Transcript Lecture 3: Sensors

Lecture 5: Orbit
• read
King et al. Appendix
Satellite Orbits
• At what location is the satellite looking?
• When is the satellite looking at a given
location?
• How often is the satellite looking at a given
location?
• At what angle is the satellite viewing a
given location?
Altitude classifications
• Low Earth orbit (LEO): Geocentric orbits
ranging in altitude from 0–2000 km (0–1240
miles)
• Medium Earth orbit (MEO): Geocentric orbits
ranging in altitude from 2000 km (1240 miles) to
just below geosynchronous orbit at 35786 km
(22240 miles). Also known as an intermediate
circular orbit.
• High Earth orbit (HEO): Geocentric orbits
above the altitude of geosynchronous orbit
35786 km (22240 miles).
• the satellite’s height, eccentricity, and
inclination determine the satellite’s path
and what view it will have of Earth.
Kepler’s laws
1. Satellites follow an elliptical orbit with the Earth
as one focus
Foci
Perigee
Apogee
3rd law (law of harmonics): The square of a planet's orbital period is
proportional to its mean distance from the Sun cubed. The mathematical way
to describe Kepler's 3rd law is:
P2 ~R3
Ellipse
• An ellipse is defined as follows: For two given points, the foci, an
ellipse is the locus of points such that the sum of the distance to
each focus is constant.
• BTW, Locus -- A word for a set of points that forms a geometric
figure or graph
Physics for satellite
Centripetal Force, Gravity
When a body moving in a circle, from Newton's 2nd law there must be a force
acting on it to cause the acceleration. This force will also be directed toward
the centre and is called the centripetal force.
F1 = ma = mv2/r = mrω2
Where m is the mass of the body and v is the speed in the circular path of radius r
Newton's 2nd law
F2 = ma
g= GM/r2
2
4

T2=
r3
Gme
Period of orbit
Period of orbit
2
4

T2=
r3
Gme
Gravitational constant
Radius of the orbit
Mass of the Earth
• Valid only for circular orbits (but a good
approximation for most satellites)
• Radius is measured from the center of the
Earth (satellite altitude+Earth’s radius)
• Accurate periods of elliptical orbits can be
determined with Kepler’s Equation
Definition of Orbital Period of a
Satellite
The orbital period of a satellite around a
planet is given by
T0  2( R p  H )
R p  H 
2
gs R p
where
T0 = orbital period (sec)
Rp = planet radius (6380 km for Earth)
H = orbit altitude above planet’s surface (km)
gs = acceleration due to gravity (0.00981 km s-2 for Earth)
Eccentricity
Eccentricity refers to the shape of the orbit. A satellite with a low eccentricity
orbit moves in a near circle around the Earth. An eccentric orbit is elliptical,
with the satellite’s distance from Earth changing depending on where it is in its orbit.
Orbital inclination
• Inclination is the angle of
the orbit in relation to
Earth’s equator. A
satellite that orbits directly
above the equator has
zero inclination. If a
satellite orbits from the
north pole (geographic,
not magnetic) to the
south pole, its inclination
is 90 degrees.
Types of orbits
• Sunsynchronous orbits: An orbit in which the
satellite passes every location at the same
time each day
– Noon satellites: pass over near noon and midnight
– Morning satellites: pass over near dawn and dusk
– Often referred to as “polar orbiters” because of the
high latitudes they cross
– Usually orbit within several hundred to a few
thousand km from Earth
Types of orbits
• Geostationary (geosynchronous) orbits:
An orbit which places the satellite above
the same location at all times
– Must be orbiting approximately 36,000 km
above the Earth
– Satellite can only “see” one hemisphere
Atmospheric Remote Sensing Sensors,
Satellite Platforms, and Orbits
• Satellite orbits and platforms
– Low Earth orbit
• Sunsynchronous and repeat coverage
• Precessing
– Geosynchronous orbit
• Sensor scanning modes
– Whiskbroom and pushbroom scanners
– Active and passive microwave radiometers
Next lecture
Sun Synchronous (Near Polar)
• Video
Sun-Synchronous Orbit at 800km
http://www.youtube.com/watch?v=NCwL
BlsAMNg
• Terra orbit http://www.met.sjsu.edu/~jin/PersonalLi
b.html
Low Earth Orbit Concepts
Descending node
Ascending
node
Perigee
Ground track
Orbit
Inclination
angle
Equator
Orbit
South Pole
Apogee
Sun-Synchronous Polar Orbit
Earth
Revolution
Equatorial
illumination
angle
Satellite
Orbit
• Satellite orbit precesses (retrograde)
– 360° in one year
• Maintains equatorial illumination angle constant throughout the year
– ~10:30 AM in this example
Sun-Synchronous Orbit of Terra
Spacing Between Adjacent Landsat
5 or 7 Orbit Tracks at the Equator
Timing of Adjacent Landsat 5 or
7 Coverage Tracks
Adjacent swaths are imaged 7 days apart
Polar-Orbiting Satellite in Low
Earth Orbit (LEO)
Example from Aqua
Tropical Rainfall Measuring
Mission Orbit (Precessing)
A precessing lowinclination (35°),
low-altitude (350
km) orbit to achieve
high spatial
resolution and
capture the diurnal
variation of tropical
rainfall
– Raised to 402 km in
August 2001
TRMM Coverage
1 day coverage
2 day coverage
Orbital Characteristics of Selected Missions
Low Earth Orbit & Precessing Missions
Satellite
Jason-1
Meteor-3M/SAGE III
Landsat 1-3
SPOT
NOAA
QuikScat
ACRIMSAT
Landsat 4-7
Terra, Aqua, Aura
ICESat
UARS
ERBS
SORCE
TRMM
TRMM
Altitude
(km)
1336
1020
907-915
832
850
803
720
705
705
Inclination
(°)
66
99.5
99.2
98.7
98-99
98.6
98.1
98.2
98.2
600
585
610
640
402
350
94
57
57
40
35
35
Orbital Period
(min)
112.3
105.5
103.1
101.5
102-104
100.9
99.1
98.8
98.8
96.6
96.3
96.8
97.5
92.6
91.5
Repeat
Coverage
10
18
26
11
16
16
–
–
–
–
–
–
Orbits/day
12.8
13.7
14.0
14.2
14.0
14.3
14.5
14.6
14.6
14.9
14.9
14.9
14.8
15.6
15.7
Sunsynchronous image (SMMR)
Sunsynchronous image
(AVHRR)
Types of orbits
• Geostationary (geosynchronous) orbits:
An orbit which places the satellite above
the same location at all times
– Must be orbiting approximately 36,000 km
above the Earth
– Satellite can only “see” one hemisphere
Video for Geo. satellite
• http://www.youtube.com/watch?v=_FfwTS
3yClc
Geostationary Image (GOES8)
Geostationary satellites
• GMS (Japan)
– Geostationary Meteorological Satellite
– Located over 140ºE longitude
– Similar to older GOES satellites
• Insat (India)
– Located over 74ºE longitude
– Insat 1B similar to GOES-8/9
• Meteosat (European Union)
– Located over 0º longitude
• FY 2 and FY 4 (China)
Geosynchronous Meteorological Satellites
WMO Member States
Sector
West-Pacific
East-Pacific
West-Atlantic
East-Atlantic
Indian Ocean
Satellites in Orbit
(+mode)
MTSAT-1R (Op)
MTSAT-2 (B)
GOES-9 (B)
Operator
Japan
Japan
USA/NOAA
Location
140°E
145°E
160°E
Launch
date
2/26/05
2/18/06
5/99
GOES-11 (Op)
GOES-10 (B)
GOES-12 (Op)
GOES-13 (P)
Meteosat-6 (B)
Meteosat-7 (B)
Meteosat-8 (Op)
Meteosat-9 (P)
Meteosat-5 (Op)
USA/NOAA
USA/NOAA
USA/NOAA
USA/NOAA
EUMETSAT
EUMETSAT
EUMETSAT
EUMETSAT
EUMETSAT
135°E
60°W
75°W
89.5°W
10°E
0°E
3.4°W
6.5°W
63°E
5/00
4/97
7/01
5/06
11/93
2/97
8/28/02
12/21/05
3/91
GOMS-N1 (B)
FY-2C (Op)
Kalpana-1 (Op)
INS AT-3A (Op)
Russia
China/CMA
India
India
76°E
105°E
74°E
93.5°E
11/94
10/19/04
9/12/02
4/10/03
Status
Fully functional
Back-up to MTSAT-1R
Dissemination not
activated
GOES-West
South America coverage
GOES-East
In commissioning
Rapid scan anomaly
To be relocated to 57.5°E
EUMETCAST
In commissioning
Functional but high
inclination mode
Standby since 9/98
Functional
Dedicated
Operational
Geostationary satellites
• GOES 4-7 (USA)
– Geostationary Operational
Environmental Satellite
– Spin stabilized... pointing toward
Earth 5% of the time
– Rotation rate of 100 rpm, 18.21
minutes are required to
complete one full scan
– VAS (VISSR Atmospheric
Sounder)
• Visible/Infrared Imaging Spin Scan
Radiometer
Geostationary satellites
• GOES-8/(9)/10/11/12 (USA)
– GHIS (GOES High Resolution
Interferometer Sounder)
– Sounder 2-3X more accurate
– 5 Visible/IR channels
– 18 IR sounder bands
(channels)
– 3-axis stabilized... always
pointing toward Earth
– 75ºW-GOES 12; 135ºW-GOES
11
•
What’s Next
•
•
•
•
GOES-13 launced in 2006
GOES-O launched on 20 July 2008
GOES-P launched on 30 May 2009
GOES-Q has no spacecraft manufacturer or
launch date (Cancelled)
• GOES-R series of spacecraft is in the
formulation phase.
GOES-R Scheduled for 2014
GOES-8/10 diagram
– Clouds
– Pollution
– Haze
– Severe
storms
Channel 1: 0.52-0.72 m (Visible)
– Nighttime fog
– Nighttime SSTs
– Liquid vs. ice clouds
– Fires and volcanoes
Channel 2: 3.78-4.03m (Shortwave infrared)
– Standard water
vapor
– Mid-level moisture
– Mid-level motion
Channel 3: 6.47-7.02 m (Upper-level water vapor)
– Standard IR channel
– Winds
– Severe storms
– Heavy rainfall
Channel 4: 10.2-11.2 m (Longwave infrared)
– Low-level moisture
– SSTs
– Volcanic dust or ash
Channel 5: 11.5-12.5 m (Infrared/water vapor)
Sounder IR bands 2, 3, 4 and 5 (temperature)
Sounder IR bands 8, 10, 11 and 12 (water vapor)
FYI
• The following section is just FYI
GOES-8/10 imager
Channel and Wavelength
Product
Clouds
Water
vapor
Surface
temp.
Winds
Albedo
Fires and
smoke
1
2
3
4
5
0.65 m
3.9 m
6.7 m
11 m
12 m
GOES-8/10 imager
Channel and Wavelength
Product
Clouds
Water
vapor
Surface
temp.
Winds
Albedo
Fires and
smoke
1
2
3
4
5
0.65 m
3.9 m
6.7 m
11 m
12 m
GOES-8/10 sounder
Resolution (km)
Temp.
profile
Land temp.
Vertical
Horizontal
Absolute
Relative
3-5
50
2-3K
1K
10
2K
1K
10
1K
0.5K
50
30%
20%
10
20%
10%
10
50mb
25mb
10
15%
5%
SST
Moisture
profile
Total
moisture
Cloud
height
Cloud
amount
Accuracy
2-4
2 layers
GOES-8/10 sounder
Resolution (km)
Temp.
profile
Land temp.
Vertical
Horizontal
Absolute
Relative
3-5
50
2-3K
1K
10
2K
1K
10
1K
0.5K
50
30%
20%
10
20%
10%
10
50mb
25mb
10
15%
5%
SST
Moisture
profile
Total
moisture
Cloud
height
Cloud
amount
Accuracy
2-4
2 layers
Non-Photographic Sensor
Systems
•
•
•
•
•
•
•
•
•
•
•
•
•
1800 Discovery of the IR spectral region by Sir William Herschel.
1879 Use of the bolometer by Langley to make temperature measurements of
electrical objects.
1889 Hertz demonstrated reflection of radio waves from solid objects.
1916 Aircraft tracked in flight by Hoffman using thermopiles to detect heat effects.
1930 Both British and Germans work on systems to locate airplanes from their
thermal patterns at night.
1940 Development of incoherent radar systems by the British and United States to
detect and track aircraft and ships during W.W.II.
1950's Extensive studies of IR systems at University of Michigan and elsewhere.
1951 First concepts of a moving coherent radar system.
1953 Flight of an X-band coherent radar.
1954 Formulation of synthetic aperture concept (SAR) in radar.
1950's
Research development of SLAR and SAR systems by Motorola,
Philco, Goodyear, Raytheon, and others.
1956 Kozyrev originated Frauenhofer Line Discrimination concept.
1960's
Development of various detectors which allowed building of imaging
and non-imaging radiometers, scanners, spectrometers and polarimeters.
1968 Description of UV nitrogen gas laser system to simulate luminescence.
Sunsynchronous satellites
• TIROS (renamed NOAA) (USA)
– Advanced Very High Resolution
Radiometer
• 1.1km resolution (LAC) or 4km (GAC)
Band #
1
2
3
4
5
Satellites:
NOAA-6,8,10
0.58 - 0.68 m
0.725 - 1.10 m
3.55 - 3.93 m
10.50 - 11.50 m
band 4 repeated
NOAA-7,9,11,12,14
0.58 - 0.68 m
0.725 - 1.10 m
3.55 - 3.93 m
10.3 - 11.3 m
11.5 - 12.5 m
Channel 3A (1.6 m) added to new AVHRR/3
sensor in spring 1996
AVHRR thermal IR imagery of Gulf Stream
AVHRR multi-channel SSTs
TIROS
AVHRR Normalized Difference Vegetation Index
Sunsynchronous satellites:
TIROS/NOAA
– TIROS Operational Vertical Sounder (TOVS)
• October 78 to present
• Three units to TOVS: MSU, HIRS, SSU (Stratospheric
Sounding Unit)
– High Resolution Infrared Radiation Sounder (HIRS/2
& /3
• Vertical temperature profiles to 40km
• 20 infrared bands
– Microwave Sounding Unit (MMU)
• Vertical temperature profile to 20km
• 4 microwave channels
• Complements HIRS when clouds are present
MSU mid-troposphere temperatures
MSU mid-troposphere vorticity
Sunsynchronous satellites:
TIROS/NOAA
– Advanced Microwave Sounding Unit (3 units)
• AMSU-A1, AMSU-A2, AMSU-B
• Replace MSU and SSU
POES Satellite Soundings
24 Hour Coverage - 2 Satellites
Total Precipitable Water
http://poes.nesdis.noaa.gov/posse/
POES Satellite Soundings
Coverage in Polar Regions
Gray:
Clear Areas
White/Blue: Clouds
Soundings Available for Both
Clear and Cloudy Conditions
POES Satellite Soundings
Individual Temperature/Moisture Profile
Sunsynchronous satellites
• Defense Meteorological Satellite Program
(DMSP) (USA)
– Operational Linescan System (OLS)
• Visible imagery (0.55km resolution)
• Visible and thermal IR channels
DMSP OLS image of Hurricane Emily
DMSP OLS image of city lights
Sunsynchronous satellites:
DMSP
– Special Sensor Microwave/Imager
• 19, 22, 37 and 85 GHz channels
• Uses include: snow cover, sea ice, precipitation
rate, oceanic wind speed, water vapor, soil
moisture
• Similar sensors: SMMR and ESMR
– Microwave temperature sounder (SSM/T)
– Microwave water vapor profiler (SSM/T2)
DMSP SSM/I precipitation rates during the Blizzard of ‘93
NPOESS
•
•
•
National Polar Orbiting Operational
Environmental Satellite System
Will converge NOAA, DoD and NASA missions
in a next generation instrument.
– Follow on to NOAA series of satellite
(AVHRR) and DoD DMSP series
– Continues NASA’s EOS Terra and Aqua
missions
Launch 2009 with missions to 2018???
NPOESS instruments
133
0
1730
2130
Visible/Infrared Imager/Radiometer Suite (VIIRS)
X
X
X
Conical Microwave Imager/Sounder (CMIS)
X
X
X
Crosstrack Infrared Sounder (CrIS)
X
X
X
Advanced Technology Microwave Sounder (ATMS)
X
X
X
Space Environment Sensor Suite (SESS)
X
X
Ozone Mapping and Profiler Suite (OMPS)
X
Advance Data Collection System (ADCS)
X
X
Search and Rescue Satellite Aided Tracking (SARSAT)
X
X
Total Solar Irradiance Sensor (TSIS)
Earth Radiation Budget Sensor (ERBS)
X
X
X
X
Aerosol Polarimeter Sensor (APS)
Survivability Sensor (SS)
X
X
X
X
X
RADAR Altimeter (ALT)
NP
P
X
X
NPOESS Preparatory Mission
• NPP is a bridge between the EOS program and
NPOESS for the development of the following
sensors:
–
–
–
–
Advanced Technology Microwave Sounder (ATMS)
Cross-track Infrared Sounder (CrIS)
Ozone Mapping and Profiler Suite (OMPS)
Visible/Infrared Imager Radiometer Suite (VIIRS)
• Its mission is to demonstrate advanced
technology and giving continuing observations
about global change after EOS-PM (Terra) and
EOS-AM (Aqua).
• Launch late ??