Characterization of Satellite Remote Sensing Systems

The most common characterization of different remote sensing (RS) satellite imaging systems results from the systems diverse spatial, temporal and spectral resolutions.

Spatial Resolution

The spatial resolution specifies the pixel size of satellite images covering the earth surface.

High spatial resolution: 0.6 - 4 m

» GeoEye-1

» WorldView-2

» WorldView-1

» QuickBird

» IKONOS

» FORMOSAT-2

» ALOS

» CARTOSAT-1

» SPOT-5

Medium spatial resolution: 4 - 30 m

» ASTER

» LANDSAT 7

» CBERS-2

Low spatial resolution: 30 - > 1000 m

Spatial Resolution

Temporal Resolution

The temporal resolution specifies the revisiting frequency of a satellite sensor for a specific location.

High temporal resolution: < 24 hours - 3 days
Medium temporal resolution: 4 - 16 days
Low temporal resolution: > 16 days

IKONOS Satellite Temporal Resolution

Spectral Resolution

In the first instance, a sensor's spectral resolution specifies the number of spectral bands in which the sensor can collect reflected radiance. But the number of bands is not the only important aspect of spectral resolution. The position of bands in the electromagnetic spectrum is important, too.

High spectral resolution: - 220 bands
Medium spectral resolution: 3 - 15 bands
Low spectral resolution: - 3 bands

Electromagnetic Spectrum

Spectral Resolution for Landsat TM7 and ASTER Satellite Sensors

Resolution Trade-Off

The different spatial, temporal and spectral resolutions are the limiting factor for the utilization of the RS data for different applications.

Unfortunately, because of technical constraints, satellite RS systems can only offer the following relationship between spatial and spectral resolution: a high spatial resolution is associated with a low spectral resolution and vice versa.

That means that a system with a high spectral resolution can only offer a medium or low spatial resolution.

Therefore, it is either necessary to find compromises between the different resolutions according to the individual application or to utilize alternative methods of data acquisition.

The trade-off may result in two different solutions:

• To lay emphasis upon the most important resolution, in direct dependency to the application, with the acceptance of low attendant resolutions at the same time, or
• To lay no emphasis on one specific resolution and at the same time the acceptance of a medium spectral, temporal and spatial resolution.

Reaction Function IKONOS or QuickBird

In most cases of the planning task, functions need regular local or regular regional data with a high spectral resolution as well as a medium or high spatial for planning functions, the resolution problem, i.e. a high spectral and ideally a high spatial resolution, is evident.

According to the above mentioned solutions for the resolution problem, three different RS systems are recommended for the acquisition of RS data:

Emphasis on high spectral resolution:

Satellite: EO-1

The National Aeronautics and Space Administration (NASA) EO-1 satellite was launched on November 21, 2000. EO-1 Sensor Hyperion is a hyperspectral sensor which offers data in 220 spectral bands. EO-1/ Hyperion offer the highest available spectral resolution in the field of satellite-borne RS systems.

The EO-1 Extended Mission is chartered to collect and distribute ALI multispectral and Hyperion hyperspectral products in response to Data Acquisition Requests (DARs). Under the Extended Mission provisions, image data acquired by EO-1 are archived and distributed by the USGS Center for Earth Resources Observation and Science (EROS) and placed in the public domain.

EO-1 Satellite Sensor Overview

EO-1 Satellite Sensor Specifications:

Sensors: Hyperspectral
Ground resolution of each band: 30 m
Imagery Spectral Response 1 Spectral Range: 0.4 - 2.4 µm
Sensor Type: MSI Resolution: 10m (20m)
Channels: 220 bands between 0.4 - 2.5 10 nm
Swath Widths 7.6 km
Revisit Frequency 16 d

Sensors: Panchromatic Multispectral

Ground resolution of each band: 2.5 & 5 meter panchromatic 10 & 20 meter multispectral
Imagery Spectral Response 1 Spectral Range: 0.48 - 1.75 µm
Sensor Type: MSI Resolution: 10m (20m)
Channels:
Band 2: 0.61 - 0.68 µm
Band 3: 0.78 - 0.89 µm
Band 4: 1.58 - 1.75 µm (20m)
Swath Widths 60 km
Viewing Angle Agile spacecraft - in-track and cross-track pointing

The Hyperion sensor on board EO-1 provides a new class of Earth observation data for improved Earth surface characterization. Unlike the most other imaging spectrometers, Hyperion capabilities provide a spectral resolution of surface properties into 220 spectral bands.

Through these spectral bands, complex land eco-systems can be imaged and accurately classified at the most detailed level.

Emphasis on high spatial resolution:

Satellite: QuickBird

Trade-off: medium spatial and medium spectral resolution

QuickBird for spatial resolution acquires only 5 bands (Red-Green-Blue-Pan-NIR).

For more information on the QuickBird satellite sensor, please visit the QuickBird Sensor page.

For more information on the IKONOS satellite sensor, please visit the IKONOS Sensor page.

Satellite: SPOT-5

SPOT-5

SPOT-5 was launched in May 2002 and was implemented by the French Space Agency (CNES) and realized in cooperation with Belgium and Sweden. SPOT-5, the last-born child of the SPOT series, has a real advance on his SPOT predecessors with new technical characteristics and unique performances thus opening new perspectives in the domains of high resolution spatial imagery and the stereoscopy.

SPOT-5 presents the trade-off between EO-1 / Hyperion and IKONOS & QuickBird for cases, where neither spatial nor spectral resolution has to be as high as possible.

SPOT-5 is the first of the high resolution satellites to truly balance large scene sizes with highly detailed imagery and a relatively high spatial resolution, with coverage of vast territories: scenes of 60 x 60 or 60 x 120 km.

For more information on the SPOT-5 satellite sensor, please visit the SPOT-5 Sensor page.