418-XO-ACXPORD-0071_V_1_1.pdf

Effective Date: September 27, 2021 418-XO-ACXPORD-0071 Expiration Date: Five years from date of last signature Baseline Version 1.1 Responsible Organization: GeoXO Flight Project/Code 418

Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document

(PORD)

Signature page

Prepared by:

Electronically approved by: 09/10/2021

Erin M. Farrell Date GeoXO Flight Project, Instrument Systems Engineer NASA GSFC, Code 418

Electronically approved by: 09/30/2021

Patrick F. Conforti Date GeoXO Flight Project, Instrument Systems Engineer

Reviewed by:

Electronically approved by: 09/08/2021

Ronald L. Williams (Acting) Date GeoXO Flight Project, Instrument Manager

Approved by:

Electronically approved by: 09/27/2021

Monica Todirita Date GeoXO Flight Project, Deputy Project Manager NOAA GSFC, Code 418

/GeoXO Flight Project ACX

ACXPORD

418-XO-ACXPORD-0071, RM Version, Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX) Performance and Operational Requirements Document (PORD)

Version: 1.1 Printed by: rkhoover Printed on: Friday, December 3, 2021

No filter applied.

No sort applied.

Generated from DOORS 9.7.2.4

Contents

1 1Scope

1.1 1Identification

1.2 1Mission Review

1.3 1Document Overview

1.4 1Terminology

1.5 2Definitions

1.6 4Requirement Applicability

2 5Documents

2.1 5Applicable Documents

2.2 5Reference Documents

3 6Sensor Requirements

3.1 6Sensor Definition

3.1.1 6ACX Modes

3.1.1.1 6Safe Mode

3.1.1.2 7Normal Operational Mode

3.1.1.3 7Instrument Diagnostic Mode

3.1.1.4 8Outgas Capability

3.1.2 8On-Orbit Operations

3.1.2.1 8Zones of Reduced Data Quality

3.1.2.1.1 8Reserved

3.1.2.1.2 8REMOVED Restricted Zone

3.1.2.2 8Reserved

3.1.2.3 8Eclipse

3.1.2.4 8Operations After Maneuvers

3.1.2.4.1 8Reserved

3.1.2.4.2 8Stationkeeping

3.1.2.4.3 9Post Storage Activation

3.1.2.5 9Detector Operating Temperatures

3.2 9Normal Operational Mode Sensor Requirements

3.2.1 9Coverage

3.2.1.1 9Coverage Rate

3.2.1.2 10Flexible and Efficient Imaging Pattern

3.2.1.3 10Reserved (CCR X00041)

Project: GeoXO Flight Project ACX Module: ACXPORD Baseline Version: 1.1

Contents ii

3.2.1.4 10Simultaneity

3.2.1.5 11Data Latency

3.2.1.6 11Data Collection Overlap

3.2.2 11Channel Definitions, SNR, Dynamic Range

3.2.2.1 11Baseline

3.2.2.2 12System Spectral Resolution

3.2.2.2.1 12Spectral Response Envelope

3.2.2.2.2 13Within Channel Spectral Response Uniformity

3.2.2.2.3 13Reserved

3.2.2.3 13Reserved

3.2.3 13Spatial Resolution and Sampling

3.2.3.1 13System Modulation Transfer Function

3.2.3.2 14Spatial Response Uniformity

3.2.3.3 15Ringing from a Sharp Edge

3.2.4 15Image Navigation and Registration

3.2.4.1 15Star Sensing

3.2.4.2 15INR Performance Requirements

3.2.4.2.1 16Navigation

3.2.4.2.2 16Frame-to-Frame Registration

3.2.4.2.3 16Within Frame Registration

3.2.4.2.4 16Reserved

3.2.4.2.5 16Channel-to-Channel Registration

3.2.5 16Radiometric Accuracy and Precision

3.2.5.1 16REMOVED

3.2.5.1.1 16REMOVED

3.2.5.2 16Repeatability

3.2.5.2.1 16Pixel-to-Pixel

3.2.5.2.2 17Removed

3.2.5.2.3 17Removed

3.2.5.2.4 17Removed

3.2.5.2.5 17Removed

3.2.5.3 17Coherent Noise

3.2.5.4 17Calibration of Channels

3.2.5.5 18Spatial Uniformity of Data

3.2.5.6 18Crosstalk

3.2.5.6.1 18Channel-to-Channel

3.2.5.6.2 19Within Channel

3.2.5.7 19Blooming

Contents iii

3.2.5.8 19Quantization Step Size

3.2.5.9 19Reserved

3.2.5.10 19Polarization

3.2.5.10.1 19Polarization Control

3.2.6 20System Linearity

3.2.7 20Data Compression

3.2.7.1 20Lossless Data Compression

3.2.7.2 20Lossy Compression

3.3 20Design Requirements

3.3.1 20Reliability

3.3.2 21Mechanical Requirements

3.3.2.1 21Design Limit Loads

3.3.2.2 21Nonlinear Loads

3.3.2.3 21Yield Strength

3.3.2.4 21Ultimate Strength

3.3.2.5 22Structural Stiffness

3.3.2.6 22Unit Stiffness

3.3.2.7 22Material Properties

3.3.2.8 23Critical Members Design Values

3.3.2.9 23Redundant Members Design Values

3.3.2.10 23Selective Design Values

3.3.2.11 23Structural Reliability

3.3.2.12 23Mechanisms

3.3.2.13 24Pressurized Units

3.3.2.14 24Alignment Reference

3.3.3 24Thermal Requirements

3.3.3.1 24Temperature Limits

3.3.3.2 24Non Operational Temperature

3.3.3.3 25Thermal Control Hardware

3.3.3.4 25Detector Cooling Margin

3.3.4 25Onboard Processors Requirements

3.3.4.1 25Flight Load Non-Volatile Memory

3.3.4.2 25Commandable Reinitialization

3.3.4.3 25Deterministic Power-on Configuration

3.3.4.4 25Fail-safe Recovery Mode

3.3.5 25Flight Software Requirements

3.3.5.1 25Language and Methodology

3.3.5.2 26Flight Software Upload

Contents iv

3.3.5.3 26Flexibility and Ease of Software Modification

3.3.5.4 26Version Identifiers

3.3.5.5 26Flight Processor Resource Sizing

3.3.5.6 27Software Event Logging

3.3.5.7 27Processor Re-Start (CCR X00041)

3.3.5.7.1 27Warm Restart (CCR X00041)

3.3.5.7.2 27Autonomous Re-Start (CCR X00041)

3.3.5.8 28Memory Integrity (CCR X00041)

3.3.5.8.1 28Memory Verification (CCR X00041)

3.3.5.8.2 28Bit Error Detection and Correction (CCR X00041)

3.3.5.9 28Memory Dump

3.3.5.10 28Telemetry

3.3.6 28Power Requirements

3.3.6.1 28Power Regulators and Supplies

3.3.6.2 28Fuses

3.3.6.3 28Test Connectors

3.3.7 28Reserved (CCR X00041)

3.3.8 29Reserved

3.3.9 29Ground Support Equipment and Development Facilities

3.3.9.1 29Electrical System Test Equipment

3.3.9.2 29Flight Software Development Environment

3.3.9.3 29Shipping Container

3.3.9.4 30Instrument Emulator

4 32Design Verification Requirements

4.1 32Performance Operating Time and Trouble-Free Performance Testing

4.2 32Structural and Mechanical Verification Requirements

4.2.1 32Reserved (CCR X00041)

4.2.2 32Minimum Workmanship

4.2.3 33Testing in Flight Configuration

4.2.4 33Structural Proof Testing

4.2.5 33Modal Survey Characterization

4.2.6 34Structural Qualification

4.2.7 36Deployment and Articulation Verification

4.2.8 36Life Test

4.2.9 36Mechanical Clearance Verification

4.3 36Electromagnetic Compatibility Requirements

4.3.1 36General

Contents v

4.3.2 36Electrostatic Arc-Discharge Susceptibility

4.3.2.1 36External Surface-to-Surface direct discharge

4.3.2.2 36Deep Dielectric Charging

4.3.2.3 37ESD Characteristics

4.4 37Reserved (CCR X00041)

4.4.1 37Reserved (CCR X00041)

4.5 37Thermal Requirements

4.5.1 37General

4.5.1.1 37Test Chronology

4.5.1.2 38Thermal Test Chronology

4.5.1.3 38Pressure

4.5.2 38Thermal Vacuum

4.5.2.1 38Transition Rates

4.5.2.2 38Corona Operation

4.5.2.3 38Hot and Cold Start Demonstrations

4.5.2.4 38Heater Verification

4.5.2.5 39Flight Temperature Sensor Verification

4.5.3 39Thermal Cycling

4.5.3.1 39Spacecraft Level TV Test

4.5.3.2 39Cumulative Cycles

4.5.3.3 39Instrument Level TV Cycling

4.5.3.4 39Unit Level TV Cycling

4.5.3.5 40Ambient Pressure Thermal Cycling Substitution

4.5.3.6 40Test Temperatures

4.5.3.6.1 40Mission Allowable Temperatures

4.5.3.6.2 40Qualification, Protoflight and Acceptance Temperatures

4.5.3.6.3 41Non-operating Temperatures

4.5.3.7 41Temperature test tolerances

4.5.3.8 41Plateau Criteria

4.5.4 41Thermal Balance (TB)

4.5.4.1 41TB Applicability

4.5.4.2 41Balance Points

4.5.4.3 42TB-Instrument Configuration

4.5.4.4 42TB Accuracy and Knowledge

4.5.4.5 42TB Steady State Criteria

4.6 42Test Condition Tolerances

4.6.1 42General

4.7 43Filtering Capacity (CCR X00041)

Contents vi

5 45Acronyms

Contents vii

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ID

ACXPORD1

ACXPORD2

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ACXPORD4

ACXPORD5

ACXPORD6

ACXPORD7

ACXPORD8

ACXPORD9

ACXPORD10

ACXPORD11

ACXPORD12

ACXPORD13

Object Number

1.1

1.1.0-1

1.2

1.2.0-1

1.2.0-2

1.2.0-3

1.2.0-4

1.3

1.3.0-1

1.4

1.4.0-1

1.4.0-2

418-XO-ACXPORD-0071, RM Version, Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

1 Scope

1.1 Identification

This Performance and Operational Requirements Document (PORD) sets forth the performance requirements for the National Oceanic and Atmospheric Administration (NOAA) Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX) instrument.

1.2 Mission Review

The ACX is a hyperspectral, UV through visible imaging spectrometer used to measure environmental data as part of a 3-axis stabilized, geostationary satellite system. The ACX remotely collects imagery of the superregional region for national air quality forecasting capability, hazard forecasting, and fire pollutant forecasting and warnings.

The ACX objectives are as follows:

a) Provide new NOAA atmospheric composition operational data that will be used by NOAA and other public and private agencies to produce forecasts of air quality and pollution.

The ACX provides data to the Ground System via the spacecraft communication system. The Ground System takes the data, spacecraft telemetry data, orbit determination data and other required information and autonomously generates radiometrically calibrated and navigated data (Level 1a and Level 1b data) for the NOAA users.

The Ground System will be procured by the Government but will implement algorithms developed by the ACX contractor to satisfy performance requirements. The Ground System will calibrate and then resample the data to generate the fixed grid. Resampling requires that the raw imagery be adequately sampled to maintain radiometric accuracy after resampling.

1.3 Document Overview

This document contains all performance requirements for the ACX instrument and Ground Support Equipment (GSE). This document, the General Interface Requirements Document (GIRD), and the ACX Unique Instrument Interface Document (UIID) define all instrument to spacecraft interfaces for the ACX instrument.

1.4 Terminology

The term “TBD” means, “to be determined.” This is applied to requirements or values that have not been defined.

The contractor shall propose a requirement or value and provide a rationale for all TBD requirements. TBD requirement proposals shall be made in coordination with the government and may involve other contractors.

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ID

ACXPORD14

ACXPORD15

ACXPORD16

ACXPORD17

ACXPORD18

ACXPORD19

ACXPORD20

ACXPORD21

ACXPORD22

ACXPORD23

ACXPORD24

ACXPORD25

ACXPORD26

ACXPORD27

ACXPORD28

Object Number

1.4.0-3

1.4.0-4

1.4.0-5

1.4.0-6

1.4.0-7

1.5

1.5.0-1

1.5.0-2

1.5.0-3

1.5.0-4

1.5.0-5

1.5.0-6

1.5.0-7

1.5.0-8

1.5.0-9

418-XO-ACXPORD-0071, RM Version, Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

The contractor shall request approval from the government before proceeding with its proposed TBD requirement or value.

The term “TBR” means, “to be reviewed.” This is applied to requirements or values that are subject to review by the government and the contractor. The contractor shall review and suggest a modified value and rationale for all TBR requirements. The “TBR” provides an indication that the value may change upon review.

TBR requirement proposals shall be made in coordination with the government and may involve other contractors.

The contractor shall request approval from the government before proceeding with its proposed TBR requirement or value.

The term “TBS” means, “to be supplied.” The government will supply TBS requirements. The Government will provide a date or milestone at which each TBS requirement will be supplied.

1.5 Definitions

Throughout this document, the following definitions apply:

Accuracy: Refers to the error in a measurement that is the difference between the measurement result and the object to be measured (the measured or true value). It includes both systematic and random errors. Systematic errors must be estimated from an analysis of the experimental conditions and techniques.

Random errors can be determined, and reduced, through repeated measurements under identical conditions.

Albedo: Refers to the fraction of the solar spectrum taken from the default MODTRAN solar irradiance file (newkur.dat) that is reflected by the Earth at the top of the atmosphere assuming a Lambertian surface.

All requirements/all performance requirements/all operational requirements:

Refers to any performance characteristic or requirement in the ACX PORD, ACX UIID, and the GIRD.

Band: A set of channels.

Channel: A measurement that is an aggregate of one or more spectral samples that meets or exceeds ACX requirements.

Collection: The set of all frames from all telescopes for a single integration period.

Derived Noise Equivalent Delta Radiance (NEDN): Refers to the NEDN required to meet the Noise Equivalent Delta Temperature (NEDT) specification or Signal-to-Noise Ratio (SNR) specification.

Detector sample or element: Refers to the output of a physical detector after the Analog-to-Digital (A/D) converter and Time Delay and Integration (TDI) processing, if applicable.

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ID

ACXPORD29

ACXPORD30

ACXPORD31

ACXPORD32

ACXPORD33

ACXPORD34

ACXPORD35

ACXPORD36

ACXPORD37

ACXPORD38

ACXPORD39

Object Number

1.5.0-10

1.5.0-11

1.5.0-12

1.5.0-13

1.5.0-14

1.5.0-15

1.5.0-16

1.5.0-17

1.5.0-18

1.5.0-19

1.5.0-20

418-XO-ACXPORD-0071, RM Version, Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

Eclipse: Defined as when the solar disk is completely occulted by the Earth or Moon, as viewed from the satellite.

Fixed Grid Format: Refers to the idealized georeferenced positions for pixel locations. The fixed grid has the following characteristics:

a) The fixed grid is rectified to a GRS80 geoid viewed from the idealized geostationary position.

b) The pixels do not have the same angular separation for East/West and North/South.

c) From the viewpoint of a right-hand coordinate system of the idealized geostationary satellite with its x-axis in the direction of the velocity and the z-axis pointed at nadir, the North/South angle is determined by a rotation about the x-axis and the East/West angle is determined by a rotation about the rotated y-axis.

d) The angular separation is 140 by 140 microradians for 5 by 5 km resolution

e) The ideal sub-satellite point is at the corner of a pixel on the 140 microradians grid.

Fully Functional Configuration: Being able to perform the following functions:

scene radiance measurement; radiometric calibration; star sensing; on-orbit monitoring of calibration sources and instrument response changes; acquisition of sensor health and status data; generation of sensor, calibration, monitoring, health and status data streams; and reception and execution of command and control data.

Frame: Collection of pixels from a contiguous region as commanded by a minimum bounding rectangle.

Launch: The time between lift off and the separation of the GeoXO satellite from the launch vehicle.

Navigation: Refers to the determination of the location of each pixel relative to a fixed reference, such as fixed-grid angle coordinates.

Navigation Error: Refers to the angular error of locations in the resampled fixed-grid frame.

Pixel: Applies to data samples after resampling during the ground processing.

Polarization Sensitivity: Defined as the ratio of the difference between maximum and minimum output to the sum of the maximum and minimum output obtained when the plane of incoming 100% linearly polarized radiation is rotated through 180 degrees.

Precision: Refers to the standard deviation of a statistically meaningful number of samples of a measurement.

Registration: Refers to maintaining the spatial relationship between pixels within frames, between frames, and between channels.

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ID

ACXPORD40

ACXPORD41

ACXPORD42

ACXPORD43

ACXPORD44

ACXPORD45

ACXPORD46

ACXPORD47

ACXPORD48

Object Number

1.5.0-21

1.5.0-22

1.5.0-23

1.5.0-24

1.5.0-25

1.5.0-26

1.6

1.6.0-1

1.6.0-2

418-XO-ACXPORD-0071, RM Version, Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

SNR: Refers to the Signal-to-Noise Ratio specification.

Spectral Sample: A measurement within a channel that may or may not be aggregated for transmission to the ground.

Superregional ACX: Defined as the equivalent of a 5000 x 3000 kilometer nadir-viewed area.

Swath: Refers to any set of detector samples that are collected during a continuous scan or stepping of the detectors over the scene, in a horizontal fashion, which covers the entire horizontal extent of the scene.

Task: Repeating data collection pattern providing coverage of one or more observing regions.

Unit: A functional subdivision of a subsystem and generally a self-contained combination of items performing a function necessary for the subsystem's operation. Examples are electronics unit and sensor unit.

1.6 Requirement Applicability

The requirements in this ACX PORD pertain to the ACX ‘system’, which may include motors, optics, detectors, signal processing electronics and software, and ground processing. The ACX contractor is not responsible for the whole Ground System, but certain specifications may require some level of ground processing after collection but before data distribution, i.e. decompression, re-sampling, and calibration.

All requirements apply over the entire life of the instrument. Data performance requirements, such as Modulation Transfer Function (MTF) and Image Navigation and Registration (INR), apply to data after all ground processing, except as indicated.

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ACXPORD49

ACXPORD50

ACXPORD51

ACXPORD52

ACXPORD53

Object Number

2.1

2.1.0-1

2.2

2.2.0-1

418-XO-ACXPORD-0071, RM Version, Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

2 Documents

2.1 Applicable Documents

The following form a part of this specification to the extent specified herein.

1. CCSDS Recommendation for Space Data System Standards, Image Data Compression, CCSDS 122.0-B-2, September 2017.

2. CCSDS Recommendation for Space Data System Standards, Low- Complexity Lossless and Near-Lossless Multispectral and Hyperspectral Image Compression, CCSDS 123.0-B-2, February 2019.

3. Structural Design and Test Factors of Safety for Spaceflight Hardware, NASA, Document Number NASA-STD-5001B, August 6, 2014

4. Removed

5. Removed

6. General Environmental Verification Specification for GSFC Flight

Programs and Projects, Document Number GSFC-STD-7000A, April 22,

7. NASA-STD-8719.24, NASA Expendable Launch Vehicle Payload Safety Requirements (Base and Annex), 2018

8. Removed

9. ACX Radiances, (TBS)

10. Payload Resource Allocation Document (PRAD), Document Number 418-

XO-RAD-0037

2.2 Reference Documents

The following reference documents are in DOORS.

1. GXI General Interface Requirements Document, Document number 418-

XO-GXIGIRD-0025

2. Report Concerning Space Data System Standards GREEN BOOK:

LOSSLESS MULTISPECTRAL AND HYPERSPECTRAL IMAGE

COMPRESSION, Informational Report CCSDS 120.2-G-1

3. “SPECTRAL PREPROCESSING TRANSFORM FOR MULTISPECTRAL AND

HYPERSPECTRAL IMAGE COMPRESSION” Recommended Standard

CCSDS 122.1-B-1.

4. General Specification for Assemblies, Moving Mechanical, for Space and Launch Vehicles, Document Number MIL-A-83577B, February 1, 1988

5. Space Mechanisms Handbook, Document Number NASA

TP-1999-206988

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ACXPORD54

ACXPORD55

ACXPORD56

ACXPORD57

ACXPORD58

ACXPORD59

ACXPORD60

ACXPORD61

ACXPORD62

ACXPORD63

ACXPORD64

ACXPORD65

Object Number

3.1

3.1.1

3.1.1.0-1

3.1.1.0-2

3.1.1.0-3

3.1.1.0-4

3.1.1.0-5

3.1.1.0-6

3.1.1.1

3.1.1.1.0-1

3.1.1.1.0-2

418-XO-ACXPORD-0071, RM Version, Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

3 Sensor Requirements

3.1 Sensor Definition

3.1.1 ACX Modes

The ACX shall execute commands to individually enable and disable each autonomous function.

Rationale: Autonomous capability needs to be able to be disengaged as well.

The ACX shall initiate all commanded mode transitions in no more than 20 seconds after receipt of command.

Rationale: Mode transitions should occur rapidly for operators.

The ACX shall make limits and triggers of autonomous functions changeable by command.

Rationale: Autonomous functions should be controlled by operators if there is a special need to do so.

The ACX shall transition from its current mode to any other mode without causing permanent damage to itself.

Rationale: Mode transitions should occur without damage.

The ACX shall indicate the mode of the instrument in housekeeping telemetry.

Rationale: Knowledge of instrument modes is needed for data processing.

The ACX shall provide command and housekeeping telemetry functions in all powered modes.

Rationale: Command and housekeeping telemetry is necessary for monitoring instrument health at all times.

3.1.1.1 Safe Mode

The ACX shall implement a Safe Mode.

Rationale: The ACX needs a Safe Mode to enable straightforward storage.

The ACX shall be in a thermally and optically safe configuration for an indefinite period of time while in Safe Mode.

Rationale: Safe Mode of instrument enables a thermally and optically safe configuration for storage.

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ACXPORD67

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ACXPORD69

ACXPORD70

ACXPORD71

ACXPORD72

ACXPORD73

ACXPORD74

ACXPORD75

ACXPORD76

Object Number

3.1.1.1.0-3

3.1.1.2

3.1.1.2.0-1

3.1.1.2.0-2

3.1.1.3

3.1.1.3.0-1

3.1.1.3.0-2

3.1.1.3.0-3

3.1.1.3.0-4

3.1.1.3.0-5

3.1.1.3.0-6

418-XO-ACXPORD-0071, RM Version, Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

The ACX shall enter Safe Mode upon detection of internal faults capable of causing permanent damage to the instrument.

Rationale: The ACX needs to employ the Safe Mode after fault detection to ensure that there is time for recovery.

3.1.1.2 Normal Operational Mode

The ACX shall be in a fully functional configuration while in Normal Operational Mode.

Rationale: Normal mode is used for observations that require full functionality.

The ACX shall meet all performance requirements while in Normal Operational Mode without receiving commands or data loads for a minimum of 7 days.

Rationale: Autonomy is required for a period of 7 days, without impacting performance.

3.1.1.3 Instrument Diagnostic Mode

The ACX shall implement an Instrument Diagnostic Mode.

Rationale: Diagnostic mode is needed for diagnosing anomalies.

The ACX shall be in a fully functional configuration while in Instrument Diagnostic Mode.

Rationale: Diagnostic mode must be fully functional.

The ACX shall by command send selected channels while in Instrument Diagnostic Mode.

Rationale: Diagnostic mode will afford commandable channel engagement for diagnosing anomalies.

The ACX shall by command send the individual measurement in those cases where Time Delay and Integration (TDI) data is digitally processed off the focal plane while in Instrument Diagnostic Mode.

Rationale: Diagnostic mode will send data from TDI if employed to help in validation and in assessing anomalies.

The ACX shall by command send data from all detectors while in Instrument Diagnostic Mode without exceeding the telemetry allocation given to ACX.

Rationale: Diagnostic mode will send data from all detectors to help in validation and in assessing anomalies.

The ACX shall by command send the same data both compressed and uncompressed if the data is capable of being compressed while in Instrument Diagnostic Mode.

Rationale: Diagnostic mode will send compressed and uncompressed to help in validation and in assessing anomalies.

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ACXPORD77

ACXPORD78

ACXPORD79

ACXPORD80

ACXPORD81

ACXPORD82

ACXPORD83

ACXPORD84

ACXPORD85

ACXPORD86

ACXPORD87

ACXPORD88

ACXPORD89

ACXPORD90

ACXPORD91

Object Number

3.1.1.3.0-7

3.1.1.3.0-8

3.1.1.4

3.1.1.4.0-1

3.1.1.4.0-2

3.1.2

3.1.2.1

3.1.2.1.1

3.1.2.1.2

3.1.2.2

3.1.2.3

3.1.2.3.0-1

3.1.2.4

3.1.2.4.1

3.1.2.4.2

418-XO-ACXPORD-0071, RM Version, Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

The ACX shall by command send all bits from the A to D converter while in Instrument Diagnostic Mode.

Rationale: Diagnostic mode will send all bits to help in validation and in assessing anomalies.

The ACX shall by command send dwell data (increased samples per second of a particular telemetry measurand) while in Diagnostic Mode.

Rationale: Diagnostic mode dwell data will help in validation and in assessing anomalies.

3.1.1.4 Outgas Capability

The ACX shall sublimate and evaporate contaminants from hardware to prevent contamination from jeopardizing performance while in Outgas Mode.

Rationale: Diagnostic mode will have an outgas capability to ensure that the instrument has contaminants removed before operations.

The post-launch outgas period shall be no longer than 14 days.

Rationale: Outgassing should occur relatively quickly to afford time for PLT testing in 6 months.

3.1.2 On-Orbit Operations

3.1.2.1 Zones of Reduced Data Quality

3.1.2.1.1 Reserved

3.1.2.1.2 REMOVED Restricted Zone

3.1.2.2 Reserved

3.1.2.3 Eclipse

During eclipse season, the ACX shall meet performance requirements.

Rationale: Eclipse season is the approximately 6 week period around the equinoxes.

3.1.2.4 Operations After Maneuvers

3.1.2.4.1 Reserved

3.1.2.4.2 Stationkeeping

Page 9 of 45 Printed Friday, December 3, 2021

ID

ACXPORD92

ACXPORD93

ACXPORD94

ACXPORD95

ACXPORD96

ACXPORD97

ACXPORD98

ACXPORD99

ACXPORD100

ACXPORD101

ACXPORD102

Object Number

3.1.2.4.2.0-1

3.1.2.4.3

3.1.2.4.3.0-1

3.1.2.5

3.1.2.5.0-1

3.1.2.5.0-2

3.2

3.2.1

3.2.1.1

3.2.1.1.0-1

3.2.1.1.0-2

418-XO-ACXPORD-0071, RM Version, Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

The ACX shall meet all radiometric, coverage and INR requirements within 2 minutes after the spacecraft interface has returned to being within specification following spacecraft stationkeeping maneuvers.

Rationale: If the spacecraft maneuver causes interface exceedances, the instrument recovery will occur in this short duration after the interface is restored to nominal conditions.

3.1.2.4.3 Post Storage Activation

The ACX shall meet all requirements within 2 days of turn-on after post storage activation.

Rationale: After activation, ACX will cool for operations in this time listed here.

3.1.2.5 Detector Operating Temperatures

The ACX detector setpoint temperature shall be selectable by command to ensure radiometric performance during degradation at end of life.

Rationale: This provides for set point temperature adjustments near the operating temperature range that may be needed due to gain changes or troubleshooting.

Knowledge of the ACX detector temperature shall be less than +/- 0.1 K.

Rationale: ACX may be thermally sensitive due to its detectors and thermal telemetry will provide information for potential corrections and troubleshooting.

3.2 Normal Operational Mode Sensor Requirements

3.2.1 Coverage

3.2.1.1 Coverage Rate

Note that these coverage requirements define a capability and not a definitive operational scenario. Rather, NOAA anticipates operating ACX in an asynchronous manner that uses information from other instruments and models to identify potential regions for scanning/stepping by ACX. To perform its tasks, commanding of ACX for these targeted observations will be based on priorities and availability.

The ACX shall acquire concurrently within 1 hour:

a) Superregional_ACX or another user programmed region consistent with this coverage rate

b) Any other observations required to meet radiometric and INR requirements

Rationale: When covering the superregional ACX, the coverage including all calibrations will take 1 hour or less to ensure a timely coverage rate for the instrument that may be used to cover smaller areas in proportionally smaller times.

Page 10 of 45 Printed Friday, December 3, 2021

ID

ACXPORD103

ACXPORD104

ACXPORD105

ACXPORD106

ACXPORD107

ACXPORD108

ACXPORD109

ACXPORD110

ACXPORD111

ACXPORD112

ACXPORD113

ACXPORD114

Object Number

3.2.1.1.0-3

3.2.1.1.0-4

3.2.1.2

3.2.1.2.0-1

3.2.1.2.0-2

3.2.1.2.0-3

3.2.1.2.0-4

3.2.1.2.0-5

3.2.1.3

3.2.1.3.0-1

3.2.1.4

3.2.1.4.0-1

418-XO-ACXPORD-0071, RM Version, Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

The ACX shall interrupt current operations by command and start the acquisition of a new frame, after a frame coordinate upload, within 30 seconds.

Rationale: The ACX must be commandable to cover regions of interest. Regions will be covered with the same instrument coverage rate, with smaller areas taking proportionally less time.

All corresponding frames in consecutive revisits shall be spaced at an average time of no more than 1 hour with peak deviation of no more than +/- 30 seconds.

Rationale: The ACX revisit of the entire region should be repeatable if commanded with a regular cadence with limited temporal deviation to support operations.

3.2.1.2 Flexible and Efficient Imaging Pattern

The ACX sensor shall observe an area of commanded size anywhere within the field of regard when commanded.

Rationale: Permits flexible tasking of ACX to regions of interest.

The scan area and geographic location shall be selectable from one frame to the next.

Rationale: Permits flexible tasking of ACX to regions of interest.

The ACX shall be designed such that the Earth-scanning patterns are fully programmable on-orbit.

Rationale: Permits flexible tasking of ACX to regions of interest.

The ACX shall accept fixed grid coordinates for all imaging patterns.

Rationale: Permits mapping to fixed grid.

The ACX shall set the center location of each frame to Fixed Grid Frame coordinates specified by command.

Rationale: Permits centering on fixed grid point for ease of Fixed Grid mapping.

3.2.1.3 Reserved (CCR X00041)

Reserved (CCR X00041)

3.2.1.4 Simultaneity

Corresponding pixels in all spectral channels shall be calculated from detector samples that are collected within 20 seconds of each other.

Rationale: Spectrally simultaneous observations provide observations of the same features and avoid artifacts in resulting data.

Page 11 of 45 Printed Friday, December 3, 2021

ID

ACXPORD115

ACXPORD116

ACXPORD117

ACXPORD118

ACXPORD119

ACXPORD120

ACXPORD121

ACXPORD122

ACXPORD123

Object Number

3.2.1.4.0-2

3.2.1.5

3.2.1.5.0-1

3.2.1.6

3.2.1.6.0-1

3.2.2

3.2.2.1

3.2.2.1.0-1

3.2.2.1.0-2

418-XO-ACXPORD-0071, RM Version, Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

All adjacent pixels shall be calculated from detector samples collected within 45 seconds of each other.

Rationale: This limits shearing in an image composed of multiple individual observations.

3.2.1.5 Data Latency

The ACX shall contribute to the total data latency for the Level 1b product of no more than 10 minutes for any coverage region.

Data latency is measured from the time the instrument acquires all samples for a scene to the time the image is available for dissemination on the ground as Level 1b data. The ACX contribution to data latency includes delay of delivery of data to the spacecraft and delay due to ground algorithm processing (i.e., resampling and INR).

Rationale: Latency between the last observation of the input data to the level 1b processing and the availability of the data for further processing should be as short as practical.

3.2.1.6 Data Collection Overlap

The ACX shall generate each pixel from detector samples contained in a single collection.

Rationale: Requirement limits resampling from different collections at different times.

3.2.2 Channel Definitions, SNR, Dynamic Range

3.2.2.1 Baseline

The ACX shall collect hyperspectral data in the range 0.300 – 0.500 um and

0.540 – 0.740 um.

Rationale: A large number of narrow adjacent spectral samples allows for flexibility for current and future algorithm development to distinguish atmospheric species.

The ACX SNR shall be greater than or equal to values in the Minimum SNR table below. The SNR for any wavelength not listed in the Minimum SNR Table will be determined by linear interpolation of the two nearest SNR values in the Table 1.

Rationale: These SNR values are needed to detect atmospheric radiance properties to enable higher level product generation.

Page 12 of 45 Printed Friday, December 3, 2021

ID

ACXPORD123

ACXPORD124

ACXPORD125

ACXPORD126

Object Number

3.2.2.1.0-2

3.2.2.1.0-3

3.2.2.2

3.2.2.2.1

418-XO-ACXPORD-0071, RM Version, Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

Table 1. Minimum SNR Table

Nominal Center Wavelength (um)

Minimum SNR Value

0.300 20

0.306 120

0.325 1650

0.355 1650

0.390 1250

0.500 1250

0.540 1250

0.635 1250

0.685 900

0.740 900

0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75

Wavelength ( m)

S N

R

Figure 1. ACX signal-to-noise ratio as a function of wavelength. Note the linearly interpolated SNR value of 1145 at a wavelength of 0.650 um.

All ACX channels shall have sufficient dynamic range for measurements between 0 to Nmax, which is defined as 110% albedo solar spectrum, without saturation of any detector element.

Rationale: Dynamic range of Earth scene signals need to be observed without saturation. Non-Lambertian clouds can yield more than 110% albedo response.

3.2.2.2 System Spectral Resolution

3.2.2.2.1 Spectral Response Envelope

Page 13 of 45 Printed Friday, December 3, 2021

ID

ACXPORD127

ACXPORD128

ACXPORD129

ACXPORD130

ACXPORD131

ACXPORD132

ACXPORD133

ACXPORD134

ACXPORD135

Object Number

3.2.2.2.1.0-1

3.2.2.2.2

3.2.2.2.2.0-1

3.2.2.2.3

3.2.2.3

3.2.3

3.2.3.1

3.2.3.1.0-1

3.2.3.1.0-2

418-XO-ACXPORD-0071, RM Version, Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

The ACX spectral resolution shall be 0.0006 um, with at least three spectral samples per resolution element.

Rationale: Spectral resolution is important for retrieving molecular column density profiles used in air quality assessment.

3.2.2.2.2 Within Channel Spectral Response Uniformity

The variation in radiance measured between the 1% (TBR) as-built response points in each spectral channel due to residual spectral differences over the focal plane shall be less than the derived noise for all channels, when viewing the simulated upwelling radiance data sets in supplied radiance spectrum (with the assumption that clouds have Lambertian reflectance with an albedo not less than 50%).

Rationale: Spectral artifacts in the Level 1b data should not be larger than the noise level.

3.2.2.2.3 Reserved

3.2.2.3 Reserved

3.2.3 Spatial Resolution and Sampling

3.2.3.1 System Modulation Transfer Function

The spatial resolution is defined by the sensor system sinusoidal MTF. The following MTF values (exact specification is in cycles/rad) are consistent with a resolution of 5 km x 5 km equivalent area in all channels, but may have a different form factor. The spatial frequencies, when referenced to kilometers, are measured at nadir.

The ACX system MTF shall meet the requirements in the MTF Coarse Spatial Direction Requirements Table over the coverage area, in the coarse resolution direction and the MTF Fine Spatial Direction Requirements Table over the coverage area in the fine resolution directions, after any ground processing, in the presence of jitter, when averaged over all resampling phases of the detector sample grid to pixel grid, and after any lossy compression/decompression. If both coarse and fine directions are equal, the MTF Equal Spatial Directions Requirements Table replaces the coarse and fine tables.

Page 14 of 45 Printed Friday, December 3, 2021

ID

ACXPORD135

ACXPORD136

Object Number

3.2.3.1.0-2

3.2.3.2

418-XO-ACXPORD-0071, RM Version, Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

Table 2. MTF Equal Spatial Directions Requirements Table

All Channels

Spatial Period

(km/cyc)

Spatial Frequency

(cyc/rad)

System MTF

40.0 900.0 0.90 (TBR)

20.0 1800.0 0.73 (TBR)

13.3 2700.0 0.53 (TBR)

10.0 3600.0 0.32 (TBR)

Table 3. MTF Coarse Spatial Direction Requirements Table

All Channels

Spatial Period

(km/cyc)

Spatial Frequency

(cyc/rad)

System MTF

35.2 1022.7 0.90 (TBR)

17.6 2045.5 0.73 (TBR)

11.7 3068.2 0.53 (TBR)

8.8 4090.9 0.32 (TBR)

Table 4. MTF Fine Spatial Direction Requirements Table

All Channels

Spatial Period

(km/cyc)

Spatial Frequency

(cyc/rad)

System MTF

12.0 3000.0 0.90 (TBR)

6.0 6000.0 0.73 (TBR)

4.0 9000.0 0.53 (TBR)

3.0 12000.0 0.32 (TBR)

3.2.3.2 Spatial Response Uniformity

Page 15 of 45 Printed Friday, December 3, 2021

ID

ACXPORD137

ACXPORD138

ACXPORD139

ACXPORD140

ACXPORD141

ACXPORD142

ACXPORD143

ACXPORD144

ACXPORD145

Object Number

3.2.3.2.0-1

3.2.3.2.0-2

3.2.3.3

3.2.3.3.0-1

3.2.4

3.2.4.1

3.2.4.1.0-1

3.2.4.2

3.2.4.2.0-1

418-XO-ACXPORD-0071, RM Version, Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

Effects of co-registration and jitter may be ignored for the purposes of evaluating these requirements.

The normalized radiance difference due to spatial response differences between corresponding pixels in any two spectral channels located X (continuous variable) microradians from an edge of a 1000 by 1000 microradian or larger target with radiance equal to Nmax surrounded by a large region of radiance equal to or less than 5% Nmax shall be less than 4% of the step function for an rms over the sampling-to-edge phasing and the channel-to-channel relative phasing. The values of X include all distances between ± 1400 microradians in both directions (coarse direction, fine direction, or equal directions).

Rationale: Requirement limits signal contamination from bright scene regions into dark scene regions.

3.2.3.3 Ringing from a Sharp Edge

For both the North/South and East/West edges, the ACX shall not overshoot the top of an edge or undershoot the bottom of edge by more than 2% of the height of the edge where:

a) The height and the overshoot/undershoot are measured in radiance units.

b) The edge delineates a 10% albedo region from a 90% albedo.

c) The overshoot is averaged over all resampling phases of the detector sample grid to fixed-grid and edge position to detector sample grid.

Rationale: Requirement limits ringing response or overshoot near a sharp edge.

3.2.4 Image Navigation and Registration

3.2.4.1 Star Sensing

If autonomous star sensing is required to meet navigation requirements, the ACX shall have an on-board star catalog provided by the ACX vendor, which is loadable and modifiable from the ground and covers a span of two weeks.

Rationale: If employed, star sensing will require a star catalog and not rely on operators.

3.2.4.2 INR Performance Requirements

All INR requirements listed herein refer to location error of the fixed-grid pixels;

i.e., the requirements apply to the end-to-end system, taking all instrument, spacecraft, and ground processing effects into account. Unless otherwise specified, all INR requirements in this document are specified as North/South and East/West angles, in microradians, 3-sigma, and all daily hours of operation.

Page 16 of 45 Printed Friday, December 3, 2021

ID

ACXPORD146

ACXPORD147

ACXPORD148

ACXPORD149

ACXPORD150

ACXPORD151

ACXPORD152

ACXPORD153

ACXPORD154

ACXPORD155

ACXPORD156

ACXPORD157

ACXPORD158

ACXPORD159

ACXPORD160

ACXPORD161

ACXPORD162

Object Number

3.2.4.2.0-2

3.2.4.2.1

3.2.4.2.1.0-1

3.2.4.2.1.0-2

3.2.4.2.2

3.2.4.2.2.0-1

3.2.4.2.3

3.2.4.2.3.0-1

3.2.4.2.4

3.2.4.2.5

3.2.4.2.5.0-1

3.2.4.2.5.0-2

3.2.5

3.2.5.1

3.2.5.1.1

3.2.5.2

3.2.5.2.1

418-XO-ACXPORD-0071, RM Version, Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

In the context of ACX INR, 3-sigma error is defined to be equal to the 99.73rd percentile of the absolute values of all INR error observations collected over all hours of operation. When INR requirements are temporarily suspended, due to Sun/Earth geometry or maneuver outages (including recovery time), the raw errors during the requirements suspension period should be ignored.

3.2.4.2.1 Navigation

Navigation error is the angular location knowledge error of pixels or features in a frame.

The ACX navigation error shall not exceed 53 urad, 3-sigma, per axis.

Rationale: This uses same Government methodology as the PRAD.

3.2.4.2.2 Frame-to-Frame Registration

Frame-to-frame registration error shall not exceed 46 urad, 3-sigma, per axis.

Frame-to-frame registration error is the difference in navigation error for any given pixel in two consecutive frames within the same channel.

Rationale: This uses same Government methodology as the PRAD.

3.2.4.2.3 Within Frame Registration

Within a frame in the same channel, any two pixels shall be separated by the known fixed distance to within a max of 53 urad, 3-sigma, measured radially.

Rationale: This uses same Government methodology as the PRAD.

3.2.4.2.4 Reserved

3.2.4.2.5 Channel-to-Channel Registration

Channel-to-channel registration error, or co-registration, is the difference in navigation errors between spectral channels for any given pixel in the same frame.

Co-registration errors between any two spectral channels shall not exceed a max of 28 urad, on a 3-sigma, per axis basis.

Rationale: This uses same Government methodology as the PRAD.

3.2.5 Radiometric Accuracy and Precision

3.2.5.1 REMOVED

3.2.5.1.1 REMOVED

3.2.5.2 Repeatability

3.2.5.2.1 Pixel-to-Pixel

Page 17 of 45 Printed Friday, December 3, 2021

ID

ACXPORD163

ACXPORD164

ACXPORD165

ACXPORD166

ACXPORD167

ACXPORD168

ACXPORD169

ACXPORD170

Object Number

3.2.5.2.1.0-1

3.2.5.2.2

3.2.5.2.3

3.2.5.2.4

3.2.5.2.5

3.2.5.3

3.2.5.3.0-1

3.2.5.4

418-XO-ACXPORD-0071, RM Version, Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

For all channels, while viewing a stable, uniform calibration source over expected geostationary environmental conditions and calibration frequency, the ACX shall have a pixel-to-pixel repeatability less than the derived NEDN. Channels will be characterized as if viewing a 100% albedo calibration source.

Rationale: Pixel-to-pixel repeatability should be less than the required noise level to not interfere with scene data collection.

3.2.5.2.2 Removed

3.2.5.2.3 Removed

3.2.5.2.4 Removed

3.2.5.2.5 Removed

3.2.5.3 Coherent Noise

For all channels, while viewing a stable, uniform calibration source over expected geostationary environmental conditions and calibration frequency, the ACX shall have no spatial coherent noise spectral component exceedances. The spatial coherent noise is defined as the variation in the 2-D Fourier transform of the pixel output of a square region of 0.084 radian by 0.084 radian following all calibration, sampling and detrending. An exceedance is defined as any spatial frequency whose scaled Fourier coefficients are greater than 25 percent of the derived NEDN. The scaled Fourier coefficients are defined using the following equations to scale the amplitude to match the amplitude of a single harmonic.

N j kj NljxlkX

)1)(1( 1 ),(),(

Ni

N e /2

M j kj MjlXklX

)1)(1( 12 ),(),(

Mi

M e /2

NM

X X a

Where x(j,l) are the radiances, N and M are the image size in pixels and Xa are the scaled Fourier coefficients. Detrending allows the removal of scene trends by subtracting the filtered scene using a square box car filter that is 10% of the minimum scene dimension. Edge effects of detrending may be reduced by using a symmetric boundary condition.

Note: The width of bin is defined by the fixed grid spacing. Channels will be characterized as if viewing a 100% albedo calibration source.

Rationale: Coherent noise in a level 1b product should be less than the one fourth of the noise level to avoid interference.

3.2.5.4 Calibration of Channels

Page 18 of 45 Printed Friday, December 3, 2021

ID

ACXPORD171

ACXPORD172

ACXPORD173

ACXPORD174

ACXPORD175

ACXPORD176

ACXPORD177

ACXPORD178

ACXPORD179

Object Number

3.2.5.4.0-1

3.2.5.4.0-2

3.2.5.4.0-3

3.2.5.4.0-4

3.2.5.5

3.2.5.5.0-1

3.2.5.5.0-2

3.2.5.6

3.2.5.6.1

418-XO-ACXPORD-0071, RM Version, Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

The ACX shall have an on-board calibration capability.

Rationale: An on-board calibration capability of high quality improves near real time calibration accuracy compared to that of vicarious calibration.

The ACX shall have a calibration capability for all channels that provides accuracy with traceability to NIST of +/- 3% or less in the earth albedo measurements for the scene of 100% albedo.

Rationale: Traceability to NIST (as documented in the SOW) provides improved absolute accuracy for near real time calibration.

The ACX shall have a calibration capability for all channels that provides drift in absolute calibrated radiances of no more than 2% (TBR) over the ACX operational lifetime.

Rationale: Instrument degradation over the lifetime, if not corrected in processing, may be misunderstood and changing geophysical parameters over time. Degradation of the instrument and correction method(s) need to be understood and reported to the Government for use in near real time through the instrument vendor calibration algorithms (updating calibration coefficients).

The ACX shall have a calibration capability for all channels that provides RMS repeatability of 0.2% or less. This requirement is met when no fewer than N independent calibrations are performed as closely as possible together in time and the RMS variation in each calibration coefficient is less than the specified level. N is the number of calibrations required to state at the 90% confidence level that the requirement has been met.

Rationale: Short term RMS repeatability of this level ensures high quality relative accuracy calibration.

3.2.5.5 Spatial Uniformity of Data

The ACX shall have less than 0.3% (TBR) change in response in the calibrated pixel data over the field of regard while viewing a stable, uniform calibration source over expected geostationary environmental conditions and calibration frequency.

Channels will be characterized as if viewing a 100% albedo calibration source.

Rationale: Calibrated data needs to spatial uniform so that variations in the data are not misinterpreted to be real signal variations.

3.2.5.6 Crosstalk

3.2.5.6.1 Channel-to-Channel

Page 19 of 45 Printed Friday, December 3, 2021

ID

ACXPORD180

ACXPORD181

ACXPORD182

ACXPORD183

ACXPORD184

ACXPORD185

ACXPORD186

ACXPORD187

ACXPORD188

ACXPORD189

ACXPORD190

ACXPORD191

Object Number

3.2.5.6.1.0-1

3.2.5.6.2

3.2.5.6.2.0-1

3.2.5.7

3.2.5.7.0-1

3.2.5.8

3.2.5.8.0-1

3.2.5.9

3.2.5.10

3.2.5.10.1

3.2.5.10.1.0-1

3.2.5.10.1.0-2

418-XO-ACXPORD-0071, RM Version, Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

The ACX channel-to-channel (electrical, optical, spatial, spectral) crosstalk shall be less than the derived NEDN. Channel-to-channel crosstalk is defined as the change in any channel output when one channel's illumination is changed from

0.1 Nmax to a radiance of Nmax while all other channels remain illuminated at a radiance level less than 0.1 Nmax.

Rationale: Crosstalk between any spectral channels needs to be less than the noise level to minimize spectral artifacts in the data that may be misunderstood to be real features in the data.

3.2.5.6.2 Within Channel

Non-adjacent pixel to pixel within channel cross talk, not including diffraction, shall be less than the derived NEDN. Within channel crosstalk is defined as the change in any non-adjacent pixel when one pixel’s radiance is changed from 0.1 Nmax to a radiance of Nmax while all other pixels in the same band remain illuminated at a radiance level less than 0.1 Nmax.

Rationale: Crosstalk within a spectral channel needs to be less than the noise level to minimize artifacts in the data that may be misunderstood to be real features in the data.

3.2.5.7 Blooming

In all directions from the edge of a 500 by 500 microradian bright target at twice Nmax, all detector outputs in all channels shall recover to normal operation within 600 microradians.

Rationale: Specular solar glint regions are limited to within this spatial distance from the solar sub-point.

3.2.5.8 Quantization Step Size

The quantizing step size for all detector samples shall be less than half the derived NEDN.

Rationale: Signal quantization by the analog to digital converter should not be the driver in the noise budget in order to avoid having discrete jumps in signal level that can lead to digital artifacts (blocky) data.

3.2.5.9 Reserved

3.2.5.10 Polarization

3.2.5.10.1 Polarization Control

Channels with center wavelengths greater than 0.5 um and less than 0.5um shall have less than 5% polarization sensitivity to the incoming light at all Earth-viewing angles.

Rationale: Polarization sensitivity should be small to limit signal variations with angle. (CCR X00041)

Reserved (CCR X00041)

Page 20 of 45 Printed Friday, December 3, 2021

ID

ACXPORD192

ACXPORD193

ACXPORD194

ACXPORD195

ACXPORD196

ACXPORD197

ACXPORD198

ACXPORD199

ACXPORD200

ACXPORD201

ACXPORD202

ACXPORD203

ACXPORD204

Object Number

3.2.6

3.2.6.0-1

3.2.7

3.2.7.0-1

3.2.7.0-2

3.2.7.1

3.2.7.1.0-1

3.2.7.2

3.2.7.2.0-1

3.2.7.2.0-2

3.3

3.3.1

3.3.1.0-1

418-XO-ACXPORD-0071, RM Version, Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

3.2.6 System Linearity

The ACX shall have linear radiometric response, before calibration, such that all points within the dynamic range vary from a linear best fit by no more than 1% of Nmax.

Rationale: Detectors may not be perfectly linear, but small deviations can be well corrected.

3.2.7 Data Compression

If needed, the ACX shall perform data compression on all data.

Rationale: Data rates may be excessive for downlink without compression.

The ACX may perform lossy data compression.

Rationale: Constraint on application is not to degrade data beyond performance levels

3.2.7.1 Lossless Data Compression

Lossless data compression shall be in accordance with Applicable Document 1 and Applicable Document 2.

Rationale: Lossless data compression when used will follow these references.

3.2.7.2 Lossy Compression

If performed, lossy compression shall not prevent the ACX from meeting requirements, most notably MTF, SNR, and coherent noise.

Rationale: Calibration data needs to be a high quality so nominally it should not be compressed as it may impact performance. Reference documents provide additional information on data compression.

All calibration data shall be lossless compressed or uncompressed.

Rationale: Calibration data needs to be a high quality so nominally it should not be compressed as it may impact performance.

3.3 Design Requirements

3.3.1 Reliability

The ACX shall demonstrate by analysis a…