|Home | Remote Sensing | Aerial Photography | Aerial Cameras | Bibliography | Contact|
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
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.
LANDSAT-7 is to have a design lifetime of five years. The overall objectives of the LANDSAT-7 Mission are:
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withdrawn from active service on 31 December 1990.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 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,
launched in September 2007, WorldView-2 launched in October 2009
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.
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.
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.
International is RADARSAT-1, LANDSAT, LANDSAT 5, LANDSAT 7, IKONOS,
IRS, ERS, QuickBird, and ENVISAT imagery distributor in Canada.
C 2010 Eco-Scientific Consultants.