Ivona Cetinić, Charles R. McClain, And P. Jeremy Werdell, Editors - NASA

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NASA/TM–2018-219027/ Vol. 6PACE Technical Report Series, Volume 6Ivona Cetinić, Charles R. McClain, and P. Jeremy Werdell, EditorsData Product Requirements and Error BudgetsConsensus DocumentZiauddin Ahmad, Ivona Cetinić, Bryan A. Franz, Erdem M. Karaköylü, Lachlan I. W. McKinna, Frederick S.Patt, and Jeremy WerdellNational Aeronautics andSpace AdministrationGoddard Space Flight CenterGreenbelt, Maryland 20771January 2019

NASA STI Program . in ProfileSince its founding, NASA has been dedicated to theadvancement of aeronautics and space science. TheNASA scientific and technical information (STI) program plays a key part in helping NASA maintain thisimportant role.The NASA STI program operates under the auspicesof the Agency Chief Information Officer. It collects,organizes, provides for archiving, and disseminatesNASA’s STI. The NASA STI program provides accessto the NASA Aeronautics and Space Database and itspublic interface, the NASA Technical Report Server,thus providing one of the largest collections of aeronautical and space science STI in the world. Resultsare published in both non-NASA channels and byNASA in the NASA STI Report Series, which includesthe following report types: TECHNICAL PUBLICATION. Reports ofcompleted research or a major significant phase ofresearch that present the results of NASA Programsand include extensive data or theoretical analysis.Includes compilations of significant scientific andtechnical data and information deemed to be ofcontinuing reference value. NASA counterpart ofpeer-reviewed formal professional papers but hasless stringent limitations on manuscript length andextent of graphic presentations. TECHNICAL MEMORANDUM. Scientificand technical findings that are preliminary or ofspecialized interest, e.g., quick release reports,working papers, and bibliographies that containminimal annotation. Does not contain extensiveanalysis. CONTRACTOR REPORT. Scientific and technicalfindings by NASA-sponsored contractors andgrantees. CONFERENCE PUBLICATION. Collectedpapers from scientific and technical conferences,symposia, seminars, or other meetings sponsored orco-sponsored by NASA. SPECIAL PUBLICATION. Scientific, technical,or historical information from NASA programs,projects, and missions, often concerned withsubjects having substantial public interest. TECHNICAL TRANSLATION. English-languagetranslations of foreign scientific and technicalmaterial pertinent to NASA’s mission.Specialized services also include organizing andpublishing research results, distributing specializedresearch announcements and feeds, providing helpdesk and personal search support, and enabling dataexchange services. For more information about theNASA STI program, see the following: Access the NASA STI program home page athttp://www.sti.nasa.gov E-mail your question via the Internet tohelp@sti.nasa.gov Phone the NASA STI Information Desk at757-864-9658 Write to:NASA STI Information DeskMail Stop 148NASA’s Langley Research CenterHampton, VA 23681-2199

NASA/TM–2018-219027/ Vol. 6PACE Technical Report Series, Volume 6Editors:Ivona CetinićGESTAR/Universities Space Research Association, Columbia, MarylandCharles R. McClainScience Applications International Corporation, Reston, VirginiaP. Jeremy WerdellNASA Goddard Space Flight Center, Greenbelt, MarylandData Product Requirements and Error BudgetsConsensus DocumentZiauddin AhmadScience Applications International Corporation, Reston, VirginiaIvona CetinićGESTAR/Universities Space Research Association, Columbia, MarylandBryan A. FranzNASA Goddard Space Flight Center, Greenbelt, MarylandErdem M. KaraköylüScience Applications International Corporation, Reston, VirginiaLachlan I. W. McKinnaGo2Q Pty, Ltd, Buderim, AustraliaFrederick S. PattScience Applications International Corporation, Reston, VirginiaJeremy WerdellNASA Goddard Space Flight Center, Greenbelt, MarylandNational Aeronautics andSpace AdministrationGoddard Space Flight CenterGreenbelt, Maryland 20771January 2019

Notice for Copyrighted InformationThis manuscript has been authored by employees of GESTAR/Universities Space Research Association,Go2Q Pty, Ltd, and Science Applications International Corporation with the National Oceanicand Atmospheric Administration and the National Aeronautics and Space Administration. TheUnited States Government has a nonexclusive, irrevocable, worldwide license to prepare derivativeworks, publish or reproduce this manuscript for publication acknowledges that the United StatesGovernment retains such a license in any published form of this manuscript. All other rights areretained by the copyright owner.Trade names and trademarks are used in this report for identification only. Their usage doesnot constitute an official endorsement, either expressed or implied, by the National Aeronauticsand Space Administration.Level of Review: This material has been technically reviewed by technical management.Available fromNASA STI ProgramMail Stop 148NASA’s Langley Research CenterHampton, VA 23681-2199Available in electronic form at http://National Technical Information Service5285 Port Royal RoadSpringfield, VA 22161703-605-6000

INTRODUCTIONIntroduction to Volume 6: Data Product Requirements and Error BudgetsThe Plankton, Aerosol, Cloud, ocean Ecosystem (PACE; https://pace.gsfc.nasa.gov) mission representsNASA’s next great investment in satellite ocean color and the combined study of Earth’s oceanatmosphere system. At its core, PACE builds upon NASA’s multi-decadal legacies of the Coastal ZoneColor Scanner (1978-1986), Sea-viewing Wide Field-of-view Sensor (SeaWiFS; 1997-2010), ModerateResolution Imaging Spectroradiometers (MODIS) onboard Terra (1999-present) and Aqua (2002present), and Visible Infrared Imaging Spectroradiometer (VIIRS) onboard Suomi NPP (2012-present)and JPSS-1 (2017-present; to be renamed NOAA-20). The ongoing, combined climate data record fromthese instruments changed the way we view our planet and – to this day – offers an unparalleledopportunity to expand our senses into space, compress time, and measure life itself.This volume presents PACE science data requirements and the studies conducted and tools developed thattranslate these requirements into performance metrics for the ocean color instrument (OCI). In manyways, these studies and tools became the Rosetta Stone that translated PACE science into OCIengineering. The volume opens with presentation of Level-1 science data product requirements deliveredto the PACE mission by NASA HQ. These requirements encompass data products to be produced andtheir associated uncertainties. The remainder of the volume describes tools developed that allocate theseuncertainties into their components, including allowable OCI systematic and random uncertainties,observatory geolocation uncertainties, and geophysical model uncertainties. To the best of ourknowledge, many of these tools did not previously exist and, thus, offer new and substantial resources tothe ocean color satellite user community.I offer my thanks to the PACE Project Science team for their ingenuity and resourcefulness in pursingthese activities. I also thank the OCI systems engineering team for the frank and honest dialog and theirwillingness to help bridge the gap between science and engineering. We collectively hope that the usercommunity benefits from – and, perhaps more importantly, builds upon – these efforts.P. J. WerdellPACE Project ScientistMarch 2018

ContentsPACE Ocean Color Science Data Product Requirements . 1Executive Summary . 1Introduction . 1Level-1 Requirements. 2Level-2 Requirements. 4Impacts on Geophysical Data Products . 5Concluding Remarks . 5Development of PACE OCI Pointing Knowledge and Control Requirements for Geolocation . 6Executive Summary . 6Introduction . 6Geolocation Pointing Requirements . 72.2.1.Pointing Knowledge . 72.2.2.Pointing Control . 72.2.3.Pointing Stability . 8Solar Calibration Pointing Requirements . 10Conclusions . 11PACE OCI Signal to Noise Performance Requirement: Assessment and Verification Approach forOcean Color Science . 12Executive Summary . 12Introduction . 12Proxy Data Source . 13Atmospheric Correction Algorithm . 13Instrument Noise Model . 13Monte Carlo Analysis . 15Analysis Example . 15Verification of Modeling Approach . 19Determining OCI SNR Performance Requirements . 20Summary. 22Derivation of PACE OCI Systematic Error Approach . 23Executive Summary . 23Introduction . 23Summary of OCI Artifacts . 23Development of Approach. 24ii

Examples of Results . 27Conclusion . 28Uncertainty in NASA ocean color observations and implications for derived biogeochemical properties. 29Executive summary . 29Introduction . 29Data and methods . 295.2.1.Bio-optical data products . 295.2.2.Reflectance datasets. 31Results and discussion . 31Appendix A: Chlorophyll concentration and uncertainty . 34Appendix B: Diffuse attenuation coefficient and uncertainty . 37Appendix C: Particulate organic carbon . 39Appendix D: Normalized fluorescent line height . 40Appendix E: Inherent optical properties . 415.8.1.The forward model . 415.8.2.Bio-optical models. 425.8.3.Inverse solution method. 435.8.4.Uncertainty propagation . 43Uncertainty in aerosol model characterization and its impact on ocean color retrievals . 45Executive Summary . 45Introduction . 45Aerosol Models . 46Atmospheric correction algorithm . 46Simulation Results . 47Discussion and Conclusions . 50References . 52iii

Chapter 1PACE Ocean Color Science Data Product RequirementsJeremy Werdell, NASA Goddard Space Flight Center, Greenbelt, Maryland1Executive SummaryThis chapter summarizes ocean color science data product requirements for the Plankton, Aerosol, Cloud,ocean Ecosystem (PACE) mission’s Ocean Color Instrument (OCI) and observatory. NASA HQdelivered Level-1 science data product requirements to the PACE Project, which encompass data productsto be produced and their associated uncertainties. These products and uncertainties ultimately determinethe spectral nature of OCI and the performance requirements assigned to OCI and the observatory. Thischapter ultimately serves to provide context for the remainder of this volume, which describes toolsdeveloped that allocate these uncertainties into their components, including allowable OCI systematic andrandom uncertainties, observatory geolocation uncertainties, and geophysical model uncertainties.IntroductionCore science objectives of any satellite mission depend primarily on the quality of science data productsdelivered by the instrument payload. In May 2015, NASA HQ Earth Science Division (ESD) deliveredthreshold Level-1 requirements to the Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) Project, whichincluded a list of science data products to be produced, along with their associated uncertainties. Theseproducts encompass ocean color, aerosol, and cloud retrievals and represent the core suite ofmeasurements required to achieve PACE mission science objectives. As the Ocean Color Instrument(OCI) remains the only required instrument on the mission observatory, it alone must be capable ofproducing all science data products. Following, the suite of required science data products ultimatelydrives the OCI design concept and all performance requirements for OCI and the PACE observatory.Within a flight project, a series of flowed-down requirements translate science into engineering. ForPACE, Level-1 requirements are managed by NASA ESD, Level-2 requirements (subordinate, moredetailed requirements necessary to meet Level-1 requirements) are derived and managed by the PACEProject, and Level-3 requirements (subordinate, more detailed requirements necessary to meet Level-2requirements) are derived and managed by specific Project elements, such as the OCI systemsengineering team. This volume presents analyses and tools developed by the PACE Project Science teamto derive Level-2 performance requirements from the ESD-provided Level-1 science data productsrequirements (Figure 1.1).NASA flight projects also typically carry two versions of requirements at each level, at least forLevel-1 requirements. Threshold requirements indicate the minimum suite necessary to proceed with themission. Baseline requirements describe those above-and-beyond threshold that a project expects toachieve. In practice, instruments systems engineering teams pursue design concepts that meet or exceedbaseline requirements. For PACE, threshold requirements are set by NASA HQ and remain unchanged,1Cite as: Werdell, P. J. (2018), PACE Ocean Color Science Data Product Requirements, in PACE Technical ReportSeries, Volume 6: Data Product Requirements and Error Budgets (NASA/TM-2018 – 2018-219027/ Vol. 6), editedby I. Cetinić, C. R. McClain and P. J. Werdell, NASA Goddard Space Flight Space Center Greenbelt, MD.

whereas baseline requirements will not be finalized until Key Decision Point C (KDP-C, scheduled forJune 2019 at the time of this writing). Under the auspices of Design-to-Cost (see Volume 3 in thisTechnical Memorandum series), baseline requirements remain in mission trade space until missionconfirmation at KDP-C.Figure 1.1. Requirement sub-allocations from Level-1 measurements uncertainties into Level-2 componentuncertainties. Chapters in this volume describe methods used to derive each Level-2 allocation. SDS indicatesScience Data Segment and represents uncertainties associated with atmospheric correction and other post-launchcomponents of the mission.The remainder of this chapter is dedicated to presenting Level-1 threshold and baseline ocean colorscience data products requirements for PACE’s OCI and example Level-2 sub-allocations of data productuncertainties, which will be presented in detail in the remainder of this volume. Level-1 requirements foraerosol and cloud products are also presented, but are not explored in detail at this time as the ocean colorretrieval requirements dominate the derivation of performance specifications for OCI. Volume 5 of thisTechnical Report series includes additional details on OCI capabilities for aerosol and cloud retrievals.Level-1 RequirementsThreshold and baseline requirements for ocean color data products are as follows:Data ProductThresholdUncertainty0.0083 or 30%BaselineUncertainty0.0057 or 20%Water-leaving reflectances centered on( 2.5 nm) 350, 360, and 385 nm (15nm bandwidth)Water-leaving reflectances centered on0.0024 or 6%0.0020 or 5%( 2.5 nm) 412, 425, 443, 460, 475,490, 510, 532, 555, and 583 (15 nmbandwidth)Water-leaving reflectances centered on 0.00084 or 12%0.0007 or 10%( 2.5 nm) 617, 640, 655, 665, 678, and710 (15 nm bandwidth, except for 10nm bandwidth for 665 and 678 nm)Ocean Color Data Products to be Derived from Water-leaving ReflectancesConcentration of chlorophyll-a (mg m-3)Diffuse attenuation coefficients from 400-600 nm (m-1)Phytoplankton absorption from 400-600 nm (m-1)Non-algal particle plus dissolved organic matter absorption from 400-600 nm (m-1)2

Particle backscattering from 400-600 nm (m-1)Fluorescence line height (mW cm-2 m-1 sr-1)Each uncertainty requirement is defined by the greater of the absolute and relative value and for 50%or more of the observable deep ocean (depth 1000 m) at a Level-2 satellite data processing level (Figure1.2; geophysical values without spatial or temporal re-projection and compositing). Only water-leavingreflectances (unitless) carry uncertainties. Note also that the PACE mission will provide a suite ofoceanographic geophysical variables beyond those listed above, including, but not limited to, carbonstocks and fluxes, photosynthetic pigment concentrations, and indices of phytoplankton communitycomposition and health.Threshold and baseline aerosol and cloud products are identical as follows:Data ProductTotal aerosol optical depth at 380 nmTotal aerosol optical depth at 440, 500, 550 and 675 nm over landTotal aerosol optical depth at 440, 500, 550 and 675 nm over oceansFraction of visible aerosol optical depth from fine mode aerosolsover oceans at 550 nmCloud layer detection for optical depth 0.3Cloud top pressure of opaque (optical depth 3) cloudsOptical thickness of liquid cloudsOptical thickness of ice cloudsEffective radius of liquid cloudsEffective radius of ice cloudsAtmospheric data products to be derived from the aboveWater path of liquid cloudsWater path of ice cloudsShortwave radiation effectRange0.05 to 50.05 to 50.05 to 5Uncertainty0.06 or 40%0.06 or 20%0.04 or 15%0.05 to 1 25%Not defined100 to 1000hPa5 to 1005 to 1005 to 50 µm5 to 50 µm40%60 hPa25%35%25%35%Each uncertainty requirement is defined by the greater of the absolute and relative value and for 65%or more of the observable atmosphere at a Level-2 satellite data processing level (Figure 1.2) for allproducts except shortwave radiation effect. The shortwave radiation effect is for a seasonal, hemisphericaverage since that is the temporal/spatial domain over which it can be validated against othersensors/observational networks.Ultimately, the Project – in particular, the Project Science team – remains responsible for ensuring thePACE’s OCI can produce these geophysical data products at the prescribed uncertainty levels, whichrequires both a high-performance OCI and a validation program. With regards to the former, the ProjectScience team works closely with the OCI systems engineering team to translate science requirements intoengineering requirements and design an OCI concept that can adequately produce these geophysicalvariables. The first step in this is development of tools that allocate total uncertainties into instrument andgeophysical model performance specifications, which become Level-2 requirements (and, can besubsequently used to verify instrument performance during its development, testing, and observatoryintegration).3

Level-2 RequirementsFollowing Figure 1.1, total uncertainty, total, is defined as the root sum square of geophysical algorithm(model), systematic, and random errors:222𝜎𝑡𝑜𝑡𝑎𝑙 𝜎𝑠𝑦𝑠𝑡𝑒𝑚𝑎𝑡𝑖𝑐 𝜎𝑟𝑎𝑛𝑑𝑜𝑚 𝜎𝑚𝑜𝑑𝑒𝑙(Eq. 1.1)An example of how total baseline uncertainties might be allocated for ocean color Level-1 requirements isas follows:Data ProductWater-leaving reflectances centeredon ( 2.5 nm) 350, 360, and 385 nm(15 nm bandwidth)Water-leaving reflectances centeredon ( 2.5 nm) 412, 425, 443, 460, 475,490, 510, 532, 555, and 583 (15 nmbandwidth)Water-leaving reflectances centeredon ( 2.5 nm) 617, 640, 655, 665, 678,and 710 (15 nm bandwidth, except for10 nm bandwidth for 665 and 678 nm)Systematic Error0.0055Random Error0.0.008Model tematic Error0.0082Random Error0.0.010Model milarly, total threshold uncertainties might be allocated as follows:Data ProductWater-leaving reflectances centeredon ( 2.5 nm) 350, 360, and 385 nm(15 nm bandwidth)Water-leaving reflectances centeredon ( 2.5 nm) 412, 425, 443, 460, 475,490, 510, 532, 555, and 583 (15 nmbandwidth)Water-leaving reflectances centeredon ( 2.5 nm) 617, 640, 655, 665, 678,and 710 (15 nm bandwidth, except for10 nm bandwidth for 665 and 678 nm)Detailed discussions on defining and deriving systematic, random, and model errors appear inChapter 3, 4, and 6 of this volume [Ahmad and Franz, 2018; Franz and Karaköylü, 2018; Patt, 2018].Briefly, for PACE, systematic errors refer to image artifacts and biases, such as radiometric stability,temperature sensitivity, polarization, crosstalk, geolocation pointing knowledge, linearity, and responseversus-scan angle, among others (Figure 1.2). Random errors flow to OCI as a uniform scene SNRrequirement. Model errors encompass atmospheric correction (that is, derivation of water-leavingreflectances, the Level-1 required data product) from calibrated, geolocated top-of-atmosphere radiancescollected by OCI.4

Figure 1.2: Science data processing levels (left) and a description of OCI systematic errors.Impacts on Geophysical Data ProductsThe PACE Project expects the final OCI to produce water-leaving reflectances that fall near the baselinerequirements, and no worse than the threshold requirements. The following provides an example of howthis range of reflectances translates into geophysical data products:Data ProductTotal absorption at 443-nmPhytoplankton absorption at 443-nmNon-algal particle plus dissolved organicmatter absorption at 443-nmParticle backscattering at inty25%25%20%25%20%Chapter 5 of this volume provides the derivation of these uncertainties[McKinna and Cetinić, 2018].These optical properties were derived from water-leaving reflectances using the Generalized InherentOptical Property (GIOP) framework [Werdell et al., 2013a], as modified in Werdell et al. [2013b] andMcKinna et al. [2016].Concluding RemarksMission science requirements get translated into engineering and instrument requirements throughprogressive sub-allocation of allowable uncertainties. This chapter presents Level-1 science data productrequirements for the PACE mission (managed by NASA ESD) and describes their flow to Level-2allocations (managed by the PACE Project at Goddard Space Flight Center), which begin to define OCIperformance specifications. Sub-elements of the Project ultimate derive Level-3 (and beyond)requirements from the Level-2’s, which ultimately translate into engineering practice and the final OCIdesign concept. The remainder of this volume describes the definition and derivation of the Level-2uncertainty sub-allocations.5

Chapter 2Development of PACE OCI Pointing Knowledge andControl Requirements for GeolocationFrederick S. Patt, Science Applications International Corporation, Reston, Virginia 22.Executive SummaryThe Phytoplankton, Aerosol, Cloud, ocean Ecosystem (PACE) Ocean Color Instrument (OCI) sciencedata product quality depends in part on the accuracy of the spacecraft and instrument pointing knowledgeand control. The quality of the geolocation processing performed by the Science Data Segment (SDS)depends primarily on the accuracy of the pointing knowledge. The pointing control and stability cansignificantly affect the radiometric accuracy and integrity of the science data. The instrument calibrationresults also depend on accurate pointing control and knowledge. This chapter describes the developmentof each of these requirements.IntroductionGeolocation, the determination of viewed locations, is a key processing step for Earth remote sensinginstruments. For satellite-based sensors, geolocation entails three steps: (1) determination of the satelliteposition in its orbit; (2) determination of the sensor viewing direction, or pointing, using the satellite andsensor orientation information with the sensor geometric model; and, (3) combining these results with amodel of the Earth’s surface to determine the viewed locations. Heritage missions such as the Seaviewing Wide Field-of-view Sensor (SeaWiFS) and Moderate-resolution Imaging Spectroradiometer(MODIS) relied upon accurate orbit and pointing knowledge determination to enable geolocationrequirements to be met by forward-stream processing [e.g. Nishihama et al., 1997] and automatedmethods of geolocation assessment to verify requirements and refine the processing methods [Patt, 2011;Wolfe et al., 2011].With the wide availability of accurate orbit data from onboard Global Positioning System (GPS)receivers, determination of the sensor pointing (#2) is subject to the largest errors by far and, hence, is theprimary focus of the geolocation error budget for the OCI. Uncertainty in the sensor pointing is the resultof contributions from both the OCI and the spacecraft attitude determination and control system (ADCS).The requirements described in this document apply to the combined errors from both sources.The OCI and sp

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