Technical Sessions

Monday, June 18, 2018

1:05 pm | Pre-launch Testing and Post-launch Performance

Assessment of pre- and post-launch calibration and performance characterization for operational remote sensing systems

  • Pre-launch and on-orbit measurement techniques
  • Instrument transition from the laboratory to space environments
  • Application of ground calibration results to on-orbit measurements
  • Operational sensor calibration lessons learned

View Abstracts (PDF)

Leveraging the GPM Microwave Imager (GMI) Calibration Standard
David Draper, David Newell, Quinn Remund, Michael Berberich, Don Figgins – Ball Aerospace & Technologies

ABSTRACT: Next-generation defense weather satellite system require accurate measurements of top-of-atmosphere brightness temperatures to determine ocean surface vector winds, tropical cyclone intensity, and other environmental products necessary to support our war fighters. At Ball Aerospace, we have built the Global Precipitation Measurement (GPM) Microwave Imager (GMI) designed to be the radiometric calibration standard for a group of national and international passive microwave instruments in the GPM constellation. Ball and Remote Sensing Systems supported the initial on-orbit operations to verify calibration performance and provide a final set of operational calibration algorithms. The GMI instrument was launched onboard the GPM spacecraft on February 28th, 2014. GMI has operated nearly continuously since March 4th, 2014. This paper presents GMI’s on-orbit performance and calibration results and provides a top-level overview of how the GMI can be leveraged for next-generation defense weather missions.

The Experimental Hyperspectral Imaging Microsatellites SPARK-01 and -02: Radiometric Calibration and Overall Performance
Hao Zhang, Zhengchao Chen, Bing Zhang – Key Laboratory of Digital Earth Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences; Benyong Yang – Hefei Institutes of Physical Science, CAS

ABSTRACT: At 3:22 am UTC on 22 December 2016, two wide-swath push broom hyperspectral imaging microsatellites, SPARK-01 and -02, which were manufactured by the Shanghai Engineering Center for Microsatellites for experimental aims, were successfully launched at the Jiuquan satellite launch center by the CZ-2D rocket. SPARK-01 and -02 have spectral ranges of 400–1000 nm, a swath of ~100 km, a spatial resolution of 50 m and 2048 pixels along the cross-track direction. This report will give a comprehensive introduction to the radiometric performance of the satellites and data acquiring status. Due to the lack of on-board calibration device and less measurements before launch, the radiometric calibration coefficients were determined for these two satellites via a calibration experiment performed from the end of February to the beginning of March 2017 at the high-altitude, homogenous Dunhuang calibration site in the Gobi Desert in China. In-situ measurements, including ground reflectance, direct transmittance, diffuse-to-global irradiance ratio, and radiosonde vertical profile, were acquired. A unique relative calibration procedure was developed using actual satellite images. This procedure included dark current computation and non-uniform correction processes. The former was computed by averaging multiple lines of long strip imagery acquired over open oceans during nighttime, while the latter was computed using images using images acquired after the adjustment of the satellite yaw angle to 90 degree. This technique was shown to be suitable for large-swath satellite image relative calibration. After relative calibration, reflectance, irradiance, and improved irradiance-based methods were used to conduct absolute radiometric calibrations in order to predict the top-of-atmosphere (TOA) radiance. The calibration uncertainty is estimated to be less than 6%.

Although these two experimental hyperspectral satellites have been decommissioned till April of 2017, a huge hyperspectral data, mostly over China and neighboring regions, have been acquired during half a year period. A number of dark current images and 90 degree yaw angle images were acquired to evaluate the relative stability of radiometric performance among the cross track pixels. Also, the relative differences of the response of detectors were also evaluated under different radiance levels by acquiring yaw 90 imageries over desert, common ground surface, snow/ice (i.e. Antarctic regions) and a comprehensive model for the relative radiometric correction of spark 01/02 was also refined. Furthermore, other radiometric performance was also evaluated, like signal-to-noise ratio, spectral wavelength shifts, bad pixels, etc.

Initial Pre-Launch Imaging and Spectral Characterization of Landsat 9 Thermal Infrared Sensor-2
Aaron Pearlman, Boryana Efremova – GeoThinkTank LLC; Joel McCorkel, Amy Simon, Jason Hair, Dennis Reuter – NASA Goddard Space Flight Center; Matt Montanaro – Rochester Institute of Technology; Brian Wenny – Science Systems and Applications, Inc. (SSAI); Allen Lunsford – Catholic University of America

ABSTRACT: The Thermal Infrared Sensor-2 (TIRS-2) scheduled to launch in December 2020 aboard Landsat 9 will continue Landsat’s four decade-long legacy of providing moderate resolution thermal imagery from low earth orbit (at 705 km) for environmental applications. Like the Thermal Infrared Sensor aboard Landsat 8, it is a pushbroom sensor with a cross-track field of view of 15 and provides two spectral channels at 10.8 and 12 µm. To ensure radiometric, spatial, and spectral performance, a comprehensive pre-launch testing program is being conducted at NASA Goddard Space Flight Center at the component, subsystem, and instrument level. This effort will focus on the results from the subsystem level testing to assess TIRS-2 imaging performance including focus, spatial performance, and stray light rejection. It is also used to provide a preliminary assessment of spectral performance. The TIRS-2 subsystem is placed in a thermal vacuum chamber with the calibration ground support equipment, which provides a flexible blackbody illumination source and optics to assess imaging performance. Spectral performance is tested using a spectral response test setup with its own illumination source outside the chamber that propagates through the calibration ground support equipment in an optical configuration designed for this purpose. The results show that TIRS-2 performance is expected to meet all of its performance requirements with few waivers and deviations.

Preflight Characterization of the OCO-3 Imaging Spectrometer
Robert Rosenberg, Gary Spiers, Richard Lee, Lars Chapsky, Shanshan Yu, Annmarie Eldering – NASA Jet Propulsion Laboratory

ABSTRACT: The Orbiting Carbon Observatory 3 is expected to complete its final thermal vacuum test in April 2018. The test program was largely the same as for OCO-2, where the radiometric, spatial, spectral, and polarimetric properties of the spectrometer were measured. Dozens of requirements were verified, including spectral resolution above 17,000 and absolute radiometric performance to within 5%. Notable changes to the hardware include a different telescope with a wider field of view, context cameras, and a Pointing Mirror Assembly. The instrument was illuminated with its internal calibration lamps, an external integrating sphere traceable to NIST standards, diffuse sunlight, collimated light on movable stages, and tunable lasers. Retrievals of uplooking measurements were validated against a collocated TCCON station.

Calibration and On-Orbit Validation of the NOAA-20 CrIS Interferometer
Kori Moore, Mark Esplin, Joe Kristl, Deron Scott, Ben Esplin – USU/Space Dynamics Laboratory

ABSTRACT: On November 18, 2017, the JPSS-1 satellite was launched into polar orbit and renamed NOAA-20. Included in its instrument suite is the Cross-Track Infrared Sounder (CrIS) that collects spectra used for atmospheric soundings with twice-daily global coverage. CrIS creates radiometrically calibrated spectra at 0.625 cm-1 resolution covering three spectral regions from 4 to 15 micrometers, with a 3x3 focal plane array and a nadir footprint of 14 km. NOAA-20 joined the orbit of its predecessor, Suomi National Polar-orbiting Platform (SNPP), with a half-orbit delay to provide better near-nadir coverage for the globe. NOAA-20 CrIS is a copy of the CrIS instrument on SNPP with a few electronics upgrades. The SNPP CrIS has performed well over its six years on orbit and continues to collect valuable data. NOAA-20’s CrIS data is in provisional status during further comparisons before an expected upgrade to full operational status later in 2018.

The NOAA-20 CrIS sensor had extensive ground calibration and has been undergoing further on-orbit validation since data collection began on January 4, 2018. Performance optimization on orbit resulted in only small changes to select pre-launch settings due to the robust on-ground calibration. In addition, on-orbit CrIS noise levels are similar to on-ground testing. This presentation will cover the results of JPSS-1/NOAA-20 CrIS noise characterization, calculated as the Noise Equivalent change in Radiation (NEdN), from both on-ground and on-orbit testing. In summary, the NOAA-20 CrIS instrument has performed well to date, meeting specified NEdN requirements. It performs comparable to SNPP CrIS, which still meets NEdN requirements. In addition, the relative responsivity (RR) of the NOAA-20 detectors has been tracked since on-orbit data collection began. RR was calculated as the difference between detector responses when viewing deep space and internal calibration targets. The NOAA-20 CrIS RR has thus far been stable after instrument optimization updates were applied on-orbit. The SNPP CrIS has performed very well in regards to RR—values are within 2% of initial RR for all but the shortest wavelengths, which have shown RR degradation of no more than 6% over the spacecraft lifetime. The latest updates on NOAA-20 and SNPP CrIS NEdN and RR will be included.

Yaw Maneuver Derived Vignetting Functions for NOAA-20 VIIRS
Jeff McIntire – Science Systems and Applications, Inc. (SSAI); Jack Xiong – NASA Goddard Space Flight Center

ABSTRACT: The NOAA-20 spacecraft (formerly JPSS-1) executed a series of yaw maneuvers on January 25 and 26, 2018 designed to validate / characterize the transmittance functions of the Visible Infrared Imager Radiometer Suite (VIIRS) instrument solar diffuser (SD) and solar diffuser stability monitor (SDSM) views. On orbit, only the product of the attenuation screen transmittance and SD bidirectional reflectance distribution function (BRDF) can be measured for the VIIRS detector and SDSM SD views. For the SDSM solar view, the attenuation screen transmittance was directly measured. All three transmittance functions were compared to the at-launch functions derived from pre-launch characterization and their effect on the instrument responsivity estimation and SD degradation trending on-orbit was investigated. While both the SD views showed good agreement with the at-launch values (within 0.1 – 0.2 % averaged over a given orbit), the differences in the SDSM solar screen vignetting function relative to the pre-launch estimate impacted the SD degradation by ±1 %. Although the vignetting function derived from the yaw maneuvers considerably improved the SD degradation trending, significant oscillations in the trending remained. The angular sampling provided by the yaw maneuver data was too coarse to capture the fine structure of the vignetting function; additional maneuvers may be added to improve the fidelity of the function. An uncertainty analysis was also conducted on all transmission functions derived.

Calibration/Validation Activities for GOES-16 and GOES-17 Products
Jon Fulbright – ASRC Federal; Elizabeth Kline – SGT, Inc.; David Pogorzala – IAI, Inc.; Kathryn Mozer, Matthew Seybold – NOAA/NESDIS/OSPO

ABSTRACT: The Geostationary Operational Environmental Satellite-R (GOES-R) series is the next generation of NOAA geostationary environmental satellites. The first satellite in the series, GOES-16 became the operational GOES-East satellite in December 2017. GOES-17, the second satellite in the series, was launched on March 1, 2018 and is currently in its Post-Launch Test phase. The satellites carry six instruments dedicated to the study of the Earth’s weather (ABI), lightning (GLM), the Sun (EXIS and SUVI), and and in-situ space environment (MAG and SEISS). For both satellites, a series of Post-Launch Test and Post-Launch Product Tests have been or are being conducted to validate, calibrate, and characterize both the instruments and the data products. In this talk, we describe some of the major cal/val activities that have taken place since launch for both satellites, focusing mainly on ABI and GLM. We will give the first status of the GOES-17 instruments, and an update of the status of the GOES-16 products, and the path forward.

The CAESAR New Frontiers Mission: Overview and Imaging Objectives
J. M. Soderblom – Massachusetts Institute of Technology, A. G. Hayes, S. W. Squyres – Cornell University; M. B. Houghton, T. T. King, R. S. Saylor – NASA Goddard Space Flight Center; M. A. Ravine – Malin Space Science Systems; J. J. Tansock – USU/Space Dynamics Laboratory

ABSTRACT: The Comet Astrobiology Exploration Sample Return (CAESAR) mission will acquire and return to Earth for laboratory analysis a minimum of 80 g of surface material from the nucleus of comet 67P/Churyumov-Gerasimenko (67P). CAESAR will characterize the surface region sampled, return the collected solid sample in a pristine state, and return evolved volatiles by capturing them in a separate gas reservoir. A key to mission success is to select a sample site that provides high science value, and that is fully compatible with safe and successful sampling. Key supporting objectives are to characterize the sample site and its geophysical and geomorphic context, and to study the comet environment to identify spacecraft hazards including moonlets, jets and plumes.

These mission objectives drive a number of key imaging requirements that in turn drive camera designs and calibration: detecting 50-cm objects from 500 km; resolving 2.5-cm particles from 650 m; obtaining 5° and 30° field of view optical navigation images; identifying 1-cm particles from 50 m; imaging at multiple colors, matching a subset of the Rosetta OSIRIS filter bandpasses; documenting the sample site before, during, and after sampling at sub-cm resolution; and documenting sample acquisition during sampling and packaging inside the return capsule. In order to accomplish these goals, CAESAR carries a high-heritage suite of six well-calibrated cameras of varying fields of view and focal ranges: narrow angle camera (NAC), medium angle camera (MAC), touch-and- go camera (TAGCAM), two navigation cameras (NAVCAMs), and a sample container camera (CANCAM).

The CAESAR New Frontiers Mission: Camera Suite Calibration Planning
Joe Tansock, John Seamons, Alan Thurgood – USU/Space Dynamics Laboratory; Alex Hayes – Cornell University; Jason Soderblom – Massachusetts Institute of Technology

ABSTRACT: The Comet Astrobiology Exploration Sample Return (CAESAR) mission has been awarded Phase A study by NASA. The CAESAR mission is to acquire and return to earth a sample of the comet 67P/Churyumov-Gerasimenko. The camera suite on the spacecraft consists of 6 cameras. This suite consists of a narrow angle camera (NAC), medium angle camera (MAC), touch-and-go camera (TAGCAM), sample container camera (CANCAM), and two navigation cameras (NAVCAMs). Following optical and mechanical validation at the sensor vendor, the Camera Suite is delivered to Space Dynamics Laboratory (SDL) for calibration. Camera designs were determined from mission requirements. The formulated pre-launch calibration plan quantifies camera performance at anticipated operational environmental conditions, verifies camera requirements, is heritage-based, utilizes existing equipment to reduce cost and schedule, and enhances the science value of camera data. The development of this plan and a subsequent pre-launch calibration matrix will be discussed. In-flight calibration verifies and validates the pre-launch calibration, monitors and updates calibration, and quantifies camera performance. In-flight considerations and a preliminary calibration matrix will also be discussed.

5:15 pm | Advancements in Radiometric Calibration State-of-the-Art

Techniques, equipment, methods, and processes to advance the productivity and value of radiometric calibration

  • Techniques and technologies to meet calibration performance requirements for advanced programs
  • Methods and techniques for efficient processing of large volumes of remote sensing data
  • Real-time calibration data analysis and performance assessment
  • Translation of program science requirements into radiometric calibration requirements
  • Efficient experiment data collection design to reduce radiometric calibration schedule and cost
  • Practices to establish and maintain traceability to accepted National standards throughout program life

View Abstracts (PDF)

A New Approach for Albedo Calibration on the Ozone Mapping and Profiler Suite
Tyler McCracken, Thomas Rogers, Eileen Saiki, Dan Soo, Stephen Bennett – Ball Aerospace & Technologies

ABSTRACT: Ball Aerospace and Technologies Corp. is building the third build of the Ozone Mapping and Profiler Suite, which measures daily ozone using three spectrometers that cover a wavelength range from 250 nm to 1000 nm. The radiometric calibration of the sensors is albedo-based, and a new method is being used for the JPSS-2 delivery. The new method is a direct, accurate, and more robust measurement of albedo where a single source is used to measure both radiance and irradiance responses with only a short amount of time between the measurements. This independent measurement of albedo will have improved wavelength-dependent uncertainties because the small temporal separation in the measurements minimizes changes in both sensor and source. This presentation details the motivation, setup, and initial results of the independent albedo measurement.

Development and Production of the Onboard Radiometric Calibration References for the MetOp SG and Meteosat Third Generation Infrared Sounders
Mathieu Maisonneuve, Manyuan Li, Robert Bouchard, Yan Montembeault, Gaetan Perron, Jacques Giroux – ABB Canada

ABSTRACT: Eumetsat’s new generation weather satellites will include improved infrared sounders, the IASI-NG on MetOp Second Generation and the IRS on Meteosat Third Generation. The data collected by the infrared sounders will be used to obtain vertical profiles of temperature and humidity as well as other climate variables (vertical profiles of the concentration of some trace gases, surface temperatures, cloud top height, etc.). That information will then be used in numerical weather prediction models and in support of climate studies. A key feature of those instruments is to embed high end traceable calibration sources in order for the instruments to fulfill their role in producing high quality data that can be used with confidence and can be successfully compared to other instruments (past and future) for long-term climate study trends.

For calibration in the infrared, the radiometric references are essentially quasi-blackbody sources: sources of high emissivity and accurately known temperature emitting energy that can be precisely predicted with Planck’s law of radiation. ABB is currently developing the onboard infrared calibration sources for all the new generation of European infrared weather forecasting space instruments in LEO or GEO orbit. That includes two blackbodies for IASI NG instrument onboard Metop-SG: BB-FTS for the sounder and BB-IIS for the cloud imager and one for the IRS onboard MTG. This paper will present an overview of these projects covering the key features of the different calibration sources, the status of their development and recent test results.

Tuesday, June 19, 2018

8:00 am | Equipment, Capabilities, and Facilities for Radiometric Calibration

Hardware and resources to support National and international requirements for radiometric calibration of remote sensing instruments, including long-term trending and performance enhancements of existing facilities

  • Design, characterization, and validation of test and calibration equipment, facilities, test chambers, and scene simulators (Earth, solar, and other objects)
  • Scene generation and projection for hardware-in-the-loop (HIL) testing
  • Specialized measurement equipment (spectral, polarization, and other)
  • Long- and short-term accuracy and precision of data sources used for validation, including models

View Abstracts (PDF)

Measuring Linearity of Detector Spectral Responsivity at Ultra-Low Incident Powers
Leibo Ding – Science and Systems Applications, Inc. (SSAI); Jinan Zeng, James Butler – NASA Goddard Space Flight Center

ABSTRACT: A LED-driven integrating sphere uniform light source within a light-tight enclosure was used to characterize the linearity of spectral responsivity for detectors at Pico-watt and sub Pico-watt incident power levels over a wavelength range from 405 nm to 1550 nm. A UV-enhanced Si detector, a Std-InGaAs detector and an Ex-InGaAs detector were used with a pre-amplifier SR-570 and a lock-in amplifier SR-830. The results of spectral responsivity linearity and measurement uncertainty at low incident power levels will be presented and analyzed. Results from the different detectors will be compared, and the measurement methodology will be discussed.

Ground and On-Orbit Calibration of High Accuracy Stellar Navigation Sensors
Emil Tchilian – Ball Aerospace

ABSTRACT: Stellar navigation using star trackers require precise radiometric and spatial calibration of the instrument over multiple environmental variables. Calibration accuracy is critical for high performance star trackers such as the Ball High Accuracy Star Tracker (HAST). This paper discusses calibration methods and capabilities that allow for sub-tenths of seconds of arc performance achieved by the HAST.

New hyperspectral BRDF Feature of a Table-Top Goniometer in the Diffuser Calibration Lab at NASA GSFC
Jinan Zeng – Fibertek, Inc.; James Butler, Jack Xiong – NASA Goddard Space Flight Center

ABSTRACT: A Table-Top Goniometer (TTG) was built in the Diffuser Calibration Lab at NASA GSFC to support solar diffuser (SD) calibrations from 350 nm to 2500 nm. So far, it has been used to complete the BRDF calibration for the J1 VIIRS SD witness sample as an effort to validate its pre-launch calibration made by the instrument vendor. The new hyperspectral BRDF feature of TTG was implemented to improve BRDF measurements with high-efficiency and high-spectral resolution, and to simulate on-orbit calibration scenarios. This enables us to figure out the potential difference of BRDF results from measurements using monochromatic and broadband light sources. The preliminary hyperspectral BRDF measurements of spectralon samples were conducted with the appropriate integration time and pixel averaging using a CCD spectrometer from 200 nm to 1100 nm and a UV enhanced broadband laser-driven plasma lamp source. The comparison of BRDF results from the spectrometer and a Si detector is made to validate the new feature. The details of methodology for realization of the hyperspectral BRDF measurement and the BRDF scale transfer algorithm are described. The short-term stability of light source, and uncertainty components are also discussed.

Development of Compact Calibration InfraRed Sources for the Meteosat Third Generation Flexible Combiner Imager
Mathieu Maisonneuve, Robert Bouchard, Manyuan Li, Yan Montembeault, Gaetan Perron, Jacques Giroux – ABB Canada

ABSTRACT: In the frame of the Meteosat Third Generation Flexible Combiner Imager (MTG-FCI) development, ABB has designed a new kind of small infrared calibration sources offering high-end performance on emissivity, temperature knowledge and radiometric accuracy within a low mass and volume allocation. Calibration sources are critical sub-systems providing reliable and traceable data for meteorological forecasting as well as long-term climate monitoring. This applies also to next generation compact constellations in order for private data operator to provide useful data for various applications.

This paper will present an overview of the blackbody design for the MTG FCI, focusing on its compactness and its validated performances. Advantages of this technology will be listed and its applicability in the context of future low-cost constellation missions will also be presented.

10:00 am | Calibration Methods Using Celestial Objects

Presentation of radiometric measurements and calibration methods using the Sun, Moon, stars, and other celestial objects in the ultra-violet, visible, and infrared wavelengths

  • Characterization and calibration of celestial sources for on-orbit sensor calibration
  • Post-launch calibration and long-term trending using celestial observations
  • Calibration accuracy using celestial objects
  • Real-life experience and lessons learned using celestial objects for radiometric sensor calibration

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ARCSTONE: Calibration of Lunar Spectral Reflectance from Space
Constantine Lukashin, Trevor Jackson, Michael Cooney, Noah Ryan, Joshua Beverly, Cindy Young, Gugu Rutherford, Warren Davis, Thuan Nguyen – NASA Langley Research Center; Rand Swanson, Michael Kehoe, Michael Stebbins – Resonon Inc.; Greg Kopp, Paul Smith – University of Colorado Laboratory for Atmospheric and Space Physics (LASP); Tom Stone – U.S. Geological Survey (USGS)

ABSTRACT: Calibration accuracy, long-term precision, and inter-consistency are key on-orbit performance metrics for Earth observing sensors. The accuracy and consistency of environmental measurements across multiple instruments in low Earth and geostationary orbits are directly connected to the scientific understanding of complex systems, such as Earth’s weather and climate. Recent studies have demonstrated the quantitative impacts of observational accuracy on the quality of science data products and the ability to detect climate change trends for essential climate variables (e.g., Earth’s radiation budget, cloud feedback, and long-term trends in cloud parameters). It is common for instruments to carry on-board references for calibration at various wavelengths, but these can be subject to degradation, and also increase mass and risk.

The Moon can be considered a natural solar diffuser in space. Establishing the Moon as a high-accuracy calibration reference enables broad inter-calibration opportunities, as the lunar reflectance is effectively time-invariant and can be directly measured by most Earth-observing instruments. Existing approaches to calibrate sensors against the Moon can achieve stabilities of tenths of a percent over a decade, as demonstrated by the SeaWIFS. However, current lunar calibration capabilities have uncertainties of 5 – 10%, attributed to the photometric model of the Moon. Significant improvements in the lunar reference and calibration are possible, and are necessary for improving accuracy of Earth climate observations.

The ARCSTONE mission goal is to provide a reliable reference for high-accuracy on-orbit calibration for reflected solar instruments. The ARCSTONE instrument is a lunar/solar spectrometer intended to fly on a CubeSat in low Earth orbit. It will provide lunar spectral reflectance with accuracy < 0.5% (k = 1), sufficient to establish an SI-traceable absolute lunar calibration standard for past, current, and future Earth environmental, weather and climate sensors. The ARCSTONE team will present the instrument design status and path forward for development, building, calibration and testing.

Assessment of GOES-16 ABI Lunar North-South Scan Data: Detector OOF, Blooming and Response Uniformity
Fangfang Yu, Xi Shao, Haifeng Qian – ERT, Inc.; Xiangqian Wu – NOAA/NESDIS/STAR

ABSTRACT: During the GOES-16 Advanced Baseline Imager (ABI) Post-launch product testing (PLPT) period, a series of the special scans of North-South Scans (NSS) were conducted across the Moon when it transited across the space within the ABI field of regard (FOR). These lunar NSS collections ensured that all the detectors of each ABI channel scanned across the illuminated lunar surface. As there is no atmosphere over the lunar surface, the lunar NSS data provide an unique opportunity to characterize the out-of-field (OOF) response and blooming effects for each detector. Preliminary results show no strong OOF and blooming effects for each detector at the VNIR bands. The detector response uniformity, especially for the detectors from the same column at the focal plane modules, are also characterized using the NSS data with very small uncertainty. The same technique and method will be applied to the future GOES-R series ABI during their PLPT periods. More details and updates, if any, will be presented in the coming meeting.

Airborne LUnar Spectral Irradiance (air-LUSI) Mission
Kevin Turpie – University of Maryland; Steve Brown, John Woodward – National Institute of Standards and Technology (NIST); Tom Stone – U.S. Geological Survey (USGS); Andrew Gadsden, Andrew Cataford – University of Guelph

ABSTRACT: The Airborne LUnar Spectral Irradiance (air-LUSI) mission has the objective to measure lunar spectral irradiance to an unprecedented level of accuracy: < 0.3% (k=1) uncertainty. This is to be accomplished by advancing a ground-based instrument system to fly on a NASA ER-2 aircraft above 90% of Earth's atmosphere, providing a new capability to potentially acquire SI-traceable lunar spectral irradiance over different lunar phases and libration angles. Initially, the air-LUSI measurements can be used to enhance the Robotic Lunar Observatory (ROLO) model of exo-atmospheric lunar spectral irradiance. The mission outcome is expected to greatly improve the accuracy of our knowledge of the Moon as a stable reference for calibration and inter-calibration of Earth-observing satellite instruments over long time periods, from the past into the future. This is of particular value for space-based ocean color measurements such as from SeaWiFS, MODIS, VIIRS and eventually PACE, which are highly sensitive to calibration drifts.

Our activities during the first year of the mission are focused on developing the three subsystems of the air-LUSI instrument. First, the IRradiance Instrument Subsystem (IRIS) is a non-imaging telescope with an integrating sphere at the focus, which feeds light via fiber optics to a spectrograph. An on-board validation source also can send light to the spectrograph via fiber optics. Second, the Autonomous Robotic Telescope Mount Instrument Subsystem (ARTEMIS) keeps the IRIS telescope pointed to the Moon to within less than 0.5°, reducing the effects of vignetting. Third, the High-altitude ER-2 Adaptation (HERA) instrument subsystem protects components from the extreme cold and low pressure during flight and high moisture from condensation during descent. The HERA team also is responsible for the integration of the air-LUSI instrument with the ER-2 aircraft. Our activities also include developing a calibration protocol and detailed uncertainty budget, conducting pre-flight system-level instrument calibrations, supporting engineering and demonstration flights, and performing post-flight data analysis. This report will provide details of the air-LUSI mission progress during the first year and our plans for the second year.

The Aerospace Spectral Energy Distribution (ASED) Program – 2018 Update
Ray Russell, Richard Rudy, Sloane Wiktorowicz, George Rossano, John Mauerhan, John Subasavage, Daryl Kim, Kirk Crawford, David Gutierrez, Michael Owens – The Aerospace Corporation

ABSTRACT: The observations-based catalog of stellar spectral energy distributions (SEDs) has been developing for over 20 years, with some look-back to data from over 40 years ago. This presentation will provide examples of the data taken and show some sources which have been remarkably constant, and some that have exhibited significant variations. The relative uncertainty of the data will be shown to be <5%, and in some cases, <1%. The absolute uncertainty is shown to be less than or about 5%. A rationale for why a smaller catalog of well-characterized sources is more beneficial than a larger, more statistical catalog will be made. An updated list of the sources, now numbering over 100,that are monitored multiple times/year will be provided. This work is supported at The Aerospace Corporation by the Internal Research and Development Program.

Using the Moon as a Calibration Source for a Fleet of Satellites
Arin Jumpasut, Adriana Fukuzato, Ignacio Zuleta – Planet

ABSTRACT: Radiometric calibration is an ongoing concern at Planet. The moon has been used as a stable calibration source by previous imaging systems, making it a natural choice for radiometric calibration efforts at Planet. Planet has been conducting an ongoing Lunar capture campaign since Q4 of 2016 and has amassed a database of over 1.7 million images of the moon so far.

Every lunar cycle over 100 satellites take collects of the moon at three phase angles in both the waxing and waning part of the cycle and a subset of these satellites take daily collects of the moon while in phase. An automated pipeline analyses these images, runs an implementation of the ROLO model and collates the statistics into a database. This allows us to easily recall data from the entire collection for studies and dashboards. Currently this data is used for radiometric validation and monitoring of satellite health over the entire fleet of satellites. Later this year though, new manouevres will be productionised to use the moon to measure other aspects of the imaging chain, e.g. sensor characterisation or stray light. Here we will be discussing the current state of Planet’s lunar campaign and give a brief overview of the future plans.

2:00 pm | Spotlight Session: Data Improvement and Reprocessing

Session Co-Chairs: Bruce Guenther, Stellar Solutions and Satya Kalluri, NOAA/NESDIS/STAR

View Abstracts (PDF)

Uncertainty, Precision and “Now I Know What That Meant When I First Saw the Effect Six Months Ago”: Conversations about Data Set Reprocessing and Utility of the Data We Produce
Bruce Guenther, Cole Rossiter – Stellar Solutions and JPSS

ABSTRACT: The metrology community provides careful attention to the uncertainty in their measurements. The National Institutes of Standards and Technology developed a Technical Note on Measurement Uncertainty NIST Tech Note 1297 which serves as the “Gold Standard” for measurement error, oops actually uncertainty. The Tech Note advocates treating uncertainty as Type A (those which are improved with statistical methods) and Type B (those which are improved with other methods). We also have familiarity with terms such as accuracy and precision, bias, and reproducibility of the measurement results. For those of us that make our career by measuring quantities, we may put nearly as much of our personal energy into identification of the uncertainty of the measurement as we put into determining the actual reported value for the measurement.

At some level, these approaches are very admirable. And I want to turn our attention toward measurement uncertainty by turning our attention away from measurement uncertainty. Folks making the Standards and establishing the true quantitative measured value must by nature of their requirements adhere strictly to measurement uncertainty protocol. And many of us are making measurements for “less noble” purposes, for the purpose of using that measurement to explain something other than say a fundamental physical quantity. Well, for an application of the measurement to a scientific problem (our most familiar problems in the Earth sciences are environmental problems), just what benefits derive from fastidious attention to uncertainty protocol? Where may we draw a line where actions beyond that demarcation for uncertainty analysis simply are not of enough value to make the added work worthy? And so what, perhaps, if we may over-perform in uncertainty analysis beyond our data user needs.

This presentation will serve as in introduction to the following papers in this Session on several approaches to identification of measurement uncertainty, and provide some insight into relationships between documented uncertainty of measurements and data reprocessing in Earth science satellite data sets.

Assimilation of CubeSat Sounder Data for High Impact Weather Forecasts - Challenges and Future Plans
Jun Li, Zhenglong Li, Fredrick Nagle, Pei Wang – Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin-Madison; Timothy Schmit, Sid Boukabara – Center for Satellite Applications and Research, NESDIS/NOAA; William Blackwell – Lincoln Laboratory, MIT, Thomas Pagano – Jet Propulsion Laboratory, Caltec; Robert Atlas – Atlantic Oceanographic and Meteorological Laboratory, OAR/NOAA

ABSTRACT:The advanced infrared (IR) and microwave (MW) sounding systems have been provided atmospheric sounding information critical for now-casting and improving weather forecasting through data assimilation in numerical weather prediction (NWP) models. Recent years, advanced IR and MW sounder systems are being proposed to be on-board the CubeSat, which is much cheaper than the ordinary satellite sounding systems. In order to evaluate the alternative of advanced MW and IR sounders with Micro-sized Microwave Atmospheric Satellite-2 (MicroMAS-2) and CubeSat Infrared Atmospheric Sounder (CIRAS) for high impact weather (HIW) forecasting in mitigating the data gap of the Advanced Technology Microwave Sounder (ATMS) and the Cross-track Infrared Sounder (CrIS) on-board Suomi-NPP and Joint Polar Satellite System (JPSS), a quick regional Observing System Simulation Experiment (r-OSSE) was carried for impact study on severe local storm (SLS) forecasts. Impacts were assessed for different orbit configurations, calibration and inter-calibration related challenges using CubeSat based sounding systems for HIW applications are discussed.

MODIS Level 1B Reprocessing: Progresses, Challenges, and Lessons
Jack Xiong – NASA Goddard Space Flight Center; Vince Salomonson – University of Utah

ABSTRACT: The MODerate Resolution Imaging Spectroradiometer (MODIS) is one of the key instruments for the NASA’s EOS program. Since launch, Terra and Aqua MODIS have successfully operated for more than 18 and 16 years, respectively. MODIS observations, which are made in the spectral range from visible (VIS) to long-wave infrared (LWIR), have enabled a broad range of science products to be generated. These data products have been openly distributed and widely used in support of various studies of the earth’s system of land, oceans, and atmosphere and numerous key environmental parameters. MODIS level 1B (L1B) data products include the TOA reflectance factors for the reflective solar bands (RSB), radiances for both the RSB and the thermal emissive bands (TEB), and the associated uncertainty indices. The RSB on-orbit calibration is performed primarily by a solar diffuser (SD), coupled with regularly scheduled lunar observations, and the TEB by an on-board blackbody (BB). Through entire missions of Terra and Aqua MODIS, several collections of the data products have been generated or reprocessed. Currently, both collections 6 and 6.1 (C6 and C6.1) are being produced and distributed. In general, the data reprocessing is made to address various calibration issues and to implement algorithm changes, and thus to produce consistent data records with improved quality. In this presentation, we describe the process of MODIS data reprocessing with a focus on the L1B calibration and data production, and illustrate the improvements made in various Collections. Also discussed are calibration challenges and lessons learned at different stages of each mission.

Suomi-NPP VIIRS Sensor Data Record Reprocessing Improvements and Status
Changyong Cao – NOAA/NESDIS/STAR; Wenhui Wang – ERT@NOAA/NESDIS/STAR; Sirish Uprety – University of Maryland

ABSTRACT: The Visible Infrared Imaging Radiometer Suite (VIIRS) has been flown on board the Suomi National Polar-orbiting Partnership (S-NPP) satellite, launched in 2011. A number of major changes in the sensor data record (SDR) algorithm and calibration parameters have been made to the NOAA operational processing of S-NPP VIIRS data, which has led to inconsistencies in the long-term data record. This paper presents NOAA STAR’s effort in reprocessing the S-NPP VIIRS SDRs from January 1, 2012 to July 31, 2016. Version 1 reprocessing has been completed. In the reprocessing, reflective solar bands (RSB) are recalibrated using consistent RSBAutoCal based F-factors. In addition, a new radiometric bias correction term was introduced to the SDR products to make the calibration consistent with the ocean color (OC) F-factors for RSB. A constant M5/M7 bias correction to reconcile OC, aerosol, and cloud teams’ concerns was also introduced. An Ltrace algorithm was developed to address the long-lasting calibration anomaly in the sea surface temperature bands (M15 and M16) observed during quarterly warm-up/cool-down (WUCD) events. Warm spikes in the daytime SST time series were successfully minimized. Day/Night band (DNB) SDR is improved using modulated spectral response functions and improved dark offset, gain ratio, and stray light correction parameters. Geolocation products were reprocessed using the latest geometric calibration parameters. In addition, terrain correction was implemented to the entire DNB geolocation data archive. Going forward, Version 2 reprocessing effort is currently in progress. RSB calibration will be further enhanced in version 2 by using Kalman filter based gain coefficients which reconciles calibration results from latest solar calibration parameters with reduced oscillations, lunar, deep convective clouds, and extended simultaneous nadir overpass. In addition, Version 2 reprocessing is being developed with the capability of on-demand SDR reprocessing.

Production of a Multi-decadal Earth Radiation Budget Climate Data Record: Balancing Accuracy, Precision, and Data Availability to Meet the Needs of the Community
Kory Priestley, Johnathon Gleason, Kathleen Moore, Anum Barki – NASA Langley Research Center

ABSTRACT: NASA’s Earth Radiation Budget Science Team, ERB-ST, (Previously known as the CERES Science Team) is a multi-disciplinary team led out of NASA’s Langley Research Center which has the responsibility for governance of the nation’s multi-decadal Earth Radiation Budget Climate Data Record, ERB CDR. The Science Data Processing System which produces the ERB-CDR is highly complex, producing Level one through Level 4 products. The system ingests data from 19 different instruments on 11 different spacecraft (6 GEO and 5 LEO) as well as other ancillary information, producing 25 different products with consistent TOA, Surface, and atmospheric radiative fluxes, cloud and aerosol properties on multiple spatial and temporal scales. Spatial scales vary from instantaneous/pixel (25 km), 1-deg grid, zonal, regional and global means while temporal scales vary across instantaneous, hourly, 3 hourly to monthly scales. Accuracy and precision values vary across the various spatial and temporal scales, with the long-term goal of measuring decadal trends of better than 0.3 W/m^2 per decade.

Instrument calibration and precision, as measured through the post-launch protocols, is one of many considerations that drive the decision to reprocess, others include, but are not limited to validation and instantiation of new algorithms across all levels of products, outside teams reprocessing the products we ingest, the launch of new instrumentation to replace operational weather imagers on Geo satellites, updates to processing hardware, and of course resource availability. These all need to be managed/considered in order to provide the global community products of sufficient accuracy and precision on a time-scale which allows continued advancement and discovery of key scientific questions such that policy makers may make informed decisions.

Monitoring GOES-R ABI Radiometric Performances with a Machine Learning System
Zhenping Li, Kenneth Mitchell – ASRC Federal; David Pogorzala – Integrity Applications Incorporated

ABSTRACT: The GOES-R Advanced Baseline Imager (ABI) instrument represents a considerable challenge for engineers to monitor its health, safety, and radiometric performance. As there are 7856 detectors across 16 spectral channels, the existing approach for monitoring the radiometric performance of the GOES N-P Imagers, each with only 16 detectors, is no-longer possible. The ABI radiometric monitoring has to be automated in order to handle such a huge volume of data. To help with this task, a machine learning system has been developed and implemented that automates the trending and monitoring of ABI radiometric calibration datasets. This machine-learning framework is used to capture the time dependent trends of these datasets through data training; the result of which consists of a time dependent function and noise level for each parameter. Because the time dependent trend for a dataset is highly sensitive to changes above its noise level, outliers that deviate from the existing pattern are detected by comparing the values of a dataset against predictions of its time dependent trend. Anomalies in the machine-learning framework are defined as unexpected data pattern changes, which are quantitatively characterized by dimensionless metrics. These metrics are used in a clustering analysis to separate anomalous datasets from the normal ones. In addition, the machine learning outputs enable the assessment of relative detector data quality by comparing the noise level of a detector with the average behavior for a given channel. A detector with a higher noise level has significant impact on the radiometric accuracy. Initial results from our radiometric monitoring show that many of the anomalies characterized in the machine learning approach cannot be detected through the existing static approach. The machine learning approach brings fundamental advances in data trending, anomaly detection, and analysis, and it leads to a more dynamic, proactive, and autonomous monitoring of ABI radiometric performance.

Designing a Human-in-the-Loop Process for Maintaining Optimal Calibration of GOES-R ABI Visible Channels
David Pogorzala, John Fulbright – Integrity Applications Incorporated; Xiangqin Wu – NOAA/NESDIS/STAR; Matthew Seybold – NOAA/NESDIS/OSPO

ABSTRACT: The Advanced Baseline Imager (ABI) onboard NOAA's Geostationary Operational Environmental Satellite-R (GOES-R) series provides high-quality, radiometrically-calibrated Earth-observing imaging data. Operational calibration of the six visible/near-infrared (VNIR) spectral channels is maintained through periodic observations of the on-board solar diffuser. Currently, the ground processing algorithm automatically updates the calibration coefficients for the VNIR channels after each solar diffuser observation. These automatic updates are working well, but it has been recognized that having a "human-in-the-loop" is preferred to optimize the long-term quality of the L1b products. In this talk, we describe the process involved in modifying the ground processing to incorporate this change. Beyond being a simple code change, the overall process involves coordinating the efforts of several teams to ensure this transitions from a research-level idea to a reliable, sustainable operational activity. Additionally, we will show examples of how this method has been used to positively impact L1b products.

Wednesday, June 20, 2018

8:00 am | National Standards Technology Advancement

Opportunities for communication and collaboration between National standards laboratories and the calibration community to improve calibration technologies and methodologies

  • Calibration traceability to standards—NIST and international
  • Relationship between primary, secondary, and transfer standards and applications to remote sensing
  • Maintenance of a valid calibration throughout instrument life
  • Activities within the community aimed at increasing the quality of our satellite-based measurements

View Abstracts (PDF)

Cryogenic Primary Standard for Optical Fiber Power Measurement
Malcolm White, Igor Vayshenker, Nathan Tomlin, Chris Yung, Michelle Stephens, John Lehman – National Institute of Standards and Technology (NIST); Zeus Ruiz – Centro Nacional de Metrología

ABSTRACT: NIST has completed commissioning of a new, state-of-the-art cryogenic primary standard for optical fiber power measurement and calibration. It establishes for the first time, a direct traceability route between the device under test and the primary standard. The expanded measurement uncertainty (k=2) is 0.4 %, which is a 20 % improvement on NIST’s previous capability. Measurement repeatability below 50 ppm is routinely achieved.

This presentation marks the culmination of an ambitious program to redefine the traceability route for optical fiber power measurement that serves the broader community with world-wide recognition. The technology behind this development is not only applicable to optical fiber power measurement, but also to radiant power measurement across the broad wavelength spectrum from the ultraviolet to THz region, with unprecedented accuracy [1] – [3]. Our ultimate goal is to develop a family of compact, fast, and easy-to-use calibration systems. The instrument uses advanced thermal filtering for exceptional stability and noise, and planar micro-machined silicon detectors, with carbon nanotube absorber arrays and superconducting transition edge sensors, for optical fiber power measurement. The detectors are vacuum coupled to laser diode sources using single mode fiber anchored at 5 K. The system operates at a radiant power level of 200 µW, -7 dBm, although this range can vary considerably depending on customer requirements.

We will discuss the application of this technology to the development of this new generation of primary standard, and the implications going forward. Recent work to overcome small deficiencies in the optical / electrical heating inequivalence will be presented. We will also present a detailed measurement uncertainty analysis which is dominated by the spectral linewidth of the source, and the temperature dependence of the beamsplitter ratio; a function of polarization dependent losses.

Finally, we will demonstrate agreement between our previous scale and our new optical fiber power scale.

From Laboratory to CubeSat - Room Temperature Absolute Bolometers for Laser Power Standards, Solar Spectral Irradiance, and Total Solar Irradiance
Michelle Stephens, Nathan Tomlin, Chris Yung, Ivan Ryger, Malcolm White, John Lehman – National Institute of Standards and Technology (NIST); Dave Harber, Greg Kopp, Karl Heuerman, Jacob Sprunck, Zach Castleman, Ginger Drake, Erik Richard – University of Colorado Laboratory for Atmospheric and Space Physics (LASP)

ABSTRACT: Planar micromachined silicon bolometers with carbon nanotube absorbers provide high accuracy, compact, and rugged radiation detection. We are building on the success of our silicon micromachined planar detectors operating at cryogenic temperatures1 to develop similar electrical substitution bolometers that operate at room temperatures. These bolometers currently have applications as both laboratory standards for laser optical power and for solar irradiance monitors in space.

Room temperature operation of these detectors for the above applications presents a different set of technical challenges from similar cryogenic detectors. The materials used for temperature measurement are different and inherently noisier, time constants are longer, and practical applications demand a greater dynamic range in power and a larger detector size.

We will describe the design and performance of three room temperature devices. The first is a laboratory based room temperature device for precision CW optical power measurements (Next-Gen C). This standard operates from 0.4 to 2 um and over a dynamic range of 50 uW to 100 mW. The second is a bolometer designed for solar spectral irradiance measurement that will be part of the Compact Spectral Irradiance Monitor (CSIM) CubeSat mission, scheduled for launch in the Fall of 2018. The third is a bolometer under development for total solar irradiance measurement as part of the Compact Total Irradiance Monitor (CTIM) instrument development.

High-efficiency Superconducting Single-photon Detectors
Thomas Gerrits, Adriana Lita, Varun Verma, Richard Mirin, John Lehman, Alan Migdall, Sae Woo Nam – National Institute of Standards and Technology (NIST)

ABSTRACT: Superconducting single-photon detectors have been shown to have extremely high detection efficiency over a large wavelength range, typically exceeding 90 % [1, 2]. Their use in quantum and classical optics is becoming more and more widespread in part due to improvements to and ease of use of the cryogenic packaging. In this talk, we will review two superconducting detector technologies, the superconducting nanowire single-photon detector (SNSPD) and the optical transition-edge sensor (TES) [3], that are being developed at NIST. We will also describe their applications in quantum and classical optics and present our recent effort to use these detectors as calibration standards, as well as our effort to establish a single-photon detector calibration service.

Superconducting Nanowire Single Photon Detectors
The SNSPD is based on a meandering, narrow, thin superconducting nanowire, current-biased close to its critical current. Our SNSPDs operate at temperatures around 1K. When a photon is absorbed in the detection region, the energy deposited drives the wire normal and a voltage pulse can be observed. Due to the speed of the detection process, the SNSPD offers high timing resolution along with detection of the photon flux at the shot-noise limit. The combination of both these features yields a detector that can measure the photon’s arrival time from a faint object or source. SNSPDs also offer single-photon detection capability beyond the wavelength detection range of silicon and InGaAs, out to at least 5000 nm [4]. SNSPDs were also recently implemented in an 8×8-pixel array enabling low-resolution, real-time imaging [5]. For our calibration service effort, we built an SNSPD system that can be used as a transfer standard between labs for single-photon detector calibrations.

Transition Edge Sensors
In contrast to the SNSPD, the TES is a photon-number resolving detector that has almost unity detection efficiency. The TES consists of a superconducting thin film, voltage-biased so that its resistance is in the transition between the superconducting regime and the normal conducting regime. The steep slope of the resistive transition allows for small temperature changes to be measured. The TES is designed such that the absorption of a single photon increases the temperature of the superconducting film enough to discern the resulting signal from the TES system noise. Therefore, the TES needs to be electrically and thermally quiet and is generally operated at temperatures around 100 mK. Due to its energy resolving capability, the TES can be also used as a spectrally resolving single-photon detector with limited resolution [6]. The TES can also be operated as a cryogenic radiometer in combination with an electrical substitution method, and can, in principle, yield absolute calibration of optical powers on the order of a few tens of femtowatts [7].


  1. A. E. Lita, A. J. Miller, and S. W. Nam, Opt. Express 16, 3032 (2008).
  2. F. Marsili, et al., Nat Photon 7, 210 (2013).
  3. R. Hadfield and G. Johansson, Superconducting Devices in Quantum Optics (Springer, 2016).
  4. F. Marsili, et al., in CLEO: 2013 (OSA, San Jose, California, 2013), p. CTu1H.1.
  5. M. S. Allman, et al., Applied Physics Letters 106, 192601 (2015).
  6. M. Fortsch, et al., Journal of Optics 17, 065501 (2015).
  7. N. A. Tomlin, J. H. Lehman, and S. Nam, Optics Letters 37, 2346 (2012).

Radiometry and Few-photon Metrology at the National Research Council of Canada
Angela Gamouras, Andrew Todd, Eric Cote, Arnold Gaertner, Jeongwan Jin, Dan Dalacu, Robin Williams – National Research Council Canada

ABSTRACT: Over the last few years, the National Research Council of Canada (NRC) has been establishing new facilities and improving capabilities in three areas of radiometry: optical power, spectral irradiance, and few-photon measurements. Canada’s realization of the optical radiant power scale now utilizes a new cryogenic electrical substitution radiometer as the primary instrument. With higher cavity absorptance, reduced non-equivalence effects, and a closed-cycle helium cryocooler, this new cryogenic radiometer has significantly contributed to improvements in measurement uncertainties. NRC’s primary spectral irradiance scale has transitioned from a detector based approach to a detector and source based realization. Filter radiometers with spectral responsivity traceable to the cryogenic radiometer and a high temperature blackbody primary light source are implemented in the calibration of transfer standard FEL lamps from 200 nm to 2500 nm. Most recently, NRC has been working to establish a few-photon metrology capability for optical radiometry. The initial goal of this new facility is to measure the detection efficiency of free-space single-photon detectors using a calibrated detector substitution technique. This capability will then be extended to the traceable characterization of NRC on-chip semiconductor quantum dot-based single-photon sources, the evaluation of these sources as new quantum standards, and using entangled photons from these sources for fundamental quantum metrology measurements. Ongoing efforts and details of these new radiometry facilities will be presented.

Progress on Embedded Radiation Pressure Sensors for Absolute Power Measurement
Alexandra Artusio-Glimpse, Ivan Ryger, Paul Williams, Josh Hadler, Brian Simonds, Nathan Tomlin, Kyle Rogers, John Lehman – National Institute of Standards and Technology (NIST)

ABSTRACT: High-accuracy power measurement of high-power lasers has traditionally involved the absorption of (ideally) all the laser energy by a large thermal mass resulting in the temperature change of that sensor. Though the measurement uncertainty of high powers can be ~1%, this thermal process can be slow (with cooling times on the order of tens of minutes for multi-kilowatt calorimeters) and excludes the laser from any operational use during the course of a measurement. Radiation pressure sensors, on the other hand, offer a means for in situ laser power measurement at much faster measurement speeds (seconds and below). The first realization of a multi-kilowatt radiation pressure power meter (RPPM) recognized a new primary standard for optical power measurement that traces the optical watt directly to the kilogram by measuring the force of reflection on a highly reflective mirror [1]. This technology now boasts measurement accuracy equal to that of thermal methods with the aforementioned benefits of speed and nonexclusive measurement of the laser beam. However, the device is sensitive to tilt with respect to gravity and to environmental sources of vibration, is relatively bulky compared to other optical components, and is slower than what some high-power laser applications require. Therefore, we are currently developing a micromachined capacitor-based RPPM that is faster than its bulk counterpart and is small enough to be embedded directly within laser processing systems.

In this presentation, we will discuss the principle of radiation pressure power measurements and highlight our current progress in developing the small-package RPPM. We will present the results of open loop measurements with a prototype device that show significant improvements. In particular, we demonstrate the ability to measure both optical (1070 nm) and RF (15 GHz) powers with the use of different mirror types. In both cases, we see a noise floor on the order of 1 W/√Hz. This agrees well with theoretical predictions of noise equivalent power at 0.44 W/√Hz, where environmental noise is not considered. We additionally measure the response time of the prototype to be less than 100 ms when operated in open loop. Furthermore, the sensor design suppresses signal noise from orientation with respect to gravity and low-frequency vibrations by using symmetric springs to reject common-mode inertial forces. We additionally carry out careful characterization of the electromechanical system to properly estimate the system responsivity, noting the nonlinear behavior of the parallel plate capacitor in open loop. From multiple overlapping tests, we characterize the spring stiffness, plate spacing, natural resonance, quality factor, and parasitic capacitance of our instrument [2,3] obtaining not only the necessary information to predict responsivity, but also demonstrating different techniques that will be used to calibrate the device. These tests demonstrate improved measurement capability for fast, sensitive detection of optical and RF power that we predict will meet the growing demand for embedded, NIST traceable, absolute power metering.

  1. P. Williams, J. Hadler, F. Maring, R. Lee, K. Rogers, B. Simonds, M. Spidell, M. Stephens, A. Feldman, and J. Lehman, Optics Express, 25(4), p.4382, 2017.
  2. I. Ryger, A. Artusio-Glimpse, P. Williams, N. Tomlin, M. Stephens, M. Spidell, and J. Lehman, Proceedings of 13th International Conference on New Developments and Applications in Optical Radiometry, Tokyo, Japan, 13-16 June 2017.
  3. I. Ryger, A. Artusio-Glimpse, P. Williams, N. Tomlin, M. Stephens, K. Rogers, M. Spidell, and J. Lehman, “Micromachined force balance for optical power measurement by radiation pressure sensing,” submitted.

Validations of Detector-based Radiometric Calibrations using Fixed-point Blackbodies
Howard Yoon, Charles Gibson, John Woodward, Ping Shaw – National Institute of Standards and Technology (NIST)

ABSTRACT: The developments of laser-based radiometric calibration facilities enable possibilities of achieving lower measurement uncertainties than those obtained with traditional sources such as lamps or lamp-based integrating sphere sources. These facilities are being developed at institutions other than major national measurement institutes due to the availability of easily tunable lasers which can span a wide range of wavelengths. Due to the extremely low claimed uncertainties of the calibrations from such facilities, it is not easy to test such claims using lamps or lamp-based sources. One way to test such claims is to utilize metal fixed-point blackbodies which are used to disseminate the International Temperature Scale of 1990 (ITS-90).

We describe the validation of the NIST Spectral irradiance and Radiance Calibrations with Uniform Sources (SIRCUS) using radiometers calibrated for spectral radiance responsivity which then are used to measure ITS-90 fixed points as well as higher temperature metal-carbon eutectic cells. We describe the SI-traceable calibration procedures and how these calibrations enable direct measurements of thermodynamic temperatures.

2:10 pm | Inter-Calibration and Validation of Operational Sensors

Performance comparison between sensors of differing scientific objectives, capabilities, and mission parameters to assess measurement bias and uncertainty

  • Post-launch calibration using onboard and/or vicarious techniques
  • Retrievals through data assimilation with various data used for validation
  • Results of particular approaches, validation campaigns, and experiments
  • Techniques, platforms, and instruments for validation
  • Application of calibration results to scientific measurements
  • Requirements and potential approaches for the calibration of global satellite observing sensors

View Abstracts (PDF)

Characterization of Deep Convective Clouds as an Invariant Target for Satellite SWIR Bands Inter-calibration
Rajendra Bhatt, Benjamin Scarino, Arun Gopalan, Conor Haney – SSAI/NASA LaRC; David Doelling – NASA Langley Research Center

ABSTRACT: Tropical deep convective clouds (DCC) are proven to be an excellent invariant target for post-launch radiometric calibration of satellite visible (VIS) and near-infrared (NIR) spectral channels. The DCC technique (DCCT) is a statistical approach that collectively analyzes DCC pixels and provides a near lambertian reflectance suitable for inter-calibration. At shortwave infrared (SWIR) wavelengths, the DCC reflectance is impacted by the ice microphysical properties of particle size and optical depth, thereby increasing the temporal noise in the DCC response. The key to improving the DCCT for satellite SWIR bands calibration is proper characterization of the DCC reflectance at SWIR wavelengths.

This paper will present empirical bidirectional reflectance distribution function (BRDF) models based on multiple years of NPP-VIIRS DCC measurements to mitigate the seasonal variation in the SWIR band DCC reflectance. The DCC BRDF models are wavelength-specific and are effective in reducing the temporal noise in the DCC response by up to 50%. Application of these BRDF models to the Aqua-MODIS and JPSS-1 VIIRS imagers for radiometric inter-comparison will be discussed. Another factor that impacts the stability of the SWIR band DCC reflectance is the infrared brightness temperature (IR-BT) threshold used for identifying the DCC pixels. The optimal BT threshold for achieving the most predictable DCC response for individual SWIR bands will also be addressed. The channel-specific BRDFs and BT thresholds will help to extend the use of DCCT to SWIR bands inter-calibration.

Absolute Radiometric Inter-calibration between MODIS and VIIRS Reflective Solar Bands without the use of Simultaneous Observations
David Doelling – NASA Langley Research Center; Rajendra Bhatt, Benjamin Scarino, Arun Gopalan, Conor Haney – SSAI

ABSTRACT: The CERES project relies on the MODIS and VIIRS sensors for cloud retrievals to convert the CERES observed radiances into fluxes. In order to produce climate quality data records, the cloud properties derived from the MODIS instruments onboard Terra and Aqua as well as from the VIIRS instruments onboard NPP and JPSS-1 must be consistent. Although MODIS and VIIRS have onboard solar diffusers to actively monitor inflight calibration, the absolute radiometric calibration may still differ between them, which could cause discontinuities between sensor records. The projected plan for the JPSS constellation is to maintain two operational satellites, which are spaced 45 minutes apart in the same 1:30 PM sun-synchronous orbit. The projected orbital configuration will provide no simultaneous nadir orbit (SNO) inter-calibration opportunities between any of the two operational VIIRS sensors. VIIRS inter-calibration approaches must then rely on Earth invariant or lunar targets.

This presentation will demonstrate the use Libya-4, Dome-C, and deep convective cloud (DCC) Earth invariant targets to radiometrically scale the spectrally matching visible channels of VIIRS to MODIS. The new 3rd generation geostationary (GEO) satellites, such as GOES-16 and Himawari-8, have multiple visible bands that are spectrally similar to those of MODIS and VIIRS. A double-difference technique of inter-calibration will be presented using GOES-16 and Himawari-8 as transfer radiometers. We will also present all-sky tropical ocean (ATO) and DCC ray-matching approaches that use coincident, co-angled, and co-located MODIS and VIIRS instantaneous radiances for inter-calibration. The ATO method captures the complete earth observed radiance range and will be used to validate the Earth invariant target and GEO transfer radiometer methods. Consistency between all of the independent MODIS to VIIRS inter-calibration approaches validates all approaches.

Data Inter-comparisons of the CrIS Interferometers on Suomi-NPP and NOAA-20
Joe Kristl, Kori Moore, Mark Esplin, Deron Scott, Ben Esplin – USU/Space Dynamics Laboratory

ABSTRACT: The Cross-Track Infrared Sounder (CrIS) collects spectra used in atmospheric soundings with twice daily global coverage. A demonstration CrIS is part of Suomi-NPP and has been collecting spectra on orbit since 2012. The S-NPP CrIS has been extensively validated against other satellite sensors and with dedicated simultaneous aircraft campaigns. NOAA-20 launched in November 2017 and its CrIS interferometer data is currently at the provisional status level. Direct data comparisons between the CrIS interferometers are essential to demonstrate that the new system is performing as well or better than the S-NPP CrIS. S-NPP and NOAA-20 are in the same orbital plane but 50 minutes apart, creating view angle and time differences when measuring the same geographical region. This talk demonstrates how these differences can be corrected using the radiative transfer model MODTRAN 6 initialized using atmospheric conditions from NASA atmospheric and NOAA numerical weather models. Initial results show excellent agreement between the two on-orbit data sets.

3:40 pm | Calibration Challenges in Remote Sensing for Environmental and Climate Change Studies

Understanding radiometric calibration and characterization of remote sensing instruments for environmental and climate change studies

  • Implications of remote sensing strategy (wide-area coverage, indirect sampling, time trending) for radiometric calibration
  • Comparison of radiometrically-calibrated measurements to direct sampling and in situ measurements
  • Validation and maintenance of calibration accuracy across measurement data gaps
  • Assimilation of radiometric calibration knowledge, information, and data products into models of complex systems
  • Plans to achieve climate-quality calibration for present and future operational sensors
  • Uncertainty budgeting for climate-quality calibration of environmental remote sensors

View Abstracts (PDF)

Calibration of the National Ecological Observatory Network's Airborne Observation Platforms
Nathan Leisso, Tristan Goulden, Ian Crocker – Battelle Ecology - National Ecological Observatory Network; Joe Boardman – Analytical Imaging and Geophysics

ABSTRACT: The National Ecological Observatory Network (NEON) is a continental-scale ecological observation facility funded by the National Science Foundation (NSF). NEON's mission is to enable understanding and forecasting of the impacts of land-use change and invasive species by providing the infrastructure and consistent methodologies for the collection of continental-scale ecological data. The Airborne Observation Platform (AOP) will play a unique role by collecting regional scale remote sensing data surrounding the NEON sites. This is expected to enable scaling of individual in-situ measurements collected by NEON or others to those collected by external satellite-based remote sensing systems.

The airborne payload consists of the NEON Imaging Spectrometer (NIS), a full waveform and discrete LIDAR, and a high-resolution digital camera integrated into a Twin Otter aircraft. Three payloads on separate aircraft will provide coverage of 80 plus sites located in the 20 NEON Domains as well as targets of opportunity and PI-driven science. A key component of the NEON design is the consistent calibration of the airborne instruments to provide reliable and accurate scientific data over the full lifetime of the NEON observatory. The NEON Sensor Test Facility provides the facilities for the laboratory calibration of the AOP instrumentation.

This work examines the spectral and radiometric calibration of the NIS in the NEON Sensor Test Facility. Recent work has focused on the traceability and uncertainty of the radiometric and spectral calibration and stability of the calibration from lab to operations. To verify the operational stability during acquisitions, a quality check algorithm has been developed to assess the raw NIS data prior to ingestion into the NEON processing framework. In addition, routine vicarious calibration flights are scheduled to independently verify the lab-based calibration. The work presented here also examines implemented improvements in characterizing the level of stray light in the NIS data. These corrections have significantly improved the fidelity of the spectroscopic data as well as improving the overall radiometric and spectral accuracy across the typical heterogeneous scenes included in the NEON collections.

Pre-Launch Calibration of the Sea and Land Surface Temperature Radiometer
Dave Smith, Mireya Etxaluze, Ed Polehampton, Arrow Lee, Dan Peters, Tim Nightingale, Elliot Newman, Brian Maddison – Science and Technology Facilities Council (STFC); Jens Nieke – European Space Agency (ESA)

ABSTRACT: The Sea and Land Surface Temperature Radiometer (SLSTR) on the Copernicus Sentinel-3 mission is a dual-view, multi-channel scanning radiometer specifically designed to measure global sea-surface temperatures SST to an uncertainty < 0.3K for climate monitoring and continue the 21 year datasets of the Along Track Scanning Radiometer (ATSR) series. Two instruments were originally planned with the first being launched in February 2016 and the second launch schedule for spring 2018 to provide daily global coverage of SST and LST data. A further two instruments are being developed as replacements when the first two reach the end their operational lifetime.

Thorough pre-launch calibration using accurate sources and agreed procedures is a fundamental prerequisite for ensuring traceability and consistency of the data generated by the two instruments. This is particularly important at thermal infrared wavelengths where verification of the calibration against traceable reference standards becomes very difficult once on orbit.

The SLSTR-A and B instruments underwent extensive pre-flight calibration campaigns to ensure that all the necessary calibration parameters are measured before launch, but more importantly that the end-to-end system performance and calibration model is fully verified against traceable calibration sources before launch. As an infrared sensor, this is essential for understanding all sources of uncertainty that affect the instrument calibration which cannot be directly measured once on-orbit.

The pre-launch calibration activities included the spectral response characterisation, instrument line-of-sight for verification of the geometric pointing model, solar channel radiometric and thermal infrared radiometric calibration. A purpose built calibration rig was developed to provide a controlled thermal environment necessary for thermal infrared wavelengths and to allow the blackbody calibration sources around the field of view of the instrument. In the paper, the authors describe the test methods and measurement results and compare the results between the two models. Results from the model A instrument were used to improve methods used for the model-B instrument. In particular, additional tests and improvements to the test setup for the visible and short-wave infrared calibration activities have shed light on results from the model-A instrument.

Testing, Verification and Calibration of the TANSO-FTS-2 Sensor
Lawrence Suwinski, Ronald Glumb, Christopher Ellsworth, Eric Beaubien, John Holder – Harris Corporation; Hiroshi Suto, Yukie Yajima, Masakatsu Nakajima – Japan Aerospace Exploration Agency (JAXA)

ABSTRACT: TANSO-FTS-2 is the primary instrument aboard the Greenhouse gases Observation Satellite-2 (GOSAT-2). It measures high-resolution spectra of upwelling earth radiance in five spectral bands to extract concentrations of greenhouse gases (CO2, CH4) and artificial emission sources. The development, testing and ground calibration of TANSO-FTS-2 was performed by Harris Corporation under a subcontract to Mitsubishi Electric Corporation, the GOSAT-2 prime contractor of the Japan Aerospace Exploration Agency (JAXA) GOSAT-2 project. This paper will summarize the functionality, test methodology, test results and calibration performance of the TANSO-FTS-2. This includes details of the system signal to noise ratio (SNR), instrument line shape (ILS), linearity, polarization, field-of-view (FOV) and scanner performance testing. Also included are expected calibration error and line of sight (LOS) performance. A summary of the TANSO-FTS-2 modules and nominal on-orbit operational scenario will also be discussed, including a description of intelligent pointing functionality and expected performance.

Creating a single radiance climate record from AIRS, IASI and CrIS
Christopher Hepplewhite – The University of Maryland, Baltimore County (UMBC); Lawrence Strow, Howard Motteler, Steven Buczkowski – UMBC/ Joint Center for Earth Systems Technology (JCET)

ABSTRACT: We investigate three key aspects for creating a climate record from multiple hyperspectral infra-red sensors. The motivation is to produce a multi-decade continuous record of global radiance measured leaving the atmosphere. Current global observation mission scenarios aim to supply multiple follow-on missions for the JPSS CrIS and MetOp IASI sensors which, in addition to the current Aqua AIRS sensor, could in principle provide a continuous radiance record from 2002 to 2025 and beyond. We aim to apply this record to studies of climate trends directly from the radiance and also to a common set of geophysical quantities using retrieval methods that share a common radiative transfer model.

The three sensors being used in this study; Aqua AIRS, NOAA CrIS and MetOp IASI share some similar characteristics; they are all low-earth, high inclination sun-synchronous polar orbiters and hyperspectral infra-red mapping missions. Deriving a common radiance record requires methods to relate their spectral capabilities, their radiometric calibration and their spatial-temporal mapping characteristics. We detail (i). a method to translate the spectral radiance measurements onto a common graduated scale, or line-shape, (ii) how to calibrate their radiometric scale and (iii) how to deal with spatial and temporal coherence differences of their global sampling.

Considerable mission overlaps of these sensors are used to make direct inter-comparisons between sensors using simultaneous nadir observations and large sample statistical methods. One of the key goals is to be able to maintain relative stability to about 10 mK per year over the long term, and in this paper we will show how this might be possible.

We demonstrate the performance of this approach by comparing top-of atmosphere radiance trends from simulations using the ECMWF ERA reanalysis, which is presently the most popular measurement-based climate data set used by the scientific community.