Active Remote Sensing Applications to
Disaster Management
Radarsat
SRTM
TRMM
JASON
Seawinds
Cloudsat
Authored by: Bryan HUNEYCUTT (NASA/ JPL)
Presented by: Thomas.vonDeak@nasa.gov
NASA HQ Spectrum Management Office
ACTIVE SENSOR TYPES

SYNTHETIC APERTURE RADARS
Sensors looking to one side of the nadir track, collecting a phase and time history of
the coherent radar echo from which typically can be produced a radar image or interferometric topographical map of the Earth’s surface

ALTIMETERS
Sensors looking at nadir, measuring the precise time between a transmit event and
receive event, to extract the precise altitude of the Earth’s ocean surface

SCATTEROMETERS
Sensors looking at various aspects to the sides of the nadir track, using the measurement of the return echo power variation with aspect angle to determine the wind
direction and speed on the Earth’s ocean surface


PRECIPITATION RADARS
Sensors scanning perpendicular to nadir track, measuring the radar echo from rainfall, to determine the rainfall rate over the Earth’s surface concentrating on the tropics
CLOUD PROFILE RADARS
Sensors looking at nadir, measuring the radar echo return from clouds, to determine
the cloud reflectivity profile over the Earth’s surface
July 26, 2007
Radarsat
JASON
Seawinds
TRMM
Cloudsat
2
ACTIVE SPACEBORNE SENSOR
CHARACTERISTICS
Characteristics
Sensor Types
SAR
Viewing Geometry
Altimeter
Nadir-looking
Typical swath width
Side-looking @20-55
deg off nadir
(1) Fixed to one side
(2) ScanSAR
500 km max (Radarsat)
Typical altitude
Scatterometer
Precipitation Radar
Cloud Radar
Fixed at nadir
Two conical scanning
beams about nadir
Scanning in azimuth
26 km (Jason)
1800 km (SeaWinds)
Scanning across nadir
track
220 km (TRMM)
790 km (Radarsat)
1336 km (Jason)
803 km (SeaWinds)
350 km (TRMM)
705 km (Cloudsat)
Typical inclination
98.5 deg (Radarsat)
66 deg (Jason)
98.2 deg (SeaWinds)
35 deg (TRMM)
98.2 deg (Cloudsat)
Antenna Beam
Fan beam
Pencil beam
Pencil beams
Pencil beam
Pencil beam
Radiated Peak Power
5000 W (Radarsat)
8-25 W (Jason)
110W (SeaWinds)
600 W (TRMM)
1700 W (Cloudsat)
Waveform
Linear FM pulses
Linear FM pulses
Linear FM pulses
Short pulses
Short pulses
Spectrum Width
50 MHz (Radarsat)
320 MHz (Jason)
375 kHz (SeaWinds)
0.6 MHz (TRMM)
300 kHz (Cloudsat)
Spatial Resolution
100m x 100m
(Radarsat)
6km x 25km
(SeaWinds)
250m x 4.3km (TRMM) 500m x 1.5km
(Cloudsat)
Key spectrum bands
0.432-0.438 GHz
1.215-1.3 GHz
3.1-3.3 GHz
5.25-5.57 GHz
8.55-8.65 GHz
9.5-9.8 GHz
Flooding, oil spills,
volcanic eruptions,
severe storms,
landslides, ice,
earthquakes, fires
0.5m x 5km with 1-2
cm accuracy over 5km
circle of ocean (Jason)
3.1-3.3 GHz
5.25-5.57 GHz
8.55-8.65 GHz
9.5-9.8 GHz
13.25-13.75 GHz
35.5-36.0 GHz
Flooding, drought,
hurricanes
5.25-5.57 GHz
8.55-8.65 GHz
9.5-9.8 GHz
13.25-13.75 GHz
17.2-17.3 GHz
35.5-36.0 GHz
Flooding, severe
storms, drought,
hurricanes, ice
13.25-13.75 GHz
17.2-17.3 GHz
24.05-24.25 GHz
35.5-36.0 GHz
94.0-94.1 GHz
133.5-134.0 GHz
237.9-238.0 GHz
Hurricanes, severe
storms
Hurricanes, severe
storms
Footprint/ Dynamics
Disaster Management
Applications
July 26, 2007
Nadir-looking
Nadir-looking
Fixed at nadir
1-2 km (Cloudsat)
3
Synthetic Aperture Radars

Provide radar images, change detection maps and/or interferometric topographical
maps of the Earth’s surface

RF center frequency depends on the Earth’s surface interaction with the EM field

RF bandwidth affects the resolution of the image pixels

RADARSAT in wide scansar mode uses 50 MHz bandwidth with 100m spatial resolution
v
SAR
Illumination
Swath
t =t1 
t t=0 0

h
F(
Xa

Chirp Spectrum   
  
July 26, 2007
f0

f1

s
4
Synthetic Aperture Radars (contd)
RADARSAT-1 is a 5-GHz radar
and has been successfully used
world wide to support disaster
response efforts during events
such as flooding, oil spills,
volcanic eruptions and severe
storms. The following Radarsat
image (right) shows two flooded
areas in north central Bulgaria
in early June 2005 with respect
to the reference Landsat image
(left).
July 26, 2007
5
Altimeters
• Provide altitude of the Earth’s ocean
surface, along with wave height, wind
speed, and residual sea level anomaly
• RF center frequency depends on the
ocean surface interaction with the EM
field
• Dual frequency operation allows
ionospheric delay compensation
• TOPEX/POSEIDON uses frequencies
around 13.6 GHz and 5.3 GHz
• JASON uses 320 MHz RF bandwidth, for
0.5m vertical resolution and 1-2 cm
height accuracy over 5km circle of ocean
t2
t1
(a)
t
t
(b)
t
(c)
t
(d)
tr
td
Illustration of Altimeter Return
July 26, 2007
6
Altimeters (contd)
Jason is a dual-frequency radar at 5-GHz and
13-GHz, using radar altimetry to collect sea
surface height data of all the world's oceans.
Understanding the pattern and effects of climate
cycles such as El Niño helps predict and
mitigate the disastrous effects of floods and
drought. Altimeter and scatterometer data are
incorporated into atmospheric models for
hurricane season forecasting and individual
storm severity. Maps of currents, eddies, and
vector winds are used in commercial shipping
and recreational yachting to optimize routes.
Cable-laying vessels and offshore oil operations
require accurate knowledge of ocean circulation
patterns to minimize impacts from strong
currents. The following altimeter
measurements taken during Hurricane Katrina
in late August 2005 are shown to the right
comparing altimeters Topex and Jason-1(top
row), ERS-2 and Envisat (center row), and
Geosat follow on (bottom row), compare the GOES 12 infrared images and the altimeters to the left. The
three columns on the right are altimeters measurements of wave height, wind speed, and sea level anomaly
as a function of latitude along the altimeter tracks.
July 26, 2007
7
Scatterometers
•
Provide the wind direction and speed over the Earth’s ocean surface along with
surface soil moisture over land
•
RF center frequency depends on the ocean surface interaction with the EM field
and its variation over aspect angle
•
SeaWinds uses H-polarization at 40 deg beam, V-polarization at 46 deg beam
•
Narrow RF signal bandwidth provides the needed measurement cell resolution
•
SeaWinds uses only 0.375 MHz RF bandwidth, giving a spatial resolution of 6km
Orbit Track
Radio scattering Coefficient (dB)
Sea Winds
800 km
5.5
5.5
12.8
12.8
30
ms-1 Horizontal Polarization
ms-1 Vertical Polarization
ms-1 Horizontal Polarization
ms-1 Vertical Polarization
15
40 deg
Nadir Track
46 Degree Beam
12.8 ms-1
VV
10
Nadir
HH
700 km
5
-1
5.5 ms
VV
Cross Track
HH
0
0
40
80
120
150
200
240
900 km
280
320
360
250 to 800 km Swath*
Azimuth Angle (degrees)
Variation of Backscatter with Aspect
Angle
July 26, 2007
SEAWINDS scanning pencil beam illuminates
scans at two different look angles from nadir, and
scans 360 degrees about nadir in azimuth
8
Scatterometers (contd)
The SeaWinds instrument on
the QuikSCAT satellite is a
specialized 13-GHz microwave
radar that measures nearsurface wind speed and
direction under all weather and
cloud conditions over Earth's
oceans. The following data are
used to monitor changes in
surface water resulting from
Hurricanes Katrina and Rita in
the Mississippi River basin in
Oct 2005. The colors represent
increases in surface soil
moisture resulting from
rainfall.
July 26, 2007
9
Precipitation Radars
•
•
•
•
•
July 26, 2007
Provide precipitation rate over the
Earth’s surface, typically
concentrating on rainfall in the
tropics
RF center frequency depends on
the precipitation interaction with
the EM field
Narrow RF signal bandwidth
provides the needed measurement
cell resolution
Tropical Rainfall Measurement
Mission (TRMM) uses only 0.6
MHz RF bandwidth, giving a
range resolution of 250m
TRMM has a narrow antenna
beam of only 0.71 deg, giving a
cross-range spatial resolution of
about 4.3km
10
Precipitation Radars (contd)
TRMM is the first 13-GHz spaceborne rain radar
that measures the vertical distribution of
precipitation over the tropics. TRMM is a
research satellite designed to help our
understanding of the water cycle in the current
climate system. By covering the tropical and
semi-tropical regions of the Earth, TRMM will
provide much needed data on rainfall and the
heat release associated with rainfall. It will
contribute to our understanding of how clouds
affect climate and how much energy is
transported in the global water cycle. In
coordination with other satellites in NASA's
Mission to Planet Earth, TRMM has begun the
process of understanding the interactions
between water vapor, clouds and precipitation
that is central to regulating the climate system.
The following TRMM image shows the
precipitation profile of the hurricane Ernesto on
26 August, 2006. TRMM reveals several deep
convective towers (shown in red) that top out
over 15km.
July 26, 2007
11
Cloud Profile Radars
• Provide three dimension profile of cloud
reflectivity over the Earth’s surface
• RF center frequency depends on the cloud
interaction with the EM field
• Antennas with very low sidelobes so as to
isolate the cloud return from the higher
surface return illuminated by the sidelobes
• Narrow RF signal bandwidth provides the
needed measurement cell resolution
• CloudSat uses only 0.3 MHz RF bandwidth,
giving a vertical resolution of 500m
• CloudSat has a narrow antenna beam of only
0.12 deg, giving a horizontal resolution of
1.5km
July 26, 2007
12
Cloud Profile Radars (contd)
CloudSat is a Cloud Profiling
Radar (CPR), a 94-GHz nadirlooking radar which measures the
power backscattered by clouds as
a function of distance from the
radar. The following Cloudsat
image is that of radar profiles of
clouds around Hurricane Ileana
on Aug 23, 2006. The top image
is from NOAA’s GOES to show
the storm from the top. The
bottom image is from CloudSat
giving a profile of the cloud
reflectivity versus distance from
the radar.
July 26, 2007
13
Disaster Management Applications and
Examples for EESS (active)
Application
Flooding
Example
Description
RADARSAT image
shows Red River
Valley from
Winnipeg to the area
just south of Morris
on April 27, 1997.
Areas of standing
water are shown in
blue.
Application
Oil Spills
Example
Description
RADARSAT
image shows
salvage operations
in July 1996 after
the Irving Whale
barge oil spill off
the coast of the
Maritimes with
three small oil
spills and their
very dark tones.
Application
Landslides
Volcanic
Eruption
SIR-C image of
Kliuchevskoi
volcano, Kamchatka,
Russia, in Oct 1994;
L-band HH red, Lband HV green, Cband HV blue
Severe Storms
SeaWinds data of
Tropical Storm
Alberto on June
10, 2006, in the
Yucatan Channel ;
image depicts
wind speed in
color and wind
direction with
small barbs.
Ice
Drought
TOPEX/Poseidon
satellite imagery of
March 23, 2000,
with persistent La
Nina pattern
dominating the
Pacific Ocean and
lower than normal
sea-surface heights,
indicating cooler
temperatures
Hurricane
TRMM rainfall
data combined
with wind data
from SeaWinds on
QuikSCAT
showing image of
Hurricane Floyd in
Sep 1999
Earthquakes
July 26, 2007
Example
Description
ERS-2 image of
November 16-17,
2000, showing the
village of Log pod
Mangartom,
Slovenia, hit by a
massive landslide.
RADARSAT
images monitoring
1999 spring ice
break-up in
Mackenzie Delta,
in the North West
Territories,
composite image
acquired on May 5
(shown in red),
May 29 (shown in
green) and June 22
(shown in blue).
ERS radar
interferogram
showing a pattern
of ground uplift
between 1996 and
2000 of South
Sister volcano in
central Oregon
with each full
color band
representing about
2.8 cm of ground
movement in
direction of radar
14
Repeat Cycles, Swath Width and Orbital
Characteristics of EESS (active)
Sensors
SARs
RadarSAT-1/2
PALSAR
ERS-1/2
JERS-1/2
ALMAZ
ASAR
TerraSAR-L/X
Altimeters
JASON-1/2
RA2
Topex/Poseidon
Scatterometers
SeaWinds
ERS-1/2
NSCAT
ASCAT
RA-2
Precipitation Radars
TRMM
GPM DPR
Cloud Radar
Cloudsat
July 26, 2007
Repeat Cycle
(days)
Table of Orbital Characteristics of Active Spaceborne Sensors
Altitude (km)
Swath Width
InclinaGlobal Coverage
(km)
tion
Swath width given repeat
Repeat cycle given swath
(deg)
cycle (km)
width (days)
16/24
46
3,35,168/35
44/35
3
35
18
790
692
785
580
300
800
514
500 max
70
102.5
100
45
406 max
200 max/ 100
98.5
98.2
98.5
98.0
73
98.55
97.4
175/117
60
932, 80, 16.6/80
60/76
803
80
147
5.6
39.2
27.3
26
53.5
6.9
13.2/26.4
10
35
10
1336
780
1336
26
16-20
75
66
98.5
66
285
80
285
110
107.3
38
2
35
41
29
35
803
780
800
835
800
1800
500
1400
360
100
98.2
98.5
98.6
98.7
98.55
1405
80
69
98
80
1.56
5.6
2
7.8
28
49
0.125 (3 hrs for core &
8-10 LEOs)
350
400
220
125-245
35
66
30
214 (11 day repeat cycle
for core)
6.6
9.6-18.8 (core)
16
705
1-2
98.2
172
>1370
15
Compatibility Studies by Frequency Band
and Spaceborne Active Sensor Type
Note: (F) Future Proposed, (P) Postulated, and Currently Operating otherwise
Frequency
Band (MHz)
July 26, 2007
SAR
432-438
Available
Bandwidth
(MHz)
6
Spaceborne Active Sensor Type
1215-1300
85
SIR-C, JERS-1
3100-3300
200
ALMAZ
RA2 (F)
5250-5570
320
TOPEX-1/2 (F)
8550-8650
100
RADARSAT-1/2,
ASAR, ERS1/2,
ENVISAT ASAR(F)
(P)
(P)
ERS1/2, NSCAT
(F), METOP
ASCAT (F)
(P)
9500-9800
300
X-SAR
(P)
(P)
9975-10025
50
13250-13750
500
TOPEX, JASON
ERS1/2
17200-17300
100
NSCAT,
SEAWINDS,
ENVISAT RA-2 (F)
(P)
24050-24250
200
35500-36000
500
78000-79000
1000
(P)
94000-94100
100
CLOUDSAT
133500-134000
500
(P)
237900-238000
100
(P)
Altimeter
Scatterometer
Precipitation Radar
Cloud Radar
(F)
TRMM (F)
(P)
(P)
(P)
(P)
(P)
16