Attachment F - LANDIS-Interface Requiremens Document-Rev A.pdf

LIRD LNEXT-LANDIS-ICD-0001 Revision A ii

Landsat Next Instrument Suite (LandIS) Interface Requirements Document (IRD)

Signature/Approval Page

Prepared by:

Electronic Signature in TDMS Approval Date in TDMS Amy DeLisa Date Landsat Next Payload Systems Engineer Org./Code 426

Approved by:

Electronic Signature in TDMS Approval Date in TDMS Wen-Ting Hsieh Date Landsat Next Payload Manager Org./Code 426

Approved by:

Electronic Signature in TDMS Approval Date in TDMS James Pontius Date Landsat Next Project Manager Org./Code 426

Approved by:

Electronic Signature in TDMS Approval Date in TDMS Evan Webb Date Landsat Next Mission System Manager Org./Code 599 iii

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 iv

Change History Log v

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

Name/Org.

Due Date

TBx-1 Section 2.4.3

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.

Launch Services Segment

(LSS)

MCDR

TBx-2 Section 3.2.1.2

LIRD-139 LandIS shall meet the dimensional envelope constraints of 1.95m (76.77 in) in the +Z by 1.37m (53.94 in) in the +Y axis by 2.0 m (78.74 in) in the X Axis under a combination of static, dynamic, and thermal conditions encountered during factory assembly, system test, transportation and handling and launch. (TBR)

Mechanical IPDR

TBx-3 Section 3.2.1.4

LIRD-160 LandIS shall have a total mass of not to exceed 550 kg (TBR) mass including all associated hardware, intra-LandIS harnessing, and any attached external harnessing extending to the spacecraft connector interface bracket.

Mechanical ISRR

TBx-4 Section 3.2.1.4

LIRD-169 LandIS center of mass, including IMSC, shall be no more than TBD from the centerline of LandIS volume.

Mechanical IPDR

TBx-5 Section 3.2.1.7

LIRD-214 The IMSC volume, including all mounting hardware and brackets, shall not exceed a Star Tracker Subassembly volume of 0.18 m^3 (TBR) and an Inertial Reference Unit (IRU) Subassembly volume of 0.12 m^3 (TBR).

Mechanical IPDR

TBx-6 Section 3.2.1.7

LIRD-208 LandIS shall accommodate an IMSC total mass not to exceed 50 Kg (TBR) on the LandIS deck.

Mechanical IPDR

TBx-7 Section 3.2.1.7

LIRD-316 The thermal heat transfer between the LandIS deck and IMSC shall be less than or equal to 0.1 W/C (TBR) over the orbit average.

Thermal IPDR

TBx-8 Section 3.2.1.7

LIRD-213 LandIS shall provide an unobstructed glint free zenith-directed field of view for the star trackers in the IMSC of 25 deg (TBR) along track by 25 deg (TBR) cross-track.

Mechanical IPDR

TBx-9 Section 3.2.2.2

LIRD-650 LandIS shall maintain alignment stability of 1 degree (TBR) or less, 3-sigma, per axis, between the IMSC mounting location and the instrument deck interface plane with the spacecraft, during a period of 18 days.

Attitude Control

System (ACS)

IPDR

vi

TBx-10 Section 3.2.2.2

LIRD-651 LandIS shall maintain alignment stability of 0.1 degrees (TBR) or less, 3-sigma, per axis, between the IMSC mounting location and the instrument deck interface plane with the spacecraft, during a period of 30 seconds.

ACS IPDR

TBx-11 Section 3.2.2.3

LIRD-478 LandIS shall maintain uncompensated momentum contribution not exceeding +/- 0.5 N-m-sec per axis. (TBR)

ACS IPDR

TBx-12 Section 3.2.2.3

LIRD-483 LandIS shall maintain periodic disturbance (with polarity change) torque magnitudes, including torques resulting from linear forces reacting from the LandIS to the spacecraft within the acceptable range of Figure 3.2.2.3-1 (TBR) for all frequencies.

ACS IPDR

TBx-13 Section 3.2.2.3

LIRD-485 LandIS shall maintain disturbance torque with no polarity change to below 4x10-3 N-m (TBR) for durations of 10 seconds (TBR) or less and 1x10-3 N-m (TBR) for durations above 10 seconds (TBR) for each axis.

ACS IPDR

TBx-14 Section 3.2.3.3

LIRD-317 The thermal heat transfer between the LandIS deck and the spacecraft shall be less than or equal to 0.1 W/C (TBR) over the orbit average.

Thermal IPDR

TBx-15 Section 3.2.4.1

LIRD-320 LandIS shall receive the following electrical interfaces and services from the spacecraft (TBR), by design.

-LandIS output data bus(es) and input bus(es) -Operational Power Service -Survival Heater Power Service -Grounding Interface -1 Pulse Per Second (PPS) Interface -Discrete commands and telemetry, as needed -Discrete Bilevel & Analog telemetry, as needed

Electrical ISRR

TBx-16 Section 3.2.4.2

LIRD-342 LandIS shall not exceed margined orbit average power of 350W (TBR). Power ISRR

TBx-17 Section 3.2.4.3.1

LIRD-351 LandIS Survival heaters shall be sized using a minimum voltage of 24 V (TBR) at the LandIS Main Bus Survival Heater power service interface.

Power ISRR

TBx-18 Section 3.2.5.1

LIRD-391 LandIS shall provide a limited amount (TBD) of LandIS Focal Plane Array (FPA) & test pattern data and raw detector diagnostic data to the spacecraft over an output data bus.

Command & Data Handling

(C&DH)

ISRR

TBx-19 Section 3.2.5.1

LIRD-538 LandIS instrument data blocks delivered to the SC for storage shall be in the range between 2.5 (TBR) seconds and 5.0 (TBR) seconds per data block.

C&DH ISRR

TBx-20 Section 3.2.5.1

LIRD-436 LandIS shall provide telemetry as polled by the spacecraft at a frequency of TBD. C&DH ISRR vii

TBx-21 Section 3.2.5.2

LIRD-425 Rationale: Note: The time-of-day signal will be accurate to 100 nanoseconds

(TBR).

Electrical IPDR

TBx-22 Section 3.2.5.4.2

LIRD-400 LandIS shall provide the "I'm alive" message at a rate of every 1 second (TBR) to the SC as an active bi-level signal.

C&DH ISRR

TBx-23 Section 3.2.6

LIRD-667 LandIS shall require a near-continuous purge from the arrival at the SC contractor facility until launch (TBD).

Contamination ISRR viii

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

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

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

LIST OF TBDS/TBRS .................................................................................................................... V

TABLE OF CONTENTS ............................................................................................................ VIII

LIST OF FIGURES ...................................................................................................................... IX

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

1.0 INTRODUCTION

1.1 Purpose

1.2 Scope

1.3 Related Documents

1.3.1 Applicable Documents

1.3.2 Reference Documents

1.3.3 Project 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 INTERFACE REQUIREMENTS

3.1 General

3.2 SUBSYSTEM REQUIREMENTS

3.2.1 Mechanical Interface

3.2.1.1 Reference Frames

3.2.1.2 Volume and Dimension

3.2.1.3 LandIS Field of View

3.2.1.4 Mass Properties

3.2.1.5 LandIS Access, Integration & Deintegration

3.2.1.6 LandIS Mounting

3.2.1.7 Instrument Mounted Spacecraft Components (IMSC) Sensor Accommodation

3.2.2 Orbit Control, Pointing and Alignment

3.2.2.1 Pointing Stability and Jitter

3.2.2.2 Alignment

3.2.2.3 Disturbance Torques

3.2.3 Thermal Interface Requirements

ix

3.2.3.1 Operating & Survival Heaters and Temperatures

3.2.3.2 Thermal Allocations

3.2.3.3 Thermal Isolation

3.2.4 Electrical Interface Requirements

3.2.4.1 Electrical Interfaces

3.2.4.2 Power Allocation

3.2.4.3 Main Bus Power

3.2.4.4 Power Distribution Interfaces

3.2.4.5 Instrument Suite Class R Grounding Interface

3.2.4.6 Electric Harnesses and Connectors

3.2.5 Command and Data Handling

3.2.5.1 Data Bus(es)

3.2.5.2 Time-of-day Signal

3.2.5.3 Discrete Commands

3.2.5.4 Discrete Telemetry

3.2.6 LandIS Purge and Venting

APPENDIX A ABBREVIATIONS AND ACRONYMS

APPENDIX B DEFINITIONS

List of Figures

Figure 2.4-1 Landsat Next Operations Concept (Generated from Landsat Next Common Mission Architecture Diagram LNEXT-SYS-DESC-0022 Rev -)

Figure 3.2.1.1-1 Observatory Orbital Reference Frame Figure 3.2.1.2-1 LandIS Triplet Radially Stowed Configuration Figure 3.2.1.6-1 Mass Acceleration Curve Figure 3.2.2.3-1 Torque Limit Figure 3.2.5.1-1 LandIS Functional Data Buses

List of Tables

Table 3.2.1.6-1 Component Design Loads (Break Points)

1.0 INTRODUCTION

1.1 PURPOSE

The Landsat Next Instrument Suite (LandIS) Interface Requirements Document (IRD) sets forth the initial interface requirements imposed between the LandIS and the Landsat Next Spacecraft, with a focus on the LandIS side of the interfaces, across the many subsystems, from Mechanical to Command and Data Handling.

1.2 SCOPE

Throughout this document references will be made to the LandIS and to the spacecraft.

References to the LandIS refer to the LandIS suite and apply only to the LandIS. References to the "Spacecraft" or "SC" applies only to the Landsat Next spacecraft.

The requirements that are indicated with "Reserved" text are applicable to the interface;

however, they are not allocated directly to that side of the interface.

The Landsat Next Interface Requirements documents (SCIRD, LIRD) are controlled and maintained by the Landsat Next Project office. The SCIRD is levied on the spacecraft contractor.

The LIRD is levied on the LandIS contractor. These IRDs are maintained at Level 3 and will contain sibling tracing to tie the SC interface requirements and LandIS interface requirements.

1.3 RELATED DOCUMENTS

1.3.1 Applicable Documents

Document Number Title Revision Section Reference EEE-INST-002 Instruction for EEE Parts Selection, Screening, Qualification, and Derating

- Section C2 (Table 5), Section F1 (Table 4), Section F3 (Table 4), Section R1 (Table 4), Section W1 (Table 4A)

MSFC-STD-3029 Guidelines for the Selection of Metallic Materials for Stress Corrosion Cracking Resistance in Sodium Chloride Environments

A Table 1

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

This document table was generated from the Landsat Next Common Reference and Applicable Documents List (LNEXT-MGMT-DESC-0008) Rev C.

1.3.2 Reference Documents

Document Number Title Revision GSFC-STD-1000 Rules for the Design, Development, Verification, and Operation of Flight Systems H

NASA-STD-4003 Electrical Bonding for NASA Launch Vehicles, Spacecraft, Payloads, and Flight Equipment

A w/CHANGE 1

Public Law #105-303 “Commercial Space Act of 1998,” Public Law #105-303, 112 Stat., 2843., H.R. 1702, 105th Congress, Adopted October 28, 1998

N/A

Document Number Title Revision Public Law #102-555 “Land Remote Sensing Policy Act of 1992,”

Public Law #102-555, 106 Stat. 4163., H.R.

6133, 102nd Congress, Adopted October 28, N/A

CCSDS 123.0-B-2 Low-Complexity Lossless and Near-lossless Multispectral and Hyperspectral Image Compression

Recommended Standard, Issue 2, Technical corrigendum

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

This document table was generated from the Landsat Next Common Reference and Applicable Documents List (LNEXT-MGMT-DESC-0008) Rev C.

1.3.3 Project Reference Documents

Document Number Title LNEXT-SYS-DESC-0016 Landsat Next Geometric Error Budget (GEB) In this document, citations are assumed to be the latest version unless otherwise noted.

This document table was generated from the Landsat Next Common Reference and Applicable Documents List (LNEXT-MGMT-DESC-0008) Rev C.

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, Visible Through Short Wave Infrared (VSWIR) reflective and Thermal Infrared (TIR) emissive 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 and management of land cover along with land and water resource change over multi-decadal time 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 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 (Generated from Landsat Next Common

Mission Architecture Diagram LNEXT-SYS-DESC-0022 Rev -)

2.4.1 Space Segment

NASA/GSFC will provide the Space Segment, which 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 Advanced Communications Capabilities for Exploration and Science Systems (ACCESS), GSFC Conjunction Assessment and Risk Analysis (CARA) and its 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 data routing capability, which transfers mission data to DPAS across wide area networks. The LGN provides communication capability for each observatory of the constellation for commanding and housekeeping data via the S-Band and will receive mission data from each observatory over a Ka-band downlink.

The DPAS ingests mission data from the GN, processes the mission data to form data products, and archives the data products (Level 0, Level 1R, Level 1Gs, Level 1T). 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 data 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 C

3.0 INTERFACE REQUIREMENTS

3.1 GENERAL

The Landsat Next Interface Requirements are maintained across two documents; namely the SCIRD and LIRD. They are controlled and maintained by the Landsat Next Project office. The SCIRD is levied on the spacecraft contractor. The LIRD is levied on the LandIS contractor.

These IRDs are maintained at Level 3 and will contain sibling tracing to link the SC interface requirements and LandIS interface requirements. Changes to a requirement with a sibling trace will require review/update of the corresponding sibling requirement and approval of both parties of the interface.

Since the Project is early in the mission, and the LandIS procurement will precede the Spacecraft procurement, the strategy is to have the LandIS contractor provide an Instrument Interface Description (IDD) Document. The IDD will be used to better inform and update these interface requirements.

For references to specific definitions and terms, refer to Appendix B.

3.2 SUBSYSTEM REQUIREMENTS

3.2.1 Mechanical Interface

3.2.1.1 Reference Frames

The Observatory Orbital Reference Frame is a right-handed, orthogonal, XYZ coordinate system defined such that the origin is at the Observatory center of mass (CM), the +Z axis points toward Geocentric Nadir, the +X axis is coplanar with both the +Z axis and the Observatory inertial velocity vector (and is in the general direction of the Observatory inertial velocity vector), and the +Y axis completes the right-handed, orthogonal coordinate system, as shown in Figure 3.2.1.1-1.

NOTE: See Appendix B Definitions for the Geocentric Nadir definition.

Figure 3.2.1.1-1 Observatory Orbital Reference Frame

LandIS is to use an optical reference coordinate system that is defined as a right-hand, orthogonal, body fixed, XYZ coordinate system with the +Z axis aligned with the LandIS optical axis and the coordinate system documented as shown in Figure 3.2.1.1-1.

LandIS contractor or provider will describe its LandIS Mechanical (or Body) Reference Frame in the LandIS's MID including the mathematical translation between the origin of the LandIS Mechanical Reference Frame and the LandIS Optical Reference Frame.

LandIS Body Frame is a right-hand, orthogonal, body-fixed XYZ system with +Y / +Z plane at the SC to LandIS interface plane, and the +Z direction pointing to nadir, the +X direction in the velocity vector, and the +Y completing the right-handed, orthogonal coordinate system.

3.2.1.2 Volume and Dimension

LIRD-139 LandIS shall meet the dimensional envelope constraints of 1.95m (76.77 in) in the +Z by 1.37m (53.94 in) in the +Y axis by 2.0 m (78.74 in) in the X Axis under a combination of static, dynamic, and thermal conditions encountered during factory assembly, system test, transportation and handling and launch. (TBR)

Rationale: The dimensional envelope constraints include the LandIS deck, IMSC and extends from the length of the flexures to the SC mounting point. A separate on-orbit volume requirement will need to be defined in the IDD if LandIS incorporates a deployable device into its operational configuration. The deployed envelope will not obstruct any observatory fields of view. Axes referenced are for the observatory body frame defined in Section 3.2.1.1.

Note: Requirements are for the stowed configuration as shown in Figure 3.2.1.2-1. The spacing of 0.22 m shown in the figure between the LandIS max envelopes is not a firm requirement, but it should stand until a full-up structural analysis and payload-level trade study can be completed.

Figure 3.2.1.2-1 LandIS Triplet Radially Stowed Configuration

LIRD-174 LandIS dimensional envelope shall enclose the fully assembled LandIS, LandIS-unique flexures, LandIS-unique fastening hardware, thermal blankets (including billowing during launch and ascent), connectors (LandIS-side only), and intra-instrument harness (with connectors), as well as any other items that constitute any part of a deliverable LandIS along with the IMSC hardware.

Rationale: The intent of this requirement is that everything provided as part of a deliverable instrument, including the items identified above, be allocated against the instrument size and weight allocations, and that everything provided by the spacecraft contractor be held against the spacecraft allocation. The IMSC is to be included in the LandIS physical envelope. Axes referenced are for a stowed configuration and are for the observatory body frame defined in Section 3.2.1.1.

3.2.1.3 LandIS Field of View

LIRD-154 LandIS boresight of the unobstructed field of view shall be parallel to the nadir (+Z) axis.

Rationale: This requirement is intended to formalize the relative orientation of the spacecraft and LandIS coordinate systems - i.e., the LandIS boresight axis is in the spacecraft +Z (nadir) direction. The SC is responsible for alignment control between the Spacecraft Attitude Determination Frame and the LandIS Interface (mounting surface datums). The details of how the mount must be oriented so as to put the LandIS boresight in the proper direction is left as a detailed item to be worked out by LandIS and spacecraft in the Interface Control Document

(ICD).

3.2.1.4 Mass Properties

The defined not-to-exceed mass defined by the LandIS dimensional envelope includes the fully assembled instrument, LandIS-unique flexures, instrument-unique fastening hardware, thermal blankets, connectors (instrument-side only), LandIS deck, and intra-instrument harness (with connectors), as well as any other items that constitute any part of a deliverable instrument along with the IMSC hardware.

LIRD-160 LandIS shall have a total mass of not to exceed 550 kg (TBR) mass including all associated hardware, intra-LandIS harnessing, and any attached external harnessing extending to the spacecraft connector interface bracket.

Rationale: This does not include the IMSC mass. This is a NTE estimate, and the reserve is contained within. It does include the LandIS deck, flexures, blankets, fasteners.

LIRD-163 LandIS mass shall be measured to an accuracy of ± 0.2%.

LIRD-169 LandIS center of mass, including IMSC, shall be no more than TBD from the centerline of LandIS volume.

LIRD-171 LandIS moments and products of inertia are to be measured or calculated using coordinates based on the spacecraft axes but passing through the LandIS center of mass.

LIRD-172 LandIS moments and products of inertia values shall be accurate to within ± 5% for calculated values, and the lesser of 1.5% or 300 kg-cm² for measured values.

3.2.1.5 LandIS Access, Integration & Deintegration

LIRD-182 LandIS shall not require access to the opposite side of the spacecraft mounting interface for attachment or removal.

LIRD-184 LandIS shall allow for access to all telescope optical surfaces during I&T without disturbing alignment that would require telescope performance revalidation.

LIRD-219 LandIS items to be installed, removed, or replaced at the spacecraft level shall be accessible without disassembly of higher levels of assembly.

LIRD-220 LandIS shall be mechanically integrated or deintegrated vertically, with the spacecraft interface horizontal.

Rationale: LandIS should be lowered to the spacecraft interface. The -X spacecraft axis is pointing upward from the ground.

3.2.1.6 LandIS Mounting

LIRD-133 LandIS mechanical interface shall incorporate alignment pins to ensure precise placement and provide repeatability should removal and reinstallation ever be required.

LIRD-187 LandIS deck shall be mounted to the spacecraft with kinematic mounts.

Rationale: Flexures that provide a pseudo-kinematic fixity are preferred for their linearity and stability, but they must be designed to suitably release the proper degrees of freedom at the mounting interface to ensure proper sensor performance and provide structural interface force reductions. The baseline assumption is that the flight mounting flexures will be provided by the Instrument Vendor, but this isn't considered a hard requirement at this time.

LIRD-189 LandIS shall accommodate IMSC sensor components mounted to the LandIS deck.

Rationale: Specific locations and accommodations will be negotiated in the ICD development process. The LandIS contractor routes harnesses provide by the SC contractor, such as power, signal, and heater harnesses.

LIRD-196 The LandIS deck shall accommodate the mounting of all LandIS components within the LandIS allocated stowed volume.

LIRD-198 LandIS mounting interfaces to the spacecraft shall be in the +Y, +Z plane, in the anti-Ram face of the Spacecraft bus.

Rationale: The anti-ram, directional reference is based on the on-orbit configuration described in Figure 3.2.1.1-1. A more detailed image to be provided with IDD.

LIRD-192 LandIS shall have a first significant mode of no less than 35 Hz, when mounted on flexures to a rigid interface.

Rationale: Sensitivity to inputs from the launch environment increases substantially if fundamental modes fall below 35 Hz. In addition, having a fundamental frequency below 35 Hz increases the chance of dynamically coupling with other observatory subsystems that may negatively impact predicted loads.

Note: A lower fundamental frequency may be allowed, with approval from the Landsat Next Project, based on demonstration of positive strength margins against the defined limit loads and evaluation of dynamic coupling with the observatory.

LIRD-200 LandIS shall comply with not-to-exceed interface limit loads based upon the

Mass Acceleration Curve (MAC) for components as shown in Figure 3.2.1.6-1.

Rationale: These loads represent the quasi-static loads due to the low-frequency launch environment. The hardware should be designed for the loads given below as well as for loads induced by the high frequency random environment. The breakpoints for the MAC are given in Table 3.2.1.6-1. Design loads shown below should be updated based on the results of coupled loads analysis. Linear interpolation may be used between break-points to determine limit loads.

Note: The MAC is expected to be superseded by a combined launch vehicle and Observatory coupled loads analysis (CLA), and the CLA will presumably be the driver for Observatory-level dynamics testing.

Figure 3.2.1.6-1 Mass Acceleration Curve

Table 3.2.1.6-1 Component Design Loads (Break Points)

Hardware Mass (kg) Quasi-static Load (g) 1 68.0 5 50.0 11 38.0 22 30.2 32 25.9 43 23.2 53 21.2 64 19.6 74 18.4 85 17.4 95 16.5 106 15.8 116 15.2 127 14.6 137 14.1 150 13.6 160 13.2 170 12.8 180 12.5 190 12.2 200 and above 12.0

LIRD-202 LandIS structural support components shall be designed to show positive margin for limit load using FS=1.25 for yield and FS=1.4 for ultimate, when constituted of MSFC-STD-3029 Table 1 materials.

3.2.1.7 Instrument Mounted Spacecraft Components (IMSC) Sensor Accommodation LIRD-205 LandIS deck shall accommodate IMSC sensors, such as gyros and star trackers, and associated mounting hardware and brackets provided by the spacecraft vendor.

LIRD-214 The IMSC volume, including all mounting hardware and brackets, shall not exceed a Star Tracker Subassembly volume of 0.18 m^3 (TBR) and an Inertial Reference Unit (IRU) Subassembly volume of 0.12 m^3 (TBR).

Rationale: These IMSC volume numbers are not to exceed values. The IMSC volume is assumed to be bookkept within the LandIS volume.

LIRD-208 LandIS shall accommodate an IMSC total mass not to exceed 50 Kg (TBR) on the LandIS deck.

Rationale: Mass of IMSC which reside on the LandIS instrument deck are provided by SC. This allocation is part of the overall SC budget and not part of the instrument budget and includes power and data harnessing. This allocation includes all hardware, secondary structure, harness, MLI and MMOD blanketing.

LIRD-316 The thermal heat transfer between the LandIS deck and IMSC shall be less than or equal to 0.1 W/C (TBR) over the orbit average.

Rationale: Heat transfer to the IMSC cannot impact thermal conditions.

LIRD-211 The IMSC radiators shall have an unobstructed FOV of space opposite the direction of the sun.

Rationale: LandIS should not obstruct any SC radiators.

LIRD-213 LandIS shall provide an unobstructed glint free zenith-directed field of view for the star trackers in the IMSC of 25 deg (TBR) along track by 25 deg (TBR) cross-track.

3.2.2 Orbit Control, Pointing and Alignment

The values contained within this section are consistent with the LNEXT-SYS-DESC-0016, Geometric Error Budget (GEB).

The requirements in this section will be iterated with the Spacecraft and LandIS teams upon selection.

Several TBRs contained in this section will be updated following line-of-sight jitter and ACS analyses. The process for developing the Finite Element Models (FEMs) is as follows: The instrument vendor is responsible for creating an Instrument Finite Element Model (FEM) based on their instrument design, and the spacecraft vendor will create a spacecraft FEM, based on their design. These are integrated by the spacecraft vendor to create an Observatory FEM. The Observatory FEM is used by the spacecraft vendor to perform analysis for instrument line-of-sight jitter generated by the spacecraft hardware, and by the instrument vendor to perform analysis for instrument line-of-sight jitter generated by instrument hardware.

3.2.2.1 Pointing Stability and Jitter

LIRD-268 All FEMs used for jitter analysis shall incorporate a damping ratio of 0.25% with a Model Uncertainty Factor (MUF) of 1 or a damping ratio of 0.5% with a MUF of 2.

Rationale: A consistent and appropriate damping ratio will allow for consistent interpretation of modeling results.

3.2.2.2 Alignment

LIRD-281 The Instrument Alignment References shall be viewable from two orthogonal directions when integrated to the Observatory.

LIRD-285 LandIS optical alignment devices shall be covered with a flight quality (and flight capable) cover.

Rationale: The covers eliminate the potential for glint/stray light from optical alignment devices on-orbit. Additionally, the covers reduce the potential of dislodging the optical device during ground processing.

LIRD-286 Any LandIS optical alignment device cover shall be accessible for removal during Instrument and Observatory Integration and Test.

LIRD-288 Any LandIS optical alignment device cover removed or installed during Observatory Integration and Test shall make use of captive fastening hardware.

Rationale: As one aspect of a Foreign Object Debris (FOD) Mitigation Plan, the use of captive hardware reduces the chance of loose hardware becoming lost during installation and removal of the cover during Observatory I&T.

Components of Boresight Alignment Knowledge Uncertainty resulting from alignment shifts allowed by clearances across the mounting interface (pin/fastener to hole tolerance) at the Instrument Interface (mounting surface datums) will be allocated to the LandIS.

LIRD-301 LandIS shall maintain alignment stability of 12 microradians or less, 3-sigma, per axis, from the VSWIR mounting interface to the Instrument Mounted Spacecraft Components mounting location, over any period of 98 minutes.

Rationale: The VSWIR to Instrument Mounted Spacecraft Components mounting location alignment must be stable over the orbit to ensure that the absolute geodetic accuracy requirements are met. Alignment drift is typically a combination of within-orbit drift and longer term seasonal drift. The seasonal component is amenable to ground calibration, but the within-orbit component is less so. LandIS deck material should be chosen to minimize detrimental distortions between the IMSC mounting location and the VSWIR mounting interface.

LIRD-299 LandIS shall maintain alignment stability of 1 microradian or less, 3-sigma, per axis, from the VSWIR mounting interface to the Instrument Mounted Spacecraft Components mounting location, over any period of 30 seconds.

Rationale: The VSWIR to Instrument Mounted Spacecraft Components mounting location alignment must be stable over the duration of 1 scene (approximately 30 seconds) to ensure that the geometric and band registration accuracy requirements are met.

LIRD-650 LandIS shall maintain alignment stability of 1 degree (TBR) or less, 3-sigma, per axis, between the IMSC mounting location and the instrument deck interface plane with the spacecraft, during a period of 18 days.

Rationale: Goal is to avoid the LandIS deck deforming and affecting the IMSC mounting location alignment stability relative to the SC body.

LIRD-651 LandIS shall maintain alignment stability of 0.1 degrees (TBR) or less, 3-sigma, per axis, between the IMSC mounting location and the instrument deck interface plane with the spacecraft, during a period of 30 seconds.

Rationale: Goal is to avoid the LandIS deck deforming and affecting the IMSC mounting location alignment stability relative to the SC body.

3.2.2.3 Disturbance Torques

LIRD-478 LandIS shall maintain uncompensated momentum contribution not exceeding +/- 0.5 N-m-sec per axis. (TBR)

Rationale: LandIS uncompensated momentum will be accommodated by the Spacecraft. This requirement may not apply to all mechanisms. For example, the requirement is not applicable to a cryocooler because there is not an accumulation of momentum (high frequency, sinusoidal).

Each mechanism will be assessed on a case-by-case basis.

LIRD-483 LandIS shall maintain periodic disturbance (with polarity change) torque magnitudes, including torques resulting from linear forces reacting from the LandIS to the spacecraft within the acceptable range of Figure 3.2.2.3-1 (TBR) for all frequencies.

Rationale: For instrument jitter-inducing mechanisms, LandIS is expected to meet a line-of-sight jitter requirement in addition to not significantly impacting Spacecraft pointing performance.

All mechanical requirements specified are to be met at the mechanical interface; that is, at the surface(s) of the spacecraft where the LandIS is in contact with the spacecraft, unless otherwise specifically indicated.

LIRD-485 LandIS shall maintain disturbance torque with no polarity change to below

4x10-3 N-m (TBR) for durations of 10 seconds (TBR) or less and 1x10-3 N-m (TBR) for durations above 10 seconds (TBR) for each axis.

Rationale: LandIS-induced fixed-polarity torque will affect Spacecraft pointing performance so it needs to be controlled.

Figure 3.2.2.3-1 Torque Limit

3.2.3 Thermal Interface Requirements

3.2.3.1 Operating & Survival Heaters and Temperatures

The operating and survival temperatures, as well as the thermal isolation requirements specified in this section are met at the mechanical interface between the spacecraft and the LandIS.

LIRD-306 LandIS shall use only power provided by its Main Bus Survival Heater power service for maintaining the LandIS survival heaters.

3.2.3.2 Thermal Allocations

LIRD-310 LandIS shall identify the location of operational temperature sensors and calibration data.

Rationale: Replace this requirement with information contained within the IDD.

3.2.3.3 Thermal Isolation

LIRD-317 The thermal heat transfer between the LandIS deck and the spacecraft shall be less than or equal to 0.1 W/C (TBR) over the orbit average.

3.2.4 Electrical Interface Requirements

3.2.4.1 Electrical Interfaces

LIRD-320 LandIS shall receive the following electrical interfaces and services from the spacecraft (TBR), by design.

-LandIS output data bus(es) and input bus(es) -Operational Power Service -Survival Heater Power Service -Grounding Interface -1 Pulse Per Second (PPS) Interface -Discrete commands and telemetry, as needed -Discrete Bilevel & Analog telemetry, as needed

Rationale: Interfaces represent known LandIS interfaces and those that may be required (designated as “as needed”), pending LandIS design. Note the reference to output bus(es) and input data bus(es) is intended to be logical or functional reference and does not necessarily imply a physical interface for each.

3.2.4.2 Power Allocation

LIRD-342 LandIS shall not exceed margined orbit average power of 350W (TBR).

Rationale: This number does include margin. Margin is maintained based on instrument lifecycle as specified in GSFC-STD-1000, Rule 1.06. Note: This does not include the power required for any IMSC.

3.2.4.3 Main Bus Power

3.2.4.3.1 Main Bus Voltage Range

LIRD-351 LandIS Survival heaters shall be sized using a minimum voltage of 24 V

(TBR) at the LandIS Main Bus Survival Heater power service interface.

Rationale: Ensure sufficient thermal control at a reduced voltage when the observatory is in a compromised state on-orbit that may prevent optimal power collection. The minimum Main bus voltage accounts for a least a single cell failure.

LIRD-355 LandIS shall operate and meet performance requirements for the voltage range of +27 to +35 VDC at the LandIS Main Bus Operational power service interface.

Rationale: This defines Main Bus operational voltage range.

LIRD-363 LandIS shall survive exposure to a Main Bus voltage range of 0 to +40 VDC at any Main Bus power service interface, for an indefinite period of time.

Rationale: This prevents the loss or damage to flight hardware that may result from human error or EGSE anomaly during ground processing.

3.2.4.3.2 Main Bus Power Quality

LIRD-358 LandIS shall meet all performance requirements in the presence of ripple voltages at the LandIS Main Bus Operational power service interface, up to 1.5V peak-to-peak over the frequency range of 30 Hz to 150 kHz.

Rationale: This defines Main Bus power quality and conducted susceptibility limits at frequency range consistent with CS101.

LIRD-360 LandIS shall meet all performance requirements in the presence of ripple voltages at the LandIS Main Bus Operational power service interface, up to 1V peak-to-peak over the frequency range of 150 kHz to 200 MHz.

Rationale: This defines Main Bus power quality and conducted susceptibility limits at frequency range consistent with CS114.

LIRD-475 LandIS shall provide Electromagnetic Interference (EMI) input filters installed on the LandIS side of the Main Bus Operational power service interface.

LIRD-476 LandIS shall provide EMI filters with both common-mode and differential-mode filtering of the Main Bus Operational power service.

3.2.4.3.3 In-Rush Current Transients

LIRD-366 LandIS shall limit the amplitude and duration of in-rush currents on the Main

Bus Operational power service interface, at both initial application of Main Bus power and subsequent internal component turn-on, to the following:

-850% load peak current for < 10 microsecond -250% load peak current for > 10 microsecond and < 10 milliseconds -100% load peak current for > 10 milliseconds

Rationale: Ensure that fault protection will not trip inadvertently due to turn-on transient, potentially rendering it difficult or impossible to turn on. Avoid damage to the power service due to the turn on transient. Minimize impact on Main Bus power quality.

3.2.4.3.4 Operational Transients

LIRD-369 LandIS shall limit the rate of change of the current for Main Bus Operational power service operational transients to be less than or equal to 20 milli-amperes/micro-seconds.

Rationale: Limits the impact on power quality by bounding Ldi/dt for operational transients.

3.2.4.4 Power Distribution Interfaces

LIRD-345 LandIS Main Bus Operational power service interfaces and Main Bus

Survival Heater power service interface shall be sized such that peak load current derating requirements of EEE-INST-002 are met over the operational voltage range, with any single conductor failed open.

Rationale: Satisfy derating requirements for bundled wire in a vacuum, allowing for a single failed conductor that would not be detectable after flight mate.

LIRD-372 LandIS shall isolate the redundant, independent interfaces to Main Bus Operational power services and Main Bus Survival Heater power services, by > 1 Mohm (power to power; return to return).

Rationale: Provides added robustness through LandIS select redundancy.

LIRD-374 LandIS shall isolate power returns for Main Bus Operational power services and Main Bus Survival Heater power services from chassis ground by > 1 Mohm.

Rationale: Preserve the observatory SPG scheme to avoid stray current and minimize EMI.

LIRD-376 LandIS shall receive Main Bus power from the spacecraft via separate connectors for the redundant Main Bus Operational power services and redundant Main Bus Survival Heater power services.

Rationale: Eliminate the possibility of catastrophic connector failure disabling both power services. It also ensures compliance with GSFC-STD-1000, Rule 1.25.

LIRD-378 LandIS shall isolate any single fault occurring on either a prime or redundant

Main Bus Operational power service or Main Bus Survival Heater power service, such that it cannot propagate to the opposite power service.

Rationale: Prevents failure of one power service from disabling both and resulting in loss of LandIS.

3.2.4.5 Instrument Suite Class R Grounding Interface

LIRD-382 Where the primary Class-R ground path from LandIS Chassis Ground Plane

(CGP) to Observatory CGP is via the LandIS mounting surface, the LandIS shall be electrically conductive and have sufficient surface area and flatness to achieve a bonding resistance of 2.5 milliohms, or less, when installed with all fasteners torqued to the specified values.

Rationale: Prevent high frequency radiated emissions from interfering with electronics by implementation of NASA-STD-4003A Class R grounding methods.

LIRD-384 Where the primary Class-R ground path from LandIS CGP to Observatory CGP is via ground straps, LandIS shall provide a minimum of three electrically conductive attach points, having sufficient surface area to achieve a bonding resistance of < 2.5 milliohms, with ground strap lugs installed and fasteners torqued to the specified values.

implementation of NASA-STD-4003A Class R grounding methods. Note: To the extent practical, ground strap attach points should be located equidistant from one another, around the perimeter of the component.

LIRD-386 Where the primary Class-R ground path from LandIS CGP to Observatory

CGP is via ground straps, LandIS shall achieve a resistance, as measured from the LandIS CGP to the Observatory CGP, of < 5 milliohms, with all ground straps installed and all ground strap fasteners torqued to specified values.

implementation of NASA-STD-4003A Class R grounding methods.

LIRD-655 Where ground straps are used as the primary Class-R ground path from the

LandIS CGP to the Observatory CGP, the ground straps shall be designed with a length-to-width ratio of ≤ 5-to-1.

Rationale: Minimize skin effects and inductance to effectively conduct high frequency energy that may result in EMI. This assumes LandIS supplies the ground straps.

3.2.4.6 Electric Harnesses and Connectors

3.2.4.6.1 Power Signal Circuits

LIRD-640 LandIS shall use separate connectors for power and signal circuits.

Rationale: Prevent EMI of power conductors coupling to signals.

3.2.4.6.2 Electrical Connectors

LIRD-335 LandIS shall have exposed contacts on all connectors receiving Main Bus or secondary power.

Rationale: Prevent inadvertent shorting of an unmated, harness connectors when powered during ground processing.

3.2.4.6.3 Keying

LIRD-644 LandIS shall key connectors of the same type and gender, including test connectors not intended for flight harness mating, where accidental mismate is possible and could cause damage to the hardware, or pose a safety hazard.

Rationale: Prevent damage to flight hardware during ground processing due to inadvertent mismate of connectors.

Note: A mismate is considered possible ONLY if the like connectors are located in such close proximity as to allow the incorrect mating connectors on the harness to reach.

3.2.4.6.4 Flight Plugs

LIRD-646 LandIS flight plugs shall be designed for installation during pre-launch operations with the three Observatories integrated together in the launch configuration and orientation without temporary removal of flight hardware, with the exception of MLI.

Rationale: Ensure that flight plugs are accessible during ground processing, including at the launch site.

3.2.5 Command and Data Handling

3.2.5.1 Data Bus(es)

Figure 3.2.5.1-1 LandIS Functional Data Buses

LandIS Output Data Bus: The interface bus where the data set containing LandIS data is transported to the spacecraft. LandIS output data is imaging sensor data, Instrument ancillary data or housekeeping data. LandIS imaging sensor data may be detector image data, test pattern data or raw detector diagnostic data.