BOMEM
NPOESS CrIS Raw Data (Level 0) to
Sensor Data (Level 1b) Processing
R. Poulin, S. Lantagne, S. Dubé, Y. Dutil, S. Levesque, and F. Chateauneuf
ABB Bomem, Special Projects in Radiometry,
585 Charest blvd East, Suite 300, Quebec, Qc, G1K 9H4, Canada
Contact: robert.h.poulin@ca.abb.com
and
J. Predina
ITT Industries, ITT Aerospace/Communications,
1919 West Cook Road, P.O. Box 3700, Fort Wayne, IN 46801, USA
Contact: joe.predina@itt.com
CrIS
SDR Algorithms, ITSC-12, Lorne, Australia, 27 Feb. - 5 Mar. 2002
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CrIS SDR
Algorithms
The Cross-track Infrared Sensor (CrIS)
• Mission
– Part of NPOESS series of polar-orbiting spacecrafts (near circular orbit, 833 km
altitude, 98.7 degree inclination, 101 minutes, NPP launch 2005, NPOESS launch
2007)
– Component of the CrIMSS (Cross-track Infrared/Microwave Sounding Suite)
– Produce cross-track IR spectra of the surface of the Earth
– IR spectral measurements to be converted to temperature, moisture and
pressure profiles of the Atmosphere
• CrIS Space Segment
– At each cross-track scan, CrIS interferometer observes 30 Earth scenes, 4
calibration targets (2 Deep Space + 2 Internal Calibration Target), with
interferometer sweeps in forward and reverse direction
– CrIS also performs a minimal amount of signal processing prior to Earth
downlink at each 1.25 orbit, 35,062 FORs, 315,562 FOVs, 946,687 IGMs
• CrIS Ground Segment
– Sensor Data Record (SDR) algorithms transform CrIS interferograms into fully
calibrated and geolocated spectra
– Environmental Data Record (EDR) algorithms transform SDRs spectra into
temperature, pressure and moisture profiles
CrIS
SDR Algorithms, ITSC-12, Lorne, Australia, 27 Feb. - 5 Mar. 2002
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2 / 18
CrIS SDR
Algorithms
• CrIS
• AMSU-A
• MHS
Overall Relationship of RDRs, SDRs and EDRs
1.
25
-O
r
bi
tD
±50°
Cross track
Scans
RD
R
ata
Du
s
m
p
Central or
Regional Ground
Stations
2,200 km
Swath
RDR = Raw Data Record (Uncalibrated)
SDR = Sensor Data Record (Calibrated)
EDR = Environmental Data Record
Decode
Spacecraft
Data
RDRs
to
Users
Raw
Uncalibrated
Data
Sensor
Calibration
Algorithms
SDRs
to
Users
Calibrated and
Geolocated
Radiance Data
EDR
Algorithms
EDRs
to
Users
• Temperature Profiles
• Moisture Profiles
• Pressure Profiles
48-km Diameter
AMSU FOV
3x3 Array of CrIS
FOVs (14-km
Diameter Each)
CrIS
SDR Algorithms, ITSC-12, Lorne, Australia, 27 Feb. - 5 Mar. 2002
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20 minutes
3 / 18
Ground Processing Algorithm Enhances
Data Quality Via Calibration Techniques
CrIS SDR
Algorithms
• Remove Sensor Unique Signature
No Matter Which
Sensor Produces
the Data
Updated once per
Orbit (101 min)
Continuously
Adapts
(t = 4 minutes)
3.7 msec/FOV
Execution Time
*NPP Channel
Center Tolerance
will be 10 ppm
CrIS
– Same ILS at every channel center…………... (within same band)
– Same ILS for all 9 FOVs ……………………...(within same band)
– Fixed SDR channel centers for all 9 FOVs…..(within same band)
• Calibrations Performed
–
–
–
–
Wavelength calibration
Spectral correction of ILS distortion
Radiometric (complex gain and offset)
Earth mapping (FOV location & FOV shape)
• Uncertainty After Processing (both sensor & algorithms)
Radiometric gain
Channel center
ILS width [main lobe]
Earth Mapping
SDR Algorithms, ITSC-12, Lorne, Australia, 27 Feb. - 5 Mar. 2002
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LWIR
0.45%
5 ppm*
1.5%
1.5 km
MWIR
0.58%
5 ppm*
1.5%
1.5 km
4 / 18
SWIR
0.77%
5 ppm*
1.5%
1.5 km
Relative to:
287 K BB
wavenumber
true FWHM
CrIS SDR
Algorithms
Ground Calibration Software Is
Partitioned into 9 Modular Groups
• Initialization
– Initialize software
– Initialize RDR reading pointers
• Data Input
– Low level data handling
– Configuration data handling
– Calibration data handling
• Ingest sensor unique cal data
• Monitor calibration data
• Compute spectrum correction matrix
– Science data handling
• Geolocation
– Map FOV to latitude & longitude
– Calculate view angles/ footprint geometry
• Preprocessing
– Perform bit trim decoding
– Convert interferograms to spectra
• Spectral Calibration
– Perform spectral calibration
– Compute laser WL from neon lamp
– Compute laser WL from diode parameters
CrIS
SDR Algorithms, ITSC-12, Lorne, Australia, 27 Feb. - 5 Mar. 2002
ITT INDUSTRIES - AER - ABB BOMEM - BALL - BOEING
• Radiometric Calibration
–
–
–
–
–
–
–
–
Average warm target spectra
Average cold target spectra
Subtract sensor background radiance
Calibrate sensor gain
Remove phase dispersion
Compute ICT radiance
Isolate/reject orthogonal noise
Apply spectrum correction matrix
• Remove ILS errors
• Apply user selectable apodization
• Map channels to fixed wavenumber grid
• Quality Control
–
–
–
–
Identify/exclude bad data
Detect/correct fringe count error
Estimate NEdN (bin by bin)
Flag bad FOVs
• Post-processing
– Select user required spectral bins
– Format data for EDRs
– Archive data
• Data Output
5 / 18
CrIS SDR
Algorithms
CrIS CCSDS
Packets Processed
in Single Scan Line
Blocks
(8 second input)
One Time
Calculation of
N x N Matrix Used
to Perform ILS
Corrections
Features of SDR Algorithm Science Code (1 of 8)
• Initialization
 Initialize software
 Initialize RDR reading pointers
• Data Input
–



CCSDS packet decoding
Low level data handling
Configuration data handling
Calibration data handling
Ingest sensor unique cal data
Monitor calibration data
Compute spectrum correction matrix
 Science data handling
• Preprocessing
– Perform bit trim decoding
 Convert interferograms to spectra
Software Auto
Configured Based
upon Content of
1st CrIS
Engineering
Packet Received
CrIS
 Included with CDR
version of science
code on 1/23/02
• No Sensor Unique Calibration
Handbook Needed
• All Necessary Data Embedded
in RDRs
SDR Algorithms, ITSC-12, Lorne, Australia, 27 Feb. - 5 Mar. 2002
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CDR Science
Code Version
Demonstrated
Using ASCI
Input Files
Requires
Completion
Prior to EDU2
Demonstration
All Data
Calibration
Operations
Executed in
Spectral Space
6 / 18
CrIS SDR
Algorithms
Once per Orbit
Metrology
Wavelength
Calibration Using
Neon Bulb 703 nm
Reference Line
Wavelength
Calibration Data
Collected Without
Disturbing Normal
Scene Data
Collection
Features of SDR Algorithm Science Code (2 of 8)
• Spectral Calibration
 Perform spectral calibration
 Compute laser WL from neon lamp
 Compute laser WL from diode parameters
Wavelength
Calibration Data
Broadcast in
Once/4 minute
Engineering Data
Packet
 Included with CDR
version of science
code on 1/23/02
CrIS
Up to 128
Calibration
Sweeps Averaged
SDR Algorithms, ITSC-12, Lorne, Australia, 27 Feb. - 5 Mar. 2002
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>2 ppm Metrology
Wavelength Drift
Detected &
Corrected by
Algorithm Over
Entire Orbit
Achieves 5 ppm Total
System Spectral
Uncertainty
(10 ppm for NPP)
7 / 18
CrIS SDR
Algorithms
30 Averages of
Warm and Cold
Target References
Used for
Calibration
Separate
Calibration
Average
Maintained for
Each
Interferometer
Sweep Direction
and Each of 27
CrIS Detector
Channels
Deep Space Used
as Cold Target
CrIS
Features of SDR Algorithm Science Code (3 of 8)
Averaging Window
Spans 4 Minutes
• Radiometric Calibration







Average warm target spectra
Average cold target spectra
Subtract background radiance
Remove phase dispersion
Calibrate sensor gain
Reject orthogonal noise
Compute warm target radiance
ICT Radiance
Calculation
Corrected for
Surrounding
Environment
Reflections & Warm
Target Emissivity
Science
Telemetry
SDR Algorithms, ITSC-12, Lorne, Australia, 27 Feb. - 5 Mar. 2002
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Calibration Equation
~
L
~
~
S0 ES   S0 DS 
ICT
~ ICT
~ DS L
 S0    S0 
 Included with CDR
version of science
code on 1/23/02
Engineering
Packet Data
8 / 18
CrIS SDR
Algorithms
Features of SDR Algorithm Science Code (4 of 8)
Instrument line shape for the Field of view
Analysis Shows Large
ILS Distortion Present
Due to
Off-axis FOV Effect If
Correction Not
Performed
0.5 Bin Smear
Normalized amplitude
0.06
0.05
MW band
s0 = 1750 cm-1
0.04
bin size (1.25 cm-1)
On-axis FOV
0.03
0.02
MW
LW
Band
Band
Side FOV
0.01
Corner FOV
0.5 Bin Offset
0
1749
1749.5
1750
1750.5
s [cm-1]
Instrument line shape for the Field of view
Instrument line shape for the Field of view
0.06
0.06
LW band
s0 = 1100 cm-1
0.04
On-axis FOV
bin size (0.625 cm-1)
0.03
0.02
LW
LW
Band
Band
Side FOV
0.01
0
Corner FOV
1099.2
1099.4
1099.6
1099.8
1100
1100.2
1100.4
Normalized amplitude
Normalized amplitude
0.05
SW band
s0 = 2548 cm-1
0.05
bin size (2.5 cm-1)
0.04
0.03
0.02
0.01
Corner FOV
0
2546
2546.5
2547
2547.5
s [cm-1]
s [cm ]
SDR Algorithms, ITSC-12, Lorne, Australia, 27 Feb. - 5 Mar. 2002
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SW
LW
Band
Band
Side FOV
-1
CrIS
On-axis FOV
9 / 18
2548
2548.5
2549
CrIS SDR
Algorithms
1st Order
Correction
Removes ILS
Distortion Due to
Off-axis FOV Sizes
and Angles
2nd Order
Correction
Removes
Remaining ILS
Distortion as
Determined by
Prelaunch ILS
Characterization
Data
Features of SDR Algorithm Science Code (5 of 8)
• Radiometric Calibration
– Apply spectrum correction matrix
Remove ILS errors
0.963 degree
(14.0 km)
Anti-sun
S/C
Velocity
3
1.100 degree
(16.0 km)
2
1
6
5
4
9
8
7
1.024 degree
(14.9 km)
CrIS Footprint @ Nadir
SDR Algorithms, ITSC-12, Lorne, Australia, 27 Feb. - 5 Mar. 2002
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CrIS FOV Angles
Measured via Spot
Scan Test During
CrIS System
Integration
0.897 degree
(13.0 km)
Engineering Data
Packet
CrIS
 Included with CDR
version of science
code on 1/23/02
10 / 18
FOV Angle
Parameters Can
Also be Retrieved
via Software
Analysis of
Spectral Scene
with Structure
CrIS SDR
Algorithms
Features of SDR Algorithm Science Code (6 of 8)
Unapodized Window
• Radiometric Calibration
– Apply spectrum correction matrix
Apply user selectable apodization
Map channels to fixed
wavenumber grid
Unapodized
.1
Magnitude
Sinc Interpolation
Used to Remap
Channel Centers
1
.01
.001
• Post-processing
 Select user required spectral bins
– Format data for EDRs
– Archive data
.0001
700
705
710
715
720
725
730
725
730
725
730
Wavenumber (cm -1 )
Hamming Window
1
Hamming
Magnitude
.1
5 ppm Channel Centers Maintained
Regardless of FOV Angular Offset &
CrIS Operating Metrology
Wavelength
.01
.001
.0001
700
705
710
715
720
Wavenumber (cm -1 )
Blackmann Window
1
Resolution
(1/2L)
(cm-1)
Spectral
Channels
per FOV
1st Channel
Center
(cm-1)
LW
650 - 1095
0.625
713
650.00
Last
Channel
Center
(cm-1)
1095.00
MW
1210 - 1750
1.25
413
1210.00
1750.00
SW
2155 - 2550
2.5
159
2155.00
2550.00
Band
Blackman
.1
Magnitude
Wavenumb
er Range
(cm-1)
.01
.001
.0001
700
705
710
715
Wavenumber (cm -1 )
CrIS
SDR Algorithms, ITSC-12, Lorne, Australia, 27 Feb. - 5 Mar. 2002
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720
CrIS SDR
Algorithms
Features of SDR Algorithm Science Code (7 of 8)
Quality Control Measures
-Fringe count error flag (high) (in
CrIS RDRs)
 Discard ES data
 Exclude from averaging ICT and DS
-Fail bit trim flag (high)
(in CrIS RDRs)
 Process ES data, set flag
 Exclude ICT or DS from averaging
-Impulse noise count (1-127)
(in CrIS RDRs)
 Discard data if count >n
 Process data if count  n (default n=1)
-Invalid interferogram data
flag(high)… saturated detector,
loss of signal (in CrIS RDRs)
 Discard ES data
 Exclude DS and ICT from averaging
-Excess NEdN flag (high)
(generated in SDR algorithm)
 Process data, set flag
NEdN Estimate
NEdN
NEdN @ ICT
NEdN @ scene
NEdN @ DS
• Quality Control




Identify/exclude bad data
Detect/correct fringe count error
Estimate NEdN (bin by bin)
Flag bad FOVs
Calibration
Calibration
Averages
AveragesMaintain
Maintain
Alignment
Integer
Alignment Even
Even
IntegerNumber
Numberof
of
When
Fringe
Count
When Fringe Count Metrology
MetrologyFringe
Fringe
errors
Occur
Count
Errors
errors Occur
Count Errors
Detected
Detectedand
and
Corrected
Corrected
Used
Usedby
byEDR
EDRAlgorithm
Algorithm to
toSet
SetError
Error
Covariance
CovarianceMatrix
Matrix
(affects
(affectsconvergence
convergence criteria
criteriaof
ofretrieval)
retrieval)
Wavenumber
CrIS
SDR Algorithms, ITSC-12, Lorne, Australia, 27 Feb. - 5 Mar. 2002
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CrIS SDR
Algorithms
Features of SDR Algorithm Science Code (8 of 8)
• Geolocation
Spacecraft
Position
Vector
CrIS
FOV
Path
Detector
Pointing
Vector
Orbital
Path
1) Earth Centered Inertial (ECI)
2) Earth Centered Earth Fixed (ECEF)
3) World Geodetic System 1984 (WGS84)
4) Spacecraft Coordinate Reference
5) Instrument Coordinate System
6) Orbital Coordinate Reference
7) Topocentric-Horizon Coordinate System
(THCS)
CrIS
SDR Algorithms, ITSC-12, Lorne, Australia, 27 Feb. - 5 Mar. 2002
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–
–
–
–
1.5 km uncertainty @ edge of scan
Map FOV to latitude & longitude @ sea level
Calculate view angles to satellite
Calculate footprint geometry
Geolocation
Geolocation
Algorithm
Algorithm
Development
Development
Begins
BeginsAfter
AfterS/C
S/C
Contractor
Select
Contractor Select
77Different
Different
Coordinate
Coordinate
Transformations
Transformations
Required
Required
Details
DetailsRequire
Require
SSPR
SSPR
Participation
Participation
13 / 18
CrIS SDR
Algorithms
Algorithm Functional Flow
~
I ( x)
ES (88%)
~
S es [n]
Scene FCE
Handling
Radiometric
Calibration
(complex)
Compute
Spectrum
L(s )
Process Calibration References
N ma  30
~
S (s )
Health
Monitoring
~
L (s )
L [r.u.]
Metrology
Monitoring
DS (6%)
~
S ds [n]
Calibration
FCE
Handling
Moving
Average
N ma  30
ICT (6%)
~
S ict [n]
Calibration
FCE
Handling
Moving
Average
Spectrum Correction
mean cold
reference
~
S ds
Spectral
Resampling
ILS
Correction
mean hot
reference
~
S ict
User Defined
Apodization
L [r.u.]
T ict
s0
CrIS
SDR Algorithms, ITSC-12, Lorne, Australia, 27 Feb. - 5 Mar. 2002
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s1
s
L(s )
NEdN
CrIS SDR
Algorithms
Only Four Types of RDR Data Packets Are Processed by
SDR Science Algorithms
• Interferogram Data Packets (918 packets per 8 seconds)
Contained in
CrIS RDR data
Stream
(1.44 Mbps)
– 306 LW, 306 MW & 306 SW packets per 8 second scan
– Includes earth scene, ICT cal & DS cal packets
• LW 2,504 byte/packet……….766,224 bits/sec
• MW 1,698 byte/packet……….519,588 bits/sec
• SW
512 byte/packet……….156,672 bits/sec
• Engineering Data Packet (1 packet every 4 minutes)
– Engineering data and sensor characterizations
• 5 kbyte packet………...166 bits/sec
• Science TLM Data Packet (1 packet every 8 seconds)
– Dynamically changing cal data
• 314 byte/packet……….314 bits/sec
From S/C RDR
Data Stream
CrIS
• Time of Day/Ephemeris Packet (1 packet/sec)
– S/C position, velocity, attitude, attitude rate, Time stamp
• 94 byte/packet………..752 bits/sec
SDR Algorithms, ITSC-12, Lorne, Australia, 27 Feb. - 5 Mar. 2002
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15 / 18
CrIS SDR
Algorithms
Calibrated
Radiance in 1305
Channels
Noise Estimates
in Each Channel
SDR Content At SDR Algorithm Output
(1 of 2)
• Calibrated Data
– Real part of the spectra after Spectral Correction
• LW 713 bins @ 0.625cm-1 (650-1095)
• MW 433 bins @ 1.25cm-1 (1210-1750)
• SW 159 bins @ 2.5cm-1 (2155-2550)
– Imaginary part of the spectra before Spectral Correction
(LW 713 bins, MW 433 bins, SW 159 bins)
– NEdN estimates (LW 713 bins, MW 433 bins, SW 159 bins)
• Geolocation Data
Mapping Data
CrIS
– Latitude/longitude @ sea level for each FOV center
– Major and minor elliptical footprint size for each FOV
– Elevation & azimuth angle from each FOV center to satellite
SDR Algorithms, ITSC-12, Lorne, Australia, 27 Feb. - 5 Mar. 2002
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CrIS SDR
Algorithms
SDR Content At SDR Algorithm Output
(2 of 2)
• Identifiers
Identifiers Help
in the Archiving
of Data
– Spacecraft ID, CrIS sensor ID, Sensor flight software version
number, SDR algorithm version number, Apodization tag
– FOR number, FOV number
– Band designator (LW,MW,SW), FOV longitude and latitude,
Slant angle, Viewing angle, Size of FOV on ground
• Quality Control
Quality of Data Is
Assessed and
Tagged
CrIS
–
–
–
–
ZPD reset, Fail bit trim, Impulse noise count (0-127)
Invalid data (RDR and SDR) and invalid geolocation flags
FCE detected and corrected in SDR algorithm
Excess NEdN, Excess Sensor Thermal drift
SDR Algorithms, ITSC-12, Lorne, Australia, 27 Feb. - 5 Mar. 2002
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CrIS SDR
Algorithms
SDR Algorithm
Execution Time
Is Very Low Risk
SDR Algorithm
Removal of
Unique Sensor
Signature
Accomplished
Thus Far
Issue of Partly
Clouded FOV
and Resultant
Uncorrected ILS
Effects May Be a
Future Limitation
CrIS
Summary of Performance to Date
• Completed CDR on 1/23/02
• Science code execution speed satisfactory
– 200 msec/FOV
– Year 2007 computer plus code optimizations can achieve the
required 3.7 msec/FOV
– Algorithm architecture can accommodates parallel
processing
• ILS Correction Successful
– Critical ILS correction algorithm demonstrated less than
0.03% correction error for all bands and all FOV positions
(simulated)
– Preliminary validation of ILS correction algorithm was
demonstrated with hardware measurements
– Further EDU2 validations planned
SDR Algorithms, ITSC-12, Lorne, Australia, 27 Feb. - 5 Mar. 2002
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Next Step Is to
Demonstrate
Algorithm on
EDU2 RDRs
18 / 18