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TITLE : Comparison for different radar sat

sensor

RADAR SATELLITE SENSOR

RADAR stands for Radio Detection

and Ranging by virtue of sending out pulses

of microwave electromagnetic radiation this

type of instrument can be classified as an

active sensor where it is measures the time

between pulses and their reflected

components to determine distance. Different

pulse intervals, different wavelengths,

different geometry and polarizations can be

combined to roughness characteristics of

the earth surface. Radar wavelengths range

less than 1 millimeter to 1 meter. All photos

can be called images but not all images

should be called photos. Images are

acquired digitally are usually not referred to

as photographs there is no such thing as a

radar photograph.

Radar uses relative long wavelength

which allows these systems to see through

clouds, smoke, and some vegetation. Also,

being an active system, it can be operated

day or night. There are disadvantages, such

as the non-unique spectral properties of the

returned radar signal. Unlike infrared data

that help us to identify different minerals or

vegetation types from reflected sunlight,

radar only shows the difference in the

surface roughness and geometry and

moisture content of the ground (the complex

dielectric constant). Radar and infrared

sensors are complimentary instruments and

are often used together to study the same

types of earth surfaces.

SEASAT

Seasat was the first Earth-orbiting

satellite designed for remote sensing of the

Earth's oceans and had on board the first

space borne synthetic aperture radar (SAR).

The mission was designed to demonstrate

the feasibility of global satellite monitoring of

oceanographic phenomena and to help

determine the requirements for an

operational ocean remote sensing satellite

system. Specific objectives were to collect

data on sea-surface winds, sea-surface

temperatures, wave heights, internal waves,

atmospheric water, sea ice features and

ocean topography.

APPLICATIONS OF SEASAT

1. SEASAT was able to detect the

wakes of submerged submarines.

2. The conspiracy theory holds that

once this was discovered, the

military shut SEASAT down, with a

cover story of a power supply short. 

GEOSAT

The Geodetic Satellite (GEOSAT)

was a dedicated US Navy military

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oceanographic satellite consisting of a radar

altimeter designed to obtain closely spaced,

precise mapping of the earth's geoid over

the ocean. GEOSAT featured an altimeter

designed to measure the marine gravity

field as accurately as possible.

APPLICATIONS OF GEOSAT

1. Geosat is an advanced satellite

data technology transfer program

for geological applications.

2. To produce geological maps and

thematic maps for mineral

exploration in environmental or

hazardous areas study.

ERS-1

ERS-1 carried an array of earth-

observation instruments that gathered

information about the Earth such as land,water, ice and atmosphere using a variety of

measurement principles. To accurately

determine its orbit, the satellite included the

PRARE (Precision Range and Range-Rate

Equipment) and a laser retroreflector. The

PRARE was non-operational since launch.

The retroreflector was used for calibrating

the Radar Altimeter to within 10 cm. ERS-1and ERS-2 satellite having similar

instrumentation and allowing applications to

profit from the operation of both satellites.

APPLICATIONS OF ERS-1

1. Radar remote sensing has the

potential to play an important role in

agricultural crop monitoring due toits independence from solar

illumination and cloud cover, besides

its sensitiveness to canopy geometry

and moisture content.

2. The ERS-1 Wind Scatterometer has

potential for the monitoring of soil

frost and the retrieval of soilmoisture/vegetation water content.

3. The ERS-1 also used for measure

ocean surface temperature and

winds at sea.

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Radar Altimeter Characteristics for

Various Satellites

REFERENCES

1. lrs.gsfc.nasa.gov/satellite_missions/li

st_of.../seas_general.html

2. en.wikipedia.org/wiki/SEASAT

3. NASA JET PROPULSION

LABORATORY

4. http://www.fas.org/spp/military/program/nssrm/initiatives/geosat1.htm

5. http://earth.esa.int/ers/satconc/ 

6. http://www.esa.int/esaEO/SEMGWH

2VQUD_index_0_m.html

7. http://ieeexplore.ieee.org/xpls/abs_al

l.jsp?arnumber=516410&tag=1

Satellite  Frequency(Ghz) 

Bandwidth  Wavelength(m) 

Range

Resolution

(m) 

PulseCompression 

WaveHeight 

ERS-1 13.50 400.00 0.02 0.10 8000.00

ERS-2 13.50 0.02 0.1 58000.00 .13 m

Geos-3 13.90 80.00 0.02 0.50 30.00±25%

(4-10 m)

GEOSAT 13.50 320.00 0.02 0.10 30000.00±10%

(1-20 m)

GEOSAT

Follow-On 13.50 0.02 0.018 58000.00 .035 m

SEASAT 13.50 320.00 0.02 0.10 1000.00± 10%

(1-20 m)

Skylab 13.90 100.00 0.02 1.00 13.00 1-2 m

TOPEX/ 

Poseidon5.3&13.6 320.00

.0566*amp;

.022050.03 58000.00 .13 m