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- Front Matter: Volume 8153
- AIRS Performance
- MODIS On-Orbit Calibration and Uncertainty Analysis
- Landsat Data Continuity Mission
- VIIRS
- New Technologies, Instruments, and Missions I
- New Technologies, Instruments, and Missions II
- Vicarious Calibration
- CERES
- Sensor Intercomparisons
- Data Processing and Products I
- Data Processing and Products II
- Image Processing
- Poster Session
Front Matter: Volume 8153
Front Matter: Volume 8153
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This PDF file contains the front matter associated with SPIE
Proceedings Volume 8153, including the Title Page, Copyright
information, Table of Contents, and the Conference Committee listing.
AIRS Performance
Science highlights and lessons learned from the Atmospheric Infrared Sounder (AIRS)
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The Atmospheric Infrared Sounder (AIRS) and companion instrument, the Advanced Microwave Sounding Unit
(AMSU) on the NASA Earth Observing System Aqua spacecraft are facility instruments designed to support
measurements of atmospheric temperature, water vapor and a wide range of atmospheric constituents in support of
weather forecasting and scientific research in climate and atmospheric chemistry. This paper is an update to the science
highlights from a paper by the authors released last year and also looks back at the lessons learned and future needs of
the scientific community. These lessons not only include requirements on the measurements, but scientific shortfalls as
well. Results from the NASA Science Community Workshop in IR and MW Sounders relating to AIRS and AMSU
requirements and concerns are covered and reflect much of what has been learned and what is needed for future
atmospheric sounding from Low Earth Orbit.
Sensitivity of AIRS and IASI radiometric calibration to scene temperature
Show abstract
High radiometric accuracy under all conditions (such as scene temperature and scan angle) is critical for establishing a
climate-quality data record. In this study we compare radiances of both AIRS and IASI using the difference each
instrument sees between the brightness temperature at 1231 cm-1 and that at 961 cm-1. We collected spectra at 17
different sites distributed around the world in tropical, temperate, desert, and arctic climates. For perfectly calibrated
instruments, the brightness temperature differences should closely agree, since diurnal differences caused by the
differing orbits cancel to first order. We examine observed differences (indicative of calibration artifacts) as functions of
scene temperature, time of day, and scan angle. AIRS is a cooled grating array spectrometer with 2378 spectral channels
in the wavelength range from 3.7 to 15.4 microns. AIRS began routine operations in September 2002. IASI is a Fourier
Transform spectrometer covering the range 3.6 to 15.5 microns in three bands. The spectral resolutions of AIRS and
IASI are similar. IASI data have been available since July 2007.
Evaluation of cloudy data as stable references for climate research using AIRS and IRIS data
Show abstract
We explore the use cloudy data, including Deep Convective Clouds (DCC) in the tropical oceans for the evaluation of
the absolute calibration accuracy and stability of infrared radiometers. For the evaluation of cloudy data we use random
nadir samples. We illustrate the method with Atmospheric Infrared Sounder (AIRS) data and data from the Infrared
Interferometric Spectrometer (IRIS) in the tropical oceans. AIRS is on the EOS Aqua satellite, which was launched in
May 2002 and is expected to continue to produce high quality data until 2015. Two copies of IRIS flew on Nimbus
satellites between April 1970 and January 1971. Based on inconsistencies between AIRS and IRIS data, the absolute
accuracy of the IRIS data is about 1K, including a significant day/night bias. Part of the observed radiometric bias may
have been introduced by quality control, which senses a temperature and spatial uniformity dependent degradation of
instrument performance. The observed biases are larger than the 0.5K accuracy claimed in the literature. This absolute
calibration uncertainty has to be taken into account in the analysis of changes in the more than 30 year time span
between IRIS and AIRS, before they can be attributed to changes in the clouds or the climate.
The method described in this paper can be applied retrospectively to any infrared radiometer like HIRS, AVHRR and
GOES. It has the capability to exposes instrument artifacts, which are not apparent from the routine quality control of the
data.
Improved surface and tropospheric temperatures determined using only shortwave channels: the AIRS Science Team Version-6 retrieval algorithm
Show abstract
The Goddard DISC has generated products derived from AIRS/AMSU-A observations, starting from September 2002 when the AIRS instrument became stable, using the AIRS Science Team Version-5 retrieval algorithm. The AIRS Science Team Version-6 retrieval algorithm will be finalized in September 2011. This paper describes some of the significant improvements contained in the Version-6 retrieval algorithm, compared to that used in Version-5, with an emphasis on the improvement of atmospheric temperature profiles, ocean and land surface skin temperatures, and ocean and land surface spectral emissivities. AIRS contains 2378 spectral channels covering portions of the spectral region 650 cm-1 (15.38 μm) - 2665 cm-1 (3.752 μm). These spectral regions contain significant absorption features from two CO2 absorption bands, the 15 μm (longwave) CO2 band, and the 4.3 μm (shortwave) CO2 absorption band. There are also two atmospheric window regions, the 12 μm - 8 μm (longwave) window, and the 4.17 μm - 3.75 μm (shortwave) window. Historically, determination of surface and atmospheric temperatures from satellite observations was performed using primarily observations in the longwave window and CO2 absorption regions. According to cloud clearing theory, more accurate soundings of both surface skin and atmospheric temperatures can be obtained under partial cloud cover conditions if one uses observations in longwave channels to determine coefficients which generate cloud cleared radiances Ri for all channels, and uses Ri only from shortwave channels in the determination of surface and atmospheric temperatures. This procedure is now being used in the AIRS Version-6 Retrieval Algorithm. Results are presented for both daytime and nighttime conditions showing improved Version-6 surface and atmospheric soundings under partial cloud cover.
MODIS On-Orbit Calibration and Uncertainty Analysis
Further investigation on MODIS solar diffuser screen vignetting function and its implementation in RSB calibration
Show abstract
The MODIS high-gain ocean color bands (B8-B16) are calibrated with its solar diffuser screen (SDS) closed to avoid
saturation so that the vignetting function (VF) of SDS is necessary for the calculation of the gain coefficients of these
detectors. Since there was no pre-launch system level characterization of the VF, a series of yaw maneuvers were carried
out at the mission beginning for both Terra and Aqua to enable its on-orbit characterization. Current VF was derived
from the low-gain bands (B1-B7 & B17-B19) data and applied to high-gain ocean color bands calibration, with the
assumption that all bands and detectors should share the same VF since it is wavelength independent. As expected, error
exists and it was carried over into the calibrated gain coefficients of those bands that use the SDS for their on-orbit
calibration. In this paper, an improved VF calculation approach, still using the yaw data as input, is presented. The new
approach takes the frame-level mismatch between different detector's footprints on the solar diffuser (SD) into account
so that a proper SD image frame adjustment is made when the VF of the low-gain bands is translated into high-gain
bands VF. A new set of band-and-detector dependent VFs can be derived using this approach. The implementation of the
new VF into calibration of high-gain bands gain coefficient has effectively reduced the undesired seasonal oscillations in
its trending from up to Terra's 0.6% and Aqua's 1.0% to nearly 0.2%.
Adjustments to the MODIS Terra radiometric calibration and polarization sensitivity in the 2010 reprocessing
Show abstract
The Moderate-Resolution Imaging Spectroradiometer (MODIS) on NASA's Earth Observing System (EOS)
satellite Terra provides global coverage of top-of-atmosphere (TOA) radiances that have been successfully used
for terrestrial and atmospheric research. The MODIS Terra ocean color products, however, have been compromised
by an inadequate radiometric calibration at the short wavelengths. The Ocean Biology Processing Group
(OBPG) at NASA has derived radiometric corrections using ocean color products from the SeaWiFS sensor as
truth fields. In the R2010.0 reprocessing, these corrections have been applied to the whole mission life span
of 10 years. This paper presents the corrections to the radiometric gains and to the instrument polarization
sensitivity, demonstrates the improvement to the Terra ocean color products, and discusses issues that need
further investigation. Although the global averages of MODIS Terra ocean color products are now in excellent
agreement with those of SeaWiFS and MODIS Aqua, and image quality has been significantly improved, the
large corrections applied to the radiometric calibration and polarization sensitivity require additional caution
when using the data.
Uncertainty assessment of the SeaWiFS on-orbit calibration
Show abstract
Ocean color climate data records require water-leaving radiances with 5% absolute and 1% relative accuracies
as input. Because of the amplification of any sensor calibration errors by the atmospheric correction, the 1%
relative accuracy requirement translates into a 0.1% long-term radiometric stability requirement for top-of-theatmosphere
radiances. The rigorous on-orbit calibration program developed and implemented for SeaWiFS by
the NASA Ocean Biology Processing Group (OBPG) Calibration and Validation Team (CVT) has allowed the
CVT to maintain the stability of the radiometric calibration of SeaWiFS at 0.13% or better over the mission.
The uncertainties in the resulting calibrated top-of-the-atmosphere (TOA) radiances can be addressed in terms of
accuracy (biases in the measurements), precision (scatter in the measurements), and stability (repeatability of the
measurements). The calibration biases of lunar observations relative to the USGS RObotic Lunar Observatory
(ROLO) photometric model of the Moon are 2-3%. The biases from the vicarious calibration against the Marine
Optical Buoy (MOBY) are 1-2%. The precision of the calibration derived from the solar calibration signal-tonoise
ratios are 0.16%, from the lunar residuals are 0.13%, and from the vicarious gains are 0.10%. The long-term
stability of the TOA radiances, derived from the lunar time series, is 0.13%. The stability of the vicariouslycalibrated
TOA radiances, incorporating the uncertainties in the MOBY measurements and the atmospheric
correction, is 0.30%. These results allow the OBPG to produce climate data records from the SeaWiFS ocean
color data.
Landsat Data Continuity Mission
An overview and the latest status of the Landsat Data Continuity Mission (LDCM)
Show abstract
The Landsat Data Continuity Mission (LDCM) will provide continuity in the multi-decadal land use/land cover change
measurements of the Landsat Program for scientific research. The project office at the National Aeronautics and Space
Administration (NASA) Goddard Space Flight Center (GSFC) is responsible for the development, launch and post
launch activation and check out for the Landsat Data Continuity Mission. The LDCM project is currently in its
development phase with launch scheduled for December 2012 on an Atlas V launch vehicle provided by the Kennedy
Space Center (KSC) from the Vandenberg Air Force Base (VAFB). The project is a partnership between NASA and the
Department of the Interior (DOI)/United States Geological Survey (USGS). DOI/USGS is responsible for development
of the ground system and will assume responsibility for satellite and ground system operations following the check-out
period. This paper will provide an overview and the latest status of the LDCM mission.
Landsat Data Continuity Mission operational land imager and thermal infrared sensor performance
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The Landsat Data Continuity Mission (LDCM) will have two pushbroom Earth-imaging sensors: the Operational Land
Imager (OLI) and the Thermal InfraRed Sensor (TIRS). The OLI has the reflective 30-meter and panchromatic 15-meter
ETM+ bands plus additional 30-meter bands at 443 nm and 1375 nm. The TIRS has two 100-meter bands that spectrally
split the ETM+ thermal band. OLI has completed performance testing and is scheduled for a late summer 2011 delivery
to the spacecraft. OLI radiometric performance has shown that polarization sensitivity is 1-2%; Signal-to-Noise Ratios at
signal levels about 5-10% of full scale are between 6-12 times better than ETM+, e.g., 250 versus 30; radiometric
stability over 16 days is better than 0.5% (2-sigma); coherent noise is not visible; detector operability is 100% (no dead
or inoperable detectors), absolute radiance calibration uncertainty is ~4%, reflectance calibration uncertainty is ~2.5%
and detector-to-detector radiometric uniformity is generally better than 0.5%. TIRS completed initial performance
testing in March 2011 and in August 2011 will be entering its primary thermal vacuum performance testing with the
integrated instrument. At this point indications are that the TIRS instrument will have noise levels roughly ¼ of the
ETM+ bands and detector-to-detector radiometric uniformity of better than 0.5%.
Landsat 8 on-orbit characterization and calibration system
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The Landsat Data Continuity Mission (LDCM) is planning to launch the Landsat 8 satellite in December 2012, which
continues an uninterrupted record of consistently calibrated globally acquired multispectral images of the Earth started in
1972. The satellite will carry two imaging sensors: the Operational Land Imager (OLI) and the Thermal Infrared Sensor
(TIRS). The OLI will provide visible, near-infrared and short-wave infrared data in nine spectral bands while the TIRS
will acquire thermal infrared data in two bands. Both sensors have a pushbroom design and consequently, each has a
large number of detectors to be characterized.
Image and calibration data downlinked from the satellite will be processed by the U.S. Geological Survey (USGS) Earth
Resources Observation and Science (EROS) Center using the Landsat 8 Image Assessment System (IAS), a component
of the Ground System. In addition to extracting statistics from all Earth images acquired, the IAS will process and trend
results from analysis of special calibration acquisitions, such as solar diffuser, lunar, shutter, night, lamp and blackbody
data, and preselected calibration sites. The trended data will be systematically processed and analyzed, and calibration
and characterization parameters will be updated using both automatic and customized manual tools. This paper describes
the analysis tools and the system developed to monitor and characterize on-orbit performance and calibrate the Landsat 8
sensors and image data products.
Modeling the image performance of the Landsat Data Continuity Mission sensors
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The LDCM will carry two new pushbroom imagers. The nine band Operational Land Imager (OLI) and the two
band Thermal Infrared Sensor (TIRS) represent significant changes in Landsat Sensor Technology, as does the plan to
generate a common data product from two sensors (registered 11 band data). This effort is designed to generate synthetic
images that will predict the LDCM performance pre-launch, will support trouble shooting of instrument behavior during
initialization and operation, and perhaps most importantly, can support Landsat remote sensing science activities
throughout the mission. This paper reports on initial results of efforts to simulate all of the phenomena that can lead to
non-uniformity variations in an image. This includes detector-to-detector and array-to-array non-uniformities due to
variations in relative spectral response (RSR), gain, bias, and non-linearities. The overall approach involves modifying
the DIRSIG image simulation model to allow detailed modeling of the Landsat orbit and LDCM sensors parameters and
generation of test scenes to allow full end-to-end image simulations incorporating illumination, atmospheric, sensor
geometry, and radiometry effects as a function of time, meteorology, spectral range from the visible through the long
wave infrared, and spatial effects. The results reported in this paper emphasize the modeling and initial demonstration of
the non-uniformity phenomenology.
The operational land imager: spectral response and spectral uniformity
Show abstract
The Landsat Data Continuity Mission (LDCM) will carry the Operational Land Imager (OLI) as one of its payloads.
This instrument is a derivative of the Advanced Land Imager (ALI), flown on Earth Observing-1 (EO1) though it's
mission is to continue the operational land imaging of the Landsat program. The OLI follows the highly successful
Landsat-5 and Landsat-7 missions in continuing to populate an archive of earth images that dates back to 1972.
The OLI has significant changes from the Landsat Thematic Mapper instruments, given that is the first pushbroom
instrument in the program. However, it is intended to be a continuity mission, so the spatial coverage and spectral bands
are similar. The suite of OLI's multispectral bands cover the same bandpasses but the panchromatic band is narrower
than that of the ETM+. The OLI also has a shorter wavelength blue band for better resolution of coastal waters and a
new band to aid in the detection of Cirrus clouds in the atmosphere. The thermal bands traditionally carried on the TM
instruments have been moved to a separate instrument, also onboard the LDCM spacecraft.
With the pushbroom design, each OLI multi-spectral band consists of nearly 7000 detectors. The OLI underwent prelaunch
to verify a host of requirements on it's spectral performance, where was characterized at three different points
during development. This paper will cover the results of the tests that attempt to validate the spectral uniformity
requirements, including in-band response, out-of-band response, and spectral uniformity across the focal plane.
Bias estimation for the Landsat 8 operational land imager
Show abstract
The Operational Land Imager (OLI) is a pushbroom sensor that will be a part of the Landsat Data Continuity Mission
(LDCM). This instrument is the latest in the line of Landsat imagers, and will continue to expand the archive of
calibrated earth imagery. An important step in producing a calibrated image from instrument data is accurately
accounting for the bias of the imaging detectors. Bias variability is one factor that contributes to error in bias estimation
for OLI. Typically, the bias is simply estimated by averaging dark data on a per-detector basis. However, data acquired
during OLI pre-launch testing exhibited bias variation that correlated well with the variation in concurrently collected
data from a special set of detectors on the focal plane. These detectors are sensitive to certain electronic effects but not
directly to incoming electromagnetic radiation. A method of using data from these special detectors to estimate the bias
of the imaging detectors was developed, but found not to be beneficial at typical radiance levels as the detectors respond
slightly when the focal plane is illuminated. In addition to bias variability, a systematic bias error is introduced by the
truncation performed by the spacecraft of the 14-bit instrument data to 12-bit integers. This systematic error can be
estimated and removed on average, but the per pixel quantization error remains. This paper describes the variability of
the bias, the effectiveness of a new approach to estimate and compensate for it, as well as the errors due to truncation
and how they are reduced.
VIIRS
Results from solar reflective band end-to-end testing for VIIRS F1 sensor using T-SIRCUS
Show abstract
Verification of the Visible Infrared Imager Radiometer Suite (VIIRS) End-to-End (E2E) sensor calibration is
highly recommended before launch, to identify any anomalies and to improve our understanding of the sensor onorbit
calibration performance. E2E testing of the Reflective Solar Bands (RSB) calibration cycle was performed
pre-launch for the VIIRS Flight 1 (F1) sensor at the Ball Aerospace facility in Boulder CO in March 2010.
VIIRS reflective band calibration cycle is very similar to heritage sensor MODIS in that solar illumination, via a
diffuser, is used to correct for temporal variations in the instrument responsivity. Monochromatic light from the
NIST T-SIRCUS (Traveling Spectral Irradiance and Radiance Responsivity Calibrations using Uniform Sources)
was used to illuminate both the Earth View (EV), via an integrating sphere, and the Solar Diffuser (SD) view,
through a collimator. The collimator illumination was cycled through a series of angles intended to simulate the
range of possible angles for which solar radiation will be incident on the solar attenuation screen on-orbit. Ideally,
the measured instrument responsivity (defined here as the ratio of the detector response to the at-sensor radiance)
should be the same whether the EV or SD view is illuminated. The ratio of the measured responsivities was
determined at each collimator angle and wavelength. In addition, the Solar Diffuser Stability Monitor (SDSM), a
ratioing radiometer designed to track the temporal variation in the SD Bidirectional Reflectance Factor (BRF) by
direct comparison to solar radiation, was illuminated by the collimator. The measured SDSM ratio was compared
to the predicted ratio. An uncertainty analysis was also performed on both the SD and SDSM calibrations.
A maximum likelihood approach to determine sensor radiometric response coefficients for NPP VIIRS reflective solar bands
Show abstract
Optical sensors aboard Earth orbiting satellites such as the next generation Visible/Infrared Imager Radiometer Suite
(VIIRS) assume that the sensors' radiometric response in the Reflective Solar Bands (RSB) is described by a
quadratic polynomial, in relating the aperture spectral radiance to the sensor Digital Number (DN) readout. For
VIIRS Flight Unit 1 (FU1) (Butler, J., Xiong, X., Oudrari, H., Pan, C., and Gleason, J., "NASA Calibration and
Characterization in the NPOESS Preparatory Project (NPP)", IGARSS, July 12-17, 2009, Cape Town, South
Africa.), the coefficients are to be determined before launch by an attenuation method, although the linear
coefficient will be further determined on-orbit through observing the Solar Diffuser. In determining the quadratic
polynomial coefficients by the attenuation method, a Maximum Likelihood approach is applied in carrying out the
least-squares procedure. Crucial to the Maximum Likelihood least-squares procedure is the computation of the
weight. The weight not only has a contribution from the noise of the sensor's digital count, with an important
contribution from digitization error, but also is affected heavily by the mathematical expression used to predict the
value of the dependent variable, because both the independent and the dependent variables contain random noise. In
addition, model errors have a major impact on the uncertainties of the coefficients. The Maximum Likelihood
approach demonstrates the inadequacy of the quadratic model. We show that using the inadequate quadratic model
dramatically increases the uncertainties of the coefficients. We compute the coefficient values and their
uncertainties, considering both measurement and model errors.
VIIRS F1 "best" relative spectral response characterization by the government team
Show abstract
The VIIRS Flight 1 (F1) instrument completed sensor level testing, including relative spectral response
(RSR) characterization in 2009 and is moving forward towards a launch on the NPP platform late in 2011.
As part of its mandate to produce analyses of F1 performance essentials, the VIIRS Government Team,
consisting of NASA, Aerospace Corp., and MIT/Lincoln Lab elements, has produced an independent (from
that of industry) analysis of F1 RSR. The test data used to derive RSR for all VIIRS spectral bands was
collected in the TVAC environment using the Spectral Measurement Assembly (SpMA), a dual
monochromator system with tungsten and ceramic glow bar sources. These spectrally contiguous
measurements were analyzed by the Government Team to produce a complete in-band + out-of-band RSR
for 21 of the 22 VIIRS bands (exception of the Day-Night Band). The analysis shows that VIIRS RSR was
well measured in the pre-launch test program for all bands, although the measurement noise floor is high on
the thermal imager band I5. The RSR contain expected detector to detector variation resulting from the
VIIRS non-telecentric optical design, and out-of-band features are present in some bands; non-compliances
on the integrated out-of-band spectral performance metric are noted in M15 and M16A,B bands and also for
several VisNIR bands, though the VisNIR non-compliances were expected due to known scattering in the
VisNIR integrated filter assembly. The Government Team "best" RSR have been released into the public
domain for use by the science community in preparation for the post-launch era of VIIRS F1.
Comparison of VIIRS pre-launch RVS performance using results from independent studies
Show abstract
The Visible Infrared Imaging Radiometer Suite (VIIRS) is a key sensor carried on the
NPOESS (National Polar-orbiting Operational Environmental Satellite System) Preparatory
Project (NPP) mission [1] (http://jointmission.gsfc.nasa.gov/viirs.html), and is
scheduled to launch in October 2011. VIIRS sensor design draws on heritage instruments
including AVHRR, OLS, MODIS, and SeaWiFS. It has on-board calibration components
including a solar diffuser (SD) and a solar diffuser stability monitor (SDSM) for the
reflective solar bands (RSB), a V-groove blackbody for the thermal emissive bands (TEB),
and a space view (SV) port for background subtraction. These on-board calibrators are
located at fixed scan angles. The VIIRS response versus scan angle (RVS) was
characterized prelaunch in lab ambient conditions and will be used on-orbit to
characterize the response for all scan angles relative to the calibrator scan angle (SD
for RSB and blackbody for TEB). Since the RVS is vitally important to the quality of
calibrated radiance products, several independent studies were performed and their
results were compared and validated. This document provides RVS results from three
groups: the NPP Instrument Calibration Support Team (NICST), Raytheon, and the Aerospace
Corporation. A comparison of the RVS results obtained using a 2nd order polynomial fit to
measurement data is conducted for each band, detector, and half angle mirror (HAM) side.
The associated RVS fitting residuals are examined and compared with the relative
differences in RVS found between independent studies. Results show that the agreement is
within 0.1% and comparable with fitting residuals for all bands except for RSB band M9,
where a difference of 0.2% was observed. Band M9 is highly sensitive to the atmospheric
water vapor variations during the sensor ambient testing at Raytheon, and its correction might be a contributor to the observed RVS uncertainty differences. In general, NICST
results have shown slightly larger RSB RVS uncertainties but still well within the 0.3%
total uncertainty allowed for the RVS characterization defined in the Performance
Verification Plan.
Assessment of NPP VIIRS ocean color data products: hope and risk
Show abstract
For several years, the NASA/Goddard Space Flight Center (GSFC) NPP VIIRS Ocean Science Team (VOST) provided
substantial scientific input to the NPP project regarding the use of Visible Infrared Imaging Radiometer Suite (VIIRS) to
create science quality ocean color data products. This work has culminated into an assessment of the NPP project and
the VIIRS instrument's capability to produce science quality Ocean Color data products. The VOST concluded that
many characteristics were similar to earlier instruments, including SeaWiFS or MODIS Aqua. Though instrument
performance and calibration risks do exist, it was concluded that programmatic and algorithm issues dominate concerns.
New Technologies, Instruments, and Missions I
The NASA enhanced MODIS airborne simulator
Show abstract
The new NASA Enhanced MODIS Airborne Simulator (eMAS) is based on the legacy MAS system,
which has been used extensively in support of the NASA Earth Observing System program since
1995. eMAS consists of two separate instruments designed to fly together on the NASA ER-2 and
Global Hawk high altitude aircraft.
The eMAS-IR instrument is an upgraded version of the legacy MAS line-scanning spectrometer,
with 38 spectral bands in the wavelength range from 0.47 to 14.1 μm. The original LN2-cooled
MAS MWIR and LWIR spectrometers are replaced with a single vacuum-sealed, Stirling-cooled
assembly, having a single MWIR and twelve LWIR bands. This spectrometer module contains a
cold optical bench where both dispersive optics and detector arrays are maintained at cryogenic
temperatures to reduce infrared background noise, and ensure spectral stability during high altitude
airborne operations.
The EMAS-HS instrument is a stand-alone push-broom imaging spectrometer, with 202 contiguous
spectral bands in the wavelength range from 0.38 to 2.40 μm. It consists of two Offner
spectrometers, mated to a 4-mirror anastigmatic telescope. The system has a single slit, and uses a
dichroic beam-splitter to divide the incoming energy between VNIR and SWIR focal plane arrays.
It will be synchronized and bore-sighted with the IR line-scanner, and includes an active source for
monitoring calibration stability.
eMAS is intended to support future satellite missions including the Hyperspectral Infrared Imager (
HyspIRI,) the National Polar-orbiting Operational Environmental Satellite System (NPOESS)
Preparatory Project (NPP,) and the follow-on Joint Polar Satellite System (JPSS.)
Development of a low-cost student-built multi-spectral sensor for the International Space Station
Show abstract
Built by students and faculty at the University of North Dakota (UND), the International Space Station (ISS)
Agricultural Camera (ISSACTM) is a multi-spectral Earth-imaging sensor currently onboard the ISS. Capabilities include
three spectral bands (green, red, near-infrared), medium (~20m) spatial resolution, and off-nadir pointing (+/-30 degrees)
for episodic rapid-response imaging. We describe the low-cost electro-optical design approach, which utilizes a studentcentered
design and operations team and relies on modified commercial components operating within a passive vibration
isolation mounting, installed inside the Window Observational Research Facility, viewing the Earth through the US
Laboratory Science Window. Interfaces, safety, and other factors unique to the human-rated operational environment of
the ISS are outlined. Pre-launch sensor characterization results, including spatial distortion and radiometric
measurements, indicate Earth remote sensing using such a sensor is a viable approach for demonstrative operational
missions. An element of the ISS National Laboratory, ISSAC was launched on HTV-2 to the ISS in January 2011. Initial
operations began in June 2011. Methods of sensor operations are described, using a student staff working within the ISS
operational environment. Some initial early imaging results are shown.
SENTINEL-2 level 1-image processing and performances
Show abstract
In partnership with the European Commission and in the frame of the Global Monitoring for Environment and Security
(GMES) program, the European Space Agency (ESA) is developing the Sentinel-2 optical imaging mission devoted to
the operational monitoring of land and coastal areas.
The Sentinel-2 mission is based on a satellites constellation deployed in polar sun-synchronous orbit. While ensuring
data continuity of former SPOT and LANDSAT multi-spectral missions, Sentinel-2 will also offer a wide range of
improvements such as a global coverage, a large field of view (290km), a high revisit capability (5 days with two
satellites), a high resolution (10m, 20m and 60m) and multi-spectral imagery (13 spectral bands). In this context, the
Centre National d'Etudes Spatiales (CNES) supports ESA to define the system image products and to prototype the
relevant image processing techniques.
First, this paper presents the Sentinel-2 system and the image products that will be delivered: starting from raw
decompressed images up to accurate ortho-images in Top of Atmosphere reflectances. The stringent image quality
requirements are also described, in particular the very accurate target geo-location.
Then, the prototyped image processing techniques will be addressed. Both radiometric and geometric processing will be
described with a special focus on the automatic enhancement of the geometric physical model involving a global set of
reference data.
Finally, the very promising results obtained by the prototype will be presented and discussed. The radiometric and
geometric performances will be provided as well as the associated computing time estimation on the target platform.
Climate-monitoring CubeSat mission (CM2): a project for global mesopause temperature sensing
Show abstract
The goals of the Climate Monitoring CubeSat Mission (CM2) are to accelerate climate projection by
obtaining global temperature, tidal and wave measurements with a simple CubeSat-based imaging
spectrograph; and to demonstrate how a high-resolution imaging spectrograph can be deployed on a
CubeSat satellite. In the middle atmosphere (50 - 100 km), beyond the reach of balloons or satellites,
thermal signatures of CO2 radiation and wave activity have been largely missing from climate model
inputs. This paper outlines an instrument to advance the state of the art in atmospheric climate projection
by providing critical global measurements of middle-atmosphere temperatures and waves with a CubeSatscale
imaging spectrograph.
The CM2 will remotely sense middle-atmosphere temperatures and waves at ~90 km by analyzing spectra
of intrinsically bright molecular oxygen emissions at near-infrared wavelengths in the O2 atmospheric
band. The core instrument will be a miniaturized imaging spectrograph based on a monolithic spatial
heterodyne spectrometer (SHS). This spectrograph will have sensitivity and spectral resolution to extract
temperatures with 10° K precision and waves with 4 km scale resolution along a ~200 km cross-track
swath. The SHS is significantly more robust than conventional interferometers, and thus better suited to
space-based observation.
Acquiring high-resolution middle-atmosphere temperature, tidal, and wave data on a daily, global basis will
significantly improve climate models, and will help assess long-term greenhouse gas mitigation policy
impact on upper-atmosphere thermal signatures. The CM2 program will also establish the efficacy of highresolution
CubeSat-based broadband (near-IR to UV) spectroscopy for application to other atmospheric
research missions.
Preliminary error budget for the reflected solar instrument for the Climate Absolute Radiance and Refractivity Observatory
Show abstract
The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission addresses the need to observe highaccuracy,
long-term climate change trends and to use decadal change observations as the most critical method to
determine the accuracy of climate change. The CLARREO Project will implement a spaceborne earth observation
mission designed to provide rigorous SI-traceable observations (i.e., radiance, reflectance, and refractivity) that are
sensitive to a wide range of key decadal change variables. The instrument suite includes emitted infrared spectrometers,
global navigation receivers for radio occultation, and reflected solar spectrometers. The measurements will be acquired
for a period of five years and will enable follow-on missions to extend the climate record over the decades needed to
understand climate change. This work describes a preliminary error budget for the RS sensor. The RS sensor will
retrieve at-sensor reflectance over the spectral range from 320 to 2300 nm with 500-m GIFOV and a 100-km swath
width. The current design is based on an Offner spectrometer with two separate focal planes each with its own entrance
aperture and grating covering spectral ranges of 320-640, 600-2300 nm. Reflectance is obtained from the ratio of
measurements of radiance while viewing the earth's surface to measurements of irradiance while viewing the sun. The
requirement for the RS instrument is that the reflectance must be traceable to SI standards at an absolute uncertainty
<0.3%. The calibration approach to achieve the ambitious 0.3% absolute calibration uncertainty is predicated on a
reliance on heritage hardware, reduction of sensor complexity, and adherence to detector-based calibration standards.
The design above has been used to develop a preliminary error budget that meets the 0.3% absolute requirement. Key
components in the error budget are geometry differences between the solar and earth views, knowledge of attenuator
behavior when viewing the sun, and sensor behavior such as detector linearity and noise behavior. Methods for
demonstrating this error budget are also presented.
Optical design of the ocean radiometer for carbon assessment
Show abstract
The Ocean Radiometer for Carbon Assessment (ORCA) is a new design for the next generation remote sensing of
oceans biology and biogeochemistry satellite. ORCA is configured to meet the requirements of the Decadal Survey
recommended Aerosol, Cloud, and Ecology (ACE ), the Ocean Ecosystem (OES) radiometer and the Pre-ACE climate
data continuity mission (PACE). Under the auspices of a 2007 grant from NASA's Research Opportunity in Space and
Earth Science (ROSES) and the Instrument Incubator Program (IIP) , a team at the Goddard Space Flight Center
(GSFC) has been working on a functional prototype of a hyperspectral imager with flightlike optics and scan
mechanisms. This paper discusses the requirements and optomechanical design of this prototype.
New Technologies, Instruments, and Missions II
Optical component performance for the Ocean Radiometer for Carbon Assessment (ORCA)
Show abstract
The Ocean Radiometer for Carbon Assessment (ORCA) is a new design for the next generation remote sensing
of ocean biology and biogeochemistry. ORCA is configured to meet all the measurement requirements of the
Decadal Survey Aerosol, Cloud, and Ecology (ACE ), the Ocean Ecosystem (OES) radiometer and the Pre-ACE
climate data continuity mission (PACE). Under the auspices of a 2007 grant from NASA Research Opportunity
in Space and Earth Science (ROSES) and the Instrument Incubator Program (IIP) , a team at the Goddard
Space Flight Center (GSFC) has been working on a functional prototype with flightlike fore and aft optics and
scan mechanisms. As part of the development efforts to bring ORCA closer to a flight configuration, we have
conducted component-level optical testing using standard spectrophometers and system-level characterizations
using nonflight commercial off-the-shelf (COTS) focal plane array detectors. Although these arrays would not be
able to handle flight data rates, they are adequate for optical alignment and performance testing. The purpose
of this presentation is to describe the results of this testing performed at GSFC and the National Institute of
Standards and Technology (NIST) at the component and system level. Specifically, we show results for ORCA's
spectral calibration ranging from the near UV, visible, and near-infrared spectral regions.
ORCA's depolarizer
Show abstract
The Ocean Radiometer for Carbon Assessment (ORCA), currently being developed at Goddard, is a hyperspectral
instrument with a spectral range extending from 350nm to 880nm in the UV and visible wavelength. Its radiometric
measurement accuracy will depend, in part, on the extent to which it is insensitive to linearly polarized light. A wedge
type depolarizer is used to reduce ORCA's polarization sensitivity over its entire spectral range. The choice for this
approach is driven by the large spectral range and to a certain extent is also influenced by the currently orbiting SeaWifs
instrument's use of a wedge depolarizer and its low polarization sensitivity. The wedge depolarizer's design, its modeled
and measured depolarization characteristics are presented.
Characteristics of a new type of Mie scattering volume diffuser and its use as a spectral albedo calibration standard for the solar reflective wavelength region
Show abstract
Emerging instrumental requirements for remotely sensing tropospheric trace species have led to a rethinking by some of
the paradigm for Système International d'Unités (SI) traceability of the spectral irradiance and radiance radiometric
calibrations to spectral albedo (sr-1) which is not a SI unit. In the solar reflective wavelength region the spectral albedo
calibrations are tied often to either the spectral albedo of a solar diffuser or the Moon.
This new type of Mie scattering diffuser (MSD) is capable of withstanding high temperatures, and is more Lambertian
than SpectralonTM. It has the potential of covering the entire solar reflective wavelength region. Laboratory
measurements have shown that the specular reflectance component is negligible, and indicate that internal absorption by
multiple scattering is small. This MSD, a true volume diffuser, exhibits a high degree of radiometric stability which
suggests that measurements at the National Institute of Standards and Technology (NIST) could provide a spectral
albedo standard. Measurements are currently in progress of its radiometric stability under a simulated space environment
of high energy ionizing and ultraviolet (UV) solar radiation for its eventual use in space as a solar diffuser.
RF-excited plasma lamps for use as sources in OGSE integrating spheres
Show abstract
Integrating spheres for optical calibration of remote sensing cameras have traditionally been made with Quartz
Tungsten Halogen (QTH) lamps because of their stability. However, QTH lamps have the spectrum of a blackbody
at approximately 3000K, while remote sensing cameras are designed to view a sun-illuminated scene. This presents
a severe significant mismatch in the blue end of the spectrum. Attempts to compensate for this spectral mismatch
have primarily used Xenon lamps to augment the QTH lamps. However, Xenon lamps suffer from temporal
instability that is not desirable in many applications. This paper investigates the possibility of using RF-excited
plasma lamps to augment QTH lamps. These plasma lamps have a somewhat smoother spectrum than Xenon. Like
Xenon, they have more fluctuation than QTH lamps, but the fluctuations are slower and may be able to be tracked in
an actual OGSE light source. The paper presents measurements of spectra and stability. The spectrum is measured
from 320 nm to 2500 nm and the temporal stability from DC to 10 MHz. The RF-excited plasma lamps are quite
small, less than 10mm in diameter and about 15 mm in length. This makes them suitable for designing reasonably
sized reflective optics for directing their light into a small port on an integrating sphere. The concludes with a
roadmap for further testing.
Thermal stability of a 4 meter primary reflector for the Scanning Microwave Limb Sounder
Show abstract
The Scanning Microwave Limb Sounder (SMLS) is a space-borne heterodyne radiometer which will measure
pressure, temperature and atmospheric constituents from thermal emission in [180,680] GHz. SMLS, planned for
the NRC Decadal Survey's Global Atmospheric Composition Mission, uses a novel toric Cassegrain antenna to
perform both elevation and azimuth scanning. These will provide better horizontal and temporal resolution and
coverage than were possible with elevation-only scanning in the two previous MLS satellite instruments. SMLS is
diffraction-limited in the vertical plane but highly astigmatic in the horizontal (beam aspect ratio ~1:20). Nadir
symmetry ensures that beam shape is nearly invariant over ±65° azimuth. A low-noise receiver's FOV will be
swept over the reflector system by a small azimuth-scanning mirror. We describe the fabrication and thermalstability
test of a composite demonstration primary reflector, having full 4m height and 1/3 the width planned
for flight. Using finite-element models of reflectors6 and structure, we evaluate thermal deformations and optical
performance for 4 orbital environments and isothermal soak. We compare deformations with photogrammetric
measurements made during soak tests in a chamber. The test temperature range exceeds predicted orbital ranges
by large factors, implying in-orbit thermal stability of 0.21 micron rms/°C; this meets SMLS requirements.
Vicarious Calibration
NEON ground validation capabilities for airborne and space-based imagers
Show abstract
Airborne remote sensing measurements provide the capability to quantitatively measure biochemical and biophysical
properties of vegetation at regional scales, therefore complementing surface and satellite measurements. The National
Ecological Observatory Network (NEON) will build three airborne systems to allow for routine coverage of NEON sites
(60 sites nationally) and the capacity to respond to investigator requests for specific projects. Each airborne system will
consist of an imaging spectrometer, waveform lidar and high-resolution digital camera. Remote sensing data gathered
with this instrumentation needs to be quantitative and accurate in order to derive meaningful information about
ecosystem properties and processes. Also, comprehensive and long-term ecological studies require these data to be
comparable over time, between coexisting sensors and between generations of follow-on sensors. NEON's calibration
plan for the airborne instrument suite relies on intensive laboratory, on-board, ground-based characterization as well as
inter-sensor comparisons. As part of these efforts, NEON organized a pathfinder mission in September 2010 to test
prototype techniques and procedures for field sampling and sensor validation. Imaging spectroscopy data from AVIRIS
and waveform lidar data were acquired in addition to ecological field sampling at the Ordway-Swisher Biological
Station near Gainesville, Florida. This paper presents NEON's capabilities for validation of at-sensor radiance of
airborne and space-based sensors and shows results from the September 2010 pathfinder mission.
Comparison of diffuse sky irradiance calculation methods and effect on surface reflectance retrieval from an automated radiometric calibration test site
Show abstract
The Remote Sensing Group (RSG) at the University of Arizona is currently refining an automated system for the
absolute radiometric calibration of earth-observing sensors. The Radiometric Calibration Test Site (RadCaTS) relies on
semi-permanent instrumentation at the Railroad Valley (RRV) test site to collect data from which surface reflectance and
an atmospheric characterization is determined. Multispectral surface reflectance is determined from calibrated ground
viewing radiometers and assimilated to determine the hyperspectral reflectance used in radiative transfer calculations.
The reflectance retrieval algorithm relies on an accurate determination of the diffuse sky irradiance for the time of
interest. Currently, diffuse sky irradiance is modeled using the atmospheric characterization as input into MODTRAN5.
This work investigates the accuracy of the diffuse sky modeling by comparing modeled results to measurements made at
the test site. Diffuse sky irradiance from several alternative methods are also presented. Surface reflectance is computed
and compared to in-situ measurements taken with a portable spectoradiometer.
ROSAS: a robotic station for atmosphere and surface characterization dedicated to on-orbit calibration
Show abstract
La Crau test site is used by CNES since 1987 for vicarious calibration of SPOT cameras. The former calibration
activities were conducted during field campaigns devoted to the characterization of the atmosphere and the site
reflectances. Since 1997, au automatic photometric station (ROSAS) was set up on the site on a 10m height pole. This
station measures at different wavelengths, the solar extinction and the sky radiances to fully characterize the optical
properties of the atmosphere. It also measures the upwelling radiance over the ground to fully characterize the surface
reflectance properties. The photometer samples the spectrum from 380nm to 1600nm with 9 narrow bands. Every non
cloudy days the photometer automatically and sequentially performs its measurements. Data are transmitted by GSM
(Global System for Mobile communications) to CNES and processed. The photometer is calibrated in situ over the sun
for irradiance and cross-band calibration, and over the Rayleigh scattering for the short wavelengths radiance
calibration. The data are processed by an operational software which calibrates the photometer, estimates the atmosphere
properties, computes the bidirectional reflectance distribution function of the site, then simulates the top of atmosphere
radiance seen by any sensor over-passing the site and calibrates it.
This paper describes the instrument, its measurement protocol and its calibration principle. Calibration results are
discussed and compared to laboratory calibration. It details the surface reflectance characterization and presents SPOT4
calibration results deduced from the estimated TOA radiance. The results are compared to the official calibration.
CERES
CERES FM-5 on the NPP observatory: predicted performance and early orbit validation plans
Show abstract
The Clouds and Earth Radiant Energy System (CERES) Flight Model FM-1 and FM-2 sensors aboard the Terra and the
FM-3 and FM-4 sensors aboard the Aqua spacecraft have provided the first decade of observations of quality suitable for
the Earth Radiation Climate Data Record (CDR). To assure continuity of this CDR the CERES FM-5 sensor will fly on
the NPP spacecraft, scheduled for launch in October 2011. The methods for calibrating the FM-5 in orbit and validating
the results so as to maintain the required level of accuracy and traceability are described. These methods include use of
on-board calibration sources and a number of tests devised for FM-1 through -4. In addition, comparisons of
measurement by the newly calibrated FM-5 with (nearly) coincident measurements by the older CERES instruments on
Terra and Aqua provide an opportunity to investigate the effects on the instruments and the on-board calibration devices
of a decade of operating in space.
Pre-launch sensor characterization of the CERES Flight Model 5 (FM5) instrument on NPP mission
Show abstract
Clouds and the Earth's Radiant Energy System (CERES) instrument was designed to measure broadband radiances
in reflected shortwave and emitted outgoing longwave energy. The 3-sensor CERES instrument measure radiances
in 0.3 to 5.0 micron region with Shortwave sensor, 0.3 to >100 microns with Total sensor and 8 to 12 micron region
with Window sensor. Flight Model 5 (FM5), the sixth of the CERES instruments is scheduled to launch aboard the
NPP spacecraft on October 2011. An accurate determination of the radiometric gains and spectral responsivity of
CERES FM5 sensors was accomplished through rigorous calibrations at Northrop Grumman Aerospace Systems'
(NGAS) Radiometric Calibration Facility (RCF). The longwave calibration of the total and window sensors are
achieved using the Narrow Field-of-View Blackbody (NFBB) source which is tied to International Scale of 1990
(ITS '90). A Shortwave Reference Source (SWRS) along with the Transfer Active Cavity radiometer (TACR) which
acts as the transfer standard of NFBB source, is used to determine the radiometric responsivity and spectral response
estimates of the SW sensor and shortwave portion of the Total sensor. The spectral responsivity in longwave region
is determined using a Fourier Transform Spectrometer (FTS) system. CERES instrument also perform calibrations
using on-board sources during pre-launch testing which serve as a traceability standard to carry the ground
determined sensor radiometric gains to orbit. This paper covers the calibration philosophy and the results from
ground calibration testing of FM5 sensors conducted in 2008. The sensor radiometric gain responses calculated
using primary sources and performance of the sensors using on-board sources will be discussed.
Longwave infrared sensitivity of the clouds and Earth's radiant energy system (CERES) instrument sensors
Show abstract
The Clouds and Earth's Radiant Energy System (CERES) mission currently employs four instruments onboard two
spacecraft to measure the earth's reflected shortwave energy and the earth emitted thermal energy that represents two
components of the earth's energy budget. These measurements are made through three sensors that measure different
spectral channels- a shortwave channel that measures the 0.3 to 5 microns wavelength band, a total channel that
measures all the incident energy (0.3 to ~200 microns) and a window channel that measures the 8 to 12 micron
wavelength band. The radiances measured in each channel (filtered radiances) are used to estimate the incident
(unfiltered) shortwave and longwave radiances using knowledge of the response functions of each of the measurement
channels as well as theoretical knowledge of the energy spectrum of the earth scene being measured. For longer
wavelengths particularly in the far infrared, both the earth scene spectra as well as the instrument spectral response
functions are not very well characterized because of the difficulties in obtaining models for the earth scene spectra as
well as the limitations in the capabilities to measure the spectral responses over a very large spectral range. This results
in errors in obtaining estimates of the unfiltered radiances. This paper will focus on studying the sensitivity of the
CERES instrument to these inaccuracies and its impact on the errors in estimation. In addition, those spectral regions in
the longwave infrared where the CERES instruments are most sensitive will be identified.
The CERES calibration strategy of the geostationary visible channels for CERES cloud and flux products
Show abstract
The Clouds and Earth's Radiant Energy System (CERES) project has greatly improved the understanding of the
role of clouds and energy cycles in global climate studies. CERES flux and cloud properties rely on not only CERES
broadband fluxes and MODIS cloud properties but also on operational geostationary (GOES, METEOSAT, MTSAT)
derived fluxes and clouds, which are acquired between CERES measurements such to properly account for the diurnal
cycle. The high quality of the CERES products is dependent on a consistent radiometric calibration of the un-calibrated
geostationary visible sensors and MODIS. To achieve this consistency, the calibration of a reference sensor must be
transferred to the other instruments. Historically, Terra-MODIS and Aqua-MODIS, both of which employ solar
diffusers, have been regarded as having a well-calibrated visible channel (650 nm). Recent analysis has revealed the
Aqua-MODIS instrument to be more stable than the MODIS instrument onboard the Terra satellite. For this reason,
Aqua-MODIS has been chosen as the reference sensor whereas Terra-MODIS adjustments can be used to put the
instrument on the same radiometric scale as Aqua-MODIS. The ray-matching technique is used to transfer the calibration
of the well-calibrated MODIS instrument to the un-calibrated GEO sensors. Additionally, empirically derived models for
pseudo-invariant test sites and deep convective clouds (DCC) have been developed and applied for monitoring and
validating the GEO calibration.
Multiple pseudo-invariant test site and DCC absolute calibration methodologies are compared. Latest results
show that GOES-13 response has drifted 5-6 percent in its first 15 months of operation. The Aqua/Terra-MODIS crosscalibration
trends are in agreement with calibration trends obtained from pseudo-invariant test sites and DCC. These
results are in preparation for CERES Edition4 products, which will include updated geostationary calibration coefficients
and cloud retrieval improvements.
Sensor Intercomparisons
Using MODIS to calibrate NOAA series AVHRR reflective solar channels
Show abstract
Nearly 30 years of continuous observations made by a series of AVHRR sensors have offered a great
potential for studies of global environment and climate change. In order to achieve this objective, each sensor
must be accurately and consistently calibrated. This is not an easy task as there is no onboard calibrator for
AVHRR reflective solar channels and vicarious calibration often needs to accumulate enough observations to
derive useful trends. In this study, we select CEOS (the Committee on Earth Observation Satellites)
endorsed Cal/Val desert sites to track the long-term stability of reflective solar channels of NOAA-17
AVHRR (launched on June 24, 2002) and re-calibrate them using well-calibrated MODIS as reference. A
site-specific Bi-directional Reflectance Distribution Function (BRDF) developed based on observations
made by MODIS is used to normalize AVHRR observed reflectances. Impacts of atmospheric water vapor on
AVHRR to MODIS reflectance ratios are corrected with measured total water vapor contents derived from
the split-window temperature difference technique. Finally, MODIS-based AVHRR calibration coefficients
on top of the AVHRR prelaunch values are provided in time-dependent look-up tables (LUT). A further
validation is performed using MODIS and AVHRR observations obtained over Antarctic Dome C site where
impact due to atmospheric water vapor is negligibly small.
Long-term cross-calibration of the Terra ASTER and MODIS over the CEOS calibration sites
Show abstract
The Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) and theModerate Resolution
Imaging Spectroradiometer (MODIS) onboard Terra satellite, which have different spatial resolution, can observe
the earth surface simultaneously. Both of these sensors have been operated more than 10 years, and it is very
useful for cross-calibration because of their simultaneous observations mostly without BRDF effect. On the
other hand, the CEOS IVOS group arranges the pseudo-invariant standard test sites for cross-calibration, which
are able to evaluate the long-term stability among multiple sensors. This paper shows the TOA reflectance
comparison between ASTER and MODIS sensor over the CEOS pseudo-invariant standard test sites.
Impact of near-cloud boundaries on radiometric performance of imaging sounders: an examination of FTS and dispersive spectrometer error sources
Show abstract
Meteorological sounding data provided by atmospheric imaging sounders have applications in weather forecasting,
atmospheric chemistry, and climate monitoring. Realistic scenes for these instruments vary in both spatial and spectral
content and such variations can impact the radiometric performance of these instruments. As sounders are developed to
provide climate records with demanding long-term radiometric accuracy requirements, it becomes increasingly
important to understand the effect of scene variations on the performance of these instruments. We have examined the
noise performance and radiometric accuracy of two geostationary sounder architectures in cloudy scenes: a Fourier
transform spectrometer (FTS) and a dispersive spectrometer. Factors such as stray light, ghosting, scattering, and line-ofsight
jitter in the presence of scene inhomogeneities are considered. For each sounder architecture, quantitative estimates
of the radiometric errors associated with sounding in cloudy scenes are made. We find that in a dispersive system the
dominant error in a cloudy scene originates from ghosting within the instrument, while in an FTS the dominant error
originates from scene modulation created by line-of-sight jitter in a partially cloudy scene coupling into signal
modulation over the scale of the changing optical path length of the interferometer. In this paper we describe the
assumptions made and the modeling performed. We also describe how each factor influences the radiometric
performance for that architecture.
Verification of the GSICS GEO-LEO inter-calibration products with GEO-GEO collocation data
Show abstract
The Global Space-based Inter-Calibration System (GSICS) geostationary (GEO) vs. low earth orbit (LEO)
inter-calibration correction products have been routinely generated for years at NOAA to improve and harmonize the
data quality of the operational GOES satellite for a better global weather monitoring, prediction and climate change
studies. In this study, the collocated GOES-13 and GOES-15 Imager infrared (IR) data are used to validate the GSICS
GEO-LEO Imager inter-calibration correction products. To compensate the impact of difference in the spectral
response function (SRF) on the GSICS corrected GEO radiance, two radiative transfer models (RTM) with different
atmospheric profiles are used to simulate the relations between the two GEO radiance values. The results of GEO-GEO
inter-calibration shows that the mean Tb difference between GOES-13 and GOES-15 is less than 0.2K(Ch2),
0.65K(Ch3), 0.08K(Ch4) and 0.35K(Ch6). The two RTM models with different atmospheric profiles have significantly
different impacts on the Tb difference at the two absorptive channels, Ch3 and Ch6, indicating that the impact of
different optical path is not well addressed in this study. Future study should apply the double difference using the RTM
as transfer to compensate for the SRF and viewing/optical path difference at each collocated pixel.
Cross-calibration of HIRS aboard NOAA satellites using IASI
Show abstract
The 30 years of observations from High-Resolution Infrared Radiation Sounder (HIRS) aboard NOAA series of satellites
have been widely used in numerical weather prediction and climate studies. However, there are significant discrepancies
in the HIRS measurements between different satellites. The HIRS data from NOAA satellites series need to be
recalibrated to establish an accurate and consistent temporal series before it can be used for climate changing detection.
To ensure the consistency and reduce the uncertainties for the climate studies of clouds using NOAA HIRS data, this
study explores the spectral calibration of longwave CO2 channels for the HIRS on board of NOAA series of satellites
using the hyper-spectral IASI radiance measurements from MetOp satellite as reference. The HIRS measurements from
each NOAA satellite are compared with the recalibrated HIRS measurements from the successive satellite at
Simultaneous-Nadir-Overpass (SNO) locations. For the satellites after NOAA 15, the comparison between the HIRS
measurements and the matched IASI measurements at SNO locations is also displayed. A preliminary analysis of the
intersatellite biases is performed to quantify the spectral causes of the biases for HIRS channels 4. By removing these
biases, our method shows the potential to recalibrate the HIRS on board of the NOAA series of satellites and make the
HIRS measurements traceable to the IASI measurements with improved spectral calibration.
Data Processing and Products I
Virtual green band for GOES-R
Show abstract
The ABI on GOES-R will provide imagery in two narrow visible bands (red, blue), which is not sufficient to
directly produce color (RGB) images. In this paper we present a method to estimate green band from a simulated
ABI multi-spectral image. To address this problem we propose to use statistical learning to train and update
functions that estimate the value for the 550 nm green channel using the values that will be present in other
bands of the ABI as input parameters. One challenge is that in order to exploit as many bands as possible,
we cannot use straightforward non-parametric methods such as a look-up tables because the number of entries
in look-up tables grows exponentially with the number of input parameters. Other simple approaches such as
simple linear regression on the multi-spectral input parameters will not produce satisfactory results due to the
underlying non-linearity of the data. For instance, the relationship among different spectra for cloud footprints
will be radically different from that of a desert surface. The approach we propose is to use piecewise multi-linear
regression on the multi-spectral input to train the green channel predictor. Our predictor is built from the
combination of a classifier followed by a multi-linear function. The classifier assigns each pixel to a class based
on the array of values from the simulated (or proxy) ABI bands at that pixel. To each class is associated a set
of coefficients for a multi-linear predictor for 550 nm green channel to be predicted. Thus, the parameters of
the predictor consist of parameters of the classifier, as well as coefficients defining the approximating hyperplane
for each class. To determine these classifiers we will use methods based on K-means clustering, as well as
multi-variable piecewise linear approximation.
Web resource to perform the atmospheric correction of satellite data
Show abstract
We describe a Web resource, developed in V.E. Zuev Institute of Atmospheric Optics, Siberian Branch,
Russian Academy of Sciences, Tomsk; it is based on a physical approach and enables a remote calculation of
the atmospheric optical parameters, required for the atmospheric correction of satellite measurements. Local
and spatially distributed information resources are used as information sources for specification of the opticalmeteorological
state of the atmosphere. At the first stage, the Web resource is intended to process the
EOS/MODIS satellite data.
South Atlantic anomaly filter for satellite UV observation
Show abstract
A South Atlantic Anomaly (SAA) filter has been developed to filter out large amounts of noise caused by high energy
protons hitting onto the optical instrument focal plane when the satellite passes through the SAA region. The filter is
based on the Principal Component Analysis (PCA)/Empirical Orthogonal Function (EOF) analysis. The EOF vectors
derived from an orbit outside of the SAA region were used to represent the observations coming from the noisy SAA
region. Then using the clear EOF vectors, the observations within SAA region are rebuilt with the most important
principle components. The filter works well in UV region. Tests on L1B data from Global Ozone Monitoring
Experiment-2 (GOME2) and Ozone Monitoring Instrument (OMI) have been conducted. It is expected that this filter can
help to improve the measurements and retrievals for the Ozone Mapping and Profiler Suite (OMPS) nadir profiler in the
SAA region.
Graphyte software for integrated remote sensing research using HPCC
Show abstract
The broad goal of GEOSS-V, creating a unified system of systems that encompasses all relevant atmospheric and
environmental remote sensing data, accesses social and economic impact information, and integrates all relevant
analysis and decision-making tools, is a monumental task. This is made more difficult in that as technology
and algorithms change at an ever-increasing pace, the ability to test, prototype, and integrate new technology
is often difficult in large production systems. We have been developing Graphyte, a very flexible lightweight
integration framework which is aimed at augmenting GEOSS-V technology by providing agile development tools
for research and development.
Data Processing and Products II
Latest decade's spatial-temporal properties of aerosols over China
Show abstract
Aerosols are one of the most important parameters affecting the Earth's energy balance and hydrological cycle1. They
can arouse uncertainties effects on climates. To narrow the uncertainties associated with the direct and indirect aerosol
effects on climates, the spatial-temporal properties of aerosol over China are investigated using the radiance
measurements performed by the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on board the
Terra and Aqua satellites from 2002 to 2010. The most prominent variational regions are the northern, eastern China.
The high AOD values occur in 2004, 2006 and 2007 year, respectively. The tendencies of AOD are in good agreement
with corresponding AOD tendencies based on data from Aerosol Robotic Network (AERONET) stations in the study
regions2. Seasonal AOD maxima are obtained in spring (March to May) and summer (June to August) seasons, due to
large humidity and biomass burning, respectively. Dust activities in spring are frequent occurrences that also lead to high
aerosol loading. AOD minima are obtained in winter (December to February) seasons. The result of our analysis reveal
significant trend of seasonal AOD in the Northern and Southern China.
Image Processing
Geometric/radiometric calibration from ordinary images for high resolution satellite systems
Show abstract
This paper presents two techniques respectively devoted to noise and geometric characteristics assessment from standard
images instead of dedicated ones.
The noise computation technique assumes that high spatial frequencies are sufficiently weakened by MTF so that only
noise remains near Nyquist frequency. It uses Fourier Transform or wavelet packet decomposition.
The second technique is based upon matching processing between spectral bands assuming the imaging system focal
plane has staggered arrays. It yields very accurate information on focal plane layout as well as high frequency attitude
disturbances.
Results obtained on simulated images as well as Worldview-2 real products are detailed
Poster Session
Radiometric quality of the MODIS bands at 667 and 678nm
Show abstract
The MODIS instruments on Terra and Aqua were designed to allow the measurement of chlorophyll fluorescence
effects over ocean. The retrieval algorithm is based on the difference between the water-leaving radiances at
667nm and 678nm. The water-leaving radiances at these wavelengths are usually very low relative to the topof-
atmosphere radiances. The high radiometric accuracy needed to retrieve the small fluorescence signal lead to
a dual gain design for the 667 and 678nm bands. This paper discusses the benefits obtained from this design
choice and provides justification for the use of only one set of gains for global processing of ocean color products.
Noise characteristics of the two bands and their related products are compared to other products of bands from
412nm to 2130nm. The impact of polarization on the two bands is discussed. In addition, the impact of stray
light on the two bands is compared to other MODIS bands.
On-orbit modulation transfer function characterization of terra MODIS using the moon
Show abstract
The on-orbit Modulation Transfer Function (MTF) of MODIS instrument can be accurately measured by its on-board
SpectroRadiometirc Calibration Assembly (SRCA). For other Earth observing instruments without calibrators similar to
SRCA, the sharp edge of moon provides a reasonable high-contrast target for their on-orbit MTF characterization. In this
paper, we propose a procedure to measure MODIS on-orbit MTF from the moon image. For Terra MODIS, lunar
calibration was performed nearly every month since its launch in 2000. For each lunar calibration, the images of the
moon from multiple scans are taken and traced across the right edge to form an edge spread function (ESF). The ESF is
used to calculate a line spread function (LSF) through differentiation. The MTF in along-scan direction is then derived
through the Fourier Transform of the LSF. The same procedure can also be applied to MTF calculation in along-track
direction. The results are compared with SRCA measured MTF, and the long-term trending of both MTF agrees. Lunar
MTF characterization appears noisier mainly because of the non-uniformity of the moon surface and moderate spatial
resolution of the moon image, which makes it difficult to accurately locate the circular lunar edge in sub-pixel level.
Improvement of the current method is discussed in the end.
Characterization of MODIS mirror side difference in the reflective solar spectral region
Show abstract
The MODIS instruments onboard the Terra and Aqua spacecraft, launched in December 1999 and May 2002,
respectively, have successfully operated through the present time. MODIS collects the Earth view (EV) data via a twosided
paddle wheel scan mirror at angles of incidence (AOI) from 10.5 to 65.5 degrees. Reflective properties between the
two mirror sides are not identical with large differences seen in Terra MODIS reflective solar bands (RSB). This paper
describes a methodology to calculate and monitor MODIS RSB mirror side differences using EV observations. The longterm
trends of response differences between two mirror sides are evaluated using different EV targets. Results show that
the on-orbit changes in the properties of the scan mirror are wavelength and AOI dependent with large mirror side
differences observed at shorter wavelengths in larger AOI. Starting from 2005, the mirror side difference has gradually
exhibited a seasonally dependent feature in Terra MODIS visible spectral bands, which is mainly due to the changes in
the scan mirror polarization property. In addition to fully characterizing on-orbit changes of the MODIS scan mirror
properties, results and discussions provided in this paper will help clarify their impacts on the Level 1B data products
and support future efforts to maintain MODIS data quality.
The VIIRS ocean data simulator enhancements and results
Show abstract
The VIIRS Ocean Science Team (VOST) has been developing an Ocean Data Simulator to create realistic
VIIRS SDR datasets based on MODIS water-leaving radiances. The simulator is helping to assess instrument
performance and scientific processing algorithms. Several changes were made in the last two years
to complete the simulator and broaden its usefulness. The simulator is now fully functional and includes
all sensor characteristics measured during prelaunch testing, including electronic and optical crosstalk influences,
polarization sensitivity, and relative spectral response. Also included is the simulation of cloud and
land radiances to make more realistic data sets and to understand their important influence on nearby ocean
color data. The atmospheric tables used in the processing, including aerosol and Rayleigh reflectance coefficients,
have been modeled using VIIRS relative spectral responses. The capabilities of the simulator were
expanded to work in an unaggregated sample mode and to produce scans with additional samples beyond the
standard scan. These features improve the capability to realistically add artifacts which act upon individual
instrument samples prior to aggregation and which may originate from beyond the actual scan boundaries.
The simulator was expanded to simulate all 16 M-bands and the EDR processing was improved to use these
bands to make an SST product. The simulator is being used to generate global VIIRS data from and in
parallel with the MODIS Aqua data stream. Studies have been conducted using the simulator to investigate
the impact of instrument artifacts. This paper discusses the simulator improvements and results from the
artifact impact studies.
Results of MODIS band-to-band registration characterization using on-orbit lunar observations
Show abstract
Since launch, lunar observations have been made on a regular basis for both Terra and Aqua MODIS and used in a
number of applications for their on-orbit calibration and characterization, including radiometric stability monitoring,
band-to-band registration (BBR) characterization, optical leak and electronic cross-talk characterization, and
calibration inter-comparisons with others sensors. MODIS has 36 spectral bands, consisting of a total of 490
individual detectors, which are located on four different focal plane assemblies (FPAs). This paper focuses on the
use of MODIS lunar observations for its on-orbit BBR characterization in both along-scan and along-track
directions. In addition to BBR, study of detector-to-detector registration (DDR) through the use of lunar
observations is also discussed. The yearly averaged BBR results developed from MODIS lunar observations are
presented in this paper and compared with that derived from its on-board calibrator (OBC). In general, results from
different approaches agree well. Results show that on-orbit changes in BBR have been very small for both Terra and
Aqua MODIS over their entire missions. It is clearly demonstrated in this paper that the lunar approaches developed
and applied to MODIS can be effectively used by other sensors for their on-orbit BBR and DDR characterization.
Enabling radiometric validation and on-orbit calibration: flight software of the CERES scanning radiometer
Show abstract
The present paper describes the evolving role of flight software in the operation of the Clouds and Earth's
Radiant Energy System (CERES) instruments. The CERES software interface allows for the instruments' onorbit
modification and control from the ground, and it enables execution of supplemental tasks. Overall, the
constant evolution of the CERES flight software plays a crucial role in the accomplishment of the mission's
scientific objectives.
The measured point response functions for the CERES Flight Model 5 instrument
Show abstract
The Clouds and Earth Radiant Energy System (CERES) Flight Model 5 (FM5) instrument is scheduled to be launched
this year aboard the NPP spacecraft in order to continue the Climate Data Record for Earth radiation budget. CERES
data will be used together with measurements from the Visible Infra-red Imager Radiometer Suite (VIIRS) to compute
cloud information for each CERES pixel. Knowledge of the point response function (PRF) of CERES is essential to
accurately align these data sets. The Radiation Calibration Facility at Northrop Grumman includes the PRF Source, an
optical devise for measuring the PRF. This paper presents the analysis of these tests and the resulting PRF for each of the
three channels.
NPP VIIRS geometric performance status
Show abstract
Visible Infrared Imager Radiometer Suite (VIIRS) instrument on-board the National Polar-orbiting Operational
Environmental Satellite System (NPOESS) Preparatory Project (NPP) satellite is scheduled for launch in October, 2011.
It is to provide satellite measured radiance/reflectance data for both weather and climate applications. Along with
radiometric calibration, geometric characterization and calibration of Sensor Data Records (SDRs) are crucial to the
VIIRS Environmental Data Record (EDR) algorithms and products which are used in numerical weather prediction
(NWP). The instrument geometric performance includes: 1) sensor (detector) spatial response, parameterized by the
dynamic field of view (DFOV) in the scan direction and instantaneous FOV (IFOV) in the track direction, modulation
transfer function (MTF) for the 17 moderate resolution bands (M-bands), and horizontal spatial resolution (HSR) for the
five imagery bands (I-bands); 2) matrices of band-to-band co-registration (BBR) from the corresponding detectors in all
band pairs; and 3) pointing knowledge and stability characteristics that includes scan plane tilt, scan rate and scan start
position variations, and thermally induced variations in pointing with respect to orbital position. They have been
calibrated and characterized through ground testing under ambient and thermal vacuum conditions, numerical modeling
and analysis. This paper summarizes the results, which are in general compliance with specifications, along with
anomaly investigations, and describes paths forward for characterizing on-orbit BBR and spatial response, and for
improving instrument on-orbit performance in pointing and geolocation.
High-temperature fixed points for pre-launch calibration of earth observing sensors
Yoshiro Yamada,
Juntaro Ishii
Show abstract
High-temperature fixed points of metal-carbon systems, currently the target of a project in the international thermometry
standards community, is also of high interest for pre-launch radiometric calibration of hyperspectral earth observing
sensor in the blue wavelengths, where the conventional copper fixed point fails to supply sufficient radiance. For such a
calibration, a fixed-point possibly around 2000 K is desired.
One requirement for application of the high-temperature blackbody fixed-point cell to remote sensor calibration is to
increase the radiating source aperture diameter to a size large enough to target with a radiance comparator based on a
grating monochromator.
In this presentation, a fixed-point cell of Co-C eutectic (1597 K) for remote sensor calibration application is described.
An enlarged 7-mm aperture design is employed for the fixed-point cell while at the same time retaining the outer
dimension to fit in existing fixed-point furnaces. The observed plateaux showed temperature and repeatability
comparable to conventional 3-mm aperture cells, while cavity breakages indicates the need for improved robustness in
the crucible design.
Extension of the technique to Pt-C eutectic (2011 K) or Cr3C2-C peritectic (2100 K) systems, and subsequent application
to calibration of the HISUI sensor is envisaged.
Using the Dome C site to characterize AVHRR near-infrared channel for consistent radiometric calibration
Show abstract
AVHRR is a heritage instrument on NOAA's polar orbiting satellites with more than 30 years of global earth
observation. Due to absence of onboard calibrator for the visible and near-infrared channels, AVHRR sensors rely on
desert sites for relative calibration with uncertainties primarily due to lack of rigorous site characterization and
atmospheric effects. This study aims at quantifying the long term degradation of the near-infrared channel (0.86 μm) of
AVHRR using the Antarctic Dome C site which has very small atmospheric effects. All afternoon-orbit NOAA series
AVHRR instruments are included in this study. Though the TOA reflectance data exists only during austral summer for
Dome C, the degradation estimated using TOA reflectance time series for the respective instruments is comparable to
those from the previous studies. The degradation estimated suggests that NOAA-7 and -9 have the largest calibration
drift (greater than -3% per year) compared to the other instruments which have less than -1.5% drift per year. The
AVHRR channel 2 (0.86 μm) calibration using desert sites has always been challenging due to high uncertainty mainly
introduced by the presence of water vapor absorption at this wavelength. The study shows that, due to the extremely cold
and dry climate of Dome C, the water vapor absorption effect is negligible and thus it is possible to calibrate nearinfrared
channel (0.86 μm) with calibration uncertainty less than 1%.
Climate change sensitivity evaluation from AIRS and IRIS measurements
Show abstract
Outgoing longwave radiation (OLR) measurements over a long period from satellites provide valuable information for
climate change. Due to the different coverage, spectral resolution and instrument sensitivities, the data comparisons
between different satellites could be problematic and possible artifacts could be easily introduced. In this paper, we
illustrate the method and procedures when we compare different satellite measurements by using the data taken by
Infrared Interferometric Spectrometer (IRIS) in 1970 and by Atmospheric Infrared Sounder (AIRS) from 2002 to 2010.
We use the spectra between 650 cm-1 and 1350 cm-1 for nadir view footprints in order to match the AIRS and IRIS
measurements. Most of the possible sources of error or biases, which include the errors from spatial coverage, spectral
resolution, spectra frequency shift due to the field of view, sea surface temperature uncertainty, clear sky determination,
and spectra response function (SRF) symmetry, can be corrected. Using the correct SRF is extremely important when
comparing spectra in the high slope spectral regions where possible large artifacts could be introduced.
Topographic mapping experiment with Chinese airborne SARMapper
Jixian Zhang,
Zheng Zhao,
Guoman Huang
Show abstract
Aiming for steep terrain relief and complex geomorphic types, the practical airborne SAR mapping system
(SARMapper) of China developed by a group led by CASM was constructed. SARMapper consists of hardware and
software mapping system. In this paper, some new methods and mapping technical flow were proposed aiming for
difficult terrain area in the process of developing mapping software system. Several key technologies and solutions were
studies, such as DEM extraction through refined interferometry, stereogrammetry, and DEM fusion, Digital Orthophoto
Map (DOM) generation with single/multi-polarization SAR images acquired from multi-direction, Digital Line Graphic
map (DLG) generation under stereo-environment. Then SAR mapping workstation is used to map in such a large area.
And then the comprehensive experiment in Qinling Mountain Area was carried on including interferometric parameters
calibration, different resolution of airborne SAR data acquisition and mapping production generation. Experimental
results have proved that these productions could satisfy the mapping accuracy of 1:10000 and 1:50000.