Attachment N -LNext Analytical Math Models Document -Rev -.pdf

LAMMD LNEXT-SYS-DESC-0003

Revision -ii

Landsat Next Analytical Math Models Definitions

Signature/Approval Page Prepared by:

Electronic Signature in TDMS 12/16/2022 Michael Pryzby Date Landsat Next Systems Engineer NASA/GSFC, Code 426

Approved by:

Electronic Signature in TDMS 12/16/2022 Mark Edison Date Landsat Next Deputy Observatory Manager NASA/GSFC, Code 426

Approved by:

Electronic Signature in TDMS 12/16/2022 Wen-Ting Hsieh Date Landsat Next Payload Manager NASA/GSFC, Code 426

Approved by:

Electronic Signature in TDMS 12/16/2022 Joy Henegar-leon Date Landsat Next Payload Technical Manager NASA/GSFC, Code 426 iii

Approved by:

Electronic Signature in TDMS 12/16/2022 Evan Webb Date Landsat Next Systems Manager NASA/GSFC, Code 599

Approved by:

Electronic Signature in TDMS 12/16/2022 James Pontius Date Landsat Next Project Manager NASA/Goddard, Code 426 iv

CM Foreword This document is a Landsat Next Project Configuration Management (CM)-controlled document.

Changes to this document require prior approval of the applicable Configuration Control Board (CCB) Chairperson or designee. Proposed changes shall be submitted to the Landsat Next CM Office (CMO), 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 Management Office Greenbelt, Maryland 20771 v

Change History Log Revision Effective Date Description of Changes

- 12/16/2022 LNEXT-CCR-0016– Initial Release vi

List of TBDs/TBRs Hyperlink to TBx Location Summary Ind.

Name/Org. Due Date

TBx-1 Section

2.4.3 The launch vehicle and launch site are TBD. Michael

Pryzby SRR/MDR vii

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

CM FOREWORD ......................................................................................................................... IV

CHANGE HISTORY LOG ............................................................................................................ V

LIST OF TBDS/TBRS .................................................................................................................. VI

TABLE OF CONTENTS ............................................................................................................. VII

LIST OF FIGURES .................................................................................................................... VIII

LIST OF TABLES ........................................................................................................................ IX

1.0 INTRODUCTION

1.1 LNEXT Related Documentation

1.1.1 Reference Documents

2.0 MISSION OVERVIEW

2.1 Mission Statement

2.2 Mission Background

2.3 Mission Objectives

2.4 Mission Implementation

2.4.1 Space Segment

2.4.2 Ground Segment

2.4.3 Launch Segment

3.0 GLOBAL MODELING GUIDELINES

3.1 Model Submittal and Configuration Control

3.2 Model Archival in the LNext Library

3.2.1 File Management Control

3.2.2 Model Log Entries

3.2.3 Access Control

3.3 Documentation

3.4 Coordinate Systems

3.5 Mass Conventions

3.6 Units

4.0 MODEL MATERIAL PROPERTIES

4.1 Structural Properties

4.2 Thermal Properties

4.3 Thermal Environmental Parameters

5.0 STRUCTURAL SOLID MODELING

5.1 Structural Model Format

5.2 Model Numbering

5.3 Documentation

5.4 Model Checks

viii

6.0 REDUCED CAD MODELING (ENVELOPE)

6.1 Structural Model Format

6.2 Model Numbering

6.3 Documentation

6.4 Model Checks

7.0 STRUCTURAL MODELING (FEM)

7.1 Finite Element Model Format

7.2 Finite Element Model Numbering

7.3 Documentation

7.4 Model Checks

7.5 Analysis Results

8.0 THERMAL MODELING

8.1 Thermal Modal Format

8.2 Thermal Model Numbering Scheme

8.3 Documentation

8.3.1 Outline of Thermal Model Exchange Document

8.4 Model Checks

9.0 REDUCED THERMAL MODELING (INTERGRATED LV ANALYSIS)

9.1 Thermal Model Size

9.2 Geometric Math Model (GMM) Configuration

9.3 Thermal Math Model (TMM) Configuration

9.4 Documentation

9.4.1 Outline of Thermal Model Exchange Document

9.5 Model Checks

10.0 STRUCTURAL/THERMAL/OPTICAL PERFORMANCE POINTING ANALYSIS

10.1 Model Format

10.2 Model Numbering Scheme

10.3 Documentation

10.4 Model Checks

11.0 ATTITUDE CONTROL SYSTEM MODELING

11.1 Scope of Attitude Control System Model

11.2 Model Naming Convention

11.3 Coordinate Systems

11.4 Documentation

11.5 Model Checks

APPENDIX A ABBREVIATIONS AND ACRONYMS

APPENDIX B DEFINITIONS

List of Figures Figure 2.4-1 Landsat Next Operations Concept Figure 3.2-1 Example of File Structure on LNext Electronic Library ix

List of Tables

Table 3.2.1-1 Example of Configuration Log Spreadsheet for Individual Models/Files ...10 Table 3.2.1-2 Configuration Log of Integrated Models Identifying Subassembly Files Table 4.3-1 Recommended Thermal Environmental Parameters for LNext

1.0 INTRODUCTION

This document defines guidelines for the format, content, and documentation that will accompany analytical models over the course of the Landsat Next (LNext) program. The analytical models are those required for pre-flight performance prediction, design verification, and post-flight assessment. All math models used to satisfy the verification requirements of mission-critical hardware or subsystems are included. Thus, lower-level math models that are delivered and are to be incorporated into the Observatory model must also adhere to these guidelines. The controlled disciplines include:

• 3D Computer Aided Design (CAD) models

• Thermal

• Structural

• Dynamic

• Attitude Control Subsystem (ACS) The integration of discipline analyses is also the subject of this document. Examples are:

• Structural configuration solid models (STEP)

• Structural Finite Element Models (FEM)

• Observatory thermal analysis models

• Combined Structural /Thermal/ Optical models defining pointing performance These guidelines apply to contractually required math models delivered to the LNext project.

Typically, these deliveries occur in support of the following element-level reviews and mission-level analysis:

• Mission Definition Review/ System Requirements Review (SRR)

• Preliminary Design Review (PDR)

• Critical Design Review (CDR)

• Math models delivered in association with interim analysis cycles

• Models updated based upon ground or flight test data The delivery dates for LandIS (LIS), Spacecraft (SC), Observatory (OBS), and Mission Payload (MP) level models as identified in the appropriate Data Requirements Description (DRDs) will be identified and tracked in the LNext Giver/Receiver list. This list will also track mutually agreed interim models generated between contractually required model deliveries. Thus, interim models should be available and will follow the guidelines in a manner consistent with contractually required deliveries.

Applicability of these guidelines is specific to the following models in both their flight (stowed and deployed) and ground based test configurations:

• SC, OBS, and MP models delivered by the SC supplier to the LNext Project Office

• LandIS model(s) delivered by Instrument supplier(s) to the LNext Project Office

1.1 LNEXT RELATED DOCUMENTATION

1.1.1 Reference Documents

Document Number Title Revision NASA/TM 2001-211221 Guidelines for the Selection of Near-Earth

Thermal Environment Parameters for Spacecraft Design

N/A

ELVL-2016-0044292 Thermal Analysis Report, LSP Flight Analysis Division Thermal Analysis Group Payload ,Thermal Model Submittal Guideline, Rev 2

MMPDS-09 Metallic Materials Properties Development and Standardization (MMPDS)

MMPDS-09

In this document, citations are assumed to be the latest version unless otherwise noted.

This document table was generated from the Landsat Next Referenced Documents List Draft Rev -

2.0 MISSION OVERVIEW

2.1 MISSION STATEMENT

Landsat Next, consistent with United States (U.S.) law and government policy, will continue the Landsat program's acquisition, archival, and distribution of multi-spectral imagery affording global, synoptic, and repetitive coverage of the Earth's land surfaces at a scale where natural and human-induced changes can be detected, differentiated, characterized, and monitored over time.

2.2 MISSION BACKGROUND

Following the successful launch of Landsat 8 (formally named Landsat Data Continuity Mission, LDCM) in February 2013, and during the development of Landsat 9, the United States Geological Survey (USGS) and National Aeronautics and Space Administration (NASA) recognized the need to assemble a team of experts from within both agencies to evaluate how to inform an acquisition strategy for the Landsat mission to follow Landsat 9. The NASA-USGS Joint Agency Sustainable Land Imaging (SLI) Architecture Study Team (AST) was formed in September 2018 and was tasked with investigating how to best satisfy the diverse set of user needs collected in the USGS “User Needs for the Sustainable Land Imaging Program – Release 2.0.” These investigations resulted in a set of recommendations to the headquarters of both agencies, delivered in December 2019. The highest-recommended “Roadmap 1” architecture described a small constellation of “superspectral” space-based sensors that would substantially improve the spectral, spatial, and temporal capabilities of previous Landsat missions, while continuing to satisfy the primary goal of ensuring a highly calibrated data set that maintains compatibility with the legacy data of the Earth’s land mass held in the National Satellite Land Remote Sensing Data Archive (NSLRSDA) at USGS’s Earth Resources and Observation Science (EROS) Center. In April 2020 NASA/Goddard Space Flight Center (GSFC) received authorization to initiate the Landsat Next project consistent with the AST’s Roadmap 1 recommendation.

The goal of Landsat Next is to continue the acquisition, archival, and distribution of multi-spectral imagery affording global, synoptic, and repetitive coverage of the Earth's land surfaces at a scale where natural and human-induced changes can be detected, differentiated, characterized, and monitored over time. This goal is in keeping with the Landsat programmatic goals stated in both the Commercial Space Act of 1998 (Public Law 105-303) and the Land Remote Sensing Policy Act of 1992 (Public Law 102-555). This policy requires that the Landsat Program provide data into the future that is sufficiently consistent with previous Landsat data to allow the detection and quantitative characterization of changes in or on the land surface of the globe.

Landsat Next continues the long-running partnership of NASA and USGS, with NASA providing the space and launch segments and USGS providing the ground system, providing the longest continuous global record of the Earth’s surface. The Landsat series of satellites have continuously acquired multispectral images of the global land surface since the launch of the Earth Resources Technology Satellite (ERTS, later renamed Landsat 1) in 1972. The Landsat data archive constitutes the longest continuous moderate-resolution record of the global land surface as viewed from space.

2.3 MISSION OBJECTIVES

Landsat Next has these major mission objectives:

• Collect and archive moderate resolution multispectral image data and thermal image data, affording seasonal coverage of the global landmass for a continuous period of not less than five (5) years.

• Ensure that Landsat Next data are sufficiently consistent with data from the earlier Landsat missions in terms of relative acquisition geometry, calibration, coverage characteristics, spectral characteristics, output product quality, and data availability to permit studies of land cover and land use change over multi-decadal periods.

• Ensure Landsat Next is responsive to critical emerging user needs and applications as characterized by periodic assessment, currently the User Needs for the Sustainable Land Imaging Program July 2018, Release 2.0, and identified by the operational requirements for collection, processing, archiving, and distribution of land surface data to the United States Government and other users.

• Distribute Landsat Next data products to the general public on a nondiscriminatory basis.

2.4 MISSION IMPLEMENTATION

NASA and USGS each have specific responsibilities for Landsat Next and will deliver the major elements to the overall mission. NASA will provide the Space and Launch Segments of Landsat Next, and USGS will provide the Ground System and mission operations. NASA/GSFC will provide overall Landsat Next project management, mission system engineering, and mission assurance during development and will transition the mission to USGS following on-orbit commissioning.

The Landsat Next post-launch nominal mission operations concept is shown graphically in the Figure below.

Figure 2.4-1 Landsat Next Operations Concept

2.4.1 Space Segment

NASA/GSFC will provide the Space Segment via competitive procurements for the science instruments and the spacecraft bus. The Space Segment will consist of a constellation of three observatories flying in coordinated sun-synchronous orbits at 653km altitude, each with nominally identical spacecraft and instrument suites. The observatories will be equally spaced in the orbit, providing in aggregate a six-day ground repeat period at the equator.

The instrument suites will each provide 26 spectral bands with a maximum ground sampling distance of 10m-60m dependent on the spectral band, covering a swath on the ground of approximately 164km on a ground track defined by a world-wide reference system known as

WRS-3.

2.4.2 Ground Segment

The Landsat Ground Segment currently supports mission operations for Landsats 8 and 9.

Landsat Next takes advantage of developments on these missions and will upgrade and expand the current systems to accommodate Landsat Next. The Landsat Ground Segment consists of the Ground System (GS) and its external interfaces, including NASA institutional services. The GS includes the Mission Operations Center (MOC), the Ground Network (GN), and the Data Processing and Archive System (DPAS). External interfaces include NASA's Near Space Network (NSN) and NASA ACCESS Space relay (i.e. TDRSS) and government/commercial ground station, NASA/GSFC Conjunction Assessment and Risk Analysis (CARA) and its NASA/GSFC Flight Dynamics Facility, along with other external interfaces.

The MOC provides the primary means to control and monitor the Landsat Next constellation.

The Landsat Next Flight Operations Team (FOT) at the MOC performs mission planning and scheduling, command and control, health and status monitoring, orbit and attitude maintenance, performance analysis, onboard memory management, and flight and ground software maintenance. The FOT utilizes MOC functionality to detect, investigate and resolve spacecraft anomalies and monitor the instrument image collections from the onboard constellation and generate special image collections. The MOC ingests, processes and archives data via the GN.

The GN includes geographically dispersed ground station resources for mission execution, and includes both the Landsat Ground Network (LGN) and a wideband or cloud-based data routing capability to transfer both mission data to DPAS, and TT&C data to the MOC. The LGN consists of US Government-owned, international, and commercial ground stations, and provides communication capability for each observatory of the constellation for commanding and housekeeping data via S-Band two-way links. The LGN will also receive mission data from each observatory via high rate Ka-band downlinks.

The DPAS ingests, processes, and archives LNext mission data from the GN. The DPAS also provides a long-term archive capability for raw data and allows the user community to query, download, and directly interact in the cloud with Landsat Next science products, via a public-facing web portal for receiving data products. The DPAS is located at USGS Earth Resources Observation and Science (EROS) near Sioux Falls, South Dakota.

The USGS will lead overall Landsat Next GS development. The USGS will also lead integration of the GS and ensure timely completion of ground readiness testing in preparation for NASA-led mission readiness activities. The MOC will perform planning, scheduling, and observatory operations activities during Landsat Next mission readiness testing.

2.4.3 Launch Segment

The Launch Segment will provide the assets and services associated with the Launch Vehicle (LV) and the constellation-to-LV integration. This will include the LV; all Launch Vehicle- Ground Support Equipment (LV-GSE), property, and facilities to integrate the constellation to the LV and verify their integration; and prelaunch testing with ground-based functions. The launch vehicle and launch site are TBD. The three observatories comprising the Landsat Next constellation will be launched together on the same launch vehicle.

Sections 2.0-2.4.3 were generated using Landsat Next Common Boilerplate (LNEXT-MGMT- DESC-0005) Rev B

3.0 GLOBAL MODELING GUIDELINES

If not specifically stated in the discipline sections, the guidelines specified in this chapter apply to all disciplines.

3.1 MODEL SUBMITTAL AND CONFIGURATION CONTROL

All models delivered will be maintained in the LNext electronic library as described in this section. The LNext electronic library will be hosted at GSFC on a server that meets current NASA/GSFC information technology standards for controlled access. Access for each of the suppliers will be controlled to protect property rights and enforce export control rules. The models deposited by the suppliers are either required deliveries or agreed-to deliveries in support of the complete mission analysis effort. Constituent models that are exchanged between suppliers and as required under each suppliers’ contract, Statement of Work (SOW), or implementation plans will be tracked in the LNext Giver/Receiver list.

LNext requests that constituent models be provided when design or analysis updates have occurred naturally during the program. This allows the program to work from the latest set of models throughout the program, regardless of formal delivery dates. As suppliers internally release or update baselines, those models should also be updated in the repository. Regarding formal deliveries, if a previously supplied model has had no changes due to its maturity or has a lack of design change or validation activity, then a new model need not be posted to the electronic library site. The LNext Analytical Math Models Definitions (LAMMD) document does not relieve suppliers of their contract, SOW, or implementation plan required deliveries.

The Contract Data Requirements List (CDRL) deliveries for contract purposes are not readily shared between suppliers and typically take a longer period of time to be available for use. It is expected that the LNext electronic copy will arrive at the repository before the CDRL delivery to the Contracting Officer (CO).

3.2 MODEL ARCHIVAL IN THE LNEXT LIBRARY

Model delivery needs to maintain an archival structure in the constituent folder of the Integrated Model folder within the LNext electronic library. GSFC will establish and maintain the file structure within the electronic library, however, proper placement and archival of model files placed within this system is the responsibility of all suppliers. Folders will be established at the top level for the model disciplines discussed herein (structural solid models [CAD], structural FEMs, thermal math models [TMMs], ACS models).

An example of the file structure to be established on the LNext electronic library is shown in Figure 3.2-1. Each model delivery should be posted in a separate folder under the appropriate discipline. Naming convention for these folders consist of two parts. The first part of the folder name consists of the date of the posting, the item modeled, and the model discipline (e.g., yymmdd_SC_Thermal_ for an SC thermal model posted on YY/MM/DD). Additional descriptive information in the folder name (Preliminary Design Review [PDR] drop, Critical Design Review [CDR] drop, etc.) are helpful but not required. All model files and description documents pertaining to the particular model drop must be included in this folder. Interim revisions to model files or documents for a given model delivery can be added to this folder only after archiving the old revision of the changed file in an “Archive” folder within the model folder. Upon completion of a given modeling cycle, the LNext Project Office may choose to freeze the folder to maintain configuration control and prevent erroneous model information from being added later. At this time write access will be removed, but read access will be retained for all suppliers.

Figure 3.2-1 Example of File Structure on LNext Electronic Library

3.2.1 File Management Control

File management factors that must be dealt with consist of the following: asynchronous design of the constituent sub-systems, several disciplines spread across numerous organizations, and computing resources that are distributed and dissimilar. To provide configuration control for LNext, file management control will be implemented in addition to the model folder configuration plan defined in Section 3.2.2. In each of the three top-level folders, a spreadsheet exists to document model deliveries and file revisions for that discipline. When models are dropped into the LNext electronic library, the appropriate descriptive information for that drop must be added into the folder’s spreadsheet, as shown in Table 3.2.1-1. All interim files that are revised as described in Section 3.2.2 must also be included in the folder’s spreadsheet ledger along with the reason for the revision and a short description of the changes. This practice provides a running log of all the models used on LNext throughout the life of the program.

Table 3.2.1-1 Example of Configuration Log Spreadsheet for Individual Models/Files

Submitted by Date Model Name Rev. Description Supplier Thermal Engineer xx/xx/xx yymmdd_SC_Thermal_ - PDR/ reduced SC thermal model for the deployed case

A fourth top-level folder labeled “Integrated Model” will reside in the LNext electronic library, and this folder will be reserved for the location, archival, and configuration control of the LNext Observatory-level models. Three folders (one for each discipline) will exist under this top-level folder, where the respective Observatory-level solid models, structural models, and thermal models will reside. Separate configuration control spreadsheets will exist for each of the integrated models so that revision tracking at the Observatory level can be maintained. This spreadsheet log will require the same effort to make sure entries are recorded every time a model is added to the LNext electronic library, however, more information is required. In addition to providing the reason for the model existence or revision, along with a short description of the changes made, it is imperative that this spreadsheet records WHICH version of each of the subelement models were used to assemble the integrated model. This is critical to maintain integrated model configuration tracking. An example using a Thermal delivery of this spreadsheet is shown in Table 3.2.1-2.

Table 3.2.1-2 Configuration Log of Integrated Models Identifying Subassembly Files

LNext Model Log Submitted by Date Model Name Re v.

Descripti on Sub-Model Names

LandIS SC Name/ Organizati on/ Contact Info xx/xx/ xx yymmdd_OBS_Ther mal_

- Support

SC CDR

yymmdd_LandIS_Ther mal_ yymmdd_SC_The rmal

3.2.2 Model Log Entries

Each analytical model resides in a folder that is labeled with a version number for that particular element based on the design state reflected in the model. Other descriptors can be included as desired or appropriate. All input files, sample case output files, and documentation needs to be grouped together in one folder. The folder name for that model will have the following form:

yymmdd_System_Discipline_Suffix Explanations of each part of the folder naming scheme are included below:

yymmdd: The year, month, and day the model was released/configured from the supplier.

_System: Refers to the portion of the Mission Payload at a given level of assembly. It could be the whole Observatory (OBS), a Space Flight element (SC or LANDIS), or possibly a particular sub-system.

_Discipline: Describes the particular engineering discipline.

_Suffix: Information pertinent to the model for identification purposes, descriptors to note

PDR/CDR/Pre-Environmental Readiness (PER) drops, or modeled subsystem or revision.

Description: Will address state of the design described by the model. An example would be the second model iteration in the Preliminary Design Review (PDR2) analysis cycle.

This column clarifies the state of the model in terms of factors such as: Stowed or Deployed; Fixed or Free; or Structural or Thermal Distortion.

Format: Details the model file format. CREO, STEP, Thermal Desktop, etc.

Folder Name: Details which folder the file is located.

Archived: Y/N. Notes the status of the file. When updates are deposited into the library, older versions can be moved to the Archive Folder and noted is this column.

Submodels: For integrated models, record the version of the subelement models. Ex. LandIS reduced thermal.

3.2.3 Access Control

Read access will generally be available to the government, the SC supplier, and the Instrument teams. Authorization for access to the model folders within the LNext electronic library is provided by LNext Mission Systems Engineering. Access to detailed FEM and detailed TMMs will not be made available to the SC and Instrument suppliers. This restriction will be removed if acceptable by the respective supplier. Reduced Instrument and SC models for structures and thermal analysis are available to all the LNext team members.

3.3 DOCUMENTATION

A textual/ graphical description of each model in an associated document, in either Microsoft (MS) Office Suite, MS Visio or text file, should be provided. For ACSs analysis and disturbance assessment, MathWorks SimuLink models should be provided. This document will reside in the model folder along with the model data files. Design features included or changed since the prior model update should be noted in the documentation-particular description. Model heritage should include descriptions of the parent models, e.g., the optical prescription and the mechanical design, structural, and/or modal models that form the basis for the model. Model configuration, in terms of the component deployment states, need to be included. For thermal analyses, necessary information includes the particular orbits (beta angle, beginning of life [BOL] or end of life [EOL] conditions, and Observatory attitude history) that are established in the model. In addition, software application version number used in the creation of the model and analysis results must be noted.

At delivery events, the documentation must include results for example cases. Input files will be included along with the documentation to allow the results to be regenerated for crosscheck.

Model checks or verification cases are defined for each model under a “Model Checks” section that follows.

3.4 COORDINATE SYSTEMS

There are five coordinate systems defined for LNext. The Observatory, Spacecraft, the Dispenser, and LNext Mission Payload reference coordinate systems are defined in the LNext Spacecraft Interface Requirements Document (LNEXT-SC-ICD-0002). The LandIS reference coordinate system is defined in the LandIS Interface Requirements Document (LNEXT-

LANDIS-ICD-0001).

It is expected that subsystem and module elements (e.g., Spacecraft, Instrument suite) coordinate systems will be parallel to the Observatory coordinate system, with origin offsets, as required.

The dispenser and Mission Payload coordinate systems will also be parallel. Any auxiliary coordinate system will need to be defined in the appropriate interface control documents, as well.

To support packaging in the fairing, the Mission Payload and Dispenser coordinate systems may not be parallel to every Observatory coordinate system. Offset and rotations will be defined in the appropriate interface requirement documents.

3.5 MASS CONVENTIONS

All analytical models delivered for inclusion in the integrated Observatory model should use the current best predicted mass as defined by the estimated mass + contingency.

3.6 UNITS

All models should use the International System of Units (SI) units (meter, kilogram, Newton) for communicating data to other models and for all inputs and outputs. Angular measures should use radians or microradians as units. Degrees measurements may be provided for human input or output interface convenience. All parameters will have units clearly marked, regardless of the unit set selected. All angles communicated between computational models will be expressed as radians.

4.0 MODEL MATERIAL PROPERTIES

All LNext suppliers are expected to use the same material properties database for all structural, dynamic, and thermal analyses. This document defines the preferred set of properties to use. If a different value is used, it must be identified in the model delivery.

4.1 STRUCTURAL PROPERTIES

Material properties used for all structural modeling should be obtained from the Metallic Materials Properties Development and Standardization (MMPDS-16, 2020) Handbook. A-basis values should be used for all metallic components when calculating margins of safety.

4.2 THERMAL PROPERTIES

Thermal and optical properties for all thermal modeling must be approved by the GSFC Material Committee. Vendors should follow the process defined in the Mission Assurance Requirements (MAR) to submit material properties to the committee for approval.

4.3 THERMAL ENVIRONMENTAL PARAMETERS

Recommended thermal environmental parameters that should be used to provide consistency across model deliveries are identified in Table 4.3-1. Usage of environmental parameter values different than those in Table 4.3-1 should be approved by the project.

Table 4.3-1 Recommended Thermal Environmental Parameters for LNext

Parameter Hot Case Cold Case Solar (Watts/ m^2) 1419 1317 Earth Infrared (IR) (Watts/ m^2) 261 215 Albedo 0.35 0.25 Optical Properties EOL BOL

5.0 STRUCTURAL SOLID MODELING

Structural modeling is used to define the solid model configuration of the LNext Instruments, Spacecraft, Observatory, Dispenser, and Mission Payload. These models are used to demonstrate Field of View (FOV) compliances, physical interferences, interface location/definitions, thermal FOVs, stay-out zones, volume envelopes, venting ports, and mechanism deployment sweeps.

These models are also used in conjunction with the FEMs to generate integrated structural analysis to validate and verify acceptable load conditions during launch and orbit. Sub-models should follow the requirements of the higher assembly model (Spacecraft and Instrument Models should follow the formats below of the Observatory Model.)

5.1 STRUCTURAL MODEL FORMAT

The preferred format for solid model exchanges is International Standards Organization (ISO) 10303-242, STEP AP242. Solid model exchanges must adhere to the following guidelines:

• To be consistent with the launch vehicle supplier, the system of units defined in Section 3.6 is used for all solid models.

• The coordinate systems should per their definitions in their respective ICDs.

• The origin of the local coordinate system should be expressed per their definitions in their respective ICDs.

• The files should be zipped when delivered to LNext.

• The model must have solids and not just surfaces.

• Unnecessary elements should be deleted to minimize model size.

• Assembly structure must be preserved and not compressed into a single part without approval from the LNext Project.

5.2 MODEL NUMBERING

Numbering or identifying elements in the solid model is not critical or required. However, attachment interfaces and locations must clearly be marked and defined so that integrated models can be accurately assembled.

5.3 DOCUMENTATION

Documentation for solid model exchanges must identify critical changes made to the model since the last model submittal. In addition, any changes to volume envelopes, including FOVs or stay-out zones, must be specified.

5.4 MODEL CHECKS

Model checks for solid model exchanges require that all internal warnings be eliminated. In addition, the supplier should verify that there are no surface interferences contained within the transferred ‘.stp’ file.

6.0 REDUCED CAD MODELING (ENVELOPE)

Reduced modeling is used to define the outer mold lines (OML) of the LNext Instruments, Spacecraft, Observatory, Dispenser, and Mission Payload. The Observatory Models includes the Spacecraft and Instrument Models. The Dispenser Model includes the Dispenser Base and three Dispenser PAFs. The Mission Payload includes three Observatories and the Dispenser. These models are used to demonstrate maximum physical envelopes, remove before flight items, install before flight items, and launch vehicle adapter protuberances. These models are used to verify close approach points to the payload static envelop. The models are also used to determine fairing access points post-encapsulation. The model is solely in the launch or stowed configuration. Sub-models should follow the requirements of the higher assembly model (reduced Spacecraft and reduced Instrument Models should follow the formats below of the Observatory Model OML.)

6.1 STRUCTURAL MODEL FORMAT

The preferred format for solid model exchanges is International Standards Organization (ISO) 10303-242, STEP AP242. Solid model exchanges must adhere to the following guidelines:

• To be consistent with the launch vehicle supplier, the system of units defined in Section 3.6 is used for all solid models.

• The coordinate system should be per their definitions in their respective ICDs.

• The origin of the local coordinate system should be per their definitions in their respective ICDs.

• The files should be zipped when delivered to LNext.

• Unnecessary elements (internal items) should be deleted to minimize model size.

• The Mission Payload Model’s OML will be intact/unaltered.

• The Observatory Model OML will include Multi-Layered Insulation (MLI), flight and/or RBF enable plugs, harness service loops, Insulating Tape, and any other items that affects the OML.

• All components internal to the Mission Payload interface ring will be included.

• The Observatory Models will be in the “Stowed for Launch” configuration.

• If there are “Remove Before Flight” (RBF) items that will stay on the Spacecraft until after Fairing Encapsulation, then those items will be included in the Model.

• Model RBF items should be clearly marked (e.g., Named as such, Red in color, etc.).

• If there are “Install Before Flight” (IBF) items that will be installed on the Observatory before flight, those items will be included in the Model.

• Model IBF items should be clearly marked (e.g., Named as such, Green in color, etc.).

6.2 MODEL NUMBERING

Numbering or identifying elements in the reduced model is not critical or required except for the RBF and IBF items. See Section 6.1. However, attachment interfaces and locations must clearly be marked and defined so that integrated models can be accurately assembled.

6.3 DOCUMENTATION

Documentation for solid model exchanges must identify critical changes made to the model since the last model submittal. In addition, any changes to volume envelopes, RBF, IBF must be specified. This documentation should include the following:

• A minimum of Eight (8) Verification “Snapshots” images will be provided; one

(1) from each of the following Spacecraft axis views: +X, -X, +Y, -Y, +Z, and –Z, as well as a minimum of two (2) Isometric views showing all six faces of the Spacecraft. With view orientation labels (+X, etc.).

• The Snapshot Images of the Spacecraft should be taken in the model’s native format and NOT of the converted STEP file model.

6.4 MODEL CHECKS

Model checks for solid model exchanges require that all internal warnings have been eliminated.

In addition, the supplier should verify that there are no surface interferences contained within the transferred ‘.stp’ file.

7.0 STRUCTURAL MODELING (FEM)

Structural modeling of the individual elements of LNext (Spacecraft and LANDIS Instrument(s)), Dispenser (Dispenser Base and Dispenser PAFs), as well as the integrated Observatory and Mission Payload will be performed to predict performance against the levied requirements. This section defines the guidelines in order to provide accurate model representation at the Observatory, Dispenser, and Mission Payload level as well as ensure that the integrated model can be seamlessly assembled with a minimum number of modifications.

Structural models are required for both the stowed (pre-launch, launch, and ascent phases) and deployed (all on-orbit phases and modes) configurations. This includes the Instrument model(s) where on-orbit deployments of radiators, Earth and Sun shields, or other one-time events result in a new configuration. Separate models may be necessary for various analyses, such as dynamics, stress, and thermal distortion. All models will follow the same guidelines.

7.1 FINITE ELEMENT MODEL FORMAT

Each model provided should be a full physical NASA Structural Analysis (NASTRAN) FEM.

There should be no reduction or simplification. If the NASTRAN model does have mass and stiffness matrices representing components, then the Observatory Craig-Bampton model will not include those points, and no Output Transformation Matrix (OTM) data for that portion of the model will be recovered from a Coupled Loads Analysis (CLA). The model coordinate system needs to be parallel to the Spacecraft coordinate system as indicated in Section 3.4 and defined by the Observatory Interface Requirements Documents, Section 3.4.1.2 Reference Frames.

The criteria for a model for CLA analysis are almost the same for all launch vehicles. There might be differences of how many total numbers of rows in the data recovery matrices are acceptable for each launch vehicle contractor, but typically a total number of rows of 3000 is acceptable, however, this number can be higher. The Observatory integrator will derive allocations between the Spacecraft and the Instruments.

The Craig-Bampton model is typically in a NASTRAN OUTPUT4 ASCII format and includes stiffness, mass, and data recovery matrices. OUTPUT4 binary format has also been used previously. Matlab files have been used as well.

7.2 FINITE ELEMENT MODEL NUMBERING

The full physical NASTRAN models delivered for LNext will use the following element numbering allocations:

Spacecraft: 1 to 1,999,999 Instrument Deck: 2,000,000 to 2,999,999 LANDIS Instrument: 3,000,000 to 3,999,999 Dispenser Base and Components: 4,000,000 to 4,999,999 Dispenser PAFs: 5,000,000 to 5,999,999 Miscellaneous Mission Payload: 6,000,000 to 6,999,999

Additional elements, as required This numbering scheme applies to the node, elements, materials, and properties assigned in the respective models. Exceptions to this are the FEMS at their interface points. The Spacecraft

FEMs must use GRID IDs starting at 101 for the three Spacecraft-to-Deployment System interface points. The LANDIS FEM must use GRID identifications (IDs) 301, 302, and 303 for the three interface points. The Dispenser Base starts at 401, and the Dispenser PAFs at 501.

7.3 DOCUMENTATION

Each FEM submittal must be accompanied by a report documenting the delivery. As a minimum, this document will include:

1) A picture representation of the model

2) GRID Point Weight Generator results to identify mass, center-of-gravity, and inertia characteristics

3) A modal mass table that identifies significant mode shapes to at least twice the predicted minimum frequency

4) The definition of all interface nodes or elements with respect to a single-reference coordinate system is needed for each delivery

5) Identification of all interface grid points and locations used in the FEM

6) Identification of all output requests for CLA cycles such as elements of interface forces, displacements, accelerations, etc. to be included in the OTM Each Craig Bampton FEM submittal must be accompanied by a report documenting the delivery.

For the model document, it should include the following:

1) Definition of degrees of freedom of stiffness and mass matrices

2) Description of the coordinate system of the model and the location of its origin

3) Coordinates of interface points

4) Clocking of Mission Payload and each Observatory relative to Launch Vehicle coordinate system

5) Damping ratios for the fixed-interface modes of the Craig-Bampton model

6) Units used for the model (stiffness and mass) and units associated with the output of the data recovery matrices

7) Description of rows of data recovery matrices (loads, accelerations, displacements …) as well as description of the format of the data recovery matrices (mode displacement versus mode acceleration)

8) Model uncertainty factor to be used in the analysis

9) Listing of model frequencies (of the Craig-Bampton Modes) – for checking purposes

10) Rigid-Body mass properties (masses, inertias, and CG location) – for checking purposes

11) Modal effective weights for the Craig-Bampton modes (preferred for checking purposes)

12) If needed, identification of rows in the displacement recovery matrix to be used in the dynamic loss of clearance (LOC) analysis

Note: There may be limits placed on the number of output requests by the Launch Vehicle provider. Should that occur, the government will work with the Spacecraft supplier to allocate the number of output requests to the various systems.

For LANDIS FEM(s), the origin and location of the “reference coordinate system” for all nodes will be defined in the Spacecraft and LANDIS IRD.

For SC, Observatory, and Dispenser FEMs, the origin and location of the “reference coordinate system” for all nodes will be defined in the LNext Spacecraft Interface Requirements Document.

The Mission Payload FEM, the origin and location of the ‘reference coordinate system’ for all nodes will be defined in the LNext Spacecraft and Launch Vehicle Interface Requirements Document.

7.4 MODEL CHECKS

Deliveries of structural models for the LNext program must include a set of appropriate standard FEM validity checks to show accurate and correct predictive capability. These checks will include, but are not limited to, grounding, free-free modes, 1-g check to sum forces and unit enforced displacement checks. See https://femci.gsfc.nasa.gov/validitychecks/ for descriptions of the specific validity checks.

7.5 ANALYSIS RESULTS

An Excel file with individual sheets for each results matrix must be provided back to the requesting organization. The information on each should include at least the Acceleration Transformation Matrix (ATM), Displacement Transformation Matrix (DTM), and Loads Transformation Matrix (LTM).

The worksheet title should state which matrix is detailed and the total number Degrees of Freedom (DOF) requested.

ATM

Column Titles should be as follows:

Description Node

ID

CID Output Request

Time History

X Y Z RX RY RZ DOF

Where:

Output Request = ‘Acceleration’ Time History: Place an X if a time history is needed X, Y, Z, RX, RY, RZ: Place an X if that DOF is being requested DOF: Enter the total number of DOF requested for each row (most likely 6)

DTM

CID Output Request

Output Request = ‘Displacement’ X, Y, Z, RX, RY, RZ: Enter an X if that DOF is being requested

LTM

A separate worksheet for each different type of element being requested (CBAR, CELAS, MPC, etc.). The content of the CBAR table is a continuous row for each element requested (The Title row below was separated to fit the page).

CBAR

Description Element ID Type CID Output

BENDING A1 BENDING A2

Description BENDING

B1

BENDING

B2

SHEAR

SHEAR

AXIAL TORQUE DOF

Output Request = ‘Elforce’ Enter an X if any of those DOFs are being requested DOF: Enter the total number of DOF requested for each row (most likely 7 or 1)

CELAS

Description Element

Type CID DIRECTION Output

FORCE DOF

Output Request = ‘Elforce’ Enter an X under force DOF: Going to be 1

MPC

Type CID Output

Output Request = ‘MPCforce’ Enter an X if that DOF is being requested DOF: Enter the total number of DOF requested for each row

8.0 THERMAL MODELING

Thermal models are used throughout the life of the LNext program to provide:

• Early predictive thermal control subsystem performance for sizing

• Thermal interface definition and compliance

• Segment and Observatory-level thermal test design and correlation

• On-orbit predictive scenario simulation Thermal models of the Observatory are required for both the stowed configuration (pre-launch, launch, and ascent phases) and the deployed configuration (all on-orbit phases and modes). The required models include the Instrument models where on-orbit deployments of radiators, Earth and Sun shields, or other one-time events result in a new configuration. The pre-launch stowed model should consider convective thermal effects during all Launch Vehicle encapsulated operations through fairing separation.

A stand-alone reduced Mission Payload thermal model may be required to support Launch Services’ integrated thermal analysis of pre-launch and ascent phases. Reference the latest revision of ELVL-2016-0044292, LSP Payload Thermal Model Submittal Guideline, for further details of the reduced thermal model.

8.1 THERMAL MODAL FORMAT

All thermal Geometric Math Model (GMM) exchanges must be in Thermal Desktop (TD) format. All Thermal Math Model exchanges must utilize Systems Improved Numerical Differencing Analyzer/Fluid Integrator (SINDA/FLUINT). Thermal GMMs must contain a geometry file with the suffix “.dwg” (example: OBS.dwg). Optical properties for all surfaces in the GMM must reside in a file with the suffix “.rco” (example: OBS.rco). Thermal material properties will reside in a file with the suffix “.tdp” (example: OBS.tdp).

8.2 THERMAL MODEL NUMBERING SCHEME

The integrated Observatory-level and Mission Payload thermal models will utilize “sub-models” during assembly, so node and surface numbering assignment is not critical. However, any node and surface numbering scheme used must be compatible with TD and SINDA.

Though node numbering convention is not critical for the thermal models, node and surface quantities for the integrated Observatory and Mission Payload models are essential for reasonable run times. The LANDIS Instrument thermal model(s) that are used for integration into the Observatory model should not exceed 5000 nodes (per instrument) to ensure acceptable run-times at the higher level models.

8.3 DOCUMENTATION

All thermal models exchanged between suppliers need to include documentation describing the layout and flow of the model logic. This includes an overall description and picture of the model, definition of heater and/or thermostat control nodes, special algorithms used for thermal hardware, and a table of the heat dissipations used and the nodes to which these sources are assigned. Heat dissipations should be provided in both orbit-average and time-varying format for easy integration into larger, Observatory-level models. These heat (power) dissipations should be provided as a function of Observatory on-orbit mode so that the model can be used for all mission phases. Use of SINDA arrays for transient heat dissipation profiles is encouraged because their use eases integration at higher levels. Heater power should be specified in terms of heater resistance to account for variance due to voltage. A description of all deployments required from the stowed to deployed mode, as well as a list of the surfaces and nodes involved is needed to transform system-level models from launch to operational configurations. Finally, a table describing the worst case hot and cold beta angles and optical property conditions (i.e., hot beta angle End-of-Life, cold beta angle Beginning-of-Life) is required to assist in overall thermal case modeling.

Liberal use of comment statements in the thermal model file will aid in accurate integration and use of the supplied model. Use of standard SINDA heater, thermostat, and heat pipe routines should be flagged so that proper callouts can be supplied in the integrated model.

8.3.1 Outline of Thermal Model Exchange Document

A representative outline of the required documentation is provided below. This outline can be tailored to meet the needs of the particular model and is dependent on the level of comments in the models themselves.

1) Purpose

a. Brief Description of the model and its ‘as delivered’ capabilities and limitations

b. Changes since last exchange

2) Definitions

c. Naming convention of delivered files

3) Assumptions

d. Include Observatory attitude and attitude history for each thermal configuration analyzed

4) Description

e. Geometry Model

• Illustrations Showing Nodal Breakdown

• External Modeling

• Internal Modeling

• Optical Properties, Environments

• Nodal Correspondence, if applicable

• Description of special techniques used, such as effective radiation node

(ERN)

• Any special considerations regarding Number of Rays, Cut-off Factors

• Results from the model for verification

f. Thermal Math Model

• Node Descriptions (which are not documented in the model or that require an additional explanation)

• Key Interface/Boundary Nodes

• Additional Table containing nodes that were not a part of the Geometry Model

• Description of Conductors (which are not documented in the model or require additional explanation)

• Table of Electronics Dissipation

• Table of Heaters showing footprint area, resistance, location by node, type of control and control temperature range, location by node of control temperature

• Description of any special logic being employed

• Results from the model for verification

5) Results

g. Geometry Model

• Radiation Conductances (Radks), Heat Rates

h. Thermal Math Model

• Temperatures, Heater Duty Cycles

8.4 MODEL CHECKS

Sample output from a known test case condition is required to confirm accurate integration of supplied thermal models after delivery.