Transcript S-HIS Aircraft Instrument Calibration and EOS Validation

Scanning High-resolution Interferometer Sounder
(S-HIS) Calibration and Earth Observing System
(EOS) Validation
Joe Taylor, F Best, N Ciganovich, R Dedecker, S Dutcher, S Ellington,
R Garcia, H Howell, R Knuteson, D Laporte, C Moeller, H Revercomb,
W Smith*, D Tobin, M Werner
University of Wisconsin, SSEC
* NASA LaRC
Seventh Workshop on Infrared Emission Measurements by FTIR,
Quebec City, February 2004
Slide 1
Calibration and Validation for IR radiance observations
are now concerned with tenths of K, not K!
High Spectral Resolution is an important
part of the reason.
(Goody and Haskins, J Climate 1998)
Slide 2
Topics
•
The Scanning High-resolution Interferometer Sounder (S-HIS)
•
Overview
•
Recent developments (Oct 2002 - present)
•
The Atmospheric Infrared Sounder (AIRS)
•
Radiance Cal / Val of AIRS with S-HIS
Slide 3
The Scanning High-resolution Interferometer Sounder (S-HIS)
Slide 4
UW SSEC S-HIS: 1998 - Present (1)
(HIS: High-resolution Interferometer Sounder, 1985 - 1998)
Characteristics
Interferometer Type: Voice coil DA plane mirror
(Custom / modified Bomem DA-5)
Resolving Power: 1000 - 6000
IFOV: 100 mrad (2 km @ 20 km, nadir)
Field Mirror Scan: Programmable
Spectral Coverage:
LW:
MW:
SW:
Spectral Resolution:
CO2
Midwave
CH4/N2O
Longwave
O3
H2O
H2O
Shortwave
N2O
CO2
CO
Slide 5
580 - 3000 cm -1
580 - 1200 cm -1
1000 - 1820 cm -1
1750 - 3000 cm -1
0.5 cm -1
UW SSEC S-HIS: 1998 - Present (2)
(HIS: High-resolution Interferometer Sounder, 1985 - 1998)
QuickTime™ and a
Motion JPEG OpenDML decompressor
are needed to see this picture.
Slide 6
S-HIS: Recent Developments (OCT 2002 - present)
• ARM - UAV Mission, Oct / Nov 2002; S-HIS on the Proteus
• Radiometric calibration budget
• Spectral band overlap
• Uplooking (Zenith) view
• Nonlinearity refinement
• Unfiltered interferogram storage
Slide 7
S-HIS on 1st ARM-UAV Mission with Proteus, October 2002
• Typically, cross-track
scanning with two
blackbody views
• Zenith view added for
the Proteus integration
Slide 8
S-HIS on the Proteus: Remote Telemetry and Command
• Exciting opportunity
• A state-of-health application for S-HIS for this deployment
• Three ‘application modules’
• The S-HIS UAV interface
• Polls for and interprets commands from the payload controller
• Monitors internal UDP traffic, periodically retrieving data
• Converts retrieved data to engineering unit, parses, and sends to
payload controller
• Monitors for critical data storage errors
• The payload controller
• Maintains ground link
• Power management
• Relays instrument commands and data files
• The ground system
• Provides a user interface to the payload
Slide 9
S-HIS on the Proteus: New Platform, New Environment
• New Interfaces (mechanical, electrical, optical)
• Vibrational environment
• Thermal environment
Slide 10
S-HIS on the Proteus: New Platform, New Environment (2)
Slide 11
Scanning-HIS Radiometric Calibration Budget for 11/21 case
TABB = 260K, THBB = 310K
3-sigma Uncertainties, similar to Best, et al., CALCON 2003 for AERI
RSS
THBB
TABB
TRFL
HBB
ABB
Slide 12
Scanning-HIS Radiometric Calibration Budget for 11/21 case
TABB = 260K, THBB = 310K
3-sigma Uncertainties, similar to Best, et al., CALCON 2003 for AERI
Slide 13
Scanning-HIS Band Overlap Agreement
Midwave
(HgCdTe)
Shortwave
(InSb)
Radiance (mW/m2 sr cm-1)
Longwave
(HgCdTe)
LW/MW overlap
MW/SW overlap
Wavenumber (cm-1)
Slide 14
S-HIS zenith and cross-track scanning Earth views
11-16-2002 from Proteus @ ~14km
HBB
Earth
ABB
Zenith
Slide 15
Observed and Calculated zenith views from Proteus @ ~14km
Calculated
Observed
Calculation based on 18Z ECMWF analysis, with 0.0004 cm H2O above 14km
Slide 16
Non-linearity Refinement
• Band-to-band overlaps are a primary source of refinement
– SW band detector is highly linear, allowing SW overlap with
MW to constrain or test the MW non-linearity
– MW overlap with LW can then constrain or test the LW nonlinearity
• Currently using up-looking constraints to refine estimates of
non-linearity coefficients and their uncertainties
Slide 17
Raw Interferogram Storage
•
•
•
•
•
Current flight software: only filtered interferograms stored
“Bench tested” software: raw interferogram storage
– All 3 bands, interferograms truncated about ZPD
– 2 bands, complete interferograms
Raw interferograms provide out-of-band nonlinearity signal information
Applications:
– Verify “defiltering” algorithm
– Improved tilt correction
– Improved nonlinearity characterization
Future work:
– All 3 bands, complete
– Filtered and raw interferogram combination
– Operational flight software
Slide 18
The Atmospheric Infrared Sounder (AIRS)
Slide 19
AIRS
•
•
AIRS is part of the EOS Aqua instrument suite
polar sun synchronous ascending 1:30 PM local
•
Managed by NASA/JPL.
•
Companion instruments
– AMSU-A (Advanced Microwave Sounding Unit - A)
– HSB (Humidity Sounder for Brazil) stopped working
in March 2003
– MODIS, CERES, AMSR-E
Timeline:
• Launched on May 4th 2002
• First L1B data made available to the science team in
mid June 2002
• L1B available from GSFC DAAC starting in March 2003
• L2 available from GSFC DAAC starting in Sept 2003
Slide 20
AIRS Design
• Hyperspectral radiometer with
resolution of 0.5 – 2 cm-1 (resolving
power of ~1200)
• Spectral range: 650 – 2700 cm-1
• Multi-order Infrared Grating
Spectrometer passively cooled to ~153K,
stabilized to 30 mK
• PV and PC HdCdTe focal plane cooled
to 60K with redundant active pulse tube
cryogenic coolers
• Focal plane has ~5000 detectors, 2378
channels. PV detectors (all below 13
microns) are doubly redundant.
• 308 K onboard blackbody and space
views provides radiometric calibration
• Clear sky upwelling radiation calculations provide spectral calibration
• NEDT (per resolution element) is very good and ranges from 0.05K to 0.5K per channel
Slide 21
Radiance Validation of AIRS with S-HIS
Slide 22
AIRS / S-HIS Comparisons
A detailed comparison should account for:
• Instrumental noise and scene variations
• Different observation altitudes (AIRS is 705 km, S-HIS is ~20 km on ER2, ~14 km on
Proteus)
• Different view angles (AIRS is near nadir, S-HIS is ~±35deg from nadir)
• Different spatial footprints (AIRS is ~15 km at nadir, S-HIS is ~2 km at nadir)
• Different spectral response (AIRS  =  / 1200, S-HIS  ≈ 0.5 cm-1) and sampling
AIRS
SHIS and AIRS SRFs
SHIS
Slide 23
AIRS / S-HIS Comparison Steps
0. Average SHIS data within AIRS FOV(s) & compare
• No attempt to account for view angle, altitude, spectral differences.
1. Compare Residuals from calculations:
AIRS residual = AIRSobs - AIRScalc
S-HIS residual = S-HISobs - S-HIScalc
• S-HIS and AIRS calculations each completed at correct altitudes,
view angles, spectral resolution and sampling.
• Monochromatic calculations completed using same forward model,
atmospheric state, and surface property inputs.
2. Difference Residuals with Spectral Resolutions made similar
AIRS residual = AIRSobs  S-HISSRF - AIRScalc  S-HISSRF
S-HIS residual = S-HISobs  AIRSSRF - S-HIScalc  AIRSSRF
• valid comparison except for channels primarily sensitive to upper
atmosphere (above aircraft altitude)
Slide 24
Terra-Aqua Experiment (TX-2002), 21 Nov 2002
Aqua Subsatellite track
ER2 Flight track
• 1905 - 1913 UTC
• 1930 - 1950 UTC
• 1941 UTC Aqua coincidence
time
coincidence
Slide 25
MODIS 12 m Band Tb(K) & near-nadir AIRS FOVs, 21 Nov 2002
10 K
Slide 26
MODIS 12 micron Band & near-nadir AIRS FOVs, 21 Nov 2002
1K
8 AIRS FOVs
used in the
following
comparisons
Slide 27
“comparison 0”
8 AIRS FOVs, 448 S-HIS FOVs, PC filtering
AIRS
S-HIS
Slide 28
“Comparison 0”, 21 Nov 2002
8 AIRS FOVs, 448 S-HIS FOVs, PC filtering
Slide 29
AIRS Compared to S-HIS (LW), 21 Nov 2002
AIRS
S-HIS
Calculated spectra in black
AIRS Observed - Calculated
S-HIS Observed - Calculated
“Comparison 2”
AIRS minus MODIS
36, 35, 34, 33
32
31
wavenumber
Slide 30
30
AIRS Compared to S-HIS (MW), 21 Nov 2002
AIRS
S-HIS
Calculated spectra in black
AIRS Observed - Calculated
S-HIS Observed - Calculated
“Comparison 2”
28
27
wavenumber
Slide 31
AIRS Compared to S-HIS (SW), 21 Nov 2002
AIRS
S-HIS
Calculated spectra in black
AIRS Observed - Calculated
S-HIS Observed - Calculated
“Comparison 2”
25
24
23
22, 21
wavenumber
Different viewing angle make daytime comparisons less accurate
Slide 32
Small Spectral Shift (3% of resolution) in AIRS Module-05 identified
from S-HIS Validation
Tb (K)
wavenumber (cm-1)
original obs-calc
shifted obs-calc
wavenumber (cm-1)
Tobin, et al., CALCON 2003, presented S-HIS Spectral Calibration
Slide 33
Observed - calculated (K)
∆Tb (K)
observed
original calculated
shifted calculated
(AIRSobs - AIRScalc)(SHISobs - SHIScalc) (K)
“Comparison 2”, 21 Nov 2002
Excluding channels strongly affected by atmosphere above ER-2
Slide 34
Summary
• The calibration uncertainty of advanced high spectral resolution
observations are approaching the 0.1K desired for climate
applications.
• The calibration uncertainty of advanced high spectral resolution
observations from the S-HIS [and the NPOESS Airborne Sounder
Testbed (NAST) are now proven tools for the detailed validation of
satellite based observations.
Slide 35
Summary (2)
• High spectral resolution aircraft instrument comparisons provide
a way to periodically evaluate the absolute calibration of
spacecraft instruments with instrumentation that can be carefully
re-calibrated with reference standards on the ground.
• This capability is especially valuable for assuring the long-term
consistency and accuracy of climate observations, including those
from the NASA EOS spacecrafts (Terra, Aqua, and Aura) and the
future operational observations from the new complement of
NPOESS instruments.
Slide 36
Thank You.
Slide 37