Lesson 7: Remote Sensing

Dr Andrew Ketsdever

MAE 5595

Outline

• Electromagnetic Radiation

• Blackbody Radiation

• Atmospheric Windows

• Instrument Parameters

• Remote Sensing Architectures

EM Radiation

• Photon wavelength, frequency and energy c

hE h = 6.626 x 10-34 J sec

EM Radiation• Communications• Microwaves: 1 mm to 1 m wavelength. The

microwaves are further divided into different frequency (wavelength) bands: (1 GHz = 109 Hz) – P band: 0.3 - 1 GHz (30 - 100 cm) – L band: 1 - 2 GHz (15 - 30 cm) – S band: 2 - 4 GHz (7.5 - 15 cm) – C band: 4 - 8 GHz (3.8 - 7.5 cm) – X band: 8 - 12.5 GHz (2.4 - 3.8 cm) – Ku band: 12.5 - 18 GHz (1.7 - 2.4 cm) – K band: 18 - 26.5 GHz (1.1 - 1.7 cm) – Ka band: 26.5 - 40 GHz (0.75 - 1.1 cm) – V band: 50 – 75 GHz– W band: 75 – 111 GHz

EM Radiation

• Heat energy is the KE of random motion of the particles in matter

• Temperature is the measure of heat energy concentrated in a substance

• Random motion results in COLLISIONS• COLLISIONS cause changes in the

internal energy of the molecules• Internal energy modes relax to ground

state by giving off photons (EM Radiation)

Blackbody Radiation• An ideal thermal emitter

– Transforms heat energy into radiant energy at the maximum rate allowed (Thermodynamics)

– Any real material at the same temperature can not emit at a rate in excess of a blackbody

• An ideal thermal absorber

• Planck’s formula1

51 1

2

T

c

ecM C1 = 3.74 x 10-16 Wm2 = 2hc2

C2 = 1.44 x 10-2 mK = hc/k

Blackbody Radiation• Wien’s

Displacement Law– Defines

wavelength in a blackbody at which the maximum energy is emitted

T

mKxm

310898.2

Blackbody Radiation

• Stefan-Boltzmann Law– Relates the power emitted

by a body to that body’s temperature

44ambsfc TTq

= 5.669 x 10-8 Wm-2K-4

Other Than Blackbody Radiation

• Emissivity– Ratio of the spectral

energy radiated by a material to that of a blackbody at the same temperature

– Can depend on• Wavelength• Temperature• Phase (solid/liquid)

44ambsfc TTq

Atmospheric Windows

Atmospheric Windows

Atmospheric Windows

Atmospheric WindowM13 ObservationsRotational Transitions in CO

Window Transmission

Glass Quartz

Sapphire

Instrument ParametersTelescopes: Microwave, Radio, IR, Vis, UV, XRay, Gamma Ray

Instrument Parameters

ionMagnificatR

r

h

f

g

d

f – focal lengthh – altituderd – radius of detector arrayRg – ½ Swath Width

Instrument Parameters

• Focal Length

Refractive System Reflective System

Instrument Parameters

• F-Stop or F-Number

D

fF #

D - Aperture

Instrument Parameters

• A telescope's spatial (or angular) resolution refers to how well it can distinguish between two objects in space which are separated by a small angular distance.

• The closer two objects can be while still seen as two separate objects, the higher the spatial resolution of the telescope.

• The spatial resolution of a telescope affects how well details can be seen in an image. – A telescope with higher spatial resolution

creates clearer and more detailed images.

Instrument Parameters• Diffraction Limited

Resolution– Rayleigh diffraction

criteria– Angular distance from

maximum brightness at the center of the image to the first dark interference ring Dr

22.1

D

hhX r

44.22

h can be replaced by slantrange for off Nadir obs.

Instrument Parameters

Aberration

Coma

Stigmatism

Instrument Parameters

Instrument Parameters

Instrument Parameters

• Silicon Imager Spectral Response

Instrument Parameters

• IR Detectors

Remote Sensing Architectures

Global Ocean Temperatures

Remote Sensing Architectures

Mie scattering (small particles)Rayleigh Scattering (large particles)

PassiveActive

Remote Sensing Architectures

Cosmic Background Explorer

SPOT Mars Reconnaissance Orbiter

What is the driver for the remote sensing architecture?

Remote Sensing Architectures

Landsat 7•a panchromatic band with 15m spatial resolution •on-board, full aperture, 5% absolute radiometric calibration •a thermal IR channel with 60m spatial resolution •an on-board data recorder

Remote Sensing Architectures

Chicago

Baghdad

Remote Sensing Architectures

Remote Sensing Architecture

Remote Sensing Architectures

Diffuse – Rough Surface Specular – Smooth Surface

Maxwell Model

Remote Sensing Architectures

Remote Sensing Architectures

• Space Radar– Mauna Loa Volcano

• Rift Zones (Orange)• Smooth Lava Flows (Red)

– Pahoehoe Flows

• Rough Lava Flows (Yellow/White)

– A’a Flows

– Obtained by sensing different Radar bands

Space Radar Systems

Remote Sensing Architectures

Remote Sensing Architectures

Remote Sensing Architectures

Remote Sensing Architectures

Remote Sensing Architectures

Remote Sensing Architectures

Remote Sensing Architectures• LIDAR

– Light Detection and Ranging

Remote Sensing Architectures

Remote Sensing Architectures

• Pushbroom Sensor