Attachment B_ACX_ Final PORD.pdf

Effective Date: October 04, 2023 418-XO-ACXPORD-0121 Responsible Organization: GeoXO Flight Project/Code 418 Baseline Version 1.0 ii

To verify the correct version of this document, please contact the GeoXO Series Configuration Management Office

Geostationary Extended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD) Signature page

Prepared by:

Electronically approved by:

08/07/2023

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

Reviewed by:

08/16/2023

Phillip A. Driggers Date GeoXO Flight Project, Instrument Manager

Electronically approved by: 08/21/2023 Sergey Krimchansky Date GeoXO Flight Project, Instrument Systems Manager

Approved by:

08/11/2023

Steven W. Bidwell Date GeoXO Flight Project, Project Manager

10/04/2023

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

/GeoXO Flight Project ACX

ACXPORD

418-XO-ACXPORD-0121, RM Version, Geostationary eXtended Observations (GeoXO) Atmospheric Composition (ACX) Performance and Operational Requirements Document (PORD)

Version: 1.0 Printed by: rkhoover Printed on: Thursday, October 5, 2023

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 6Documents

2.1 6Applicable Documents

2.2 6Reference Documents

3 7Sensor Requirements

3.1 7Sensor Definition

3.1.1 7ACX Modes

3.1.1.1 7Safe Mode

3.1.1.2 8Normal Operational Mode

3.1.1.3 8Diagnostic Mode

3.1.1.4 9Outgassing

3.1.2 9On-Orbit Operations

3.1.2.1 9Scanning Across the Sun

3.1.2.2 9Eclipse

3.1.2.3 9Operations After Maneuvers

3.1.2.3.1 9Spacecraft Maneuvers

3.1.2.3.2 10Post Storage Activation

3.1.2.4 10Detector Operating Temperatures

3.2 10Normal Operational Mode Sensor Requirements

3.2.1 10Coverage

3.2.1.1 10Coverage Rate

3.2.1.2 11Flexible and Efficient Imaging Pattern

3.2.1.3 11Simultaneity

3.2.1.4 11Data Latency

3.2.2 12Channel Definitions, SNR, Dynamic Range

3.2.2.1 12Baseline

3.2.2.2 14System Spectral Resolution

Project: GeoXO Flight Project ACX Module: ACXPORD Baseline Version: 1.0

Contents ii

3.2.2.2.1 14Spectral Response Envelope

3.2.2.2.2 14Within Channel Spectral Response Uniformity

3.2.2.2.3 15Channel Center Wavelength Knowledge

3.2.3 15Spatial Resolution and Sampling

3.2.3.1 15System Modulation Transfer Function

3.2.3.2 16Spatial Response Uniformity

3.2.3.3 16Ringing from a Sharp Edge

3.2.4 16Image Navigation and Registration

3.2.4.1 16Star Sensing

3.2.4.2 17INR Performance Requirements

3.2.4.2.1 17Navigation

3.2.4.2.2 17Frame-to-Frame Registration

3.2.4.2.3 17Within Frame Registration

3.2.4.2.4 17Channel-to-Channel Registration

3.2.5 17Radiometric Accuracy and Precision

3.2.5.1 17Repeatability

3.2.5.1.1 17Pixel-to-Pixel

3.2.5.2 18Coherent Noise

3.2.5.3 18Calibration of Channels

3.2.5.4 19Spatial Uniformity of Data

3.2.5.5 19Crosstalk

3.2.5.5.1 19Channel-to-Channel

3.2.5.5.2 19Within Channel

3.2.5.6 20Blooming

3.2.5.7 20Quantization Step Size

3.2.5.8 20Reserved

3.2.5.9 20Polarization

3.2.5.9.1 20Polarization Control

3.2.6 20System Linearity

3.2.7 20Data Compression

3.2.7.1 21Lossless Data Compression

3.2.7.2 21Lossy Compression

3.2.7.3 21Vizualization Algorithm

3.2.7.4 21Stray Light

4 22Design Requirements

4.1 22Reliability

4.2 22Redundancy

Contents iii

4.2.1 22Redundant Component Selectability

4.2.2 22Interchangeability of Flight Model Units

4.2.3 22Reserved

4.3 22Mechanical Requirements

4.3.1 22Design Limit Loads

4.3.2 23Yield Strength

4.3.3 23Ultimate Strength

4.3.4 24Unit Stiffness

4.3.5 24Critical Members Design Values

4.3.6 24Redundant Members Design Values

4.3.7 24Selective Design Values

4.3.8 24Fracture Control

4.3.9 25Mechanisms

4.3.10 26Pressurized Units

4.3.11 26Alignment Reference

4.3.12 26Precision Component Assembly

4.4 26Thermal Requirements

4.4.1 26Mission Allowable Temperatures

4.4.2 27Thermal Gradients

4.4.3 27Non-Operational Temperatures

4.4.4 27Thermal Control Hardware

4.4.5 27Detector Cooling Margin

4.4.6 28Radiator

4.4.7 28Heat Pipe (Two-phase Heat Transfer Device)

4.5 28Power Requirements

4.5.1 28Power Regulators and Supplies

4.5.2 28Fuses

4.5.3 29Covers for test Connectors

4.5.4 29Keyed Connectors

4.6 29Onboard Processors Requirements

4.6.1 29Flight Load Non-Volatile Memory

4.6.2 29Commandable Reinitialization

4.6.3 29Deterministic Power-on Configuration

4.6.4 29Fail-safe Recovery Mode

4.7 29Flight Software Requirements

4.7.1 29Language and Methodology

4.7.2 29Flight Software Upload

4.7.3 30Flexibility and Ease of Software Modification

Contents iv

4.7.4 30Version Identifiers

4.7.5 30Flight Processor Resource Sizing

4.7.6 31Software Event Logging

4.7.7 31Warm Restart

4.7.7.1 31Processor Re-Start

4.7.7.2 32Autonomous Re-Start

4.7.8 32Memory Integrity

4.7.8.1 32Memory Verification

4.7.8.2 32Bit Error Detection and Correction

4.7.9 32Memory Dump

4.7.10 32Telemetry Cadence and Dwell Control

4.7.11 32Long-Duration Test

4.7.12 32Unnecessary and Unreachable Software

5 33Ground Support Equipment and Development

5.1 33Electrical System Test Equipment

5.2 33Flight Software Development Environment

5.3 33Ground Processing Demonstration System

5.4 34FM and GSE Shipping Containers

6 35ACX Simulators

6.1 35ACX Instrument Hardware Simulator (ACX-IHS)

6.2 35ACX Instrument Software Simulator (ACX-ISS)

7 37FM Design Verification Requirements

7.1 37Powered-on Operating Time and Trouble-Free Performance Testing

7.2 37Structural and Mechanical Verification Requirements

7.2.1 37Mechanical Test Factors and Duration

7.2.2 39Minimum Workmanship

7.2.3 40Testing in Flight Configuration

7.2.4 40Structural Proof Testing

7.2.5 40Modal Survey Characterization

7.2.6 41Structural Qualification

7.2.7 41Deployment and Articulation Verification

7.2.8 41Life Test

7.2.9 41Mechanical Clearance Verification

7.3 42Electromagnetic Compatibility Verification

7.3.1 42General

7.3.2 42Electrostatic Arc-Discharge Susceptibility

Contents v

7.3.2.1 42External Surface-to-Surface direct discharge

7.3.2.2 42Deep Dielectric Charging

7.3.2.3 42ESD Characteristics

7.4 43Thermal Test Requirements

7.4.1 43General

7.4.1.1 43Thermal Test Chronology

7.4.1.2 43Pressure

7.4.2 43Thermal Vacuum

7.4.2.1 43Transition Rates

7.4.2.2 44Corona Operation

7.4.2.3 44Hot and Cold Start Demonstrations

7.4.2.4 44Heater Verification

7.4.2.5 44Flight Temperature Sensor Verification

7.4.3 44TV Thermal Cycling

7.4.3.1 45Cumulative Cycles

7.4.3.2 45Ambient Pressure Thermal Cycling Substitution

7.4.3.3 45Qualification, Protoflight and Acceptance Temperatures

7.4.3.4 46Survival Heater Verification

7.4.3.5 46Temperature test tolerances

7.4.3.6 46Plateau Criteria

7.4.4 46Thermal Balance (TB)

7.4.4.1 46Balance Points

7.4.4.2 46 Instrument Configuration

7.4.4.3 47Accuracy and Knowledge

7.4.4.4 47Steady State Criteria

7.5 47Test Condition Tolerances

8 50Acronyms

Contents vi

Page 1 of 51 Printed Thursday, October 5, 2023

ID

ACXPORD1

ACXPORD2

ACXPORD3

ACXPORD4

ACXPORD5

ACXPORD6

ACXPORD7

ACXPORD8

ACXPORD9

ACXPORD10

ACXPORD11

ACXPORD534

ACXPORD536

ACXPORD537

ACXPORD12

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

1.4.0-3

1.4.0-4

418-XO-ACXPORD-0121, 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:

⦁ 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 1b data) for the NOAA users.

The Ground System procured by the Government will implement algorithms developed by the ACX contractor. The Ground System will calibrate and navigate the data to generate Level 1b data.

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 use of “shall” designates a requirement that must be met.

The use of “will” designates a statement of fact or intention of the Government.

The use of “may” designates that permission has been granted by the Government.

The term “TBD” means, “to be determined” and is used when no value is available with subsequent study needed to obtain it.

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ID

ACXPORD15

ACXPORD19

ACXPORD20

ACXPORD21

ACXPORD22

ACXPORD23

ACXPORD24

ACXPORD25

ACXPORD26

ACXPORD13

ACXPORD27

ACXPORD28

ACXPORD29

Object Number

1.4.0-5

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

1.5.0-10

1.5.0-11

418-XO-ACXPORD-0121, RM Version, Geostationary eXtended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

The term “TBR” means “to be refined/reviewed” for a value that is subject to review for appropriateness and is subject to revision. The contractor is liable for compliance with the information marked “TBR” as if the “TBR” notation did not exist.

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 (see ACX Radiances for values).

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.

Credible Failure: A failure condition that has a reasonable likelihood of occurrence over the mission life. With consideration of reliability analysis and engineering experience, the Government technical authority will determine credibility of failure.

For the purposes of this document, failures of structure, pressure vessels, and pressurized lines and fittings are not considered credible failure modes if those elements comply with the applicable requirements of this document.

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.

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

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ID

ACXPORD547

ACXPORD31

ACXPORD32

ACXPORD33

ACXPORD568

ACXPORD569

ACXPORD570

ACXPORD571

ACXPORD572

ACXPORD34

ACXPORD35

Object Number

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

1.5.0-21

1.5.0-22

418-XO-ACXPORD-0121, RM Version, Geostationary eXtended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

Fixed Grid Angle: Refers to North/South (NS) and East/West (EW) Euler angles defined as follows. Starting with the orbit reference frame (ORF) in GIRD62 at the ideal satellite location, a positive NS angle is a rotation of the ORF about its +x axis, and a positive EW angle is a subsequent rotation of the rotated frame about its +y axis. The +z axis of the final frame is the line of sight (LOS) represented by the EW and NS fixed-grid angles.

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

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.

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

Level 0: Raw data reconstructed to unprocessed instrument data at full space-time resolution with all available supplemental information to be used in subsequent processing (e.g., ephemeris, health and safety) appended.

Level 1a: Unpacked and reformatted Level 0 data with all supplemental information to be used in subsequent processing appended. Data generally presented as full space/time resolution. A wide variety of sub-level products are possible. Note: For ACX, data are not resampled.

Level 1b data: Unpacked and reformatted Level 0 data with all supplemental information to be used in subsequent processing appended. Radiometric calibration and navigation are applied to produce parameters in physical units. Data generally presented as full space/time resolution. Note: For ACX, data are not resampled.

Level 2+: Retrieved environmental variables (e.g., sea surface temperature) and higher products.

Mission Allowable Temperatures (MAT): Mission Allowable Temperatures are the established range of temperatures that instrument units are permitted to experience while operating in orbit. MAT are established based upon analytical temperature predictions with appropriate margin based on the state of the thermal design. MAT encompasses worst-case operating temperature predictions, uncertainty, and any contractor desired temperature margin.

Navigation: Refers to the determination of the location of each pixel relative to a fixed reference, namely for the ACX, the Geodetic Reference System 80 (GRS80) geoid viewed from the idealized geostationary position, with latitude and longitude information appended in the Level 1b product.

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

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ID

ACXPORD573

ACXPORD36

ACXPORD37

ACXPORD38

ACXPORD39

ACXPORD40

ACXPORD41

ACXPORD42

ACXPORD43

ACXPORD44

ACXPORD45

ACXPORD46

ACXPORD47

Object Number

1.5.0-23

1.5.0-24

1.5.0-25

1.5.0-26

1.5.0-27

1.5.0-28

1.5.0-29

1.5.0-30

1.5.0-31

1.5.0-32

1.5.0-33

1.6

1.6.0-1

418-XO-ACXPORD-0121, RM Version, Geostationary eXtended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

Non-operational Temperatures (NOT): Non-operational Temperatures are the established range of temperatures that instrument units are permitted to experience while not operating and not powered. NOT represent the permissible range while the hardware is powered off. Survival heaters maintain hardware at or above the cold NOT limits and passive design maintains hardware below the upper NOT limits.

NOT are also known as non-operating MAT.

Pixel: All spectral channels associated with a given spatial resolution element after processing (detector element projection), including calibration and navigation (Level 1b).

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.

SNR: Signal-to-Noise Ratio.

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

Superregional ACX: Defined as a rectangle 8.0215° x 4.8129°, the equivalent at nadir of 5000 kilometer East/West x 3000 kilometer North/South, nominally centered at 30° N and 97° W.

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.

Page 5 of 51 Printed Thursday, October 5, 2023

ID

ACXPORD48

Object Number

1.6.0-2

418-XO-ACXPORD-0121, RM Version, Geostationary eXtended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

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.

Page 6 of 51 Printed Thursday, October 5, 2023

ID

ACXPORD49

ACXPORD50

ACXPORD51

ACXPORD52

ACXPORD53

Object Number

2.1

2.1.0-1

2.2

2.2.0-1

418-XO-ACXPORD-0121, 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

4) General Environmental Verification Standard (GEVS) for GSFC Flight Programs and Projects, Document Number GSFC-STD-7000B

5) NASA Payload Safety Requirements, NASA-STD-8719.24A with NASA- STD-8719.24-ANNEX Rev B

6) Geostationary eXtended Observations (GeoXO) Flight Project Atmospheric Composition (ACX) Radiances Upwelling Document, Document Number 418-XO-RPT-0075

2.2 Reference Documents

The following reference documents are in DOORS.

1. Report concerning Space Data System Standards: LOSSLESS

MULTISPECTRAL AND HYPERSPECTRAL IMAGE COMPRESSION,

Informational Report CCSDS 120.2-G-2, GREEN BOOK, December 2022

2. SPECTRAL PREPROCESSING TRANSFORM FOR MULTISPECTRAL AND

HYPERSPECTRAL IMAGE COMPRESSION Recommended Standard, CCSDS 122.1-B-1, BLUE BOOK, September 2017.

3. Moving Mechanical Assemblies for Space and Launch, AIAA S-114A-2020, Jan. 14, 2021

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

5. Space Mechanisms Handbook, Document Number NASA TP-1999-206988, March 1, 2002

Page 7 of 51 Printed Thursday, October 5, 2023

ID

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-0121, 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, electrically, 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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ID

ACXPORD66

ACXPORD67

ACXPORD68

ACXPORD69

ACXPORD70

ACXPORD71

ACXPORD202

ACXPORD203

ACXPORD72

ACXPORD73

ACXPORD74

ACXPORD75

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

3.1.1.3.0-7

418-XO-ACXPORD-0121, RM Version, Geostationary eXtended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

The ACX shall enter Safe Mode upon receipt of a ground command, receipt of an autonomous safe mode command from the observatory, or 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 Diagnostic Mode

The ACX shall implement a Diagnostic Mode.

Rationale: Diagnostic mode is needed for diagnosing anomalies.

The ACX shall enter Diagnostic Mode only on command.

The ACX data transmission rate in Diagnostic Mode shall comply with the allocation in the ACX UIID.

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

Rationale: Diagnostic mode must be fully functional.

The ACX shall by command send telemetry for selected channels while in 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 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 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.

Page 9 of 51 Printed Thursday, October 5, 2023

ID

ACXPORD76

ACXPORD77

ACXPORD78

ACXPORD79

ACXPORD80

ACXPORD81

ACXPORD82

ACXPORD86

ACXPORD549

ACXPORD87

ACXPORD88

ACXPORD89

ACXPORD91

ACXPORD92

Object Number

3.1.1.3.0-8

3.1.1.3.0-9

3.1.1.3.0-10

3.1.1.4

3.1.1.4.0-1

3.1.1.4.0-2

3.1.2

3.1.2.1

3.1.2.1.0-1

3.1.2.2

3.1.2.2.0-1

3.1.2.3

3.1.2.3.1

3.1.2.3.1.0-1

418-XO-ACXPORD-0121, RM Version, Geostationary eXtended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

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

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

The ACX shall by command send all bits from the A to D converter while in 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 Outgassing

Reserved

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

Rationale: The ACX will sublimate and evaporate contaminants from hardware to prevent contamination from jeopardizing performance while outgassing.

3.1.2 On-Orbit Operations

3.1.2.1 Scanning Across the Sun

The ACX shall survive the presence of the sun within the Field of Regard (FOR) without sustaining any permanent degradation in performance.

Rationale: The sun must not result in damage to the instrument.

3.1.2.2 Eclipse

During eclipse season, the ACX shall meet performance requirements.

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

3.1.2.3 Operations After Maneuvers

3.1.2.3.1 Spacecraft Maneuvers

With the exception of a yaw flip, 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 maneuvers.

Rationale: If the spacecraft executes a different maneuver than a yaw flip, the instrument recovery will occur in this short duration after the interface is restored to nominal conditions.

Page 10 of 51 Printed Thursday, October 5, 2023

ID

ACXPORD93

ACXPORD94

ACXPORD95

ACXPORD96

ACXPORD97

ACXPORD98

ACXPORD99

ACXPORD100

ACXPORD101

ACXPORD102

ACXPORD103

ACXPORD104

Object Number

3.1.2.3.2

3.1.2.3.2.0-1

3.1.2.4

3.1.2.4.0-1

3.1.2.4.0-2

3.2

3.2.1

3.2.1.1

3.2.1.1.0-1

3.2.1.1.0-2

3.2.1.1.0-3

3.2.1.1.0-4

418-XO-ACXPORD-0121, RM Version, Geostationary eXtended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

3.1.2.3.2 Post Storage Activation

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

3.1.2.4 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.

The ACX detector temperature shall be included in telemetry to support radiometric performance assessment.

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.

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.

Page 11 of 51 Printed Thursday, October 5, 2023

ID

ACXPORD105

ACXPORD106

ACXPORD107

ACXPORD108

ACXPORD109

ACXPORD110

ACXPORD113

ACXPORD114

ACXPORD115

ACXPORD116

ACXPORD117

Object Number

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

3.2.1.3.0-2

3.2.1.4

3.2.1.4.0-1

418-XO-ACXPORD-0121, RM Version, Geostationary eXtended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

3.2.1.2 Flexible and Efficient Imaging Pattern

The ACX sensor shall observe an area of commanded size anywhere within the FOR 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 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.

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.

3.2.1.4 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. 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.

Page 12 of 51 Printed Thursday, October 5, 2023

ID

ACXPORD120

ACXPORD121

ACXPORD122

ACXPORD123

Object Number

3.2.2

3.2.2.1

3.2.2.1.0-1

3.2.2.1.0-2

418-XO-ACXPORD-0121, RM Version, Geostationary eXtended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

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 micrometers

(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, computed for each spectral sample, shall be greater than or equal to values in the Minimum SNR table below for the at-aperture radiance provided in the ACX Radiances file, document number, 418-XO-RPT-0075. 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 13 of 51 Printed Thursday, October 5, 2023

ID

ACXPORD123

Object Number

3.2.2.1.0-2

418-XO-ACXPORD-0121, RM Version, Geostationary eXtended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

Page 14 of 51 Printed Thursday, October 5, 2023

ID

ACXPORD123

ACXPORD124

ACXPORD125

ACXPORD126

ACXPORD127

ACXPORD128

ACXPORD129

Object Number

3.2.2.1.0-2

3.2.2.1.0-3

3.2.2.2

3.2.2.2.1

3.2.2.2.1.0-1

3.2.2.2.2

3.2.2.2.2.0-1

418-XO-ACXPORD-0121, RM Version, Geostationary eXtended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

Figure 1. ACX signal-to-noise ratio as a function of wavelength.

Note: The linearly interpolated SNR value of 1143 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

The ACX spectral resolution shall be less than or equal to 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.

Note: That the spectral resolution element width is the full width half maximum

(FWHM).

3.2.2.2.2 Within Channel Spectral Response Uniformity

Excluding regions of terrestrial atmospheric features between 0.300 – 0.350 um,

0.585 – 0.603 um, 0.625 – 0.635um , 0.645 – 0.664 um, and 0.685 – 0.740 um, any relative spectral radiance features, resulting from a difference between each spectral location “i” at each spatial location along the FPA “j” and the nominal on-axis spectrum shall comply with inequality below. An example of a spectral radiance feature yielding a radiance difference is provided in Figure ACXPORD129.

Derived NEdN is defined in ACXPORD27 and here has units of radiance.

RSSE = Spring Equinox Reference Spectrum from 418-XO-RPT-0075 ACX Radiance

Page 15 of 51 Printed Thursday, October 5, 2023

ID

ACXPORD129

ACXPORD130

ACXPORD131

ACXPORD132

ACXPORD133

ACXPORD134

ACXPORD135

Object Number

3.2.2.2.2.0-1

3.2.2.2.3

3.2.2.2.3.0-1

3.2.3

3.2.3.1

3.2.3.1.0-1

3.2.3.1.0-2

418-XO-ACXPORD-0121, RM Version, Geostationary eXtended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

Upwelling SRFSE = Spring Equinox Measured Spectral Response Function TOA = Top of Atmosphere Irradiance from 418-XO-RPT-0075 ACX Radiance

Upwelling SRFTOA = Top of Atmosphere Measured Spectral Response Function

* = convolution

Figure ACXPORD129. Example of spectral radiance features across FPA yielding radiance difference.

3.2.2.2.3 Channel Center Wavelength Knowledge

The spectral sample center wavelength shall be reported to within an accuracy of 0.02nm.

Rationale: Spectral-sample center information across the FOV is needed for reliable higher-level product usage.

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/radian) 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 Equal Spatial Directions Requirements Table after any ground processing, in the presence of jitter and after any lossy compression/decompression.

Page 16 of 51 Printed Thursday, October 5, 2023

ID

ACXPORD135

ACXPORD136

ACXPORD137

ACXPORD138

ACXPORD139

ACXPORD140

ACXPORD141

ACXPORD142

ACXPORD143

Object Number

3.2.3.1.0-2

3.2.3.2

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

418-XO-ACXPORD-0121, 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/cycle)

Spatial Frequency (cycles/radian)

System MTF

40.0 900.0 0.90

20.0 1800.0 0.73

13.3 2700.0 0.53

10.0 3600.0 0.32

3.2.3.2 Spatial Response Uniformity

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.

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 phases of the detector sample grid to edge position.

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.

Page 17 of 51 Printed Thursday, October 5, 2023

ID

ACXPORD212

ACXPORD144

ACXPORD145

ACXPORD146

ACXPORD147

ACXPORD149

ACXPORD150

ACXPORD151

ACXPORD152

ACXPORD153

ACXPORD155

ACXPORD156

ACXPORD157

ACXPORD158

ACXPORD161

ACXPORD162

Object Number

3.2.4.1.0-2

3.2.4.2

3.2.4.2.0-1

3.2.4.2.0-2

3.2.4.2.1

3.2.4.2.1.0-1

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

3.2.4.2.4.0-1

3.2.4.2.4.0-2

3.2.5

3.2.5.1

3.2.5.1.1

418-XO-ACXPORD-0121, RM Version, Geostationary eXtended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

If ACX uses an on-board star catalog, it shall be loadable and modifiable from the ground and cover a minimum span of two weeks.

3.2.4.2 INR Performance Requirements

All INR requirements listed herein refer to location error of detector samples as expressed in fixed-grid angles; 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 fixed-grid angles, in microradians, 3-sigma, and all daily hours of operation.

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 a daily 24-hour window. 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

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

3.2.4.2.2 Frame-to-Frame Registration

Frame-to-frame registration error shall not exceed 46 microradians, 3-sigma, per axis. Frame-to-frame registration error is the difference in navigation error for an earth location in two consecutive frames within the same channel.

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 an error of 53 microradians, 3-sigma, measured radially.

3.2.4.2.4 Channel-to-Channel Registration

Channel-to-channel registration error, or co-registration error, is the difference in line-of-sight fixed-grid angles between spectral channels for any given pixel in the same frame.

Rationale: Co-registration for Level 1b applies to true line-of-sight fixed grid angles rather than the knowledge of those angles.

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

3.2.5 Radiometric Accuracy and Precision

3.2.5.1 Repeatability

3.2.5.1.1 Pixel-to-Pixel

Page 18 of 51 Printed Thursday, October 5, 2023

ID

ACXPORD163

ACXPORD168

ACXPORD169

ACXPORD170

ACXPORD171

Object Number

3.2.5.1.1.0-1

3.2.5.2

3.2.5.2.0-1

3.2.5.3

3.2.5.3.0-1

418-XO-ACXPORD-0121, 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 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.

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.

3.2.5.3 Calibration of Channels

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.

Page 19 of 51 Printed Thursday, October 5, 2023

ID

ACXPORD172

ACXPORD173

ACXPORD174

ACXPORD175

ACXPORD176

ACXPORD177

ACXPORD178

ACXPORD179

ACXPORD180

ACXPORD181

Object Number

3.2.5.3.0-2

3.2.5.3.0-3

3.2.5.3.0-4

3.2.5.4

3.2.5.4.0-1

3.2.5.4.0-2

3.2.5.5

3.2.5.5.1

3.2.5.5.1.0-1

3.2.5.5.2

418-XO-ACXPORD-0121, RM Version, Geostationary eXtended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

The ACX shall have an on-board calibration capability for all channels that provides absolute accuracy with traceability to NIST of 3%, 1-sigma, 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% 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 contractor 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.

3.2.5.4 Spatial Uniformity of Data

The ACX shall have less than 0.3%, 1-sigma, change in response in the calibrated pixel data over the FOR 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 be spatially uniform so that variations in the data are not misinterpreted to be real signal variations.

3.2.5.5 Crosstalk

3.2.5.5.1 Channel-to-Channel

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.

3.2.5.5.2 Within Channel

Page 20 of 51 Printed Thursday, October 5, 2023

ID

ACXPORD182

ACXPORD183

ACXPORD184

ACXPORD185

ACXPORD186

ACXPORD187

ACXPORD188

ACXPORD189

ACXPORD190

ACXPORD192

ACXPORD193

ACXPORD191

ACXPORD194

Object Number

3.2.5.5.2.0-1

3.2.5.6

3.2.5.6.0-1

3.2.5.7

3.2.5.7.0-1

3.2.5.8

3.2.5.9

3.2.5.9.1

3.2.5.9.1.0-1

3.2.6

3.2.6.0-1

3.2.6.0-2

3.2.7

418-XO-ACXPORD-0121, RM Version, Geostationary eXtended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

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.

3.2.5.6 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.

3.2.5.7 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.

3.2.5.8 Reserved

3.2.5.9 Polarization

3.2.5.9.1 Polarization Control

All channels 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.

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.

The ACX measured error over the dynamic range in radiometric response as a function of input radiance shall be less than or equal to 0.5% of the radiometric response.

3.2.7 Data Compression

Page 21 of 51 Printed Thursday, October 5, 2023

ID

ACXPORD195

ACXPORD196

ACXPORD197

ACXPORD198

ACXPORD199

ACXPORD200

ACXPORD201

ACXPORD204

ACXPORD205

ACXPORD206

ACXPORD207

ACXPORD208

ACXPORD209

ACXPORD210

ACXPORD211

Object Number

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

3.2.7.3

3.2.7.3.0-1

3.2.7.3.0-2

3.2.7.3.0-3

3.2.7.3.0-4

3.2.7.3.0-5

3.2.7.4

3.2.7.4.0-1

418-XO-ACXPORD-0121, RM Version, Geostationary eXtended Observations (GeoXO) Atmospheric Composition (ACX)

Performance and Operational Requirements Document (PORD)

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…