The A-Train
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Presentation Schedule
11/25 (Tuesday): Clouds and Climate
Nick Mangieri-- Noctilucent clouds using CloudSat (15-minutes)
Allison Marquardt--The Earth Radiation Budget Experiment (15-minutes)
Ross Alter -- MODIS / Atmosphere (15-minutes)
Lynn DiPretore -- Raman Lidar (15-minutes)
12/2 (Tuesday): Biological Oceanography
Chris Devito, Rob Reale, Antonio Riggi -- Sea Surface Temperature and Phytoplankton (30-minutes)
Emily French -- Phytoplankton and ENSO
Nicole Mentel -- Satellite Detection of Oil Spills (15-minutes)
Americo DeLuca -- Satellite Remote Sensing of Titan and the early Atmosphere of Earth (15-minutes)
12/4 (Thursday): Weather Detection
Reynir Winnar and Steve Sekula -- Severe Weather Detection (20-minutes)
Geoffrey Grek -- Mobile Tornado Radars (15-minutes)
Justin Godynick -- Sea Ice Detection by Satellite (15-minutes)
12/9 (Tuesday): Remaining presentations
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A-TRAIN CONSTELLATION
The Afternoon or "A-Train" satellite constellation presently
consists of 5 satellites; NASA's Aqua and Aura satellites,
CNES' PARASOL satellite, and the CALIPSO and CloudSat
satellites inserted in orbit behind Aqua in April 2006.
Two additional satellites, OCO and Glory,
will join the constellation in
late 2008.
Approx equator
crossing times
The satellites in the A-Train are
maintained in orbit to match the World
Reference System 2 (WRS-2) reference
grid used by Landsat.
CloudSat and CALIPSO travel within
15 seconds of each other so that
both instrument suites view the
same cloud area at nearly the same
moment. This is crucial for studying
clouds which have lifetimes often
less than 15 minutes.
The constellation has a nominal orbit altitude of 705 km and inclination of 98o.
Aqua leads the A-train with an equatorial crossing time of about 1:30 pm.
CloudSat and CALIPSO lag Aqua by 1 to 2 minutes separated from each other by 10 to 15
seconds.
The World Reference System 2 (WRS-2) was developed to facilitate regular
sampling patterns by remote sensors in the Landsat program.
Landsat-7 and Terra are “morning” satellites in the same orbit as the A-train.
Each satellite completes 14.55 orbits per day with a separation of 24.7 degrees
longitude between each successive orbit at the equator.
The orbit tracks at the equator progress westward 10.8 degrees on succeeding days,
which over a 16-day period produces a uniform WRS grid over the globe. The WRS grid
pattern of 233 orbits with separation between orbits at the equator of 172 km.
The Aqua satellite will be controlled to the WRS grid to within +/- 10 km.
17:40 UTC = 12:40 pm EST
20:55 UTC = 12:55 pm PST
The World Reference System 2 (WRS-2) was developed to facilitate regular sampling
patterns by remote sensors in the Landsat program.
Landsat-7 and Terra are “morning” satellites in the same orbit as the A-train.
Each satellite completes 14.55 orbits per day with a separation of 24.7 degrees longitude
between each successive orbit at the equator.
The orbit tracks at the equator progress westward 10.8 degrees on succeeding
days, which over a 16-day period produces a uniform WRS grid over the globe. The
WRS grid pattern of 233 orbits with separation between orbits at the equator of 172
km.
The heart of Formation Flying, as it is called, is control
boxes.
The satellites are allowed to drift inside control boxes until
they approach the boundaries of the box, then maneuvers
are initiated to adjust the orbit.
This is crucial both to maintain the observing times and
geometries of the instruments, but especially to avoid
collisions, which would produce a debris field that would
threaten the entire formation.
Aqua is kept inside a control box of ±21.5 seconds (about ±158 km) so that it makes precisely
233 complete orbits in 16 days (WRS-2 grid).
CALIPSO is maintained in a ±21.5 second control
box averaging 73 seconds, about 547 km, behind
Aqua, so CALIPSO is never closer than 30 sec
(225 km) to Aqua.
Parasol flies about 131 seconds behind Aqua, and
Aura flies about 900 seconds behind Aqua.
CloudSat flies in a mini formation 12.5±2.5 seconds ahead
of CALIPSO.
The satellites are controlled by different agencies: Aqua and
Aura by NASA/Goddard, CloudSat by US Air Force, PARASOL
by CNES, and CALIPSO by NASA/Langley and CNES.
Horizontal separation is another aspect of Formation
Flying. The first four A-Train satellites fly in tight
formation so they view the same locations from above
in a brief time span. Aura is positioned substantially
behind the others such that its Microwave Limb
Sounder views horizontally the same portion of the
atmosphere that Aqua views from above.
Afternoon Constellation Coincidental Observations
Aura
Glory
OMI - Cloud heights
OMI & HIRLDS – Aerosols
MLS& TES - H2O & temp profiles
MLS & HIRDLS – Cirrus clouds
CALIPSO
CloudSat
PARASOL
Aqua
OCO
OCO - CO2 column
CALIPSO- Aerosol and cloud heights
MODIS/ CERES
Cloudsat - cloud droplets
PARASOL - aerosol and cloud polarizationIR Properties of Clouds
OCO - CO2
AIRS Temperature and
H2O Sounding
(Source: M. Schoeberl)
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CALIPSO
• Joint NASA/CNES satellite
• Three instruments:
– Cloud-Aerosol Lidar with Orthogonal Polarization
(CALIOP): Two wavelength polarization-sensitive
Lidar that provides high-resolution vertical profiles of
aerosols and clouds
– Wide Field Camera (WFC): Fixed, nadir-viewing
imager with a single spectral channel covering the 620670 nm region
– Imaging Infrared Radiometer (IIR): Nadir-viewing,
non-scanning imager
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Calipso
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Energy Absorbed by Atmosphere
94 GHz
35 GHz
Maximum
Propagation
Distance
10-15 km
20-30 km
3.2 mm
8 mm
Radar Wavelength
CloudSat
• NASA satellite with the Cloud Profiling
Radar (CPR) instrument, a 94-GHz nadirlooking radar
– Measures the power backscattered by
clouds as a function of distance from the
radar.
• Developed jointly by NASA’s Jet Propulsion
Laboratory (JPL) and the Canadian Space
Agency (CSA).
• Will advance our understanding of cloud
abundance, distribution, structure, and
radiative properties.
• First satellite-based millimeter-wavelength
cloud radar
– > 1000 times more sensitive than existing
ground weather radars
– Able to detect the much smaller particles
of liquid water and ice (ground-based
weather radars use centimeter
wavelengths)
Cloud
Profiling
Radar
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CloudSat (Hurricane Ike)
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CloudSat
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Radar/Lidar Combined Product
Development
• Formation flying is a key design element in cloudsat
• CloudSat has demonstrated formation flying as a practical observing strategy for EO.
• Overlap of the CloudSat footprint and the CALIPSO footprint, within 15 seconds, is achieved
>90% of the time.
lidar/radar combined ice microphysics - new A-Train ice cloud
microphysics
Preliminary
example from Zhien
A-train Cloud ice
MLS
ECMWF
CloudSat
10 µm
Microwave Absorption (Opacity) in Arctic
(Westwater et al., 2006)
EOS Aura
Researches the composition, chemistry,
and dynamics of the Earth’s atmosphere
as well as study the ozone, air quality, and
climate.
Instruments
• HIRDLS: High Resolution Dynamics Limb Sounder – Observes global distribution of
temperature and composition of the upper troposphere, stratosphere, and mesosphere
• MLS: Microwave Limb Sounder – Uses microwave emission to measure stratospheric
temperature and upper tropospheric constituents
• OMI : Ozone Monitoring Instrument – Distinguishes between aerosol types, such as smoke,
dust, and sulfates. Measure cloud pressure and coverage, which provide data to derive
tropospheric ozone.
• TES: Tropospheric Emission Spectrometer – High-resolution infrared-imaging Fourier
transform spectrometer that offers a line-width-limited discrimination of essentially all radiatively
active molecular species in the Earth's lower atmosphere.
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HIRDLS
• multi-channel, microwave radiometer
– radiated thermal emissions from the atmospheric limb
– spectral intervals in the range (6 to 17) mm, chosen to
correspond to specific gases and atmospheric "windows".
– global 3-D fields of atmospheric temperature, several
minor constituents, and geostrophic winds.
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Microwave Limb Sounder (MLS)
• The EOS MLS measures thermal emission from
broad spectral bands centered near 118, 190,
240, 640 and 2250 GHz
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Microwave Limb Sounder (MLS)
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OMI : Ozone Monitoring Instrument
The OMI instrument can distinguish between aerosol types, such as
smoke, dust, and sulfates, and measures cloud pressure and coverage,
which provide data to derive tropospheric ozone.
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TES: Tropospheric Emission Spectrometer
• Example of TES products
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