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Space-borne Platforms

Common Earth Observation Space-borne Platforms (Satellites)

This short review is not intended to provide an exhaustive list of various space programs undertaken by many nations around the world since the first US satellite Explorer VI was launched in August of 1959. It focuses mainly on the most recent earth resource observation satellites whose data is commonly used in ecology and related environmental science applications. 

Earth observation satellites are satellites specifically designed to observe Earth from orbit. They are intended for non-military uses such as environmental monitoring, agriculture, forestry, range resources, water resources, coastal resources, land use monitoring, mapping, and geology. 

in 1972 the United States started its Landsat program, the largest program for acquisition of imagery of Earth from space. The LANDSAT-1, -2 had a three-channel RBV (return beam vidicon) camera system and a four-channel MSS (multi-spectral scanner) system with 80 meter resolution on board. The LANDSAT-3 acquired one 505-750 nm, 30 m resolution RBV band and a fifth MSS channel (band 8) operating in thermal infrared region of the spectrum which failed shortly after launch. The following LANDSAT-4 and -5 satellites were equiped with essentially the same MSS as their predecessors, but in addition, they possessed a TM (Thematic Mapper); a highly advanced multi spectral scanner with GSD of 30 m resolution except the thermal band 10400-12500 nm operating with GSD of 120 m. The latest, LANDSAT-7 was launched in April 1999. It is equiped with an upgrade of successful TM - Enhanced Thematic Mapper or ETM+ sensor.
 

Satellites LANDSAT-4, -5 LANDSAT-7
Sensor MSS, TM ETM+
Type Multispectral Panchromatic
Multispectral
Band Width (GSD Resolution)
(mm)            (meters)
MSS
(4) 0.5 - 0.6 (82)
(5) 0.6 - 0.7 (82)
(6) 0.7 - 0.8 (82)
(7) 0.8 - 1.1 (82)
TM
(1) 0.45 - 0.52 (30)
(2) 0.52 - 0.60 (30)
(3) 0.63 - 0.69 (30)
(4) 0.76 - 0.90 (30)
(5) 1.55 - 1.75 (30)
(6) 10.4 - 12.5 (120)
(7) 2.08 - 2.35 (30)
ETM+
(1) 0.45 - 0.52 (30)
(2) 0.52 - 0.60 (30)
(3) 0.63 - 0.69 (30)
(4) 0.76 - 0.90 (30)
(5) 1.55 - 1.75 (30)
(6) 10.4 - 12.5 (60)
(7) 2.08 - 2.35 (30)
PAN 0.50-0.90(15)

LANDSAT-7 is to have a design lifetime of five years. The overall objectives of the LANDSAT-7 Mission are:

  • Provide data continuity with Landsats 4 and 5.
  • Offer 16-day repetitive Earth coverage.
  • Build and periodically refresh a global archive of Sun-lit, substantially cloud free, land images.
  • Make data widely available for the cost of fulfilling a user request (called COFUR).
  • Support Government, international and commercial communities.
  • Play a vital role in NASA's Earth Observing System (EOS) by promoting interdisciplinary research via synergism with other EOS observations. (In particular, orbit in tandem with EOS-AM1 for near coincident observations.) 
LANDSAT Missions Portal


SPOT - the Satellite Earth Observation System was designed in France by the CNES (Centre National d'Etudes Spatiales), and developed with the participation of Sweden and Belgium. The SPOT orbit is polar, circular, sun-synchronous and phased. A polar orbit In conjunction with the rotation of the earth around the polar axis, the inclination of the orbital plane (98 degrees) allows the satellite to fly over any point of the earth during a 26 day cycle.

SPOT 1 was launched on 22 February 1986 with 10m panchromatic and 20m multispectral capability. The satellite was withdrawn from active service on 31 December 1990.
SPOT 2 was launched on 22 January 1990 and is still operational.
SPOT 3 was launched on 26 September 1993. An incident occurred on 14 November 1997 and after 4 years in orbit the satellite stopped functioning.
SPOT 4 was launched on 24 March 1998 and includes an extra Short Wave Infrared band and a (low resolution) vegetation instrument.
SPOT 5 was launched on 4 May 2002 with 2.5m, 5m and 10m capability, as well as along-track stereoscopic sensors.

Geoimage

 
Satellites SPOT 1,2 & 3 SPOT 4 SPOT 5
Instruments 2 HRVs 2 HRVIRs+Vegetation 1 2 HRGs+Vegetation 2
Type & resolution 1 panchromatic (10 m)
3 multispectral (20 m)
1 panchromatic (10 m)
3 multispectral (20 m)
1 short-wave IR (20 m)
2 panchromatic (2.5 m)
3 multispectral (10 m)
1 short-wave IR (20 m)
Spectral Range P:  0.50 - 0.73
B1:0.50 - 0.59
B2:0.61 - 0.68
B3:0.78 - 0.89
M: 0.61 - 0.68
B1:0.50 - 0.59
B2:0.61 - 0.68
B3:0.78 - 0.89
B4:1.58 - 1.75
P:  0.48 - 0.71
B1:0.50 - 0.59
B2:0.61 - 0.68
B3:0.78 - 0.89
B4:1.58 - 1.75
Revisit Interval 1 - 4 days 1 - 4  days 1 - 4 days

SPOT IMAGE Portal


DigitalGlobe is a private enterprise providing commercial high-resolution satellite imagery. It presently operates a constellation of three advanced satellites offering high spatial and spectral resolution imagery.

QuickBird launched in October 2001, WorldView-1 launched in September 2007, WorldView-2 launched in October 2009
 
 

Satellites QuickBird WorldView-1 WorldView-2
Imaging Resolution Panchromatic 0.6m
Multispetral 2.4m
Panchromatic 0.5m Panchromatic 0.46m
Multispectral 1.84m
Spectral Range P: 0.45 - 0.90
B: 0.45 - 0.52
G: 0.52 - 0.60
R: 0.63 - 0.69
IR:0.76 - 0.90
P: 0.40 - 0.90 P: 0.45 - 0.90
B: 0.40 - 0.45
B: 0.45 - 0.51
G: 0.51 - 0.58
Y: 0.58 - 0.62
R: 0.63 - 0.69
R: 0.70 - 0.74
IR:0.77 - 0.89
IR:0.86 - 1.04
Revisit Interval 1 - 3.5 days 1.7 days 1.1 days


GeoEye set geospatial industry standards with the launch of IKONOS®, the world's first sub-meter commercial satellite. Currently, the scientific community is served by high-resolution imagery from three of its satellites. OrbView-2 was launched in 1997, IKONOS launched in 1999, and  GeoEye-1 launched in September 2008.
 

Satellites OrbView-2 IKONOS GeoEye-1
Imaging Resolution LAC/HRPT 1130m
GAC 4500m
B&W 0.82m
Multispectral 3.2m
Panchromatic 0.41m
Multispectral 1.65m
Spectral Range V:  0.40 - 0.42
VB:0.43 - 0.45
B:   0.48 - 0.50
G:   0.50 - 0.52
G:   0.54 - 0.56
R:   0.66 - 0.68
IR:  0.74 - 0.78
IR:  0.84 - 0.88
BW:0.53 - 0.93
B:    0.44 - 0.52
G:    0.51 - 0.59
R:    0.63 - 0.70
IR:   0.76 - 0.85
P: 0.45 - 0.80
B: 0.45 - 0.51
G: 0.51 - 0.58
R: 0.65 - 0.69
IR:0.78 - 0.92
Revisit Interval 1 day ~ 3 days < 3 days


RapidEye AG is a German geospatial information provider focused on assisting in management decision-making through services based on their own Earth observation imagery. The company owns a five satellite constellation producing 6.5 meter resolution imagery. They were all launched in August 2008, and are equiped with a pushbroom multi-spectral imager, the Jena Spaceborne Scanner JSS 56.
 
 

Satellite RapidEye
Imaging Resolution GSD 6.5 meters
Spectral Range B: 440 - 510 nm
G: 520 - 590 nm
R: 630 - 690 nm
IR:690 - 730 nm
IR:760 - 880 nm
Revisit Interval 1 day


Radar-based remote sensing works on principles different from those of optical systems. SAR (Synthetic Aperture Radar) systems transmit their own microwave energy towards the surface and record the reflections. Thus, Radarsat satellites can image the Earth, day or night, in any atmospheric condition, such as cloud cover, rain, snow, dust or haze. Radarsat-1 uses a SAR sensor to image the Earth at a single microwave frequency of 5.3 GHz, in the C band (wavelength of 5.6 cm). Each of Radarsat-1's seven beam modes offer a different image resolution. The modes include Fine, which covers an area of 50 km by 50 km (2500 km²) with a resolution of 10 meters; Standard, which covers an area of 100 km by 100 km (10,000 km²) and has a resolution of 30 meters; and ScanSAR wide, which covers a 500 km by 500 km (250,000 km²) area with a resolution of 100 meters. Radarsat-1 also has the unique ability to direct its beam at different angles. With an orbital period of 100.7 minutes, Radarsat-1 circles the Earth 14 times a day. The orbit path repeats every 24 days, this means that the satellite is in exactly the same location and can take the same image (same beam mode and beam position) every 24 days.

Radarsat-1 was launched in November 1995 and is operated by the Canadian Space Agency (CSA). Radarsat-2 was launched in December 2007 and is operated by the MDA Geospatial Services International.

RADARSAT International is RADARSAT-1, LANDSAT, LANDSAT 5, LANDSAT 7, IKONOS, IRS, ERS, QuickBird, and ENVISAT imagery distributor in Canada.
 

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