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Chapter 11 Images from Space
right behind Landsat 7 (within 1 minute). EO-1 features a multispectral sensor
called ALI (Advanced Land Imager) that is similar to ETM+ but can image 10
different bands in a 37-kilometer swath width at 30-meter resolution (along
with a 10-meter panchromatic band). ALI was also used to test and validate
sensor technology planned for use in LDCM. EO-1 also carries Hyperion, a
sensor that detects 220 bands at 30-meter resolution in a smaller swath width
of 7.7 kilometers. Hyperion is an example of a hyperspectral sensor, which
can measure hundreds of wavelengths simultaneously.
Although Landsat data has been widely used for numerous environmental studies, 30-meter resolution isn’t nearly enough to do very detailed, highresolution studies. At 30-meter resolution, broad land-use change modeling
and studies can be performed, but a much finer spatial resolution would be
required to pick out individual details in an image. High-resolution sensors
have a different purpose than Landsat imagery—with a very fine spatial resolution, crisp details can emerge from a scene. Spy satellites or military surveillance satellites would require this type of finer spatial resolution, but of course
the imagery they acquire remains classified. Much of the non-classified and
available high-resolution satellite imagery is obtained and distributed commercially rather than from government sources.
What Satellites Have High-Resolution
Sensors?
There are several remote sensing satellites with high-resolution capabilities.
This section describes a few of the more prominent ones. The SPOT (Satellite
Pour l’Observation de la Terre) program is operated by a French company called
The Landsat Program has been ongoing since
1972, providing global coverage of imagery and a
mainstay of the United States remote sensing program. However, it currently relies on the Landsat 5
(launched in 1984, long past its shelf life but still
doing the job) and Landsat 7 (launched in 1999 and
now impaired due to the SLC error) satellites. With
the next stage of the Landsat Program (LDCM) not
planned for launch until late 2012, the potential is
there for a gap in the acquisition of Landsat imagery if Landsat 5 should fail and Landsat 7’s issues
should become unsustainable. While this may sound
like something of a doomsday scenario, if LDCM is
delayed or if disaster should strike and LDCM should
fail to achieve orbit (like Landsat 6), and Landsats 5
and 7 would somehow be unavailable for imagery
acquisition, then what happens? Would the United
States have to purchase imagery from other sources
or countries to make up the data gap until another
Landsat mission could be launched? Are there other
sources that the United States government could
use to make up for the lack of Landsat imagery?
What impact would a lack of continuous Landsat imagery have on the numerous applications and studies previously described?
What if There Was No Landsat Data Continuity Mission?
Thinking Critically with Geospatial Technology 11.2
ALI the multispectral
sensor onboard EO-1.
Hyperion the
hyperspectral sensor
onboard EO-1.
hyperspectral
sensor a sensor that
can measure hundreds
of different wavelength
bands simultaneously.
SPOT a satellite
program operated
by the French Space
Agency and the Spot
Image Corporation.
Chapter 11 Images from Space
right behind Landsat 7 (within 1 minute). EO-1 features a multispectral sensor
called ALI (Advanced Land Imager) that is similar to ETM+ but can image 10
different bands in a 37-kilometer swath width at 30-meter resolution (along
with a 10-meter panchromatic band). ALI was also used to test and validate
sensor technology planned for use in LDCM. EO-1 also carries Hyperion, a
sensor that detects 220 bands at 30-meter resolution in a smaller swath width
of 7.7 kilometers. Hyperion is an example of a hyperspectral sensor, which
can measure hundreds of wavelengths simultaneously.
Although Landsat data has been widely used for numerous environmental studies, 30-meter resolution isn’t nearly enough to do very detailed, highresolution studies. At 30-meter resolution, broad land-use change modeling
and studies can be performed, but a much finer spatial resolution would be
required to pick out individual details in an image. High-resolution sensors
have a different purpose than Landsat imagery—with a very fine spatial resolution, crisp details can emerge from a scene. Spy satellites or military surveillance satellites would require this type of finer spatial resolution, but of course
the imagery they acquire remains classified. Much of the non-classified and
available high-resolution satellite imagery is obtained and distributed commercially rather than from government sources.
What Satellites Have High-Resolution
Sensors?
There are several remote sensing satellites with high-resolution capabilities.
This section describes a few of the more prominent ones. The SPOT (Satellite
Pour l’Observation de la Terre) program is operated by a French company called
The Landsat Program has been ongoing since
1972, providing global coverage of imagery and a
mainstay of the United States remote sensing program. However, it currently relies on the Landsat 5
(launched in 1984, long past its shelf life but still
doing the job) and Landsat 7 (launched in 1999 and
now impaired due to the SLC error) satellites. With
the next stage of the Landsat Program (LDCM) not
planned for launch until late 2012, the potential is
there for a gap in the acquisition of Landsat imagery if Landsat 5 should fail and Landsat 7’s issues
should become unsustainable. While this may sound
like something of a doomsday scenario, if LDCM is
delayed or if disaster should strike and LDCM should
fail to achieve orbit (like Landsat 6), and Landsats 5
and 7 would somehow be unavailable for imagery
acquisition, then what happens? Would the United
States have to purchase imagery from other sources
or countries to make up the data gap until another
Landsat mission could be launched? Are there other
sources that the United States government could
use to make up for the lack of Landsat imagery?
What impact would a lack of continuous Landsat imagery have on the numerous applications and studies previously described?
What if There Was No Landsat Data Continuity Mission?
Thinking Critically with Geospatial Technology 11.2
ALI the multispectral
sensor onboard EO-1.
Hyperion the
hyperspectral sensor
onboard EO-1.
hyperspectral
sensor a sensor that
can measure hundreds
of different wavelength
bands simultaneously.
SPOT a satellite
program operated
by the French Space
Agency and the Spot
Image Corporation.