The document discusses the basics and technologies of remote sensing, particularly focusing on aerosols and their optical properties. It explores the types, characteristics, and applications of remote sensing, emphasizing the significance of satellites in observing the Earth's atmosphere and surface without physical contact. Challenges in remote sensing, such as cloud cover and atmospheric temperature variations, are also highlighted.

1. Remote Sensing of
Aerosols
Student Tutorial Series: Lecture-2
ENV6130 Aerosol Mechanics
March 29, 2016
kalaivanan murthy

2. Note!
this is...
an introductory material
presented in an new-age interactive fashion
best viewed with the lecture video

3. Contents
Remote Sensing Basics
Aerosol Application
Summary

4. Two Areas
remote sensing
technology to capture
optical wave changes
satellite - sensors
aerosol technology
deducing true form from remote
sensing inputs
optical properties

5. Remote Sensing Basics
1

6. What is Remote Sensing?
Science of acquiring information about an object
without having a physical contact.

7. Terminology
“Science – and the art – of
identifying, observing, and measuring an object
without coming into direct contact with it.”
Ms. Evelyn Pruitt
US Office of Naval Research
1950’s
Source: Earth Observatory, National Aeronautics and Space Administration

8. What others say?
“acquisition of information about an object or phenomenon without making physical
contact with object.. thus in contrast to site observation”
“..in modern usage.. use of aerial sensor technologies to detect and classify objects on
earth.. surface, atmosphere, oceans.. by means of propagated signals on earth”
– Wikipedia (Feb 2016)
“collecting and interpreting information about the environment and the surface.. from a
distance.. primarily by sensing radiation that is naturally emitted or reflected.. by sensing
signals transmitted from a device and reflected back to it.”
– Environmental Systems Research Institute (Feb 2016)

9. brief-Timeline
c.1820’s camera
1840’s photographs of earth (balloons)
1960’s aerial photography..

10. Physical Contact
Touch
site observation..?

11. What kind of information?
Changes in spatial and temporal characteristics.
spatial - space (x, y, z)
temporal - time (t)
optical

12. How?
Absorption and reflection of radiation by the object.
Max Planck (1858-1947)

13. Types (source)
based on light source,
passive active
external source self source
(sun, earth) (electromagnetic pulse)
eg. Landsat, ASTER, AVHRR eg. LIDAR, RADAR, SONAR
not only visible

14. Types (orbit)
based on orbit,
geo-synchronous polar
orbital period 24h orbital period <2h
high altitude (~36000 km) low altitude (700 - 800 km)
same location all time weather forecast, landuse,
communication sea-surface temperature
http://scijinks.jpl.nasa.gov/orbit/

15. Characterization
Resolution and Coverage
spatial smallest unit of an image, pixel
spectral wavelength resolution (Δλ)
radiometric magnitude of detectable radiation
temporal time frequency

16. i) spatial
how much can it see?
how clear?
coverage
resolution (pixel)

17. ii) spectral
how much can it see?
how clear?
bandwidth
(Δλ)

18. iii) radiometric
sensitivity to magnitude
of electromagnetic energy
ability to detect minute changes
in incoming energy
bits
8 bits 11 bits

19. iv) temporal
how continuously can you watch?
since when?
revisit period
eg. MODIS (1 day, since 2000)

20. Why remote sensing?
 inaccessible locations by ground transport
 continuous monitoring and observation
 non-destructive observation (no physical contact)
 macroscale observations (national-scale and continent-scale)
 observations less affected by weather catastrophes
 high precision (no bias or manipulation)
 energy efficient (sourced by solar energy)
 versatility (one device, many applications)
 longer life (no wear/tear)
 less maintenance issues

21. key terms
to communicate, we need language
to be specific, vocabulary
词汇

22. key terms
Instantaneous Field of View
(IFOV)

23. key terms
Swath

24. key terms
MODIS
Moderate Resolution Imaging Spectroradiometer
sensor (device)
mounted on AQUA & TERRA satellites
HIGH… radiometric (12 bits),
multi spectral (36 bands, 0.4 – 14.4 µm)
polar orbit
sun-synchronous?
revisit period (1 - 2 day)
http://modis.gsfc.nasa.gov/about/design.php

25. key terms
MISR
Multiangle Imaging Spectroradiometer
sensor (device)
9 cameras x 4 spectral bands
red, blue, green, near-infrared
http://www-misr.jpl.nasa.gov/

26. key terms
SeaWIFS
Sea-viewing Wide Field-of-view Sensor
sensor (device)
polar orbiting
8 bands
global ocean bio-optic properties
(marine phytoplankton)
http://oceancolor.gsfc.nasa.gov/SeaWiFS/SEASTAR/SPACECRAFT.html

27. key terms
spatial
(space)
temporal
(time)

28. key terms
vector
(point.. line.. polygon..)
raster
(pixel.. value..)

29. key terms
Radiation
..coming in next section

30. Applications
 air quality
 road networks and urbanization
 meteorology
 disaster management
 aerosol source regions
 global transport patterns
 agriculture crop yield, land use management
 ocean and land surface characteristics
 national security
 explore terrestrial bodies
 astronomy and cosmology applications

31. Satellites

32. Phytoplankton
phyto - plant
plankton - made to wonder
..microscopic organisms that
live in watery environment

33. Organizations
founded
NASA National Aeronautics and Space Administration 1958
IKI RAN Russian Space Research Institute 1965
ISRO Indian Space Research Organization 1969
NSDAJ National Space Development Agency of Japan 1969
GAC German Aerospace Center 1969
ESA European Space Agency 1975
RSC Russian Federal Space Agency 1992
CNSA China National Space Administration 1993

34. Image
2D vs 3D
image
object

35. Aerosol Application
2

36. How?
scattering

37. Scattering
Rayleigh’s
Mie
P (θ)

38. Characterization
f (x, y, z, t, D, C, S, X)
x, y = ground location
z = altitude
t = time
D = particle diameter
C = composition
S = shape
X = mixing

39. Factors
f (x, y, z, t, D, C, S, X)
Diameter: 0.1 - 10 µm
Composition: phase, constituents
Shape: conical, spherical..
Mixing: internal, external

40. Efficiency
fine particle mode has
greater scattering

41. Vertical Layers
based on…
aerosol type
residence time
mixing characteristics
internal mixing

42. distinct terms
radiation
emission or transmission of energy
..in form of waves or particles
electromagnetic
particle (α, β, neutron)
acoustic (ultrasound,sound,seismic)
gravitational
electromagnetic radiation
radiant energy released
..by electromagnetic process
radio, infrared, visible etc.

43. EMR
James Clerk Maxwell
(1831 -1879)
wave form of electric & magnetic equations

44. Reflectance
presence of aerosol can
increase
decrease
reflectance

45. How to know?
deciding criteria
𝑃
𝑅0
..three cases
< 1
P - phase function = 1
R0 - surface reflectance > 1

46. case-(i)
phase function is lesser than surface reflectance
𝑃
𝑅0
< 1
addition of aerosols
decrease
true reflection
http://earthobservatory.nasa.gov/IOTD/view.php?id=84557

47. case-(ii)
phase function is equal to surface reflectance
𝑃
𝑅0
= 1
addition of aerosols
will not change
apparent reflection

48. case-(iii)
phase function is greater than surface reflectance
𝑃
𝑅0
> 1
addition of aerosols
increase
apparent reflection

49. Validity
the above cases
not valid
for thick aerosol layer
why?

50. What do you think?
Let’s do an activity

51. Here is your task!
You are given a satellite image.
You are asked to deduce
aerosol, land, water features.
qualitatively

52. Satellite Image
here is your satellite image..

53. Recollect the reflectance

54. Recollect the reflectance
..three color channels
Blue (412 nm)
Green(555 nm)
Red (670 nm)

55. What does ‘blue’ do?
aerosol depth

56. What does ‘red’ do?
land use
aerosol above water

57. How to get ‘water’?
subtract?
black in infrared (~865nm)

58. your results!
surface = land + water (ocean)

59. your results!
yes finally!

60. Summary
3

61. Challenges
clouds cover 60% of earth’s atmosphere
atmospheric temperature… aerosol phase change
sensing technologies (coverage and accuracy)
upgradation of obsolete satellites (600+ geosynchronous)
data interpretation techniques (aerosol techniques)
space infrastructure is very expensive

62. let’s summarize
remote sensing is a science, technology and art
two types of sensing: active and passive
two types of orbits: geosynchronous and polar
four characteristics: spatial, spectral, radiometric, temporal
one governing phenomenon: optical properties
challenges: surface reflectance and clouds

63. Sources
Satellite-based measurement of atmospheric aerosols
Rudolf B. Husar
Department of Energy, Environmental and Chemical Engineering,
Washington University, Missouri
Earth Observatory
National Aeronautics and Space Administration
Wikipedia
Wikimedia Foundation
and other sources as well…

64. Further Reading
Atmospheric Chemistry and Physics:
from air pollution to climate change (2006)
John H. Seinfeld - Spyros N. Pandis
Visibility: Science and Regulation (2002)
John G. Watson
Remote Sensing of Tropospheric Aerosols from Space (1999)
Michael D. King
Remote Sensing of Particulate Pollution from Space:
have we reached the promised land (2009)
Raymond M. Hoff - Sundar A. Christopher
The characterization of aerosols distributed with respect to size
and chemical composition (1970)
S.K. Friedlander

65. The End