv2 data

During October 2011, version 2 of Global Digital Elevation Model was publicly released.[17] This is considered an improvement upon version 1. These improvements include increased horizontal and vertical accuracy,[18] better horizontal resolution, reduced presence of artifacts, and more realistic values over water bodies.[3] However, one reviewer still regards the Aster version 2 dataset, although showing 'a considerable improvement in the effective level of detail', to still be regarded as 'experimental or research grade' due to presence of artefacts.[19] A 2014 study[18] showed that over rugged mountainous terrain the ASTER version 2 data set can be a more accurate representation of the ground than the SRTM elevation model.

Version 3

ASTER v3 was released on August 5, 2019.[20]

The improved GDEM V3 adds additional stereo-pairs, improving coverage and reducing the occurrence of artifacts. The refined production algorithm provides improved spatial resolution, increased horizontal and vertical accuracy. The ASTER GDEM V3 maintains the GeoTIFF format and the same gridding and tile structure as V1 and V2, with 30-meter postings and 1 x 1 degree tiles. Version 3 is claimed to have significant improvements over the previous release. Automated processing of 2.3 million scenes from the ASTER archive was used to create the ASTER GDEM, which included stereo-correlation to create individual scene-based ASTER DEMs, masking to remove cloudy pixels, stacking all cloud-screened DEMs, removing residual bad values and outliers, averaging selected data to create final pixel values.

References
  1. Wigglesworth, Alex (6 November 2019). "Satellite image shows Kincade fire burn scar". Los Angeles Times. Retrieved 7 November 2019.
  2. "LP DAAC - ASTER User Advisory (updated: January 14, 2009)".
  3. "METI and NASA Release Version 2 ASTER Global DEM". U.S. Geological Survey / NASA LP DAAC. Archived from the original on 21 December 2013. Retrieved 21 December 2013.
  4. "NASA, Japan Make ASTER Earth Data Available At No Cost | NASA". 31 March 2016.
  5. "Earthdata Search".
  6. "EarthExplorer".
  7. "Characteristics".
  8. "ASTER Global Digital Elevation Map". NASA. 29 June 2009. Archived from the original on 3 July 2009. Retrieved 30 June 2009.
  9. "ASTER Imagery". NASA. 29 June 2009. Retrieved 30 June 2009.
  10. "Most complete earth map published". BBC News. 30 June 2009. Retrieved 1 July 2009.
  11. "NASA, Japan publish detailed map of Earth". Canada.com. 30 June 2009. Archived from the original on 4 July 2009. Retrieved 1 July 2009.
  12. "What is ASTER?". Archived from the original on 27 April 2009. Retrieved 1 July 2009.
  13. Nikolakopoulos, K. G.; Kamaratakis, E. K; Chrysoulakis, N. (10 November 2006). "SRTM vs ASTER elevation products. Comparison for two regions in Crete, Greece" (PDF). International Journal of Remote Sensing. 27 (21): 4819–4838. Bibcode:2006IJRS...27.4819N. doi:10.1080/01431160600835853. ISSN 0143-1161. S2CID 1939968. Archived from the original (PDF) on 21 July 2011. Retrieved 1 July 2009.
  14. "Virtual Earth Products Reviews". Archived from the original on 31 May 2009. Retrieved 1 July 2009.
  15. Hirt, C.; Filmer, M.S.; Featherstone, W.E. (2010). "Comparison and validation of recent freely-available ASTER-GDEM ver1, SRTM ver4.1 and GEODATA DEM-9S ver3 digital elevation models over Australia". Australian Journal of Earth Sciences. 57 (3): 337–347. Bibcode:2010AuJES..57..337H. doi:10.1080/08120091003677553. hdl:20.500.11937/43846. S2CID 140651372. Retrieved 5 May 2012.
  16. "METI and NASA Release ASTER Global DEM". Archived from the original on 29 May 2009. Retrieved 1 July 2009.
  17. "Release of ASTER GDEM Version 2". Archived from the original on 29 May 2009.
  18. Rexer, M.; Hirt, C. (2014). "Comparison of free high-resolution digital elevation data sets (ASTER GDEM2, SRTM v2.1/v4.1) and validation against accurate heights from the Australian National Gravity Database" (PDF). Australian Journal of Earth Sciences. 61 (2): 213. Bibcode:2014AuJES..61..213R. doi:10.1080/08120099.2014.884983. hdl:20.500.11937/38264. S2CID 3783826. Archived from the original (PDF) on 7 June 2016. Retrieved 24 April 2014.
  19. de Ferranti, Jonathan. "ASTER Digital Elevation Data". Viewfinder Panoramas, UK. Retrieved 21 December 2013.
  20. "ASTER Global Digital Elevation Map".
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