LNEXT-SYS-DESC-0004 Rev - LNext Common Lexicon 20230105.pdf

LNext Common Lexicon LNEXT-SYS-DESC-0004 Revision -ii

Landsat Next Common Lexicon

Signature/Approval Page

Prepared by:

Electronic Signature in TDMS

01/05/2023 Andrew McLennan Date Landsat Next Requirements Manager NASA/GSFC, Code 426

Approved by:

Dawn Sierfeld Date Landsat Next Digital Process Engineering Manager

Approved by:

Dorothy Wertz Date Landsat Next Lead Digital Process Engineer iii

CM Foreword This document is a Landsat Next Project Signature Controlled document. Changes to this document require prior approval via a Signature Controlled Change Request (SCoRe). Proposed changes shall be submitted to the Landsat Next Configuration & Data Management Office, along with supportive material justifying the proposed change. Changes to this document will be made by complete revision.

Questions or comments concerning this document should be addressed to:

NASA/Goddard Space Flight Center Landsat Next Project Office, Code 426 Attention: Configuration & Data Management Office Greenbelt, Maryland 20771 iv

Change History Log Revision Effective Date Description of Changes

- 01/05/2023 LNEXT-SCoRe-0003 - Draft LandIS RFP Baseline – Initial Release

List of TBDs/TBRs v

Hyperlink to TBx Location Summary Ind.

Name/Org.

Due Date

TBx-1 Section 2.12

The set of ground stations that are used for routine mission operations in support of the Landsat. The stations are located in Sioux Falls, South Dakota and Fairbanks, Alaska. A backup site is located in To Be Determined (TBD).

D. Sierfeld SRR

TBx-2 Section 2.15

A continuous recording of Landsat Next image sensor data or a Landsat Next data product not yet processed into a 164-kilometer (km)-(cross-track) by TBD-km (along-track) multispectral image of the Earth’s surface where the original image data is derived from an off-nadir observation.

D. Sierfeld SRR

TBx-3 Section 2.19

A set of Landsat Next image sensor data, or an Landsat Next data product, representing a 164-km- (cross-track) by TBD-km (along-track) multispectral image of the Earth’s surface.

D. Sierfeld SRR

TBx-4 Section 2.23

A path/row coordinate system used to define the ground tracks of the Landsat Next Observatory. The system specifies latitudinal and longitudinal coordinates for image centers and corners. In addition, the WRS assigns integer path (ground track) and row designations to each image center.

The corner points corresponding to each path/row designation subtend a 164-km-by-TBD-km area on the Earth’s surface.

D. Sierfeld SRR

TBx-5 Section 2.23

The multi-spectral digital, image data acquired from the Landsat 9 Observatory, processed into a single image. The corner points of a processed image correspond to a path/row designation that subtends a continuous 164-km (cross-track) by TBD-km (along-track) area on the Earth’s surface. The original image data is derived from a nadir observation.

D. Sierfeld SRR vi

Table of Contents SIGNATURE/APPROVAL PAGE ................................................................................................ II

CM FOREWORD ..........................................................................................................................III

CHANGE HISTORY LOG .......................................................................................................... IV

LIST OF TBDS/TBRS .................................................................................................................. IV

TABLE OF CONTENTS .............................................................................................................. VI

LIST OF FIGURES ...................................................................................................................... VI

LIST OF TABLES ....................................................................................................................... VII

1.0 FRONT MATTER ............................................ ERROR! BOOKMARK NOT DEFINED.

2.0 LEXICON

2.1 Numbers and Symbols

2.2 A

2.3 B

2.4 C

2.5 D

2.6 E

2.7 F

2.8 G

2.9 H

2.10 I ……………………………………………………………………………………... 11

2.11 J

2.12 L

2.13 M

2.14 N

2.15 O

2.16 P

2.17 Q

2.18 R

2.19 S

2.20 T

2.21 U

2.22 V

2.23 W

2.24 Z

APPENDIX A - GENERAL MARGIN DEFINITIONS

APPENDIX B: GENERAL MASS DEFINITIONS DIAGRAM

List of Figures

No table of contents entries found.

vii

List of Tables No table of contents entries found.

LNext Common Lexicon DRAFT LNEXT-SYS-DESC-

1.0 LEXICON

1.1 NUMBERS AND SYMBOLS

1-Sigma – A set of values with a standard distribution is considered to meet a 1-sigma requirement if no fewer than 68.26% of the values are within the specified limits of the requirement.

2-Sigma – A set of values with a standard distribution is considered to meet a 2-sigma requirement if no fewer than 95.44% of the values are within the specified limits of the requirement.

3-Sigma – A set of values with a standard distribution is considered to meet a 3-sigma requirement if no fewer than 99.73% of the values are within the specified limits of the requirement.

Lmax – The maximum response of an instrument as a polarizer analyzer is rotated.

Lmin – The minimum response of an instrument as a polarizer analyzer is rotated.

1.2 A

Acceptance Tests – The verification process that demonstrates that hardware is acceptable for flight. It also serves as a quality control screen to detect deficiencies and, normally, to provide the basis for delivery of an item under terms of a contract.

Alignment – The relative orientation of 2 reference frames.

Alignment Control – The process of controlling the maximum difference between the actual orientation of a reference frame and its nominal orientation.

Alignment Control Error – The maximum difference between the actual orientation of a reference frame and its nominal orientation.

Alignment Drift – Changes in the alignment between 2 reference frames that occur during normal on-orbit operations, excluding effects due to jitter. For the alignment of LandIS relative to the spacecraft, one source of drift is structural distortions arising from orbital and seasonal changes in thermal conditions.

Alignment Knowledge – The estimate of the relative orientation between 2 reference frames.

Alignment Knowledge Uncertainty – The uncertainty in the knowledge of the relative orientation between 2 reference frames.

Alignment Shift – A change in the alignment between 2 reference frames that occurs over one finite, defined, period of time, typically prior to and not changing significantly during normal on orbit operations. For the alignment of the LandIS relative to the spacecraft, alignment shifts arise from structural distortion effects such as launch loads, moisture outgassing and the relief of gravity loads.

Allocated Mass – [syn. Allowable Mass] - The limit against which mass margins are calculated.

Allocation – An allocation is a requirement which is derived by partitioning a higher-level requirement into lower-level component requirements and making an assignment of values to that lower level. Allocation statements use the verb “shall.”

Altitude Range – Range of altitudes around the orbit. Altitude varies around the orbit because the orbit is not circular and because the Earth is not spherical.

We assume that a frozen orbit will be maintained, so the altitude over a given latitude does not change.

The range of altitudes is based on the nominal orbit and the allowed altitude variation of +/- 1 km.

Ancillary Data – A selected subset of observatory telemetry that provides information about the on-orbit environment and observatory status at the time of the image sensor data collections.

Ancillary data includes all observatory telemetry necessary to produce a scene data product.

Ancillary data typically includes relevant LandIS parameters, calibration parameters, observatory attitude and ephemeris, etc.

Anomaly – An unexpected event that is outside of design/performance specification limits or is inconsistent with proper system behavior. Note: Design limits are those identified in approved design-level documents.

Argument of Perigee – The angle that specifies the location of perigee in the orbit, relative to the ascending node.

Assembly – A functional subdivision of a component consisting of parts or subassemblies that perform functions necessary for the operation of the component as a whole. Examples are a power amplifier and gyroscope.

See level of assembly.

Attitude Reference Frame Knowledge – The pointing information for the three orthogonal axes of rotation as calculated by the observatory attitude control system and displayed in observatory housekeeping telemetry. It is expressed as an angular rotation offset about each axis from a pre-defined nominal pointing orientation.

Audit – A review of a developer’s, contractor's, or subcontractor's documentation or hardware to verify that it complies with project requirements.

Authentication – A security measure designed to establish the validity of a transmission, message, or originator. Authentication provides the assurance that information transmitted from a claimed source (i.e., a source's identity) actually originated from that source.

Autonomy – Autonomous operations consists of the actions taken by a component or system based on logic contained in the flight code (software, Field Programmable Gate Array [FPGA], Application Specific Integrated Circuits [ASIC], etc.). Autonomy does not preclude or include stored command sequences (absolute or relative) or pre-defined command sequence responses to on-orbit conditions.

Auxiliary Data – Supporting data sets provided outside the Landsat Next mission data stream.

These data are used to apply corrections or adjustments to the Landsat Next mission data, thus producing images that meet Landsat Next processed image requirements. Examples include previously derived calibration parameters, ground control data, digital elevation data, and Global Positioning System (GPS) offset data.

Azimuth – Angle measured in the ecliptic or equatorial plane as part of a spherical polar coordinate system (radius or altitude, azimuth and elevation).

1.3 B

Ballast – Mass that is added to help meet mass property requirements.

Basic Mass – [syn. Current Best Estimate] - Current mass of hardware without growth allowance or uncertainty mass.

Bi-directional Reflectance Distribution Function (BRDF) – A function that expresses reflectance from a surface into a unit-projected solid angle as a function of both the direction of illumination and the direction of observation.

Boresight – The LandIS pointing reference direction coinciding with or at a known offset to the LandIS optical axis, nominally intersecting the center of the focal plane array.

Boresight Alignment Control Error – For a specific LandIS, the maximum difference between the actual and the nominal orientation of its LandIS Boresight relative to the Spacecraft Attitude Determination Frame. This error will be considered to be composed of the following factors:

• Static Alignment Control Error (not changing significantly during normal on orbit operations)

• Measurement uncertainty during installation alignment

• Limitations associated with fabrication and installation.

• Alignment Shifts.

• Dynamic Alignment Control Error (changing significantly during normal on orbit operations)

• Alignment Drifts.

• Jitter

Boresight Alignment Knowledge Uncertainty – For a specific LandIS, the uncertainty in the knowledge of the relative orientation between its LandIS Boresight and the Spacecraft Attitude Determination Frame. This uncertainty will be considered to be composed of the following factors:

• Static Alignment Knowledge Uncertainty (not changing significantly during normal on orbit operations)

• Measurement uncertainty during installation alignment.

• Alignment Shifts.

• Dynamic Alignment Knowledge Uncertainty (changing significantly during normal on orbit operations)

• Alignment Drifts.

• Jitter

Bright Target Recovery – The recovery of the system from a saturation event, such as a sun glint.

1.4 C

Calibrate – The process of characterizing system behavior to a known standard or controlled input. Calibration is performed to determine correction parameters (e.g., gains and offsets) that can be applied to the data to correct for systematic errors.

Calibration Maneuver – A single spacecraft attitude adjustment made to view a calibration source (i.e., deep space, moon, earth limb, ground target).

Channel Access Data Unit (CADU) – A Channel Access Data Unit is a Consultative Committee on Space Data Systems (CCSDS)-defined frame format.

Characterize – The use of a set of measurements and analyses to describe the performance of a device or product over the relevant operating range. Characterization includes taking point measurements, modeling the variation in a characteristic as a function of one or more parameters (e.g., temperature, time), measuring stability over a range of conditions, and computing error estimates.

Circuitware – Hardware description code, associated data, and documentation used to define or configure analog or digital circuitry for use within a microelectronic circuit. Hardware descriptions encompass code and data for various levels of design abstraction; for example, transaction-level modeling, behavioral (e.g., register transfer level models), circuit element (e.g., digital logic circuits, transistors, interconnect, bitstream), and physical design (e.g., technology-specific transistors, interconnect routing, integrated circuit artwork database).

Coherent Noise – A spurious, periodic pattern of noise within an image, generally of electronic origin.

Cold Boot – A complete reboot of the operational flight software loaded from nonvolatile (flash, EEPROM, PROM, etc.) on-board memory and initialization of RAM.

Collect – To acquire, downlink, and subsequently transfer data from the observatory to the ground system.

Collected Volatile Condensable Material (CVCM) – The quantity of out gassed matter from a test specimen that condenses on a collector maintained at a specific constant temperature for a specified time.

Command and Telemetry Data Bus – The data bus containing the command and telemetry data set. The reference to command and telemetry data bus is a logical interface and is not meant to imply a physical interface requirement.

Component – 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 electronic box, transmitter, gyro package, actuator, motor, battery. For the purposes of this document, "component" and "unit" are used interchangeably.

Configuration – The functional and physical characteristics of the payload and all its integral parts, assemblies and systems that are capable of fulfilling the fit, form and functional requirements defined by performance specifications and engineering drawings.

Constellation – One or more observatories flying in formation about the orbit. For LNext, the constellation is comprised of 3 identical observatories, flying in formation approximately equidistance around the orbit plane.

Contact – A single Observatory Acquisition of Signal (AOS) to Loss of Signal (LOS) session taken at either a ground station or a communication satellite such as the Tracking and Data Relay Satellite System (TDRSS).

Contamination – The presence of materials of molecular or particulate nature which degrade the performance of hardware.

Contingency Mass – [syn. Growth Mass] - Alternative term for growth allowance, but it is vague, and its use is disfavored. Not to be confused with Subsystem Contingency.

Critical Weld – A weld in which a single failure will result in loss of load carrying capability under the applied loading condition.

CTSS – Command and Telemetry Simulator - low fidelity software simulator to support T&C testing at LGNs and within MOC.

1.5 D

Data Reduction – The process (e.g., time-delayed integration [TDI] and dynamic range windowing, etc.) used to reduce the image data size without sacrificing image quality.

Dark Data – Data acquired from the instrument focal plane while on the ground or with the shutter closed. This data is unlit and no image pattern exists. Alternatively the dark data can be injected for a specifc test scenario.

Dark Detectors – Detectors on the focal plane of the instrument that are masked from receiving all incoming light, but they are otherwise identical to the detectors observing the Earth reflected radiation.

Dead Pixels – See Inoperable Pixels.

Definitive Ephemeris Data – A data set that provides post-processed, time-varying, orbital states derived from a set of observations. Typically, this includes the position, velocity and time expressed over a regular time interval.

Demonstrate – To show that the current knowledge of one or more system parameters is correct and accurate by collecting and processing test data using current calibration parameters and analyzing the performance of the processed results.

Detector – A single physical sensing element that produces an electrical output in response to incident electromagnetic radiation. If time-delayed integration (TDI) is used, the outputs of multiple detectors in a column are summed to produce a single output. This single output may also be considered as the output of a single “detector.” In the case of redundant detectors, only the selected active detectors are considered in defining the “detector.”

Detector Column – A set of physical detectors imaging the same spatial locations for a single band, which are treated as a single sensing element by having their outputs combined in time-delay integration (TDI). Within the detector column, individual detectors may be deselected.

Design Qualification Tests – Tests intended to demonstrate that the test item will function within performance specifications under simulated conditions more severe than those expected from ground handling, launch, and mission operations. Their purpose is to uncover deficiencies in design and method of manufacture. They are not intended to exceed design safety margins or to introduce unrealistic modes of failure. The design qualification tests may be to either “prototype” or “protoflight” test levels.

Design Specification – Generic designation for a specification that describes functional and physical requirements for an article, usually at the component level or higher levels of assembly.

In its initial form, the design specification is a statement of functional requirements with only general coverage of physical and test requirements. The design specification evolves through the project life cycle to reflect progressive refinements in performance, design, configuration, and test requirements. In many projects the end-item specifications serve all the purposes of design specifications for the contract end-items. Design specifications provide the basis for technical and engineering management control.

Digital Number (DN) – The output from a detector sample quantized to a discrete integer value.

Discrepancy – Refer to Nonconformance

Displacement Damage – Degradation in a bipolar or opto-electronic device resulting from displacement of atoms in the semiconductor lattice by energetic particles.

Dynamic Range – The range of radiances over which instruments and sensors are sensitive. The upper end of the dynamic range is the saturation radiance. The lower end is the noise floor, i.e., the radiance corresponding to the low radiance noise level of the instrument. These radiances may be expressed as equivalent blackbody temperatures for thermal bands.

1.6 E

Edge Response – The response of an imaging system to an edge target (i.e., a low/high or high/low step function), normalized so that the mean response on the low side of the edge target is set to zero and the mean response on the high side of the edge target is set to 100%.

Electromagnetic Compatibility (EMC) – The condition that prevails when various electronic devices are performing their functions according to design in a common electromagnetic environment.

Electromagnetic Interference (EMI) – Electromagnetic energy which interrupts, obstructs, or otherwise degrades or limits the effective performance of electrical equipment.

Electromagnetic Susceptibility – An undesired response by a component, subsystem, or system to conducted or radiated electromagnetic emissions.

Encryption – A security measure designed to prevent unauthorized access to data or control of the observatory. Encryption is achieved by converting plain text to equivalent cipher text by means of a code.

End-to-End Tests – Tests performed on the integrated ground and flight system, including all elements of the observatory, its control, stimulation, communications, and data processing to demonstrate that the entire system is operating in a manner to fulfill all mission requirements and objectives.

Entropy – State of disorder or randomness within data. Traditionally the higher the entropy the lower the compression.

Ephemeris Data – A set of data that provides the position, velocity, and time of a celestial body (including a manmade satellite) for regular intervals in time. Ephemeris data helps to characterize the conditions under which remote sensing data are collected and may be used to correct the sensor data prior to analysis.

Equatorial Altitude – The altitude when the satellite crosses the equator. We assume the orbit remains frozen, therefore the equatorial altitude does not vary over time.

Expedited Production – Orders for Landsat Next data products to be generated from the archive with a rapid (expedited) turnaround time.

1.7 F

Failure – A departure from specification that is discovered in the functioning or operation of the hardware or software.

Failure Modes, Effects and Criticality Analysis (FMECA) – A procedure by which each credible failure mode of each item from a low-indenture level to the highest is analyzed to determine the effects on the system and to classify each potential failure mode in accordance with the severity of its effect.

Fail-safe – Ensures that, because of structural redundancy, a structural element will not cause collapse of the remaining structure or have any detrimental effects on mission performance.

Federal Geographic Data Committee (FGDC) – Established by the Office of Management and Budget for purposes of coordinating the development, use, sharing, and dissemination of geographic data.

Field of View – The instantaneous object space sampled with the sensor scanner or observatory at a fixed position. If the instrument does not include a scanning methodology, the Field of View is equivalent to the Field of Regard. It is a solid angle through which the detectors are sensitive to electromagnetic radiation.

Field of Regard – The field of regard (FOR) is the total area that can be captured by a movable sensor. It should not be confused with the field of view (FOV), which is the angular cone perceivable by the sensor at a particular time. The field of regard is the total area that a sensing system can image by pointing the sensor, which may be much larger than the sensor's FOV (as was in the case of the L7/ETM+). For a stationary sensor, the FOR and FOV are identical.

Flight Acceptance – See Acceptance Tests.

Flight Hardware – Hardware to be used operationally in space.

Focal Plane – The detectors and associated electronics assembled with the spectral bandpass filters.

Follow-On Hardware – Flight hardware built in accordance with a design that has been qualified either as prototype or as protoflight hardware; follow-on hardware is subject to a flight acceptance test program.

Fracture Control Program – A systematic project activity to ensure that hardware intended for flight has sufficient structural integrity as to present no critical or catastrophic hazard as well as to ensure quality of performance in the structural area for any observatory (spacecraft) project.

Central to the program is fracture control analysis, which includes the concepts of fail-safe and safe-life.

Frozen Orbit – The orbit where the eccentricity and argument of perigee have been chosen to prevent perigee from drifting.

As a result, the altitude over a given latitude stays nearly constant.

For Landsat we set argument of perigee near 90 deg, so perigee is at the north end of the orbit.

Functional Tests – The operation of a unit in accordance with a defined operational procedure to determine whether performance is within the specified requirements.

1.8 G

Geocentric Nadir – Geocentric Nadir is defined at any point in the orbit as the direction toward the center of the mass of the Earth.

Geodetic Reference System – A comprehensive geodetic model of the Earth that includes a geodetic reference frame, a best-fit earth ellipsoid/spheroid model, and an earth gravitational model. The inclusion of all these components allows a geodetic reference system to serve as a horizontal and vertical datum. The standard Landsat Next geodetic reference system is the World Geodetic System 1984 (WGS84).

Ghost Image – A ghost image, or ghost, is a secondary image of an object, which appears as either an attenuated rendition of the original object or a blurred and attenuated version of the original object. A ghost also has a constant displacement vector from the original image. A significant ghost is defined as an image artifact when its peak signal after background level subtraction and radiometric calibration is above 2% of the typical radiance (Ltypical) for that band.

Ground Sample Distance (GSD) – The distance on the ground between adjacent detector sample centers.

Ground System to Spacecraft Integration Rack (GSSIR) – USGS provided system attached to Spacecraft throughout I&T. Provides TLM from S/C to MOC and Science Data to DPAS.

Contains key GN functionality

Ground Track Spacing at Equator – The distance between two adjacent ground paths at the equator. This equals the equatorial circumference of 40,075 km divided by the number of paths in the Repeat Ground Track.

Growth Allowance – Predicted change to the basic mass based on an assessment of the item's maturity, category, and fabrication status.

1.9 H

Hardware – As used in this document, there are two major categories of hardware.

• Prototype Hardware

• Flight Hardware

Heartbeat vs. I'm Alive – “Heartbeat” refers more specifically to a communication protocol that is used to negotiate and monitor the availability of a resource. Within this protocol there are two or more members of a high-availability system/function, where the high-availability system/function periodically send a "I'm still alive" message(s).

Thus, a one-way “I’m Alive” signal (typically a pulse or change in state on a unidirectional Bi- Level signal line) would be monitored by the host or controlling resource to ensure there is activity on the line. If there is not activity, then the controlling resource would take action to reset, change power, etc., in order to get the functional resource working again (depending on the system’s fault management scheme).

Typically, Heartbeat implementation is accomplished by either a state machine, processor, or other function that will set a flip/flop or register. Then in a specified time or count it will affect a change on the state of the flip/flop. Thus the cycle repeats until there is a failure or the function is turned off.

If the monitoring (controlling) resource doesn’t see activity in “n” counts (where n is typically a small number), then it will take action. The monitoring resource will notify the ground, send a reset, or swap power, depending on how the system fault management is defined.

High Entropy – Realistic image data having significant randomness impacting the compression algorithm. Example is cumulus (popcorn) clouds over mountains or plains during green up.

This data is not a test pattern.

High Fidelity Ancillary – Realistic ancillary that accompanies and relates to image data. This data is properly formatted and corresponds with the instrument state of the imagery.

Housekeeping Data – Data that provide information about the health and status of the LandIS.

Housekeeping (Telemetry) – The engineering, health and safety, monitoring, and diagnostic telemetry data that are used in the control and operations of the observatory (spacecraft and image sensor[s]).

1.10 I

Image-to-Image Co-registration – The geolocation difference in images of the same Worldwide Reference System-3 (WRS-3) path and row acquired at different times.

Image Interval – The period of time that the output from the image sensor is either recorded or directly transmitted to the ground. An image interval includes nominal, calibration and off-nadir pointing of the imaging system.

Imaging Sensor Data – The acquired science data whose characteristics are specified in the Landsat Next Requirements Documents. Sensor data includes calibration data that provides information on the instrument response to dark images (dark calibration) and white images (lamp calibration) or other external calibrations (solar, lunar, ground/ vicarious).

Inclination – The angle from equator to orbit plane.

Inertial Velocity – The inertial velocity is the spacecraft velocity relative to the Earth-Centered Inertial (ECI J2000.0) reference frame.

Inoperable Detector – A detector that does not meet the definition of operable detector (see Operable Detector).

Inoperable Pixel – A pixel is considered dead or inoperable if greater than 30% of its ground projected area is not imaged by operable detectors.

Installation Alignment – The process of setting, measuring, and/or adjusting the relative orientation of an instrument or hardware reference frame with respect to another reference frame in order to satisfy required alignment criteria.

Instrument – A spacecraft subsystem consisting of sensors and associated hardware for making measurements or observations in space. For the purposes of this document, an instrument is considered a subsystem (of the spacecraft).

Instrument Data – Combination of imaging sensor data and instrument ancillary data.

Instrument Interface – The mechanical interface and associated datum(s) at the location where the instrument attaches to the spacecraft.

Instrument Suite – The instrument or set of instruments that will reside on one LNext observatory to provide all the required spectral bands for LNext. The constellation will be comprised of 3 observatories, each flying an identical instrument suite.

1.11 J

Jitter – High-frequency variations in sensor position and/or angular orientation leading to deviations in the actual sensor line of sight relative to the ideal line of sight over time periods up to a few seconds. Jitter may be induced by mechanical vibrations from external disturbances or internal mechanisms.

1.12 L

Land Database – The database of land and coastal regions onboard the LNext Observatories that is used along with the onboard position information to determine when imaging data is recorded for subsequent downlink.

LandIS Chassis Ground Plane (CGP) – A contiguous ground plane meeting the intent of NASA-STD-4003A for Class-R grounding of electronics. The LandIS CGP originates at the spacecraft mounting interface to the LandIS and extends throughout the LandIS from that point.

For electronics components, the CGP originates at the primary Class R ground path to LandIS CGP (either mounting surface or bond strap attach points). Every sufficiently conductive element of the component that connects to the CGP per the requirements levied herein is, by definition, a part of the CGP.

LandIS Input Data Bus – The interface bus where the data set containing commands is transported from the spacecraft. It is a functional reference and not intended to be a physical reference.

LandIS Simulator (LIS) – The Interface simulator provided by LandIS to the spacecraft. It allows data injection of canned data for interface check-out.

LandIS Operational Simulator (LOPS) – Realistic Instrument simulator. It is a high fidelity operational simulator that simulates realistic instrument telemetry and command respond and instrument modes of operations and respond to autonomous actions. LOPS provides science data output (compress and uncompressed) and the abiliity to inject known Image earth data to perform GRT tests. LOPS provides platform for Mission database checkout and obervatory intergration and test procedure development.

LandIS Output Data Bus – The interface bus where the data set containing LandIS data is transported to the spacecraft. LandIS data is imaging sensor data, test pattern data, raw detector diagnostic data, Instrument ancillary data or housekeeping data. It is a functional reference and not intended to be a physical reference.

Landsat Ground Network (LGN) – The set of ground stations that are used for routine mission operations in support of the Landsat. The stations are located in Sioux Falls, South Dakota and Fairbanks, Alaska. A backup site is located in To Be Determined (TBD).

Landsat Next Phases – Design, Build, and Test Phase begins at delivery order award and continues through the start of instrument integration, excluding any storage periods.

Level 0 Data Product – Image data with all data transmission and formatting artifacts removed, time provided, spatial, and band-sequentially ordered multi-spectral digital image data.

Level of Assembly – The environmental test guidelines of the General Environmental Verification Standard (GEVS) for GSFC Flight Programs and Projects generally start at the component or unit level assembly and continue through the system level. The assurance program includes the part level. Verification testing may also include testing at the assembly and subassembly levels of assembly; for test record keeping, these levels are combined into a "subassembly" level. The verification program continues through launch, and on-orbit performance.

Level 1Gs Data Products – Level 1Gs data products consist of Level 1R data products resampled for registration to a cartographic projection, referenced to the World Geodetic System 1984 (WGS84), G873 or current version.

Level 1T Data Products – Level 1T data products consist of Level 1R data products resampled for registration to a cartographic projection, referenced to the WGS84, G873 or current version, orthorectified, and corrected for terrain relief.

Level 1R Data Products – Level 1R data products consist of radiometrically corrected image data derived from Level 0 data linearly scaled to at-aperture spectral radiance.

Limit Level – The maximum expected flight level (consistent with the minimum probability levels of Table 2.4-2).

Lossless Compression – A data compression process such that the data, after compression and decompression, is identical numerically to the data prior to compression.

Lossy Compression – A data compression process such that the data, after compression and decompression, is nearly identical numerically to the data prior to compression. Lossy compression reduces an image data size by permanently eliminating certain information, especially redundant information.

Low Entropy – Image data having little randomness allowing for highly compressed imagery.

Examples include ice/snow covered regions, deserts, or night scenes.

Long-Term Acquisition Plan (LTAP) – Long-Term Acquisition Plan (LTAP) is to define the science data acquisition strategy of the mission.

LTAP Collection Reqest (LCR) – Landmask for the current effective period containing path, row and priority.

1.13 M

Main Bus Power – The unregulated power bus connected directly to the spacecraft bus battery.

Margin – The amount by which hardware capability exceeds requirements.

Mass Margin – The difference between predicted mass and allocated mass and is available for in-scope changes.

Mass Storage Device (MSD) – Generic terminology used instead of Solid State Recorder (SSR).

Mature Current Best Estimate (CBE) – The current best estimate including tolerances plus the maturity factor. See Appendix A.

Mean Eccentricity – The orbit eccentricity in Brouwer-Lyddane mean orbit elements. (Mean orbit elements are contrasted with osculating orbit elements, which change over the course of an orbit.)

Mean Local Time at the Descending Node – Local Time at the Descending Node, averaged over the annual variation in Sun position.

Mean Semimajor Axis – Orbit semimajor axis in Brouwer-Lyddane Mean Orbit Elements.

Measure – Provide a value for a particular system parameter or performance characteristic by direct observation

Memory Dwell Data – Repeatedly sampled processor addressable memory.

Metadata – A set of descriptive information about the scene data contained in the archive.

During the process of scene query and selection, the information is sufficient for a user to determine at a minimum: geographic coverage, date of collection, sensor gain mode, time of acquisition, cloud cover, and other qualitative measurements.

Mission Data – The time-correlated data set containing Landsat Next imaging sensor data, spacecraft and LandIS ancillary data.

Mission Operations Center (MOC) – The facility used to coordinate command and control the constellation observatories for on-orbit operations. This facility will be used during End-to-end testing of all elements of the Landsat Next before launch.

Mission Lifetime – The Landsat Next Mission lifetime starts at the NASA acceptance of the Landsat Next Observatory and continues until the completion of the Decommissioning Phase of all three observatories in the constellation.

Mixed Entropy – Image data having regions with both high and low randomness. Typically a full interval showing a swath containing both cloudy areas and uniform landscapes.

Model Calibration – The process of adjusting numerical or modeling parameters in the model to improve agreement with a referent. Note: Model correlation is understood to be equivalent terminology.

Model Validation – The process of determining the degree to which a model or a simulation is an accurate representation of the real world from the perspective of the intended uses of the model.

Model Verification – The process of determining the extent to which a model is compliant with its requirements and specifications as detailed in its conceptual models, mathematical models, or other constructs.

Modulation Transfer Function Compensation (MTFC) Resampling – This technique assigns a value to each output (resampled) pixel, computed as a weighted combination of the surrounding input pixels. The input pixel value weights are computed based on the output pixel location relative to the surrounding input pixels, using an interpolation function with a spatial frequency response that has been designed to compensate for the spatial frequency attenuation characteristics of the imaging system's modulation transfer function.

Module – A major subdivision of the payload that is viewed as a physical and functional entity for the purposes of analysis, manufacturing, testing, and recordkeeping. Examples include spacecraft bus, science payload, and upper stage vehicle.

1.14 N

Nadir – The direction from the observatory towards the center of the Earth. (See Reference:

Space Mission Analysis and Design, Wiley J. Larson and James R. Wertz, page 94, Second Edition - 1992.)

Narrowband Data – Observatory data down linked over a narrow band width, typically S-band, which includes housekeeping data, tracking data, commands and diagnostic telemetry. In addition, narrowband data includes the commands, software updates, and hard commands up linked to the observatory.

Near Infrared – The spectral region covering 700-1000 nanometers (nm).

Nonconformance – A condition of any hardware, software, material, or service in which one or more characteristics do not conform to specified requirements.

Non-Uniformity Correction (NUC) – The process of performing a reversible on-board relative correction of gain and offset for each pixel to reduce the entropy of a scene to improve data compressibility and/or reduce errors in on-board aggregation or resampling.

1.15 O

Observatory – The spacecraft plus LandIS, that are flown as part of the Landsat Next mission.

The LNext constellation is comprised of 3 identical observatories.

Observatory Chassis Ground Plane (CGP) – A contiguous ground plane meeting the intent of NASA-STD-4003A for Class-R grounding of electronics. The Observatory CGP originates at the spacecraft Single Point Ground (SPG) and extends outward from that point. For electronics components, the CGP originates at the primary Class R ground path to Observatory CGP (either mounting surface or bond strap attach points). Every sufficiently conductive element of the component that connects to the CGP per the requirements levied herein is, by definition, a part of the CGP.

Observatory Command Types: Relative Time Sequence – Commands that are required to be executed in a relative sequence to one another.

Observatory Design Lifetime – The LNext Observatories design lifetime is defined as the 5-year period following the NASA Acceptance of the Observatory/Constellation on-orbit.

Off-nadir Image Intervals – A continuous recording of Landsat Next image sensor data or a Landsat Next data product not yet processed into a 164-kilometer (km)-(cross-track) by TBD-km (along-track) multispectral image of the Earth’s surface where the original image data is derived from an off-nadir observation.

Off-the-shelf Software – (a) Commercial-off-the-shelf (COTS) software - Software that is sold, leased, or licensed to the general public, either as a standalone software product or embedded in a software system.

(b) Modified-off-the-shelf (MOTS) software - COTS software that is modified to meet unique requirements of a specific customer. This software requires ongoing unique maintenance for the life of the system not normally offered by the vendor.

(c) Government-off-the-shelf (GOTS) software - Software provided to the customer as government-furnished equipment (GFE) with no warranty or maintenance provided.

Onboard Calibration – Sensor calibration data that provides information on the instrument's response to dark images (dark calibration) and white images (lamp calibration) for the reflective bands. Sensor calibration data that provides information on the instrument's response to known cold and hot sources (black-body calibration sources) for the thermal bands.

Operable Detector – A detector is considered operable, even if out of spec, when it meets the following requirements:

Operational Power – Main Bus Power supplied to the subsystems or instrument for the purpose of powering the functions necessary to accomplish mission objectives.

Operational Simulators (OOPS) – OOPS consists of Spacecraft Operational Simulator (SOPS) and Landis Operational Simulator (LOPS).

Optical Axes – The X, Y, and Z axes of the Cartesian coordinate system that aligns its positive Z-axis with the vector of the optical axis of the telescope optical system traveling from the focal plane towards the objective mirror of the telescope. The optical axes form a right-handed coordinate system with the X-axis normal to the line formed by the detectors in each band, and its positive direction is defined to be towards the leading spectral band (the first band that images a ground target object). The Y-axis is constructed as the cross product of the Z-axis and the X-axis.

Orbit Average Power – The orbit average power allocated by the system for use by the Spacecraft/LandIS/Subsystem for a specified mode (i.e. if left in a particular mode for an entire orbit, how much power is needed?). Orbit Average is used to determine adequate energy balance for the observatory.

Offgassing – The emanation of volatile matter of any kind from materials into a crewed pressurized volume.

Outgassing – The emanation of volatile materials under vacuum conditions resulting in a mass loss and/or material condensation on nearby surfaces.

1.16 P

Part – A hardware element that is not normally subject to further subdivision or disassembly without destruction of design use. Examples include resistor, integrated circuit, relay, connector, bolt, and gaskets.

See Level of Assembly.

Part – A hardware element that is not normally subject to further subdivision or disassembly without destruction of design use. Examples include resistor, integrated circuit, relay, connector, bolt, and gaskets.

Payload – An integrated assemblage of modules, subsystems, etc., designed to perform a specified mission in space. For the purposes of this document, "payload" and "spacecraft" are used interchangeably. Other terms used to designate this level of assembly are Laboratory, Observatory, Satellite and System Segment.

See Level of Assembly.

Payload – The integrated assemblage of observatories, adapters and dispenser structure as well as any other co-manifested flight hardware.

Performance Verification – Determination by test, analysis, or a combination of the two that the payload element can operate as intended in a particular mission; this includes being satisfied that the design of the payload or element has been qualified and that the particular item has been accepted as true to the design and ready for flight operations.

Pixel – Short for “picture element.” It is the smallest discrete piece of image data in an image and corresponds to a single spatial sample.

Pixel Column – A column of image pixels in the direction of the WRS3 path that has not been geodetically resampled but has been radiometrically calibrated.

Note: these pixels may have an intermediate resampling and/or aggregation of digital numbers from multiple detectors such as time-delayed integration (TDI) or frame stacking.

Pixel Row – A row of image pixels in the cross-track direction of the WRS3 path that has not been geodetically resampled but has been radiometrically calibrated.

Note: these pixels may have an intermediate resampling and/or aggregation of digital numbers from multiple detectors such as time-delayed integration (TDI) or frame stacking.

Pointing – The process of controlling the location or direction of a line of sight with respect to an intended target location or direction.

Polarization Factor (PF) – The modulation ratio PF = (Lmax-Lmin)/(Lmax+Lmin) associated with a polarization sensitivity measurement.

Polarization Sensitivity – The sensitivity of the system to changes in the polarization of the signal.

Power Service – Comprises all parts, wire, connectors and board traces in series between the Main Bus and the individual load for power, and between the load and Spacecraft Single Point Ground (SPG) for power return. May include fault protection and switching.

Priority Scenes – Special image collection requests that are marked by the observatory for priority data delivery, processed immediately into Level 1 data products, and made available to the user.

Priority Schedules – Observatory command schedule uploads that are developed, uploaded, and executed on a particular observatory of the constellation in an expedited fashion, i.e. outside of the nominal schedule upload cycle.

Protoflight Testing – See Hardware.

Prototype Hardware – Hardware of a new design. Prototype hardware is subject to a design qualification test program, and it is not intended for flight.

Prototype Testing – See Hardware.

1.17 Q

Qualification – See Design Qualification Tests.

1.18 R

Raw Detector Data – The digital number output from the Analog-to-Digital Converters.

Redundancy (of design) – The use of more than one independent means of accomplishing a given function.

Reference Ellipsoid – The WGS 84 reference ellipsoid is defined by NIMA TR8350.2.

Reflective Band Sensor Data – Reflective Band Sensor Data are the originally measured detector or detector column output counts at the native spatial and spectral possibly adjusted by reversible offset and scale corrections. Offset and scale correction reversibility implies that the relationship between the original detector counts and the remapped data counts is one-to-one for all measured detector output values. See imaging sensor data.

Reflight Hardware – Flight hardware that has been used operationally in space and is to be reused in the same way. The verification program to which it is subject depends on its past performance, current status, and the upcoming mission.

Relative Response – Within the context of the specifications for the Landsat Next Spectral Bands, the term Relative Response has the same definition as the Relative Spectral Radiance Response Curve.

Relative Spectral Radiance Response Curve – Is a normalized (unitless) function of Spectral Radiometric Sensitivity divided by the peak in-band Spectral Radiometric Sensitivity. The resultant data plotted against wavelength generally appears to be a continuous smoothly varying function or “curve”. This is an instrument-level response (can have a filter-level spectral response curve, too) that incorporates the optical transmission of the telescope and optical bandpass filters, and the photon detector's radiance responsivity.

Reserve Mass – Mass reserved by the customer's program management for potential changes or unforeseen impacts to the mass budget.

1.19 S

Safe-life – Ensures that the largest flaw that could remain undetected after non- destructive examination would not grow to failure during the mission.

Safe Configuration – The subsystems or instrument will survive indefinitely for the conditions described.

Scattered Light – Undesired light contamination projected on a focal plane caused primarily by uneven surface features on optical surfaces. This optical surface roughness is usually measured by performing a bidirectional reflectance (BRDF) measurement for each optical surface.

Scene – A set of Landsat Next image sensor data, or an Landsat Next data product, representing a 164-km-(cross-track) by TBD-km (along-track) multispectral image of the Earth’s surface.

Scene Quality – Scoring systme used by USGS to notify the end user of the data integrity.

Quality score is a value 0 (Worst) - 9 (Best)

Ingest verifies checksum placed by the instrument. This is a demerit-based system where:

100 CRC errors within a scene decrease the quality score by one (1) count. (L8/L9)

Science Data – Instrument Imagery and Instrument Ancillary output in the format provided to the Spacecraft Mass Storage…