View source for Advanced Spaceborne Thermal Emission and Reflection Radiometer

{{short description|Japanese imaging device aboard NASA's Terra satellite}}
{{Use dmy dates|date=February 2025}}
[[Image:Etna TAS2002209.jpg|thumb|right|230px|ASTER image draped over terrain model of [[Mount Etna]]]]
The '''Advanced Spaceborne Thermal Emission and Reflection Radiometer''' ('''ASTER''') is a Japanese [[remote sensing]] instrument onboard the [[Terra (satellite)|Terra satellite]] launched by [[NASA]] in 1999. It has been collecting data since February 2000.

[[Image:Rub' al Khali (Arabian Empty Quarter) sand dunes imaged by Terra (EOS AM-1).jpg|thumb|ASTER image of [[Rub' al Khali]] (Arabia's Empty Quarter)]]

ASTER provides high-resolution images of Earth in 14 different [[spectral bands|band]]s of the [[electromagnetic spectrum]], ranging from [[visible light|visible]] to thermal [[infrared]] light. The [[Angular resolution|resolution]] of images ranges between 15 and 90 meters. ASTER data is used to create detailed [[Satellite temperature measurements|maps of surface temperature]] of land, [[emissivity]], [[reflectance]], and elevation.<ref name="LAT 019-11-05">{{Cite news|url=https://www.latimes.com/california/story/2019-11-05/kincade-fire-burn-scar-satellite-image|title=Satellite image shows Kincade fire burn scar|last=Wigglesworth|first=Alex|date=2019-11-06|newspaper=[[Los Angeles Times]]|language=en-US|access-date=2019-11-07}}</ref>

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.<ref>{{cite web| url = https://lpdaac.usgs.gov/news/aster-user-advisory-updated-january-14-2009/| title = LP DAAC - ASTER User Advisory (updated: January 14, 2009)}}</ref>

The ASTER Global [[Digital Elevation Model]] (GDEM) is available at no charge to users worldwide via electronic download.<ref name="lpdaac.usgs.gov">{{cite web|title=METI and NASA Release Version 2 ASTER Global DEM|url=https://lpdaac.usgs.gov/about/news_archive/meti_and_nasa_release_version_2_aster_global_dem|publisher=U.S. Geological Survey / NASA LP DAAC|access-date=21 December 2013|archive-url=https://web.archive.org/web/20131221042244/https://lpdaac.usgs.gov/about/news_archive/meti_and_nasa_release_version_2_aster_global_dem|archive-date=21 December 2013|url-status=dead}}</ref>

As of 2 April 2016, the entire catalogue of ASTER image data became publicly available online at no cost.<ref>{{cite web| url = https://www.nasa.gov/feature/jpl/nasa-japan-make-aster-earth-data-available-at-no-cost| title = NASA, Japan Make ASTER Earth Data Available At No Cost {{!}} NASA| date = 31 March 2016}} </ref> It can be downloaded with a free registered account from either NASA's Earth Data Search delivery system<ref>{{cite web| url = https://search.earthdata.nasa.gov/search| title = Earthdata Search}}</ref> or from the [[USGS]] Earth Explorer delivery system.<ref>{{cite web| url = https://earthexplorer.usgs.gov/| title = EarthExplorer}}</ref>

==ASTER bands==
[[File:2010 Eruption at Mount Merapi, Indonesia (ASTER).jpg|thumb|ASTER false-colour satellite image of [[2010 eruptions of Mount Merapi|2010 eruption of Mount Merapi]], showing evidence of a large [[pyroclastic flow]] along the [[Gendol River]] south of Mount Merapi]]
{|class="wikitable"
|-
!|Band
!|Label
!|[[Electromagnetic radiation|Wavelength]]<br />([[Micrometre|μm]])
!|[[Image resolution|Resolution]]<br />(m)
!|[[Nadir]] or<br />backward
!|Description
|-
||B1
||[[VNIR]]_Band1
||0.520 - 0.60
||15
||Nadir
|align="center"|Visible green/yellow
|-
||B2
||VNIR_Band2
||0.630 - 0.690
||15
||Nadir
|align="center"|Visible red
|-
||B3N
||VNIR_Band3N
||0.760–0.860
||15
||Nadir
|align="center" rowspan="2"|Near infrared
|-
||B3B
||VNIR_Band3B
||0.760–0.860
||15
||Backward
|-
|colspan="6"|
|-
||B4
||SWIR_Band4
||1.600–1.700
||30
||Nadir
|rowspan="6" align="center"|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
|-
|colspan="6"|
|-
||B10
||TIR_Band10
||8.125–8.475
||90
||Nadir
|rowspan="5" align="center"|Long-wave infrared<br />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
|-
|}<ref>{{cite web| url = https://asterweb.jpl.nasa.gov/characteristics.asp| title = Characteristics}}</ref>

==ASTER Global Digital Elevation Model==
[[File:Comparison SRTM3 vs ASTER.jpg|thumbnail|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.<ref name=ASTER>{{cite web |title=ASTER Global Digital Elevation Map |publisher=[[NASA]] |date=29 June 2009 |url=http://asterweb.jpl.nasa.gov/gdem.asp |access-date=2009-06-30 |archive-url=https://web.archive.org/web/20090703003436/http://asterweb.jpl.nasa.gov/gdem.asp |archive-date=3 July 2009 |url-status=dead |df=dmy-all }}</ref><ref>{{cite web |title=ASTER Imagery |publisher=[[NASA]] |date=29 June 2009 |url=http://www.nasa.gov/topics/earth/features/20090629.html |access-date=2009-06-30}}</ref>
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.<ref name=BBC>{{cite web |title=Most complete earth map published |work=[[BBC News]] |date=30 June 2009 |url=http://news.bbc.co.uk/1/hi/sci/tech/8126197.stm |access-date=2009-07-01}}</ref>
The previous most comprehensive map, NASA's [[Shuttle Radar Topography Mission]], covered approximately 80% of the Earth's surface,<ref name=Canada>{{cite web |title=NASA, Japan publish detailed map of Earth |publisher=[[Canada.com]] |date=30 June 2009 |url=http://www.canada.com/Technology/NASA+Japan+publish+detailed+Earth/1747699/story.html |access-date=2009-07-01 |archive-url=https://web.archive.org/web/20090704010544/http://www.canada.com/technology/NASA+Japan+publish+detailed+Earth/1747699/story.html |archive-date=4 July 2009 |url-status=dead |df=dmy-all }}</ref> with a global resolution of 90 meters,<ref name='ersdac compare'>{{cite web |url=http://www.ersdac.or.jp/GDEM/E/2.html |title=What is ASTER? |access-date=2009-07-01 |url-status=dead |archive-url=https://web.archive.org/web/20090427215109/http://www.ersdac.or.jp/GDEM/E/2.html |archive-date=27 April 2009 |df=dmy-all }}</ref> and a resolution of 30 meters over the US.
The GDEM covers the planet from 83 degrees North to 83 degrees South (surpassing [[SRTM]]'s coverage of 56&nbsp;°S to 60&nbsp;°N), becoming the first earth mapping system that provides comprehensive coverage of the polar regions.<ref name=Canada/> It was created by compiling 1.3&nbsp;million [[VNIR]] images taken by ASTER using single-pass<ref>{{cite journal|last1=Nikolakopoulos |first1=K. G. |last2=Kamaratakis |first2=E. K |last3=Chrysoulakis |first3=N. |date=10 November 2006 |title=SRTM vs ASTER elevation products. Comparison for two regions in Crete, Greece |journal=International Journal of Remote Sensing |volume=27 |issue=21 |pages=4819–4838 |issn=0143-1161 |url=http://www.iacm.forth.gr/_docs/pubs/4/Nikolakopoulos_et_al_2006.pdf |access-date=1 July 2009 |doi=10.1080/01431160600835853 |bibcode=2006IJRS...27.4819N |s2cid=1939968 |url-status=dead |archive-url=https://web.archive.org/web/20110721081314/http://www.iacm.forth.gr/_docs/pubs/4/Nikolakopoulos_et_al_2006.pdf |archive-date=21 July 2011 }}</ref> [[stereoscopic]] [[digital image correlation|correlation]] techniques,<ref name=ASTER/> with terrain elevation measurements taken globally at 30-meter (98&nbsp;ft) intervals.<ref name=BBC/>

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.<ref>{{cite web|url=http://www.viewfinderpanoramas.org/reviews.html#aster|title=Virtual Earth Products Reviews|access-date=2009-07-01| archive-url= https://web.archive.org/web/20090531011246/http://www.viewfinderpanoramas.org/reviews.html| archive-date= 31 May 2009 | url-status= live}}</ref><ref>{{cite journal|last1=Hirt|first1=C.|last2=Filmer|first2=M.S. |last3=Featherstone|first3=W.E.|date=2010|title=Comparison and validation of recent freely-available ASTER-GDEM ver1, SRTM ver4.1 and GEODATA DEM-9S ver3 digital elevation models over Australia.|journal=Australian Journal of Earth Sciences|volume=57|issue=3|pages=337–347|url=http://espace.library.curtin.edu.au:80/R?func=dbin-jump-full&local_base=gen01-era02&object_id=137777|access-date=5 May 2012|bibcode = 2010AuJES..57..337H |doi = 10.1080/08120091003677553 |hdl=20.500.11937/43846|s2cid=140651372|hdl-access=free}}</ref>

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".<ref>{{cite web|url=http://www.ersdac.or.jp/GDEM/E/4.html|title=METI and NASA Release ASTER Global DEM|access-date=2009-07-01|archive-url=https://web.archive.org/web/20090529050255/http://www.ersdac.or.jp/GDEM/E/4.html|archive-date=29 May 2009|url-status=dead}}</ref>

===Version 2===
{{expand section|date=October 2011}}
[[File:Penang island.stl|thumb|[[STL (file format)|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.<ref>{{cite web|url=http://www.ersdac.or.jp/GDEM/E/4.html|title=Release of ASTER GDEM Version 2|url-status=dead|archive-url=https://web.archive.org/web/20090529050255/http://www.ersdac.or.jp/GDEM/E/4.html|archive-date=29 May 2009}}</ref> This is considered an improvement upon version 1. These improvements include increased horizontal and vertical accuracy,<ref name="geodesy.curtin.edu.au">{{cite journal|last1=Rexer|first1=M.|last2=Hirt|first2=C.|date=2014|title=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|journal=Australian Journal of Earth Sciences|volume=61|issue=2|pages=213|url=http://geodesy.curtin.edu.au/local/docs/Rexer_Hirt_2014_DEM_AJES_av.pdf|access-date=24 April 2014|doi=10.1080/08120099.2014.884983|bibcode=2014AuJES..61..213R|hdl=20.500.11937/38264|s2cid=3783826|url-status=dead|archive-url=https://web.archive.org/web/20160607102637/http://geodesy.curtin.edu.au/local/docs/Rexer_Hirt_2014_DEM_AJES_av.pdf|archive-date=7 June 2016|hdl-access=free}}</ref> better horizontal resolution, reduced presence of artifacts, and more realistic values over water bodies.<ref name="lpdaac.usgs.gov"/> 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.<ref>{{cite web|last=de Ferranti|first=Jonathan|title=ASTER Digital Elevation Data|url=http://www.viewfinderpanoramas.org/reviews.html#aster|publisher=Viewfinder Panoramas, UK|access-date=21 December 2013}}</ref>
A 2014 study<ref name="geodesy.curtin.edu.au"/> 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 5 August 2019.<ref>{{cite web| url = https://asterweb.jpl.nasa.gov/gdem.asp| title = ASTER Global Digital Elevation Map}}</ref>

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.
*[[Ground sample distance]]
*[[Shuttle Radar Topography Mission|Shuttle Radar Topography Mission (SRTM)]]

==References==
{{Reflist|30em}}

==External links==
{{Commons category}}
*{{Official website|http://asterweb.jpl.nasa.gov }}
*[https://terra.nasa.gov/about/terra-instruments/aster NASA site on ASTER]
*[https://web.archive.org/web/20090704214738/http://www.ersdac.or.jp/GDEM/E/ Official METI ASTER GDEM Site]
*[http://asterweb.jpl.nasa.gov/gdem.asp Official NASA ASTER GDEM Site] {{Webarchive|url=https://web.archive.org/web/20090703003436/http://asterweb.jpl.nasa.gov/gdem.asp |date=3 July 2009 }}

{{Jet Propulsion Laboratory}}
{{Authority control}}

{{DEFAULTSORT:Advanced Spaceborne Thermal Emission And Reflection Radiometer}}
[[Category:2000 establishments]]
[[Category:2008 disestablishments]]
[[Category:Radiometry]]
[[Category:Space science experiments]]
[[Category:Earth observation satellite sensors]]