MODIS OVERVIEW

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MODIS OVERVIEW at NASA HQ REVIEW August 23,
2005 of EOS AQUA INSTRUMENT ANOMALIES Vincent
V. Salomonson MODIS Science Team Leader X. (Jack)
Xiong MODIS Characterization Support Team (MCST)
Leader And MODIS Project Scientist
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MODIS Key Specifications
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Instrument Overview
MODIS RSB Key Specifications
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Instrument Overview
MODIS TEB Key Specifications
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Ocean Chlorophyll (top) and sea surface
temperature (SST) observed via the Aqua MODIS
instrument.
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MODIS/Aqua SeaWiFS Global Mean Chlorophyll
Time Series Consistency
Clear-water chl-a lt 0.15 mg/m3
Deep-water depth gt 1000 m

• Coastal depth lt 1000 m
• Offset due to chlorophyll-a algorithm difference
  at high concentrations

Dashed line MODIS Solid line SeaWiFS
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Frequency of clear sky conditions (cloud fraction
less than 20 in 1 grid box) over land (King,
Platnick, et al. NASA/GSFC
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2-D probability density function of cloud visible
optical thickness and effective radius for marine
boundary layer clouds off the coast of
California. (King/Platnick, et al., NASA/GSFC
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MODIS/TerraAqua Albedo 16-Day L3 Global 0.05Deg
CMG for July 2002 (C. Schaaf, A Strahler---Boston
College

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Fires continued in central Alaska, as seen in
this MODIS Aqua image. According to the Fairbanks
North Star Borough, air quality conditions are
hazardous (Code Maroon, over 300 ug/m3). Hourly
concentrations earlier in the week spiked over
1000 ug/m3. According to AIRNow, hazardous
conditions are expected to continue.
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Global emissivity of land surfaces from MODIS
(Zhengming Wan--UCSB
The 5km MODIS LST product retrieved by the
day/night LST algorithm from MODIS data provides
new knowledge of emissivities at 3.75µm, 3.96µm,
4.05µm, 8.75µm, 11µm and 12µm (MODIS bands 20,
22, 23, 29, and 31-32) at the global scale
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EOS Direct Readout Sites

• 100 Ingest sites around the world for
  Terra/Aqua DB downlink
• Over 800 Users of data extending from 82 ingest
  sites
• List is located on the Direct Readout Portal

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MODIS On-orbit Calibration and Characterization

• MODIS On-board Calibrators (OBCs)

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Schematic of MODIS On-orbit Calibration
SDSM
Solar Diffuser
SRCA
SDSM
Blackbody
SD/SDSM (weekly first year to bi-weekly) SRCA
(monthly radiometric, bi-monthly spatial,
quarterly spectral) BB (quarterly
warm-up) Maneuvers (roll monthly Moon yaw 2
for Terra and 1 for Aqua pitch 2 for Terra)
Scan Mirror
Space View
Moon
Starting from July 2, 2003, Terra MODIS SD door
fixed at open with SD screen down more efforts
for SD calibration data analysis
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Aqua Spatial Characterization (along-track)
Days are counted from 2002
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Aqua Spatial Characterization (along-scan)
Days are counted from 2002
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Aqua MODIS Spectral - lC Shift
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BACKUP SLIDES
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Spatial and Spectral Characterization Using SRCA
Spatial
Frame -gt x
Spectral
Grating step -gt q
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SRCA Functions
In the spectral calibration mode, a light source
from the integrating sphere (SIS) provides
illumination for the visible (VIS), near infrared
(NIR), and short wave infrared (SWIR) bands. The
light coming from the integrating sphere is
bounced off of a toroidal (3-D doughnut shape)
relay mirror into the entrance of a modified
Czerny-Turner monochromator (an instrument that
obtains the light of one wavelength or very
narrow band of the light spectrum). The
monochromator contains a motor-driven
grating/mirror assembly, which is used in
conjunction with a filter wheel (to block
out-of-band energy) to diffract the light into
one of the VIS, NIR, or SWIR bands. The
diffracted light coming out of the monochromator
is then sent into a Cassegrain telescope that
moves the light to the right elevation and angle
(called collimating) and then bounces it off of a
fixed-fold mirror onto the Scan Mirror. The light
from this point moves through MODIS main optical
system and onto the detectors where the resultant
calibration data is integrated into the general
scan data. At minimum, one SRCA spectral
wavelength measurement is taken per revolution of
the Scan Mirror. Computer modeling has shown that
the accuracy of this calibration method is within
1 nanometer.
The SRCA system is also able to perform
self-calibration by inserting didymium glass near
the light source and sensing the SRCAs response
profile using a photodiode at the exit of the
monochromator. In the radiometric calibration
mode, the entrance and exit slits to the SRCA are
open and a silvered mirror replaces the grating.
This difference makes the monochromator into a
relay, where light from the integrating sphere is
sent to the entrance aperture for the calibration
of MODIS reflective bands. In this mode, the
SRCA is designed to provide six radiance levels
that are stable to within one percent over an
orbital period of 100 minutes. This stability is
achieved by a radiance feedback loop that is
based on input from a temperature-controlled
photodiode.
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SRCA Functions (continued)
In the spatial registration mode, the entrance to
the monochromator is open, and a reticle pattern
(a grid or pattern that establishes scale or
position) is placed at the exit of the
monochromator. In addition to the VIS-NIR-SWIR
illumination, the radiation from a resistive
heater is coupled into the system via an ITO
dichroic beamsplitter (splits the light into two
colors), which provides energy to support the
spatial registration for the thermal bands. The
specially designed reticle patterns at the exit
slit of the monochromator are then projected into
the MODIS optical system, which are then
re-imaged and scanned by the various FPAs to
generate the data for the spatial registration
algorithm. The result is a record of the FPA
spatial registration over the life of the
instrument, which is very important to
demonstrating MODIS reliability.
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Terra Spatial Characterization (along-scan)
SD door open impact.
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Terra Spatial Characterization (along-track)
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Terra MODIS Spectral - lC Shift