Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Geog319RmSns > Radiation Framework > Flashcards

Radiation Framework Flashcards

1
Q

What are 3 methods to collect RS data?

A
  • Satellite
  • Airborne
  • Ground-based in situ
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

ENVISAT Mission

A
  • Set of instruments and sensors that analyze different parts of the spectrum
  • Failed mission
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Sentinel-1 Mission

A
  • Single Instrument, 1 sensor mission
  • C-Band Synthetic Aperture Radar (SAR)
  • Imaging Radar
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Most often means?

A
  • Utilize electormagnetic radiation (EMR) recorded by an instrument and converted to digital format
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are some exceptions to EMR?

A

Sound, gravity fields

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the generalized RS process?

A
  • Energy Source (sun or sensor)
  • Atmospheric Interaction
  • Target Interaction (Earth surface)
  • Energy Recorded (at sensor)
  • Processing (image)
  • Analysis and Interpretation
  • Application
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the 3 basic models for digital remote sensing?

A

Passive:
- Reflected solar radiation, sun as direct energy source
- Emitted radiation, sun as original energy source, absorbed, then re-radiated
Active:
- Backscattered radiation, instrument is own source of illumination (Pulse and echo)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

EMR structure, wave and particle theory

A
  • Wave: Streams of continuous waves, classical physics, for EMR structure
  • Particle: Discrete packets of particles as per modern physics, quantum theory, for EMR energy content
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Wave theory

A
  • Oscillating electric and magnetic fields
  • Orthogonal to each other
  • Perpendicular to the direction of travel
  • Travel at speed of light
  • Both electric and magnetic field travel at speed of light perpendicular to direction of travel
  • For EMR structure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Quantum theory

A
  • EMR as discrete packets of energy called quanta

- A single quantum or ‘particle’ of energy called a photon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Wavelength and frequency, eqn

A

velocity of light (3.8 x 10^8m/s) = wavelength (m) x frequency in cycles per second (Hertz)

  • wavelength can be derived from freq and vice versa
  • Freq inversely propotional to wavelength, shorter wavelength = higher frequency
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Electromagnetic Radiation (EMR)

A
  • Sun’s visible surface or photosphere radiates EMR over continuous spectrum of wavelengths
  • Wavelengths from 10m plus down to micrometers (gamma)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Atmospheric Transmission

A
  • Atm windows: EMR passes through atm w/ minimal or no absorption or scattering
  • Almost complete transmission at microwave spectrum
  • Therefore transmits trough cloud cover and minimal sunlight (or no sun)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the frequency of Microwaves often expressed as?

A
  • GigaHertz (GHz)

- 1 GHz = 10^9 Hz

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Microwave desc

A
  • Interval of continuous EMR spectrum that includes wavelengths from 1mm or 1cm to 1m (extends into radio waves)
  • Range not rigidly defined
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the length of microwaves in comparison to optical portion of EMR spectrum?

A
  • Microwaves approx. 100,000 times longer than optical
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are 2 big benefits of microwave sensing>

A
  • Sunlight not required

- Clouds are transparent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are some benefits of all weather, day/night sensing?

A
  • Emergency response (rapid mapping of floods)
  • Iceberg detection for shipping
  • Maritime safety
  • Management of hazards
  • Oil spills
  • Arctic sea ice area and long-term change
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Can microwaves be attenuated by atmospheric particles and rain?

A
  • Yes, small wavelength microwaves
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Quantum theory, calculating radiant energy (Q)

A
  • Radiant energy (Q), the energy content of a photon = planck’s constant (h, 6.6 x 10^-34Js) x frequency (Hz)
  • If frequency is unknown, can sub in wavelength/freq calc (freq = speed of light (c)/wavelength
  • Q = hc/wavelength
  • Longer wavelength radiation has lower energy content
21
Q

What is the relationship with small wavelengths to radiant energy (Q) and frequency?

A
  • Smaller wavelength = high frequency and high Q

- Q of microwaves much less than Q of visible

22
Q

Radiant energy (Q)

A
  • Energy of electromagnetic radiation
  • Its capacity to do work
  • Units in Joules
23
Q

Radiant energy (Q)

A
  • Energy of electromagnetic radiation
  • Capacity of radiation to do work
  • Units in Joules
24
Q

Directional Power

A
  • Sunlight measured on Earth

- Sun approximates an isotropic radiator, a point source which radiates energy uniformly in all directions

25
Q

Radiant flux density

A
  • Power per unit area

- Units in Watts per sq. m (W m^-2, or J/s*m^2)

26
Q

Irradiance and Exitance

A
  • Radiant flux incident upon a surface, per unit area of that surface
  • Radiant flux leaving a surface, per unit area of that surface
27
Q

Why does passive radiation have low spatial resolution and large swaths?

A
  • Sensor ‘hoovers up’ energy available when passing overhead
  • More energy needed to acquire high spatial resolution, therefore more time over spot
  • However, time is short, so a wide swath is used to build up enough signal for the sensor
28
Q

Why does active sensing usually have higher spatial resolution?

A
  • Controls radiant flux

- Therefore can control spatial res and ‘crank it up’

29
Q

Black-body radiator

A
  • Theoretical perfect absorber and re-emitter of energy at all wavelengths
  • Nothing is lost to reflection and transmission (conservation of energy)
  • Water is close to black-body (0.95 of 1)
30
Q

Black-body radiator

A
  • Theoretical perfect absorber and re-emitter of energy at all wavelengths
  • Nothing is lost to reflection and transmission (conservation of energy)
  • Real-world objects are not black-body radiators
  • Most objects approach black-body
  • Water is close to black-body (0.95 of 1)
31
Q

Emissivity

A
  • Ratio of radiant existence of an object to that of a black-body at the same physical temperature
  • ex. snow = 0.8, soil = 0.9, water = 0.95
32
Q

What is exitance from a black-body proportional too?

A
  • Proportional to the 4th power of its temperature
  • black-body total emitted radiation, M (Watts/m^2) = Stefan-Boltzman constant, sigma (5.67 x 10^-8) x Temp ^4 (Kelvin)
  • Warmer objects radiate more energy
33
Q

What is exitance from a black-body proportional too?

A
  • Proportional to the 4th power of its temperature
  • black-body total emitted radiation, M (Watts/m^2) = Stefan-Boltzman constant, sigma (5.67 x 10^-8) x Temp ^4 (Kelvin)
  • Warmer objects radiate more energy (ex. IR camera where warmer = brighter)
34
Q

Wien’s Displacement Law

A
  • Dominant wavelength of exitance from black-body is temp dependent
  • Max wavelength = Wiens constant, k (2898 um K)/ Temp (Kelvin)
  • Increase temp and dominant wavelength decreases
35
Q

Planck’s Radiation Law

A
  • Combination of Stefan-Boltzman and Wiens laws

- Describes temp and wavelength-dependent exitance of black-body

36
Q

What is the dominant wavelength of the sun?

A
  • In the visible spectrum
  • Fire is in IR and TIR
  • Earth is in microwaves
37
Q

Beyond 10um, where is the energy available at the Earth’s surface from?

A
  • From the Earth itself, not the sun
  • Due to solar energy reduced by inverse-square law dispersion of energy w/ distance from source
  • Earth is closer than sun at those wavelengths
38
Q

What is the energy like at microwave spectrum?

A
  • Very low

- Not optimal for Earth surface observing but still useful b/c it can capture info regardless of time or cloud cover

39
Q

What are the 3 ways the energy is transferred?

A
  • Conduction (pot on stove)
  • Convection (warm ground heats air near surface)
  • Radiation (EMR, sun to Earth)
40
Q

Conservation of Energy

A

Energy interacting w/ matter (surface or object) is subject to conservation of energy laws such that it is:

  • Absorbed
  • Reflected
  • Transmitted
  • Fractions of each all add to 1
41
Q

What are the proportions based on with the factors of conservation of energy (Abs, refl, trans)?

A
  • Vary based on properties of material, wavelength of the energy, angle of illumination
  • Increase angle of illumination, and more is reflected, less absorbed, but total fractions will still = 1 (conservation of energy)
42
Q

Energy-Matter interactions: Refraction

A
  • Bending of EMR relative to surface normal as it encounters a medium of different density (ex. from air to water)
43
Q

Energy-Matter interactions: Reflection - 3 types

A

Scattering:

  • Specular reflection
  • Diffuse scattering
  • Isotropic scattering
44
Q

Energy-Matter interactions: Specular reflection

A
  • Perfect reflection
  • Reflection angle predictable
  • Calm water body
45
Q

Energy-Matter interactions: Diffuse scattering

A
  • Partially diffuse
  • Reflection angle not predicable
  • Slightly windy water surface
46
Q

Energy-Matter interactions: Isotropic Scattering

A
  • Lambertian
  • Perfectly diffuse, energy scattered equally in all directions
  • Very windy water surface
47
Q

Energy-Matter interactions: What is the wavelength dependency of absorption, transmission, and scattering?

A
  • Complex function of size of wavelength relative to material and physical/chemical properties of material
48
Q

Energy-Matter interactions: Size of wavelength relative to material

A
  • Rule of thumb: shorter wavelengths more likely to be scattered and/or absorbed, longer wavelengths transmitted
49
Q

Physical and chemical properties of the material

A
  • Complex, subject of research

Geog319RmSns (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions