Terra and Aqua MODIS Overview

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Terra and Aqua MODIS Overview V. V.
Salomonson MODIS Science Team Leader MODIS DATA
WORKSHOP University of Maryland/Baltimore
County January 8-10, 2007
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NASA Earth Observation System (EOS)
NASAs EOS Receives 2006 Space Systems Award
(AIAA-Sept 2006)
SeaWiFS
EO-1
IceSat
ACRIMSAT
Toms-EP
ERBS
Jason
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Terra
Launched December 18, 1999
MODIS
MOPITT
ASTER
MISR
CERES
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Aqua
Launched on May 4, 2002
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MODIS Instrument Overview
130 P.M (Aqua) equator crossing Ascending Orbit
1030 A.M. (Terra) equator crossing Descending
Orbit
16-Day Repeat Cycle, Complete Daylight Coverage
every 2 days
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Aquas Orbit

• Altitude of 705 km
• Near-polar, sun-synchronous, orbiting the Earth
  every 98.8 minutes, crossing the equator going
  north at 130 p.m. and going south at 130 a.m.

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Global Level-1B Composite Image
May 28, 2001
R 0.65 µm G 0.56 µm B 0.47 µm
example data granule coverage (5 min)
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MODIS Specifications and Applications

• 36 spectral bands 4 focal plane assemblies
  (FPA) 3 spatial resolutions
• 20 reflective solar bands (1-19, and 26) from
  0.41-2.2mm
• 16 thermal emissive bands (20-25, 27-36) from
  3.5-14.4mm

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Instrument Overview
MODIS RSB Key Specifications
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Instrument Overview
MODIS TEB Key Specifications
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MODIS On-orbit Calibration and Characterization
MODIS On-board Calibrators (OBCs)

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MODIS On-orbit Calibration
SDSM
BB (quarterly) SD/SDSM (weekly first year to
bi-weekly) SRCA (monthly radiometric, bi-monthly
spatial, quarterly spectral) Maneuvers (roll
monthly Moon yaw 2 for Terra and 1 for Aqua
pitch 2 for Terra)
Solar Diffuser
SRCA
SDSM
Blackbody
Scan Mirror
Space View
Moon
Starting from October 2005, SRCA has been
operated at reduced frequencies (no 30W
configurations for Aqua). This has no impact on
radiometric calibration.
Starting from July 2, 2003, Terra SD door fixed
at open with SD screen down more efforts for SD
calibration data analysis
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Terra and Aqua MODIS TEB NEdT Comparison
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MODIS Focal Plane Assemblies (FPAs)
S scan direction T track direction B13 and
B14 have 2 columns of detectors for TDI high and
low gain output
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MODIS Geolocation Overview

• Started with stable platforms and instruments
  with very accurate knowledge of the orbit and
  attitude
• Performed detailed error analysis pre-launch
• by removing static and slowly varying terms, goal
  was in reach
• Used Parametric geolocation approach with a
  detailed physical model
• finer resolution ground control points only used
  to remove biases and modeled trends
• per-scene geometric correction not needed
• Digital Elevation Model (DEM) used to remove
  terrain induced distortion
• Continue long-term geometric error analysis

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MODIS Geolocation

• Geolocation accuracy specification is 150 m (1
  s) and goal is 50 m (1 s) at nadir
• Geolocation goal driven by Land 250 m change
  product requirements
• MODIS is a moderate resolution whisk-broom sensor
  with 36 spectral bands 2 at 250 m, 5 at 500 m
  and 29 at 1 km nadir spatial resolution
• Ideal band is geolocated
• 250m band 1 (645 nm, red)

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MODIS Scanning Geometry
(distance exaggerated in track direction)
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MODIS SCANNING PATTERN OVER 2300 KM SWATH
Three consecutive MODIS scans each consisting of
ten 1km lines. Due to the panoramic "bow tie" 
effect, the scans are partially overlapping at
off nadir angles. The first and third scan are
represented by the light grey grids, while the
second scan is shown in black.
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Updated Ground Control Points (GCPs)

• Image chips from Landsat TM/ETM scenes

366 old chips (blue)51 chips removed (red)990
new chips (green)
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Geolocation C4 results
Aqua
Terra

• Good results C4 RMS error is
• better than goal in track direction
• but slightly over goal in scan direction
• (but much better than specification
• 150 m)
• Early post-launch coordinate system
• issue resolved before C4
• Definitive ephemeris is used for best results
  causes up to 24 hr processing delay

• Excellent results C4 Root Mean
• Square (RMS) error in nadir equivalent units
  is better than accuracy goal
• Small remaining northern/ southern hemisphere
  difference
• Large errors occur after orbit
• maneuvers (about 6 per year)
• accuracy in following orbit suspect

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24 MODIS P.I.s creating Products
MODIS Products
(MOD for Terra/MYD for Aqua)
MOD01 Level-1A Radiance Counts
MOD02 Level-1B Calibrated Geolocated Radiances
-also Level 1B subsampled 5kmX5km pro
MOD03 Geolocation Data Set MOD04 Aerosol
Product MOD05 Total Precipitable Water
MOD06 Cloud Products MOD07 Atmospheric
Profiles MOD08 Gridded Atmospheric Product
(Level 3) MOD09 Atmospherically-corrected
Surface Reflectance MOD10
Snow Cover MOD11 Land Surface Temperature
Emissivity MOD12 Land Cover/Land Cover
Change MOD13 Vegetation Indices
MOD14 Thermal Anomalies, Fires Biomass
Burning MOD15 Leaf Area Index
FPAR MOD16 Surface Resistance
Evapotranspiration MOD17 Vegetation
Production, Net Primary
Productivity MOD18 Normalized Water-leaving
Radiance MOD19 Pigment Concentration
MOD20 Chlorophyll Fluorescence
MOD21 Chlorophyll_a Pigment Concentration
MOD22 Photosynthetically Active Radiation (PAR)
MOD23 Suspended-Solids Conc, Ocean
Water MOD24 Organic Matter Concentration
MOD25 Coccolith Concentration MOD26 Ocean
Water Attenuation Coefficient
MOD27 Ocean Primary Productivity MOD28 Sea
Surface Temperature MOD29 Sea Ice Cover
MOD32 Processing Framework Match-
up Database MOD33 Gridded Snow Cover
MOD34 Gridded Vegetation Indices
MOD35 Cloud Mask MOD36 Total Absorption
Coefficient MOD37 Ocean Aerosol Optical
Thickness MOD39 Clear Water Epsilon
MOD43 Albedo 16-day L3 MOD44 Vegetation Cover
Conversion
http//oceancolor.gsfc.nasa.gov/PRODUCTS/
Note All products except MOD/MYD 43,44, are
Standard Products
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MODIS Cloud Mask(S. A. Ackerman, W. P. Menzel,
R. A. Frey, K. I. Strabala)

• MODIS cloud mask uses multispectral imagery to
  indicate whether the scene is clear, cloudy, or
  affected by shadows
• Cloud mask is input to rest of atmosphere, land,
  and ocean algorithms
• Mask is generated at 250 m and 1 km resolutions
• Mask uses 20 spectral bands ranging from
  0.55-13.93 µm (including new 1.38 µm band)
• 11 different spectral tests are performed, with
  different tests being conducted over each of 5
  different domains (land, ocean, coast, snow, and
  desert)
• Temporal consistency test is run over the ocean
  and at night over the desert
• Spatial variability is run over the oceans
• Algorithm based on radiance thresholds in the
  infrared, and reflectance and reflectance ratio
  thresholds in the visible and near-infrared
• Cloud mask consists of 48 bits of information for
  each pixel, including results of individual tests
  and the processing path used
• Bits 1 2 give combined results (confident
  clear, probably clear, probably cloudy, cloudy)

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Terra/MODIS Cloud Mask (S. A. Ackerman, W. P.
Menzel NOAA/NESDIS, Univ. Wisconsin)
True Color Composite (0.65, 0.56, 0.47)
Cloud Mask
Confident Clear
Probably Clear
Cloudy
Probably Cloudy
King et al. (2003)
June 4, 2001
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approaching 7 years
just over 4.5 years
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Performance Summary (I)

• Reflective Solar Bands (20 bands and 330
  detectors)
• Terra MODIS
• Noticeable optics degradation (wavelength
  dependent, mirror side dependent) small gain
  changes after configuration changes or instrument
  reset events SDSM works well with normalization
  approach
• 21 noisy detectors (20 of band 7 from pre-launch)
  and 0 inoperable detectors
• Aqua MODIS (more stable)
• Noticeable optics degradation (wavelength
  dependent) SDSM works well with normalization
  approach
• 4 noisy detectors and 15 inoperable detectors (13
  in B6 from pre-launch)
• Applications of Lunar Response Trending (Relative
  Calibration)
• Calibration Uncertainty (Radiometric)
• Requirements 2 in reflectance and 5 in
  radiance at radiances from 0.3Ltpy to 0.9Lmax and
  viewing angles within 45º.
• Performance Most RSB bands/detectors meet the
  calibration requirements (excluding Terra MODIS
  SWIR bands and Aqua MODIS B6)
• Concerns SWIR electronic xtalk impact, Terra SD
  screen impact

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Performance Summary (II)

• Thermal Emissive Bands (16 bands and 160
  detectors)
• Terra MODIS
• Stable short-term and long-term response trending
  (excluding sensor configuration change and
  instrument reset events)
• 24 noisy detectors (10 in B36 from pre-launch)
  and 0 inoperable detectors
• Aqua MODIS
• Better response trending than Terra MODIS
• 4 noisy detectors (3 in B21 from pre-launch) and
  0 inoperable detectors
• Calibration Uncertainty (Radiometric)
• Requirements1 at typical radiances and viewing
  angles within 45º except 0.5 for B31 and B32
  and 10 for B21 (low gain fire band) extra 1
  uncertainty added for non-typical radiance levels
  or at viewing angles outside the 45º range.
• Performance Most TEB bands/detectors meet the
  calibration requirements (excluding noisy
  detectors and Terra PC bands 33-36 with
  noticeable mirror side dependent noise)
• Concerns Terra MODIS PC bands 33-36 noise

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Performance Summary (III)

• Spectral (RSB only)
• Terra MODIS
• Center wavelength shifts (relative to pre-launch)
  are less than 0.5nm for most RSB (except 0.6nm
  for B8) On-orbit drifts are less than 0.2nm for
  all bands
• Aqua MODIS
• Center wavelength shifts (relative to pre-launch)
  are less than 0.5nm for most RSB (except 1nm for
  B2) On-orbit drifts are less than 0.2nm for all
  bands
• Spatial (RSB and TEB)
• Terra MODIS
• BBR in specification in along scan direction
• BBR in specification in along track direction,
  except 2 bands slightly out specification
• Aqua MODIS
• BBR in specification for bands within VIS/NIR and
  bands within SMIR/LWIR
• 300m along scan shifts and 350m along track
  shifts for SWIR and LWIR FPAs (relative to NIR
  FPA) one of the Aqua MODIS problems identified
  pre-launch
• Post launch BBR are relatively stable

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MODIS Science Team/Organization
Instrument Calibration/CharacterizationDr. Jack
Xiong MODIS Project ScientistMODIS
Characterization Support Team (MCST) http//www.
mcst.ssai.biz/mcstweb/index.html MODIS
Atmospheres Discipline GroupDr. Michael
King http//modis-atmos.gsfc.nasa.gov/ MODIS
Oceans Discipline GroupDr. Charles
McClain http//oceancolor.gsfc.nasa.gov/PRODUCTS
MODIS Land Discipline GroupDr. Chris
Justice http//modis-land.gsfc.nasa.gov/
Reminder Data are at four different archive and
distribution centers Atmospheres and Level-1 at
LAADS Oceans at Ocean Color Site Land at LPDAAC
in Sioux Falls, SD Cryosphere (snow and ice) at
NSIDC in Boulder, CO
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Why is MODIS unique? What is the expected
lifetime and final length of the data set? Why
and how was it decided to break up the products
into the three existing areas? What is the
processing stream from the satellite to
distribution to the three data product areas? How
are the product areas related to each other - is
there ancillary data used by all three product
areas?  Does everyone use the same atmospheric
corrections?  Cloud masks? Is the era of single
sensors coming to an the end? single sensors. 
What about the "A - train" or other formation
flying?. Are there multi-sensor products being
done or contemplateddata fusion?. How can the
user community can stay abreast of multi-sensor
research, products and developments? 
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Visible and Infrared Imaging Radiometer Suite
(VIIRS) (re R. Murphy IPO/George Mason U.)

• Purpose Global observations of land, ocean,
  atmosphere parameters at high temporal resolution
  ( daily)
• Predecessor Instruments AVHRR, OLS, MODIS,
  SeaWiFS
• Management Integrated Program Office
• StatusPhase C/D (Raytheon)
• Approach Multi-spectral scanning radiometer (22
  bands between 0.4 ?m and 12 ?m) 12-bit
  quantization
• Swath width 3000 km

• Changes to specifics of band dynamic ranges,
  bandpasses band centers being negotiated
• Consideration of adding 6.7 micrometer water
  vapor band to FM2 later models
• CDR March 2002

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Satellite Transition Schedule(NPP not earlier
than 2009, NPOESS around 2013)
Projected End of Life based on 50 Need
CY
99
00
11
12
13
14
15
16
17
18
03
08
09
10
01
02
07
04
05
06
0530
F20
F18
F16
C3
NPOESS
DMSP
0730 - 1030
F17
F19
F15
C1 or C2
NPOESS
NPOESS
DMSP
M
POES
METOP
Local Equatorial Crossing Time
?
1330
N
N
C2 or C1
L (16)
NPOESS
POES
Earliest Need to back-up launch
?
S/C Deliveries
Earliest Availability
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Backup Slides
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MODerate-resolution Imaging Spectroradiometer
(MODIS)

• NASA, Terra Aqua
• launched 1999, 2002
• 705 km polar orbits, descending (1030 a.m.)
  ascending (130 p.m.)
• Sensor Characteristics
• 36 spectral bands ranging from 0.41 to 14.385 µm
• cross-track scan mirror with 2330 km swath width
• Spatial resolutions
• 250 m (bands 1 - 2)
• 500 m (bands 3 - 7)
• 1000 m (bands 8 - 36)
• 2 reflectance calibration accuracy
• onboard solar diffuser solar diffuser stability
  monitor

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Instrument Overview

• 36 spectral bands (490 detectors) cover
  wavelength range from 0.4 to 14.5 mm
• Spatial resolution at nadir 250m (2 bands), 500m
  (5 bands) and 1000m
• 4 FPAs VIS, NIR, SMIR, LWIR
• On-Board Calibrators SD/SDSM, SRCA, and BB (plus
  space view)
• 12 bit (0-4095) dynamic range
• 2-sided Paddle Wheel Scan Mirror scans 2330 km
  swath in 1.47 sec
• Day data rate 10.6 Mbps night data rate 3.3
  Mbps (100 duty cycle, 50 day and 50 night)

Velocity Vector