Environmental monitoring from aircraft and spacecraft


North, G.W.

International Archives of Photogrammetry and Remote Sensing 19(5): 1-12

1972


Concern for environmental problems appears to be increasing throughout the world. This, of course, has led many people to expect a global solution to many problems. While this is a worthy goal to pursue, it does not appear' that we can find a global solution for each problem or even that we know now what each solution might require. National and/or regional programs will probably have to take the first steps.

:YVIRCx::.:
?AL
MOITORING
Gar
,
/
...
North
United
States
De
;
.
-
partment
of
the
Interior
Geological
Survey
EarL'h
Resources
Observa
t
ion
Systems
(EROS)
Program
Missisziooi
Test
Facility
.Bay
St.
Louis,
Mississippi
39520
,)L,„e,..L01\
The
probl
global
scale
i
to
face
on
thi
President
of
the
United
"The
comp
to
exoe
econ
cost
envi
nece
the
prob
boun
rega
more
envi
reco
its
m
of
pollution
and
the
need
for
preventive
methods
on
a
fast
becoming
one
of
the
greatest
problems
man
has
had
planet.
Nixon
in
his
1970
Environmental
Message
to
the
Congress
tates
summarized
the
situation
as
follows:
basic
causes
of
our
environmental
troubles
are
ex
and
deeply
imbedded.
They
include:
our
oast
ncy
to
emohasize
quantitative
growth
at
the
,se
of
qualitative
growth;
the
failure
of
our
my
to
provide
full
accounting
for
the
social
of
environmental
pollution;
the
failure
to
take
onmental
factors
into
account
as
a
normal
and
sary
part
of
our
planning
and
decision
making;
nadequacy
of
our
institutions
for
dealing
with
Lems
that
cut
across
traditional
political
aries;
our
dependence
on
conveniences,
without
d
for
their
impact
on
the
environment;
and
fundamentally,
our
failure
to
perceive
the
onment
as
a
totality
and
to
understand
and
to
nize
the
fundamental
interdependence
of
all
arts,
including
man
himself."
Today
we
mental
quality
these
words
ar
of
the
reiatio
environment.
change
for
thi
ecological
or
remote
sensing
we
are
trying
various
ecolog
.these
natural
dous
impact
on
of
the
consequ
Tf'
.
..e
XII
Co.r4
-
7e
Ottawa,
Cana
-
ear
such
key
words
as
pollution,
environment,
environ-
natural
resources,
endangered
species,
etc.
Quite
often
all
combined
under
the
term
ecology,
meaning
the
science
ships
of
a
living
organism
and
his
living
and
non-living
he
real
key
word
that
should
concern
us,
however,
is
is
what
one
is
really
trying
to
determine
in
any
nvironmental
study.
The
same,
of
course,
is
true
for
studies
of
the
environment.
Be
it
positive
or
negative,
o
assess
and
monitor
the
changes
brought
about
within
cal
cycles
and
determine
what
factors
change
or
upset
alances.
We
are
beginning
to
see
that
man
has
a
tremen-
his
environment,
and
we
sometimes
learn
too
late,
some
nces
of
our
actions.
s
of
International
Society
for
Photogrammetry
-
July
31,
1972
In
the
Nile
River
Valley,
man
built
a
large
dam
for
economic
and
industrial
reasons
and
soon
found
that
the
fish
population
in
the
Mediterranean
Se,
decreased;
that
the
number
of
disease
bearing
aquatic
snails
increased;
and
that
the
fertility
of
the
valley
itself
was
diminished.
CloOer
to
the
site
of
this
conference,
we
can
examine
the
results
of
the
c9nstruction
of
the
Welland
Canal
connecting
Lakes
Erie
and
Ontario.
The
completion
of
the
canal
allowed
the
predatory
sea
lamprey
eel
to
eater
the
interior
lakes
and
quickly
reduce
the
fisheries
of
trout
and
other
commerical
species.
Soon
the
smaller
alewife
flourished
since
they
had
always
served
as
food
for
the
commercial
fisheries.
The
s
udden
increase
in
these
fish
has
often
resulted
in
massive
kills,
quite
common
along
the
shores
of
Lake
Michigan.
In
recent
years
ecologists
have
introduced
the
coho
salmon
which
has
thrived
and
cut
back
on
the
alewife
population.
These
fish,
however,
have
had
to
be
removed
from
commercial markets
from
time
to
time
because
of
high
DDT
concentrations
in
their
bodies.
These
two
cases
are
significant
examples
of
how
fragile
the
environment
is
an8
how
careful
one
must
be
when
he
deals
with
it.
Impact
on
the
environment
can
also
be
measured
simply
in
terms
of
the
ever
increasing
number
of
people
that
must
interact
with
it.
For
example,
in
the
pist
forty
years
the
National
Parks
of
the
United
States
have
had
to
accep
a
number
of
visitors
that
has
ranged
from
3
million
in
1940
up
to
150
million
in
1970.
How
man
plans
for
and
copes
with
changes
such
as
these
will,
to
a
great
extent,
determine
the
quality
of
our
environment
in
s
the
years
to
come.
Alvin
Toffle]
in
the
introduction
of
his
book
Future
Shock
discussed
change
1.n
this
manner:
"...
I
gradually
came
to
be
appalled
by
how
little
is
actually
known
about
adaptivity,
either
by
those
who
call
foi
and
create
vast
changes
in
our
society,
or
by
those
who
supposedly
prepare
us
to
cope
with
those
changes.
Earnest
intellectuals
talk
bravely
about
'educating
for
change'
or
'preparing
people
for
the
future.'
But
we
know
virtually
nothing
about
how
to
do
it.
In
the
most
rapidly
changing
environment
to
which
main
has
ever
been
exposed,
we
remain
pitifully
ignorant;
of
how
the
human
animal
copes."
THE
PROBLEM
To
see
how
the
human
animal
copes
and
how
the
environment
fares
with
his
coping,
rrin
has
begun
to
employ
remote
sensing
devices
to
provide
him
with
environmental
data.
These
sensors
have
many
limita-
tions
but
may
prove
to
be
the
key
to
global
pollution
monitoring
in
the
years
to
come.
To
l
say
that
they
are
capable
of
detecting
or
"con-
trolling"
pollutioh
is
often
not
true
and
many
times
unfair
to
the
sensor
for
we
have
yet
to
define
what
pollution
is.
Definitions
will
vary
from
nation
to
nation,
province
to
province,
or
person
to
person.
The
man
dependent
8n
soft
coal
to
heat
his
house
or
run
his
factory
will
2
have
a
much
highEr
tolerance
of
sulfur
dioxide
fumes
and
acid
mine
wastes
than
the
person
trying
to
live
and
raise
fish
downstream
from
the
mine.
Therelhave
always
been
elements
in
the
environment
which
were
undesirable
to
u
and
beyond
our
control,
such
as
specific
occurrences
of
algae,
salty
water,
acid
water,
volcanic
dust,
smoke,
and
silt.
These
cannot
be
categorically
classified
as
pollution
because
they
are
products
of
natural
processes--but,
on
the
other
hand,
we
must
be
capable
of
coping
with
these
by-products
of
nature.
Our
society
has
removed,
or
greatly
modified,
certain
aspects
of
the
natural
environment
and
ignored
many
others.
By
stimulating
or
restricting
natural
processes
and
increasing
our
consumption
rates,
modern
man
is
locally
overburdening
his
environment,
and,
in
so
doing,
is
causing
pollution
and
degradation
of
environmental
quality.
The
reason
for
this
is
simply
that
the
problem
multifaceted;
and,
to
properly
study
it,
one
must
consider
a
variety
of
factors
such
as:
numbers
of
people,
land
use,
misplaced
economilc
incentives,
value
systems,
technology,
mobility,
limits
of
government
units,
depletion
of
resources,
health,
aesthetics,
costs,
effects
on
natural
systems,
and
many
others.
Remote
sensing
devices
cannot
prvide
answers
for
each
of
these
categories,
but
they
can
provide
data
on
which
decisions
in
these
categories
can
be
based.
They
sometimes
mate
it
possible
to:
detect
alien
substances
in
the
environment;
idenify
specific
pollutants
and
classes
of
pollutants;
measure
varying
concentrations
of
pollutants
through
time;
monitor
the
source,
movement,
and
fate
of
pollutants;
determine
the
effects
of
pollutants
on
the
environment;
assist
in
determining
environmental
quality;
determir4
the
susceptibility
of
the
environment
to
degradation;
and
provide
data
or
comprehensive
environmental
planning
and
modeling.
Data
obtained
by
emote
sensing
must
be
understood,
interpreted,
and
carefully
used
beore
it
can
provide
many
of
the
answers
that
users
desire
of
it.
Ina
remedial
context,
its
role
is
direct,
for
it
consists
of
locating
and
monitoring,
while
in
a
preventative
context
it
is
indirect,
for
it
can
only
point
out
potential
problems
on
the
basis
of
previous
detections.
REMOTE
SENSING
ANLJ
ENVIRONMENTAL
MONITORING
SYSTEMS
Remote
sensirlg
is
a
term
used
to
describe
a
series
of
activities
relating
to
the
use
of
airborne
or
spaceborne
instruments
that
measure
properties
of
objcts,
generally
at
or
near
the
Earth's
surface,
without
coming
into
direct!
contact
with
them.
Most
often
the
properties
being
measured
are
either
absorbed,
emitted, scattered,
transmitted,
or
reflected
electromagnetic
energy.
This
energy
is
generated
by
the
sun
and
travels
in
haLIuonic
waves
toward
the
Earth
at
the
speed
of
light.
The
wavelengths
of
this
energy
range
from
very
short
to
very
long,
but
human
senses
perceive
only
a
small
amount
of
this
energy
as
sight
or
temperature.
Remote
sensing
devices,
however,
can
be
built
to
detect
specific
wavelengths,
or
parts
of
this
electromagnetic
spectrum,
beyond
the
range
of
the
efre;
thus
expanding
man's
range
of
sensory
perception.
Electromagnetiic
energy
is
continuous
from
one
end
of
the
spectrum
to
the
other,
but
for
convenience
purposes
it
is
divided
into
spectral
3
Visible
Table
I
l
SPECTRAL
RANGE
OF
OPERATION
4-UltravioletA
)
Human
Eye
Photography
I
Thermal
Scanners
)
i
Multi—Spectral
Scanners
I
>i
t
I
I
I
I i
1
1
1
1
.2
.4
.6
.81.0
I
11111
1
I
2.0
4.0
6.0
10
20
I
40
FOR
COMMON
REMOTE
SENSING
INSTRUMENTS
Radar
-0
-
0
-0-0
c
c
0
0
0
0
m
ao
(..)
X
3..
I
1
,
Passive
Microwave
kt---
,
,
T
f
11111
i
\\
-.;
60
100
200.5
mm
1
mm
1
cm
irn10m
i3Om
WAVELENGTH
,
MICRONS
(
Not
To
Sca
I
0
)
regions.
Table
I
indicates
the
regions
in
which
most
remote
sensing
devices
are
capable
of
operating
at
the
present
time.
Note
that
the
human
eye
only
perceives
energy
in
the
0.4
to
0.7
micron
range.
Each
object
on
the
Earth's
surface
emits,
absorbs,
or
reflects
energy
differently.
By
determining
the
values
of
reflectivity
and
emissivity,
one
can
predict
how
an
object
should
appear
in
each
region
and
thus
establish
its
unique
spectral
characteristics.
For
example,
coolant
effluents
from
power
plants
can
best
be
recorded
in
the
thermal
infrared
portion
of
the
spectrum
because
in
this
region
temperature
differences
are
easily
discernible.
Shape,
color,
or
texture
may
also
be
important
keys
to
identifying
an
object.
These
characteristics
can
easily
be
recorded
on
photographs
taken
in
the
visible
portion
of
the
spectrum.
Thus,
by
knowing
something
about
the
spectral
characteristics
of
an
object,
a
remote
sensing
device
can
be
built
to
discriminate
those
objects
that
can
best
be
recorded
in
each
spectral
region.
Research
is
now
underway
to
determine
the
spectral
characteristics
of
various
pollutants.
The
slides
accompanying
the
Ottawa
presentation
of
this
paper
will
present
examples
of
how
different
pollutants,
or
pollution
processes,
appear
in
various
spectral
regions
and
will
illustrate
which
regions
are
best
for
recording
information
relative
to
particular
environmental
problems.
In
defining
"remote
sensing"
it
should
be
noted
that
the
term
applies
to
a
series
of
activities.
It
includes
not
only
the
selection
of
an
appropriate
instrument
but
data
acquisition,
collection,
pro-
cessing,
distribution,
and
analysis.
Furthermore,
remote
sensing
can
be
said
to
be
based
on
inference,
i.e.,
"if
cause
C
1
exists,
then
effect
E
l
will
be
observed,
and
if
effect
E
1
is
observed,
then
cause
C
1
must
exist."
2
The
science
of
remote
sensing
is
rapidly
advancing
to
a
point
4
where
it
could
become
the
most
important
data
source
for
environmental
studies
and
management
problems.
The
remainder
of
this
section
will
briefly
describe
many
of
the
sensor
systems
that
can
provide
such
data.
Photographic
Systems
The
oldest,
best
known,
and
most
widely
used
remote
sensing
device
is
the
camera.
dameras
have
long
been
used
in
aircraft,
and
more
recently
in
spacecraft,
to
collect
photographs
of
the
earth
below.
Cameras,
for
example,
have
been
successfully
employed
on
Gemini
and
Apollo
spacecraft;
and,
many
examples
appear
in
various
reports.
Aerial
photography
is
aril
effective
medium
for
storing
environmental
informa-
tion;
for
photographs
can
be
enlarged,
enhanced,
and
taken
with
suffi-
cient
overlap
to
yield
stereographic
coverage
of
the
area
of
concern.
By
combining
various
film
and
filter
combinations,
it
is
also
possible
to
record
selected
spectral
regions
from
the
ultraviolet
to
the
near
infrared.
Basically,
all
cameras
operate
on
the
same
principle--reflected
visible
light
is
allowed
to
pass
through
a
lens
and
is
then
recorded
on
a
piece
of
film
which
is
sensitive
to
the
visible
light.
The
film
is
then
processed,
and
the
resulting
photograph
becomes
a
piece
of
remotely
sensed
data.
Various
modifications,
or
changes,
can
be
made
to
camera
systems.
Lenses
are
made
to
be
interchangeable
so
that
varying
scale
images
can
be
produced,
and
so
that
area
coverage
can
be
enlarged
or
reduced.
Film
too
can
be
changed,
thus
allowing
the
use
of
particu-
lar
types
that
are
sensitive
to
portions
of
the
spectrum,
outside
that
recorded
by
the
human
eye.
An
example
of
one
of
these
special
films
is
color
infrared,
which
records
reflected
energy
in
the
near
infrared
portion
of
the
spectrum.
On
this
film
green
vegetation
appears
bright
red
if
it
is
in
leaf
and
healthy,
or
bluish-grey
if
it
is
dormant,
diseased,
or
dying.
The
following
is
a
list
of
the
more
common
film
types
and
some
of
their
special
characteristics:
A.
Panchromatic
Film
Panchromatic
film
is
the
msot
economical
and
widely
used
film
for
aerial
mapping
throughout
the
world.
This
black
and
white
film
has
approximately
the
same
sensitivity
to
reflected
light
as
the
human
eye.
It
has
a
wide
exposure
latitude
and
provides
'reasonably
good
tonal
contrast.
On
this
film
the
light-sensitive
silver
salts
are
contained
in
one
layer
affixed
to
a
stable
base
material.
B.
Black
and
White
Infrared
Film
By
extending
the
sensitivity
of
panchromatic
film
to
include
the
near
infrared
region
of
the
spectrum
(0.7-1.2
microns),
black
and
white
infrared
film
is
produced.
This
film
is
identical
to
the
panchromatic
except
that
some
of
the
grey
5
where
it
could
become
the
most
important
data
source
for
environmental
studies
and
management
problems.
The
remainder
of
this
section
will
briefly
describe
many
of
the
sensor
systems
that
can
provide
such
data.
Photographic
Systems
The
oldest,
Iciest
known,
and
most
widely
used
remote
sensing
device
is
the
camera.
Cameras
have
long
been
used
in
aircraft,
and
more
recently
in
space7aft,
to
collect
photographs
of
the
earth
below.
Cameras,
for
example,
have
been
successfully
employed
on
Gemini
and
Apollo
spacecraft;
and,
many
examples
appear
in
various
reports.
Aerial
photography
is
an
effective
medium
for
storing
environmental
informa-
tion;
for
photographs
can
be
enlarged,
enhanced,
and
taken
with
suffi-
cient
overlap
to
yield
stereographic
coverage
of
the
area
of
concern.
By
combining
various
film
and
filter
combinations,
it
is
also
possible
to
record
selected
spectral
regions
from
the
ultraviolet
to
the
near
infrared.
Basically,
ai
1
cameras
operate
on
the
same
principle--reflected
visible
light
is
llowed
to
pass
through
a
lens
and
is
then
recorded
on
a
piece
of
film
w
ich
is
sensitive
to
the
visible
light.
The
film
is
then
processed,
y:1
the
resulting
photograph
becomes
a
piece
of
data.
remotely
sensed
Various
modifications,
or
changes,
can
be
made
to
camera
systems.
Lenses
are
made
to
be
interchangeable
so
that
varying
scale
images
can
}e
produced,
and
so
that
area
coverage
can
be
enlarged
or
reduced.
Film
too
can
be
changed,
thus
allowing
the
use
of
particu-
lar
types
that
ar(4
sensitive
to
portions
of
the
spectrum,
outside
that
recorded
by
the
human
eye.
An
example
of
one
of
these
special
films
is
color
infrared,
which
records
reflected
energy
in
the
near
infrared
portion
of
the
spectrum.
On
this
film
green
vegetation
appears
bright
red
if
it
is
in
19af
and
healthy,
or
bluish-grey
if
it
is
dormant,
diseased,
or
dying.
The
following
l
is
a
list
of
the
more
common
film
types
and
some
of
their
special
characteristics:
A.
Panchromatic
Film
Panchromatic
film
is
the
msot
economical
and
widely
used
film
for
aerial
mapping
throughout
the
world.
This
black
and
white
film
has
approximately
the
same
sensitivity
to
reflected
light
as
[the
human
eye.
It
has
a
wide
exposure
latitude
and
provides
[the
good
tonal
contrast.
On
this
film
the
light-senitive
silver
salts
are
contained
in
one
layer
affixed
tip
a
stable
base
material.
B.
Black
and
White
Infrared
Film
By
extending
the
sensitivity
of
panchromatic
film
to
include
the
near
infrared
region
of
the
spectrum
(0.7-1.2
microns),
black
and
white
infrared
film
is
produced.
This
film
is
identical
to
the
panchromatic
except
that
some
of
the
grey
5
tones
in
the
photograph
are
produced
by
reflected
energy
wavelengths
longer
than
those
the
human
eye
can
see.
This
film
is
i
particularly
effective
in
discriminating
vegetation
types
and
open
water.
C.
Color
Film
Color
film
is
similar
to
panchromatic
except
that
its
sensitive
silver
alts
are
arranged
in
three
layers,
each
sensitive
to
different
wavelengths
of
visible
light.
The
top
layer
is
sensitive
to
blue
light,
the
middle
layer
to
green
and
blue,
and
the
bottom
layer
to
red
and
blue.
It
has
a
more
limited
exposure
latitude
than
panchromatic
and
a
slower
speed,
but
presents
each
scene
almost
exactly
as
the
eye
sees
it.
A
haze
filter
should
be
used
when
the
film
is
exposed
from
aircraft
or
spacecraft
altitudes
because
of
its
high
sensi-
tivity
to
blue
light.
Color
film
is
a
valuable
aid
in
water-
quality
studies
involving
wave
and
current
patterns,
sediment
patterns,
and
discoloration
due
to
agricultural,
municipal,
and
industrial
discharges.
D.
Color
In
frared
Film
Like
color
film,
color
infrared
film
has
three
layers
of
silver
salts
seiasitive
to
light
from
different
parts
of
the
spectrum.
The
significant
feature
of
this
film
is
that
its
range
is
increase
from
below
0.3
microns
to
above
0.9
microns.
Thus
any
objept
reflecting
ultraviolet,
long-wave
red,
or
infrared
light
will
appear
red
on
the
photograph.
The
other
two
sensitive
layers
image
green
light
as
blue
and
red
light
as
green,
causing
the
film
to
be
referred
to
as
"false
color"
film.
This
film
is
insensitive
to
the
blue
portion
of
the
spectrum
f
and
thus
has
greater
haze
penetration
capability
than
oth6r
film.
The
use
of
a
yellow
filter
is
required
to
guarantee
that
no
blue
wavelengths
are
recorded.
The
Apollo
9
S065
pho
-
Lography
experiment
produced
some
spectacular
results
Ifiith
this
film,
and
overall
it
can
be
said
that
it
is
perhaps
the
most
useful
film
for
recording
environmental
and
resoirce
information.
E.
Aero-Neg
Color
Film
The
Koda
Aero-Neg
is
a
"true"
color
film
that
produces
a
negative
from
which
color
prints,
black
and
white
prints,
color
diapositives,
black
and
white
diapositives,
or
color
trans-
parencie
can
be
made.
This
allows
the
user
to
choose
the
most
useful
type
of
film
output
to
meet
his
particular
needs.
It
has
the
same
spectral
characteristics
as
color
film,
but
the
greaer
variety
of
film
output
gives
it
an
added
advantage.
In
addition
to
film
and
lens
changes,
the
use
of
a
variety
of
special
filters
on
a
camera
allows
only
selected
wavelengths
of
energy
to
pass
through
0
the
film;
thus,
it
is
possible
to
record
only
red
6
light,
or
blue
light,
etc.
An
example
of
a
special
sensing
system
employing
this
technique
is
the
multiband
camera.
When
this
system
is
used,
several
cameras
or
a
multiple-lens
camera
record
several
pictures
of
the
same
scene
at
the
same
time.
Each
photograph
records
the
maximum
information
in
a
particular
spectral
band.
Data
from
these
systems
may
be
useful
in
helping
to
establish
a
data
bank
of
specific
spectral
characteristics
for
various
environmental
pollutants.
Perhaps
the
most
useful
airborne
camera
system
is
one
employing
metric
cameras.
These
instruments
produce
large
scale
data
on
9
inch
x
9
inch
film
of
excellent
geometric
fidelity.
Precise
locations,
accurate
measurements,
and
controlled
mosaics
can
be
made
from
metric
camera
photography.
There
are
several
problems
involved
in
using
camera
systems
for
remote
sensing
from
aircraft
or
spacecraft:
1)
camera
systems
are
restricted
in
normal
use
to
daytime
and
virtually
cloud-free
conditions;
2)
the
lenses
must
be
color
corrected
so
that
they
record
an
accurate
picture
of
the
scene;
3)
lenses
must
be
free
of
geometric
distortion,
so
that
the
resulting
photograph
is
an
accurate
map-like
representation
of
the
scene;
and
4)
in
order
to
record
particular
items
such
as
junk-
yards,
industrial
pollutants,
and
crops,
long
focal
length
lenses
are
required
for
use
from
spacecraft
and
high-altitude
aircraft.
Radiometer
A
radiometer
is
a
non-imaging
sensor
which
measures
emitted
or
reflected
electromagnetic
energy.
It
can
detect
energy
from
the
ultra-
violet
to
the
infrared
region
of
the
spectrum,
depending
upon
its
detector.
It
converts
incoming
radiation
into
an
electrical
impulse
which,
in
this
case,
is
recorded
on
a
gauge,
or
as
a
line
trace
on
a
strip
chart
recorder.
These
instruments
have
been
extremely
useful
in
laboratories
and
in
the
field
for
recording
spectral
characteristics
of
various
objects.
Infrared
Scanners
The
infrared
scanner,
or
scanning
radiometer,
is
a
sensor
specially
built
to
detect
the
thermal
infrared
energy
emitted
by
objects.
The
sensor
can
be
used
day
or
night
as
it
records
energy
emittance,
as
well
as
the
sun's
reflected
energy.
This
device
is
sometimes
referred
to
as
an
optical-mechanical
scanner,
or
line
scanner.
The
word
scanner
is
used
in
connection
with
this
sensor
because
the
detection
system
involves
the
use
of
a
rotating
or
scanning
mirror,
which
directs
the
emitted
energy
from
the
ground
to
a
detector
in
the
system
onboard
the
aircraft
or
spacecraft,
translates
that
energy
into
an
electrical
signal
and
then
records
each
scan
on
a
piece
of
unexposed
film
or
magnetic
tape
for
computer
processing.
The
detector
contains
an
infrared
or
heat
sensitive
material
such
as
indium
antimonide
or
copper-doped
geranium,
which
is
kept
at
tempera-
tures
approaching
0
0
Kelvin
by
either
liquid
helium
or
nitrogen.
Infrared
photons
reflected
off
the
scanning
mirror
strike
the
detector,
7
generating
an
electrical
impulse
which
varies
in
intensity
according
to
the
amount
of
infrared
energy
emitted
from
the
object
on
the
ground.
This
impulse
is
then
recorded
on
black
and
white
film
as
a
shade
of
grey:
the
more
energy,
the
stronger
the
impulse
and
the
darker
the
shade
of
grey
on
the
negative
film.
In
this
manner
a
thermal
picture
of
the
ground
is
ipieced
together,
line
by
line,
as
the
mirror
spins
at
rates
proportional
to
the
forward
speed
of
the
aircraft
or
spacecraft.
Multispectral
Scanners
Multispectrall
scanners
operate
on
the
same
principle
as
the
infra-
red
scanners
except
that,
by
adding
additional
detectors
and
a
special
defraction
gratin
to
separate
the
energy
coming
from
the
scanning
mirror,
informati
n
in
the
ultraviolet
and
visible
portions
of
the
spectrum
can
also
be
recorded.
By
recording
the
impulses
coming
from
each
detector
on
a
separate
piece
of
film
or
magnetic
tape,
the
same
ground
scene
can
be
recorded
in
several
so-called
channels.
Scanners
are
now
capable
c4
dividing
the
spectrum
into
as
many
as
24
channels.
This
allows
analysts
the
opportunity
to
determine
which
part
of
the
spectrum
is
best
for
recording
each
type
of
environmental
data.
The
use
of
this
instrument
also
allows
the
researcher
to
compare
and/or
combine
several
channels
to
determine
more
precisely
the
spectral
characteristics
of
an
object.
Side-Looking
Airborne
Radar
(SLAR)
Side-looking
airborne
radar
is
an
all
weather,
day
or
night
sensor
which
is
particularly
effective
in
imaging
large
areas
of
terrain.
It
is
called
an
active
sensor
because
it
generates
its
own
energy,
which
it
tl
y
sends
out
in
shor
pulses
from
a
transmitter
on
the
side
of
the
air-
craft.
This
energ
travels
to
the
Earth,
bounces
off
the
ground
or
objects
on
the
ground,
and
is
returned
to
the
aircraft
where
a
receiving
antenna
collects
it,
converts
it
into
an
electronic
impulse,
and
displays
it
on
a
cathode
ray
or
television
tube.
The
cathode
ray
tube
is
then
photographed,
and
a
permanent
record
of
the
illuminated
terrain
is
made.
The
imagO:y
resulting
from
this
sensor
is
similar
in
appear-
ance
to
a
black
and
white
photograph,
but
contains
much
less
detail
than
a
camera
produced
ipicture.
The
black
areas
on
the
imagery
represent
either
radar
shadows
or
voids
created
when
the
energy
leaving
the
air-
craft
strikes
a
smooth
surface
such
as
a
body
of
water,
and
"skips"
off
at
the
same
angle
fit
which
it
arrived.
If
the
energy
strikes
a
large
object,
however,
a
bright
or
white
return
will
be
recorded
because
a
large
part
of
the
Olergy
is
reflected
back
from
the
object
to
the
receiving
antenna.
The
principal
advantages
of
using
SLAR
are
speed
and
scope
of
areal
coverage,
enhancem6nt
of
the
Earth's
physical
features,
and
the
fact
that
it
can
be
flown
day
or
night
in
any
type
of
weather.
In
addition,
some
SLAR
systems
can
penetrate
certain
types
of
vegetation,
thus
pro-
viding
a
picture
o
the
surface
below
the
trees
or
bushes.
The
scale
at
N.i7hich
SLAR
imagery
is
usually
collected
is
approxi-
mately
1:240,000.
Thus,
the
scale
is
too
small
to
record
most
types
of
8
environmental
pollution.
It
can be
used,
however,
to
detect
disturbed
ground
associated
with
mining
and
quarrying
activities,
or
to
detect
large
oil
spills,
1
since
these
spills
tend
to
subdue
wave
action
and
consequently
image
darker
than
the
surrounding
waters.
Correlation
Spectrometers
The
correlation
spectrometer
is
a
device
built
to
detect
gases
in
the
atmosphere
frbm
spacecraft,
aircraft,
or
ground-based
platforms.
It
is
capable
of
detfcting
sulfur
dioxide
and
nitrogen
dioxide,
two
air
pollutants
which
are
major
components
of
smog.
The
operation
of
a
spectrometer
depends
upon
reflected
or
scattered
energy,
which
is
follected
by
a
telescope
on
the
imaging
platform
and
passed
through
a
special
grating
or
prism.
This
spectrum
of
incoming
radiation
is
thenlprojected
onto
an
optical
mask,
which
contains
a
photographic
repll_ca
of
the
spectrum
of
gas
that
is
being
sought.
By
vibrating
the
incoming
spectrum
across
this
mask,
a
correlation
can
(or
cannot)
be
established.
If
the
gas
sought
is
present,
the
two
spectra
will
match
and
a
so-called
beat
signal
will
be
generated.
By
recording
the
amplitude
of
these
signals,
a
quantitative
measurement
of
the
amount
of
gas
in
the
ana]1yzed
air
column
below
the
aircraft
or
spacecraft
can
be
made.
The
more
gas
present,
the
better
the
match
and
the
stronger
the
signal.
This
signal
intensity
is
recorded
on
a
strip
chart
recorder;
and,
thus,
by
plotting
these
readings
along
the
line
of
flight,
a
profile
of
gas
concentrations
can
be
made.
Correlation
Spectrometers
have
been
used
mostly
in
aircraft,
but
they
may
also
be
placed
in
balloons
or
in
mobile
vans
for
use
on
the
ground.
They
could
also
be
placed
in
a
spacecraft
for
experimental
pur-
poses
at
some
timed
in
the
future.
Fraunhofer
Line
Di
scriminator
(FLD)
The
Fraunhofer
line
discriminator
is
an
experimental
remote
sensor
built
to
detect
and
measure
fluorescence.
The
prototype
instrument
was
built
to
detect
solar-stimulated,
yellow
fluorescence
emitted
by
Rhodamine
WT
dye.
This
dye
is
widely
used
as
a
trace
element
in
current
and
flow
studies
of
harbors,
lakes,
and
rivers.
In
recent
tests
in
San
Francisco
Bay,
for
example,
dye
concentrations
as
small
as
5
parts
per
billion
were
recorded
from
both
helicopter
and
ship
platforms.
3
The
FLD
operates
on
the
principle
that
sunlight
stimulates
certain
substances
in
the
natural
environment
to
fluoresce.
This
means
that,
while
each
substanCe
reflects
solar
radiation,
it
also
emits
some
of
its
own
energy
at
a
specific
point
or
line
on
the
electromagnetic
spectrum.
Fluorescence
is
very
difficult
to
see
with
the
naked
eye
because
sun-
light
is
so
bright;
but,
by
designing
the
sensor
to
record
energy
only
at
a
particular
line,
one
can
detect
the
presence
of
the
substance
emitting
the
energy.
Preliminary
research
indicates
that
additional
FLD's
can
be
built
to
detect
such
substances
as
crude
oil,
fish
oil,
the
pulp
mill
pollutant
called
lignin
sulfonate,
and
other
natural
and
man-
made
substances
that
fluoresce.
One
limiting
factor
in
the
use
of
FLD's
is
that
they
can
only
be
used
when
the
sun
is
shining.
9
Scintillation
Deectors
A
scintillatlion
detector
is
a
special
device
built
to
detect
gamma
radiation
with
enrgy
levels
greater
than
50
Kev
(kilo
electron
volts).
These
devices
are
usually
referred
to
as
aeroradioactivity
equipment
and
are
mounted
in
lot'-flying
aircraft
to
detect
and
monitor
nuclear
radia-
tion
including
comic
radiation,
radionuclides
in
the
air,
and
radio-
nuclides
in
the
sprficial
layer
of
the
Earth.
The
sensors
are
internally
calibrated
in
cycles
per
second
(cps)
and
use
a
series
of
thallium-
activated
sodium
iodide
crystals
to
detect
energy
pulses
greater
than
50
Kev.
Once
an
O
ncoming
signal
is
detected,
it is
then
split
and
channeled
through
two
rate
meters.
One
meter
is
designed
to
measure
total
radiation,
end
the
other
is
designed
to
subtract
cosmic
and
air-
craft
background
radiation
which
may
be
contributing
to
the
incoming
energy
signal.
Once
this
is
done,
a
correction
is
made
for
the
altitude
of
the
aircraft
and
a
net
radiation
signal
is
recorded.
These
data
are
then
collected
ancri
compared
with
similar
flight
data.
The
resulting
changes
are
plotted
on
maps,
and
individual
ranges
or
radioactivity
levels
are
assign4d
to
each
area.
CONCLUSIONS
Environmental
monitoring
programs
using
remote
sensing
systems
in
spacecraft
and
aircraft
have
been
conducted
sporadically
across
the
United
States
by
Universities,
research
groups,
government
agencies,
and
private
industry.
Examples
of
data
from
these
efforts
can
be
seen
in
various
scientific
journals,
professional
reports,
technical
papers,
etc.
For
the
mosti
part,
these
studies
demonstrate
that
remote
sensors
do
possess
unique
(capabilities
which
make
them
valuable
for
environ-
mental
monitoring.
Some
specific
advantages
are:
1.
They
proviide
a
synoptic
or
small
scale
view
of
a
region,
thus
making
it
possible
to
study
the
whole
area
as
the
sum
of
its
parts.
2.
They
provide
a
permanent
record
of
a
situation
at
a
particular
location
and
point
in
time.
Then
when
a
second
record
has
been
collected
a
comparison
can
be
made
to
determine
change.
In
this fason
many
significant
seasonal,
cause
and
effect,
or
time
laps
factors
can
be
determined.
3.
In
providing
certain
kinds
of
environmental
data,
this
type
of
approach
is
inexpensive
if
one
wishes
to
survey
large
areas
of
terrain.
lIn
fact,
a
natural
fallout
of
any
regional
land
use
study
will.
be
the
identification
of
critical
environmental
zones
and
many
evidences
of
pollution.
4.
The
employment
of
remote
sensing
devices
allows
scientists
and
planners
the
opportunity
to
study
pollution
by
monitoring
it
in
different
(
parts
of
the
electromagnetic
spectrum:
thus,
expanding
the
users'
range
of
sensory
perception.
10
5.
Data
produced
by
remote
sensors
can
be
analyzed
and
enhanced
using
special
equipment,
thus
providing
supplementary
informa-
tion
l
in
addition
to
the
original
record.
Since
remote
sensing
should
not
be
considered
a
panacea
for
every
type
of
environmental
study,
certain
disadvantages
should
be
pointed
out.
1.
The
determination
of
whether
something
is
a
pollutant
or
not
usually
is
based
on
a
subjective
analysis
of
the
data
rather
than,
a
quantitative
one.
This
is
true
since
most
of
the
presently
available
sensors
only
record
color
or
temperature
differences.
2.
The
identification
and
time
lapse
monitoring
of
most
effluents,
or
pollution
sources,
requires
large
scale
data.
Currently
scheduled
satellite
systems
and
high
altitude
small
scale
data
will
not
allow
monitoring
of
many
types
of
pollutants.
3.
The
cost
of
using
remote
sensing
systems
is
very
high
if
one
is
only
j_nterested
in
covering
a
small
area
or
identifying
a
few
sources
of
pollution.
4.
In
order
to
correctly
use
and
understand
remote
sensing
systems
and
derived
data
products,
education
and
training
programs
need
Ito
be
established.
This
applies
not
only
for
scientists
and
other
users
but
for
judges
and
lawyers
who
may
have
to
accept
these
data
as
evidence
in
court
cases.
RECOMMENDATIONS
Concern
for
environmental
problems
appears
to
be
increasing
through-
out
the
world.
This,
of
course,
has
led
many
people
to
expect
a
global
solution
to
many
problems.
While
this
is
a
worthy
goal
to
pursue,
it
does
not
appear'
that
we
can
find
a
global
solution
for
each
problem
or
even
that
we
khow
now
what
each
solution
might
require.
National
and/or
regional
programs
will
probably
have
to
take
the
first
steps.
Recommendations
have
been
made
by
many
groups
and
individuals
within
the
remote
sensing
community
concerning
needs
in
the
environmental
monitoring
area.
Perhaps
the
most
critical
need
at
the
present
time
is
the
lack
of
adequate
information
on
the
physical,
chemical,
and
ecolog-
ical
aspects
of
the
environment.
In
1970
the
report
of
the
study
of
critical
environmental
problems
entitled
Man's
Impact
on
the
Global
Environment,
the
following
set
of
recommendations
were
made.
1.
We
recommend
the
development
of
new
methods
for
gathering
and
compiling
global
economic
and
statistical
information,
which
organize
data
across
traditional
areas
of
environmental
responsibility,
such
as
air
and
water
pollution.
We
further
recomirend
the
propagation
of
uniform
data-collection
standards
to
enslure,
for
example,
that
industrial
production
data
collection
across
the
world
will
be
of
comparable
precision
and
focus.
11
2.
We
recommrd
a
study
of
the
possibility
of
setting
up
inter-
national
physical,
chemical,
and
ecological
measurement
stan-
dards,
to
l
be
administered
through
a
monitoring
standards
center
with
a
"real
time"
data
analysis
capability,
allowing
for
prompt
feedback
to
monitoring
units
in
terms
of
monitoring
or
measure-
ment
parameters,
levels
of
accuracy,
frequency
of
observation,
and
other
factors.
3.
We
recommend
an
immediate
study
of
global
monitoring
to
examine
the
scientific
and
political
feasibility
of
integration
of
existing
and
planned
monitoring
programs
and
to
set
out
steps
necessary
I
to
establish
an
optimal
system.
In
1971
a
50-Man
team
of
the
leading
United
States
authorities
in
the
field
of
remotelsensing
of
pollution
published
a
summary
of
work
and
recommendations
entitled
Remote
Measurement
of
Pollution
(NASA-SP-285).
In
addition
to
many
recommendations
for
monitoring
specific
land,
air
and
water
pollutants,
the
report
suggested
establishing
a
Prototype
Operational
EnvironMental
Monitoring
System
(POEMS)
for
use
on
both
a
local
and
regional
]basis
to
solve
specific
environmental
problems.
In
general,
it
I
can
be
said
that
more
research
and
development
for
environmental
monitoring
is
required
especially
in
the
development
of
quantitative
sensor;
that
training
courses
need
to
be
established
so
that
a
wider
range
6f
users
can
learn
to
use
remote
sensing;
and
that
more
emphasis
needslto
be
placed
on
the
international
exchange
of
data/
information
and
the
l
establishment
of
global
monitoring
programs.
FOOTNOTES
1
Scherz,
James
P.
and
Stevens,
Alan
R.:
1970,
An
Introduction
to
Remote
Sensing
for
Environmental
Monitoring:
University
of
Wisconsin,
Institute
for
Envirdnmental
Studies,
Report
1,
p.
5.
2
Michigan,
University,
Willow
Run
Labs.:
1966,
NASA/MSC
Training
Course
in
Remote
Sen
i
sing:
Ann
Arbor,
Michigan,
Section
2,
p.
2.
3
Stoertz,
Georg
E.,
Hemphill,
William
R.
and
Markle,
David
A.:
1969,
Airborne
Fluorlometer
Applicable
to
Marine
and
Estaurine
Studies:
Marine
Technology
Solciety
Journal,
v.
3,
no.
6,
p.
11.
12