The A-Train

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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)
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• 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)
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• 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)
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• 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
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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
130 pm. CloudSat and CALIPSO lag Aqua by 1 to 2
minutes separated from each other by 10 to 15
seconds.
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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.
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1740 UTC 1240 pm EST
2055 UTC 1255 pm PST
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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.
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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.
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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 12.52.5 seconds ahead of
CALIPSO. The satellites are controlled by
different agencies Aqua and Aura by
NASA/Goddard, CloudSat by US Air Force,
PARASOLby 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.
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Afternoon Constellation Coincidental Observations
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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 620-670 nm region
• Imaging Infrared Radiometer (IIR) Nadir-viewing,
  non-scanning imager

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Calipso
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94 GHz
35 GHz
Maximum Propagation Distance
Energy Absorbed by Atmosphere
10-15 km
20-30 km
3.2 mm
8 mm
Radar Wavelength
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CloudSat

• NASA satellite with the Cloud Profiling Radar
  (CPR) instrument, a 94-GHz nadir-looking radar
• Measures the power backscattered by clouds as a
  function of distance from the radar.
• Developed jointly by NASAs 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
• gt 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 gt90 of
  the time.

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lidar/radar combined ice microphysics - new
A-Train ice cloud microphysics
Preliminary example from Zhien
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A-train Cloud ice
MLS
ECMWF
CloudSat
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10 µm
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Microwave Absorption (Opacity) in Arctic
(Westwater et al., 2006)
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EOS Aura

• Researches the composition, chemistry, and
  dynamics of the Earths 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