Elements of a Remote Sensor

Signals, Noise, Definitions

Detector

Signal post-conditioning to enable detection (sampling and averaging)

Signal preconditioning to enable detection (change frequency, amplitude, etc.)

Signal +Noise (1)

Electronic Noise (2)

Aperture

(Antenna)Receiver (Rx)

Detector

STIMULATED

Signal +Noise (1)

Aperture

(Antenna)Receiver (Rx)

Signal Generator

Transmitter(Tx)

Bistatic System

Detector

STIMULATED

Signal +Noise (1)

Aperture

(Antenna)Receiver (Rx)

Signal Generator

Transmitter(Tx)

Circulator or Mixer

Monostatic System

Spherical Coordinate System

Solid Geometry

• Steradians

• The solid angle of a cone with apex angle , 2

2

2 1 cos

sindA

d d dr

Energy Flux and Radiance

• The radiant flux, is the rate at which energy is transported toward or away from a surface, with units of watts (W). The radiant flux is called power in radar meteorology!

• The radiant intensity is the radiant flux per unit solid angle, with units of (W sr-1) and is used in the description of radiation propagating from a point source.

/I d d

Energy Flux and Radiance

• The flux density has units of W m-2, and is the radiant flux per unit area that is either incident upon or emitted from a unit surface area .– termed “Irradiance”, in atmospheric science

and oceanography– Surface radiometer measures irradiance

/d dA

E

Energy Flux and Radiance

• The radiance, ,has units of W m-2 sr-1 and is the radiant flux propagating toward or away from a surface in a specified direction with a solid angle . The flux is emitted from or incident upon a differential unit area inclined at an angle to the direction of energy propagation.

L

d

2

cos

dL

d dA

•Emitted radiances are called RADIANCE and denoted with the symbol L•Incident radiances are called BRIGHTNESS and denoted with the symbol B

Solid Angle Resolution, s

sA

Lf

h

FOVA

sA

h

FOVA

L FOV

s

f A

s

Solid Angle Resolution, s

sA

Lf

h

FOVA

sA

Lf

h

FOVA

s FOV

s

A A

sh

Illumination Angle,

sA

h

FOVA

Illumination Angle,

sA

h

FOVA

Sphere of outward propagating radiation

Object with Radiant Flux, (Watts)

r

24

dflux density

dA r

Illumination Angle,

sA

h

FOVA

2

A

h

Solid Angle Resolution, s

sA

Lf

h

FOVA

sA

Lf

h

FOVA

sh