ASTER

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ASTER
ASTER
Image from asterweb, 2005
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Terra

• Orbit Terra has a 705 km altitude that is
  sun-synchronous (at a given latitude it crosses
  directly overhead at the same time each day)
• Orbit period 98.88 minutes
• Equator crossing 10.30 a.m. (north to south)
• Ground track repeat cycle Every 16 days (233
  orbits) the pattern of orbits repeats itself
• Builder Lockheed Martin 

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Terra

• Terra is part of the NASAs Earth Observing
  System.
• Spacecraft in this system observe Earth from the
  unique vantage point of space.
• Spacecraft in the system focus on key
  measurements identified by a consensus of U.S.
  and international scientists, enabling new
  research into the ways Earths land, oceans, air,
  ice and life function as a total environmental
  system.
• Launched into orbit on December 18, 1999, Terra
  started sending data back to earth in February
  2000.
• Orbit 705 km
• Orbit period 98.88 minutes
• Equator crossing 10.30 a.m. (north to south)
• Ground track repeat cycle Every 16 days (233
  orbits) the pattern of orbits repeats itself
• In addition to ASTER, Terra carries four
  additional scientific instruments CERES, MISR,
  MODIS, and MOPITT.

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What is ASTER(R)?

• ASTER is situated on the Terra spacecraft.
• ASTER is an acronym for Advanced Spaceborne
  Thermal Emission and Reflection Radiometer
• ASTER is a remote sensing device used to obtain
  detailed maps of land surface temperature,
  reflectance, and elevation.
• ASTER provides the next generation in remote
  sensing imaging capabilities compared to older
  sensing systems such as the Landsat Thematic
  Mapper and Japan's JERS-1 OPS scanner.

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What is ASTER?

• ASTER is a cooperative effort between NASA, 
  Japan's Ministry of Economy, Trade and Industry
  (METI), and Japan's Earth Remote Sensing Data
  Analysis Center (ERSDAC).
• ASTER captures high spatial resolution data in 14
  bands, from the visible to the thermal infrared
  wavelengths and provides stereo viewing
  capability for digital elevation model creation.
• As the "zoom lens" for Terra, ASTER data are used
  by other Terra and space-borne instruments for
  validation and calibration.

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Data Application

• land surface climatology -- investigation of
  land surface parameters, surface temperature,
  etc., to understand land-surface interaction and
  energy and moisture fluxes
• vegetation and ecosystem dynamics --
  investigations of vegetation and soil
  distribution and their changes to estimate
  biological productivity, understand
  land-atmosphere interactions, and detect
  ecosystem change
• volcano monitoring -- monitoring of eruptions
  and precursor events, such as gas emissions,
  eruption plumes, development of lava lakes,
  eruptive history and eruptive potential
• hazard monitoring -- observation of the extent
  and effects of wildfires, flooding, coastal
  erosion, earthquake damage, and tsunami damage

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Mount St. Helens

• Captured one week after the March 8 ash and steam
  eruption
• New lava dome in the southeast part of the crater
  is clearly visible, highlighted by red areas
  where ASTERs infrared channels detected hot
  spots from incandescent lava.
• In this band combination, vegetation is green,
  snow is light blue, and bare rocks are tan.
• This image combines visible and infrared bands.

Image from asterweb, 2005
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Eruption of Mt. Etna, Italy
Image from asterweb, 2005
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New Orleans after Hurricane Katrina

• Top image ASTER mosaic acquired in April and
  September 2000.
• Bottom image ASTER image acquired September 13,
  2005.
• The flooded parts of the city appear dark blue,
  such as the golf course in the northeast corner,
  where there is standing water.
• Areas that have dried out appear light blue gray,
  such as the city park in the left middle.
• On the left side of the image, the failed 17th
  street canal marks a sharp boundary between
  flooded city to the east, and dry land to the
  west.

Image from asterweb, 2005
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Banda Aceh, Indonesia after tsunami
Image from asterweb, 2005
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Data Application

• hydrology -- understanding global energy and
  hydrologic processes and their relationship to
  global change included is evapotranspiration
  from plants
• geology and soils -- the detailed composition
  and geomorphologic mapping of surface soils and
  bedrocks to study land surface processes and
  earth's history
• land surface and land cover change -- monitoring
  desertification, deforestation, urbanization
  providing data for conservation managers to
  monitor protected areas, national parks,
  wilderness areas.
• mineral exploration -- bands in the 2.3 micron
  region for improved mineral mapping and
  discrimination between individual minerals

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Mineral Exploration

• Distinguishing clay minerals by different
  absorption features
• Standard USGS reference spectra for Na-Sericite,
  K-sericite, phengite and Mg/Fe phengite showing
  the progress shift of the absorption band
  position to longer wavelengths (top) and the same
  spectra convolved to the ASTER band configuration
  showing the variation in the shape of the 2209nm
  absorption band for the same minerals (bottom).

from www.rsinc.com, 2005
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The Moon

• In mid-April, the Terra spacecraft was turned
  upside down and pointed at the Moon.
• This ASTER image was acquired at that time,
  showing band 3 visible in black and white.
• This maneuver was performed to provide a
  well-characterized radiometric and geometric
  target to the Terra instruments to help refine
  performance.

Image from asterweb, 2005
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Mineral Exploartion in Nevada with Visible-Near
IR
Image from asterweb, 2005
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Sensor Popularity

• Growing popularity
• Relatively Low Cost e.g. 99 for a single scene
  data from the USGS.
• Broad Area Coverage
• Provides 3 Times the Spectral Information
  provided in Landsat images

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ASTER location on the Terra Spacecraft
Image from asterweb, 2005
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ASTER Components

• ASTER is comprised of three separate instrument
  subsystems.
• Each ASTER subsystem
• operates in a different spectral region
• has its own telescope(s)
• was manufactured by a different Japanese company

Image from asterweb, 2005
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VNIR

• The VNIR subsystem operates in three spectral
  bands at visible and near-IR wavelengths
• It consists of two telescopes--one nadir-looking
  with a three-spectral-band detector, and the
  other backward-looking with a single-band
  detector.
• It has a resolution of 15 m
• The backward-looking telescope provides a second
  view of the target area in Band 3 for stereo
  observations.

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VNIR

• Cross-track pointing to 24 degrees on either side
  of the track is accomplished by rotating the
  entire telescope assembly.
• Band separation is through a combination dichroic
  elements and interference filters that allow all
  three bands to view the same ground area
  simultaneously.
• The VNIR subsystem produces by far the highest
  data rate of the three ASTER imaging subsystems
  with all four bands operating (3 nadir and 1
  backward) the data rate can reach up to 62 Mbps.

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VNIR Component
Backward Looking Telescope
Nadir Looking Telescope
Image from asterweb, 2005
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SWIR

• The SWIR subsystem operates in six spectral bands
  in the near-IR region
• It uses a single, nadir-pointing telescope
• It has a resolution of 30 m
• Cross-track pointing can be accomplished by a
  pointing mirror.
• The maximum data rate is 23 Mbps.

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SWIR Component
Pointing Mirror
Telescope
Cryocooler
Image from asterweb, 2005
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TIR

• The TIR subsystem operates in five spectral bands
  in the thermal infrared region.
• It uses a single, fixed-position, nadir-looking
  telescope.
• It has a resolution of 90 m.
• Unlike the other ASTER instrument subsystems, the
  TIR mirror functions both for scaning along-track
  (push broom) or cross-track pointing.
• Each band uses 10 detectors in a staggered array
  with optical bandpass filters over each detector
  element.
• The maximum data rate is 4.2 Mbps.

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TIR Component
Scanning Mirror
Telescope
Reference Plate (for calibration purposes)
Cryocooler
Image from asterweb, 2005
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from Keller presentation, 2005
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ASTER Instrument Characteristics
from asterweb, 2005
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Visible-NIR
Visible-NIR
Thermal IR
Short Wave IR
Image from asterweb, 2005
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Comparison with other RS instruments
2048 km swath
AVHRR/ MODIS
global coverage, 2 days
spatial resolution, 250m, 500m, 1000m
On the Terra spacecraft.
MISR
global coverage, 9 days
360 km
spatial resolution, 275m, 550m, 1100m
16 day orbital repeat
Landsat
185 km
seasonal global coverage
spatial resolution, 15m, 30m
ASTER
60 km
spatial resolution 15m, 30m, 90m
Commercial Systems
20 km
spatial resolution 1m, 5m
from Keller presentation, 2005
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Image from PACES website, 2005
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Browse Image Mosaic
925,661 scenes observed as February 9th, 2005
Image from asterweb, 2005
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References

• Keller, G.R., 2005, Remote Sensing course
  presentation
• PACES website
• http//paces.geo.utep.edu
• Jet Propulsion Laboratory website (ASTER
  section)
• http//asterweb.jpl.nasa.gov/eos.asp
• Department of Industry,Tourism and Resources
  (Australia) Geoscience Australia
  http//www.ga.gov.au/ausgeonews/ausgeonews200503/p
  roductnews.jsp
• RSI website (ENVI section)
• http//www.rsinc.com/Envi/envi_app_aster.asp