Attachment_B-Specification.pdf

PACE and WFIRST S/C TWTA Spec PACE-COMM-SPEC-0053, Revision -

Reference: WFIRST-SPEC-09699, Revision -

Effective Date: October 23, 2017 i Check https://ipdtdms.gsfc nasa.gov to verify that this is the correct version prior to use

400-FORM-0002 (4/16/2014)

PACE and WFIRST Spacecraft

Traveling Wave Tube Amplifier (TWTA)

Specification

Signature/Approval Page

Prepared By:

Mike Powers/Adan Rodriguez Arroyo

Reviewed By:

Noosha Haghani

Kathy McIntyre

John Blackwood

Gary Davis

Beth Weinstein

Kevin Novo-Gradac

Jack Sanders

Gary Won

Tim Johnson

Shavesha Rutledge

Mike Xapos

Mike Powers

Adan Rodriguez-Arroyo

Nicole Hackley

Michelle Rizzo

Bob Kraeuter

Craig Stevens

Dan Powers

Dan McGuinness

Approved By:

Andre’ Dress

Electronic Signatures available online at: https://ipdtdms.gsfc.nasa.gov/ ii

400-FORM-0002 (4/16/2014)

Preface

This document is under Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) Mission configuration control. Changes to this document require prior approval of the PACE

Configuration Control Board (CCB) Chairperson or designee. Proposed changes shall be submitted to the PACE Configuration Management Office (CMO), along with supportive material justifying the proposed change. Changes to this document will be made by complete revision.

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Change History Log

Revision Effective Date Description of Changes

(Reference the SCoRe & Approval Date)

Revision - 10/23/2017 Baseline release following approval of PACE-CCR-0148

(WFIRST-CIR-04632)

iv

Table of TBDs/TBRs/TBSs

Action Item

No.

Location Summary Individual/

Organization

Actionee v

Table of Contents

1.0 Introduction

1.1 General Information

1.2 Scope

2.0 Applicable Documents

3.0 Contract Description

3.1 Traveling Wave Tube Amplifier Description

4.0 Functional/Performance Requirements

4.1 TWTA Flight Unit Functional/Performance Requirements

Center Frequency

Operating Band

Saturated Output Power

Stability

RF Interface

4.1.5.1 RF Input Interface

4.1.5.2 RF Input Return Loss

4.1.5.3 RF Output Interface

4.1.5.4 RF Output Return Loss

4.1.5.5 Load Return Loss

Input RF Power

Over Drive Capability

Noise Figure

Carrier to Intermodulation Ratio

Signal Phase Shift

AM to PM Conversion

Signal Gain

Spurious

Harmonics

Protection Circuits

4.1.15.1 Undervoltage Protection

4.1.15.2 Overpower Protection and Auto Restart

Helix Overcurrent Protection

4.2 Resource Allocations

Mass Allocation

Nominal Power Allocation

4.3 Power

Primary (Unregulated) Power Input Requirements

4.3.1.1 Operating Voltage Range

4.3.1.2 Abnormal Voltages

4.3.1.3 Voltage Ripple

4.3.1.4 Voltage Transients

4.3.1.5 Sudden Removal of Power

4.3.1.6 Polarity Reversal Protection

4.3.1.7 Over-Current Protection

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4.3.1.8 Primary Power Return Ground

4.3.1.9 Power Wiring Redundancy

Load Induced Noise Requirements

4.3.2.1 Turn-on Current Transients

4.3.2.2 Operational Current Transients

4.3.2.3 Repetitive Transients

4.4 Electrical Grounding

Primary Power DC Isolation

Internally Generated Secondary Returns

Internally Generated Secondary to Primary DC Isolation

Mechanical Contact Resistance

Mating Method

Ground Strap, Non-Conductive Surface

4.4.6.1 Ground Lug Contact Area

Reserved

Connector DC Resistance

4.5 Signal And Data Interfaces

Active Analog Telemetry

4.5.1.1 Active Analog Telemetry

4.5.1.2 Active Analog Telemetry Short Circuit Protected

4.5.1.3 Active Analog Telemetry Source and Load Resistance

4.5.1.4 Anode Voltage, Helix Current, and DC Power Telemetry Characteristics

4.5.1.5 TWTA RF Power Output Telemetry

Passive Analog Telemetry

4.5.2.1 Passive Analog Telemetry Interface

4.5.2.2 Passive Linearizing Resistor

4.5.2.3 Thermistor Resistor Conditioning

Digital Telemetry

4.5.3.1 Digital Status Telemetry

4.5.3.2 Digital Telemetry Voltage Range

4.5.3.3 Digital Telemetry Short Circuit Protected

4.5.3.4 Digital Telemetry Source and Load Resistance

4.5.3.5 Digital Status Max Voltage

4.5.3.6 Digital Status Return Line

Reserved

Pulse Commands

RF Signals

4.5.6.1 Reserved

4.5.6.2 Multipaction

4.6 Operating Modes

TWTA States

4.7 Command and Data Services

Commands and ON/OFF Sequences

5.0 Physical Requirements

5.1 Interface Documentation

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Mechanical Interface

Electrical Interface

5.2 Mass Properties

Component Masses

Center of Mass Location

Center of Mass Accuracy

Determination of Moments and Products of Inertia

5.3 Physical Envelope

5.4 Mounting

6.0 Environmental Requirements

6.1 Mechanical Factors of Safety

6.2 Quasi-Static Acceleration

6.3 Frequency Requirement

Fundamental Launch Frequencies

6.4 Vibration

Sinusoidal Vibration

Random Vibration

6.5 Shock

6.6 Reserved

6.7 Transportation

Transportation Cleanliness

6.8 Pressure

Operating Pressure Range

Maximum Depressurization Rate

6.9 Reserved

6.10 Ground Environments

6.11 Thermal Requirements

Flight Interface Design Temperature Limits

6.12 Charged Particle Radiation Requirements

Definitions

Total Ionizing Dose

6.12.2.1 Minimum TID Tolerance for EEE Parts and Materials

6.12.2.2 ELDR Evaluation

Displacement Damage Dose

Single Event Effects

6.12.4.1 Destructive Events (SELs)

Charging Environment

7.0 Cleanliness

7.1 Surface Contamination

Surface Contamination Levels at Delivery

7.1.1.1 Particulate Contamination

Surface Contamination Generation

7.1.2.1 Particulate Generation

7.1.2.2 Molecular Generation

7.1.2.3 Intentional and Unintentional Vents

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7.1.2.4 Intentional and Unintentional Vents – Filters

7.1.2.5 Intentional Vents - Pressure Buildup Prevention

Cleanability

7.1.3.1 Cleanability – Sensitive Surfaces

7.1.3.2 Cleanability – Sensitive Surface Cleaning Methods

7.2 Electrostatic Cleanliness

Conductive Surface Ground Path

Reserved

Closeout of Gaps and Apertures

7.2.3.1 Conductive Tape Surface Resistivity

7.2.3.2 Conductive Tape, Grounding

Exposed Harness Specific Requirements

8.0 Design & Construction Requirements

8.1 Parts, Materials & Processes (PMP)

EEE Parts

Materials

8.1.2.1 Material Conductivity

8.1.2.2 Material Limitations for Debris Casualty Area

8.2 Electrical

Test Sensors

Interface Requirements

8.2.2.1 Connector Selection

8.2.2.2 Signal Segregation

8.2.2.3 Test and Flight Signal Isolation

8.2.2.4 Test Interfaces

Mitigation of Internal Charging

8.2.3.1 Mitigation Strategies for Internal Charging

8.2.3.2 Floating Conductors

8.2.3.3 Dielectric Structures

8.3 Safety

8.4 Electromagnetic Compatibility

Conducted Emissions

8.4.1.1 Applicability of Conducted Emissions

8.4.1.2 CE101 – Differential Mode Current Emission Limits

8.4.1.3 CE102 – Differential Mode Current Emission Limits

8.4.1.4 Common Mode Bulk Current Emissions Limits

Conducted Susceptibility

8.4.2.1 Applicability of Conducted Susceptibility

8.4.2.2 CS101 – Low Frequency Ripple

8.4.2.3 CS114 – Radio Frequency Ripple

8.4.2.4 CS106 – Power Transients

8.4.2.5 CS114 – Power and Signal Cables, Common Mode

Radiated Emissions

8.4.3.1 RE102 - Electric Field Emissions

Radiated Susceptibility ix

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8.4.4.1 RS103 - Electric Field

RF Component Unique Tests

8.4.5.1 CE106 – Conducted Emissions, Antenna Terminals

8.5 Identification and Marking

8.6 Workmanship

Workmanship Standards

Connector

8.6.2.1 Reserved

8.6.2.2 Prevention of Connector Mismating

8.6.2.3 Test Connectors

8.6.2.4 Connector Identification

8.6.2.5 Protection of Unused Test Connectors

8.6.2.6 Connector Savers

8.7 Reliability and Mission Lifetime

Mission Life

Operating Time

8.7.2.1 Total Time

8.7.2.2 Failure Free Time

Mean Time to Failure

Operating Times

On/Off Cycles

9.0 Mechanical Design Requirements

9.1 Structural Requirements

Component Fatigue

Fracture Control Requirements

9.2 Fastening Systems

Fastener Performance Analysis

9.2.1.1 Factors of Safety

9.2.1.2 Supplemental Factor

9.2.1.3 Ultimate Design Loads

9.2.1.4 Yield Design Loads

9.2.1.5 Design Separation Load

Fastener Locking and Retention

9.2.2.1 Locking Features

9.2.2.2 Verification

9.2.2.3 Locking Features

9.2.2.4 Installation Torque Specification and Control

Fastened Joints Criteria

9.2.3.1 Minimum and Maximum Preload

9.2.3.2 Analysis Addressing Potential Rupture

9.2.3.3 Ultimate Strength Analysis

9.2.3.4 Applied Shear Loading

9.2.3.5 Shear Loading

9.2.3.6 Simultaneous Applied Tensile and Shear Loads

9.2.3.7 Allowable Yield Tensile Load

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9.2.3.8 Separation Analysis

9.2.3.9 Seal Analysis

10.0 Reserved

11.0 Verification Requirements

11.1 Verification Methods

Inspection

Analysis

Test

11.2 Inspection Requirements

Visual Inspection

Physical Measurement

Documentation Search

11.3 Analysis Requirements

11.4 Test Requirements

Definitions

Test Factors

Test Tolerances

Test Restrictions

11.4.4.1 Failure During Tests

11.4.4.2 Modification of Hardware

11.4.4.3 External Adjustment

11.4.4.4 Re-Test Requirements

11.5 Required Tests

Performance Tests

11.5.1.1 Comprehensive Performance Test

11.5.1.2 Limited Performance Test

11.5.1.3 Abbreviated Functional Test

Mass Properties Measurement

Static Loads/Strength Test

11.5.3.1 Sine Burst

11.5.3.2 Static Pull

Sine Sweep Survey

Sine Vibration

Random Vibration

Reserved

Reserved

Shock

Thermal Vacuum Bake-out

Thermal Vacuum Test

11.5.11.1 Thermal Vacuum Test Parameters

11.5.11.2 Thermal Vacuum Test Profile

Reserved

Reserved

Reserved

EMI/EMC Tests xi

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11.5.15.1 Conducted Emissions Tests

11.5.15.2 Conducted Susceptibility Tests

11.5.15.3 Radiated Emissions Tests

11.5.15.4 Radiated Susceptibility Tests

Appendix A Abbreviations and Acronyms xii

List of Figures

Figure Page

Figure 3-1: Ka-band TWTA Block Diagram

Figure 6-1 Sine Vibration Environment

Figure 6-2 Reserved

Figure 6-3 Shock Envelope

Figure 6-4 Total Ionizing Dose-Depth Curves (“WFIRST”)

Figure 8-1 CE101/CE102 Differential Mode Current Emission Limits

Figure 8-2 Common Mode Current Emission Limits

Figure 8-3 CS106 Transient Waveform

Figure 8-4 Bulk Cable Injection (CS114) Calibrated Test Levels

Figure 8-5 Component Level RE102 Radiated Electric Field Emission Limits

Figure 11-1 Thermal Vacuum Profile

List of Tables

Table Page

Table 2-1 Applicable Documents

Table 6-1 Factors of Safety

Table 6-2 TWTA Design Limit Loads

Table 6-3 TWTA Sine Vibration Environment

Table 6-4 TWTA Random Vibration Environment

Table 6-5 Reserved

Table 6-6 Qualification Level Shock Response Spectrum

Table 6-9 Transportation Loads

Table 6-10 Temperature Limits at Box Mounting Interface

Table 8-1 Limited materials for debris casualty area

Table 8-2 Emission and Susceptibility Requirements

Table 8-3 Receiver Notch RE102 Test Limit Levels (TBR)

Table 8-4 RS103 Radiated Susceptibility Levels

Table 11-1 Test Factors and Durations

Table 11-2 Test Tolerances

Table 11-3 Thermal Vacuum Test Parameters

Check https://ipdtdms.gsfc.nasa.gov to verify that this is the correct version prior to use

1.0 INTRODUCTION

1.1 GENERAL INFORMATION

The Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission is a strategic climate continuity mission that will extend the high quality ocean ecological, ocean biogeochemical, cloud, and aerosol particle data records begun by NASA in the 1990s. The mission will be capable of collecting radiometric and polarimetric measurements of the ocean and atmosphere, from which these biological, biogeochemical, and physical properties will be determined. PACE data products will not only add to existing critical climate and Earth system records, but also answer new and emerging advanced science questions related to Earth’s changing climate.

WFIRST, the Wide Field InfraRed Survey Telescope, is a NASA observatory designed to settle essential questions in the areas of dark energy, exoplanets, and infrared astrophysics. The telescope has a primary mirror that is 2.4 meters in diameter (7.9 feet), and is the same size as the Hubble

Space Telescope's primary mirror. WFIRST will have two instruments, the Wide Field Instrument, and the Coronagraph Instrument.

WFIRST is designed for a 5 year mission, and will launch on a EELV. The targeted launch date is

2026. After transfer trajectory, the observatory will operate ~ 1.6 e6 km from the Earth, in an orbit around the L2 point of the Sun-Earth System.

1.2 SCOPE

This specification describes the electrical, mechanical, environmental, and verification testing requirements for a space-qualified Traveling Wave Tube Amplifier (TWTA), from this point on referred to as the TWTA, for the NASA Goddard Space Flight Center (GSFC) PACE and WFIRST

Missions. Although this specification includes requirements for both the PACE and WFIRST missions, only PACE will be referenced from this point on for simplicity.

2.0 APPLICABLE DOCUMENTS

The following documents and drawings in effect on the day this specification was signed shall apply to the fabrication and to the electrical, mechanical, and environmental requirements of the

TWTA to the extent specified herein. In the event of conflict between this specification and any referenced document, this specification will govern, with the exception of the PACE TWTA

Statement of Work (PACE-COMM-SOW-0021), in which case the Statement of Work takes precedence.

The following is a list of the applicable specifications and publications.

Table 2-1 Applicable Documents

Document Number Title

PACE-COMM-SOW-0021 PACE TWTA Statement of Work

PACE-COMM-LIST-0008 PACE TWTA Deliverable Items List and Schedule

(DILS)

NASA-STD-8719.24 NASA Expendable Launch Vehicle Payload Safety

Requirements

NASA-HDBK-7005 Dynamic Environment Criteria

NASA-STD-7001 Payload Vibroacoustic Test Criteria

IEST-STD-CC-1246E Product Cleanliness Levels And Contamination Control

Program

ASTM E-595-07 Standard Test Method for Total Mass Loss and

Collected Volatile Condensable Materials from

Outgassing in a Vacuum Environment

MIL-DTL-5541 Chemical Conversion Coatings on Aluminum and

Aluminum Alloys

MIL-A-8625F Anodic Coatings for Aluminum and Aluminum Alloys

EEE-INST-002 Instructions for EEE Parts Selection, Screening, Qualification, and Derating

MIL-STD-461F Military Standard, Electromagnetic Emission And

Susceptibility Requirements For The Control Of

Electromagnetic Interference (EMI)

GSFC-STD-7000A General Environmental Verification Standard (GEVS)

NASA-STD-5019A Fracture Control Requirements for Spaceflight Hardware

NASA-STD-5020 Requirements for Threaded Fastening Systems in

Spaceflight Hardware

FAA AC 20-71 Federal Aviation Administration Advisory Circular

(AC) 20-71, “Dual Locking Devices on Fasteners".

NASM 33540 Safety Wiring, Safety Cabling, Cotter Pinning, General

Practices for

541-WI-5330.1.41 Fastener Locking Using Arathane 5753

Document Number Title

MSFC-STD-3029A Guidelines for the Selection of Metallic Materials for

Stress Corrosion Cracking Resistance in Sodium

Chloride Environments

MIL-STD-462, Notice 2 Electromagnetic Interference Characteristics, Measurement of, 1 May 1970

NASA-STD-6016 Standard Materials and Processes Requirements for

Spacecraft

3.0 CONTRACT DESCRIPTION

3.1 TRAVELING WAVE TUBE AMPLIFIER DESCRIPTION

The TWTA will function as the transmitting element in a Spacecraft communications system and will include a Traveling Wave Tube (TWT), Electronic Power Conditioner (EPC) and interconnecting umbilical wiring harness. A block diagram of the PACE Ka-Band TWTA is shown in Figure 3-1.

The EPC will contain a power supply that produces all required voltages from an unregulated source for operation of the TWTA including monitoring and control circuitry. The TWTA will amplify an input modulated signal to 70W minimum at the output. The TWTA will incorporate a timer, called the High Voltage Timer, to delay the application of high voltage to the TWT until a safe time interval has elapsed following the turn ON of filament heater power.

Figure 3-1: Ka-band TWTA Block Diagram

4.0 FUNCTIONAL/PERFORMANCE REQUIREMENTS

The TWTA shall be designed to withstand the operational and non-operational environments specified in the following section without degradation to mission goals and performance requirements.

All performance requirement in this document shall apply for the TWTA operating with an RF output power of 70W, minimum. Unless otherwise indicated, all specifications apply over the operating bandwidth.

4.1 TWTA FLIGHT UNIT FUNCTIONAL/PERFORMANCE REQUIREMENTS

Center Frequency

The nominal center frequency shall be between 26 and 27 GHz, to be specified at the time of contract.

Operating Band

The operating bandwidth shall be at least ±700 MHz from the center frequency.

Saturated Output Power

The nominal and End-of-Life saturated output power shall be at least 70 Watts.

Stability

The saturation point shall not change by +/- 0.25 dB across all temperatures, bus voltages, life, and frequency.

A Pout vs Pin curve from Psat to (Psat–10 dB) shall be provided in 1 dB increments.

The TWTA shall be unconditionally stable under the following conditions:

At all input drive levels from 0 to 9 dB above the saturation drive level, no permanent damage or performance degradation (after the input drive level is restored to nominal value) shall result from prolonged periods (30 minutes or greater) of overdrive.

When simultaneously terminated with input source and output load impedance having a maximum VSWR of 2.0:1 over the unity gain bandwidth, there shall be no damage or oscillation. The vendor shall provide the unity gain bandwidth.

This requirement shall be met without the use of isolators.

The TWTA shall meet the stability requirements, stated above, over the electrical and thermal operating ranges.

RF Interface

4.1.5.1 RF Input Interface

The type of RF input interface, coaxial or waveguide, shall be recommended by the supplier and approved by the Contracting Officer’s Representative (COR).

If the recommended interface is waveguide, WR-34 shall be used.

If the recommended input interface is coaxial, the flange configuration shall be recommended by the supplier and approved by the COR.

The RF input signal shall be designated RF-IN.

4.1.5.2 RF Input Return Loss

The input return loss cold (non-operating) shall be ≥ 13 dB.

The input return loss hot (operating) shall be ≥ 9.5 dB.

4.1.5.3 RF Output Interface

The RF output interface shall be a WR-34 wave-guide interface.

The flange configuration shall be recommended by the supplier and approved by the COR.

The RF output signal shall be designated RF-OUT.

4.1.5.4 RF Output Return Loss

The output return loss cold (non-operating) shall be ≥ 14 dB.

The output return loss hot (operating) shall be ≥ 6 dB.

4.1.5.5 Load Return Loss

The operating load return loss will be ≥ 15 dB.

Input RF Power

Saturated input power is defined as the minimum input RF power level that produces a maximum TWTA RF output. The saturated power input signal level shall be between 0 and -10 dBm.

The saturated input power flatness over acceptance temperature levels shall be ≤ 2.5 dBpp.

The saturated input power flatness over any 15° C Range shall be ≤ 1.0 dBpp.

The saturated input power flatness versus frequency shall be ≤ 1.0 dBpp.

With a saturation level signal applied at the input, the specified saturation output power level shall be obtainable within 300 seconds after the filament power is turned ON, i.e. the High

Voltage Timer has timed out and TWT high voltage has been enabled.

Over Drive Capability

The overdrive capability shall be ≥ saturation point +6 dB.

Noise Figure

The Noise figure shall be ≤ 40 dB.

Carrier to Intermodulation Ratio

The carrier to intermodulation ratio shall be:

Drive*:

-3 dB ≥ 9 dB

-10 dB ≥ 15 dB

-17 dB ≥ 25 dB

*Drive relative to saturation.

Signal Phase Shift

The output signal phase shift shall be:

Drive*:

0 dB ≤ 47°

-3 dB ≤ 38°

-6 dB ≤ 30°

-10 dB ≤ 25°

-15 dB ≤ 5°

-20 dB ≤ 0°

*Drive relative to saturation.

AM to PM Conversion

The AM to PM conversion shall be:

Drive*:

0 dB ≤ 4.5° / dB

-3 dB ≤ 3.5° / dB

-10 dB ≤ 2.5° / dB

*Drive relative to saturation.

An AM to PM curve from Psat to (Psat-10 dB) shall be provided in 1 dB increments

Signal Gain

The gain compression at saturation shall be ≤ 8.5 dB.

The gain flatness at saturation over the operating band shall be ≤ 0.4 dBpp.

The gain slope at saturation shall be ≤ 0.025 dB / MHz.

The group delay within the operating band shall be ≤ 2 ns.

The group delay slope shall be ≤ 0.03 ns / MHz.

Spurious

The in-band spurious over any 4 kHz band shall be at least -70 dBc.

The in-band spurious over any 1 MHz band shall be at least -60 dBc.

The out-of-band spurious shall be at least -70 dBc.

Harmonics

The second harmonic level at saturated drive, shall be ≤ -25 dBc.

The third harmonic level at saturated drive shall be ≤ -30 dBc.

Protection Circuits

4.1.15.1 Undervoltage Protection

If the spacecraft DC bus voltage drops below the unit’s undervoltage trip-off level, the unit shall autonomously power itself OFF and remain in this state until restarted, by means of an ON command, sent by the ground station.

4.1.15.2 Overpower Protection and Auto Restart

If the unit’s input power/current draw rise 130 to 200% of nominal power/current draw, the unit shall autonomously go on standby mode and initiate restart within 50 ms and if the overpower trip-off level is still present, then the unit shall autonomously power itself OFF and remain in this state until restarted, by means of an ON command, sent by the ground station.

Helix Overcurrent Protection

The unit shall be equipped with a helix overcurrent protection circuit, which, when enabled, will prevent continued unit operation under conditions of excessive helix current, which can damage the TWT. This feature prevents unit damage due to excessive helix current resulting from a fault within the unit or from extreme overdrive conditions because of operator error or test equipment failure.

It shall be possible to disable helix overcurrent protection by means described/provided (TBD) by the Vendor.

If a Helix Overcurrent Condition is triggered, it shall be possible to restart the unit by sending an

ON command, when the condition has cleared.

4.2 RESOURCE ALLOCATIONS

Mass Allocation

Requirements in this section are for the assembly. Section 5.2.1 contains more requirements on mass properties and individual component mass.

The TWTA shall have a mass of less than or equal to 3.1 kg.

Nominal Power Allocation

The pre-heating (standby mode) prime power consumption shall be ≤ 15W.

The DC (peak) power consumption at saturated input drive level shall be ≤ 165W.

The DC power consumption with TWTA ON and input drive OFF shall be ≤ 95W.

4.3 POWER

Primary (Unregulated) Power Input Requirements

The TWTA shall accept redundant prime power and prime power return lines. The two power inputs should be diode ORed inside the Transponder.

4.3.1.1 Operating Voltage Range

The TWTA shall be designed to operate over the bus voltage range of +24 to +35 VDC at their primary power inputs.

4.3.1.2 Abnormal Voltages

The TWTA shall survive without performance degradation after indefinite exposure to an anomalous voltage range of 0 to +40 VDC. This requirement is to be verified by analysis or test of a non-flight unit.

4.3.1.3 Voltage Ripple

The TWTA shall be designed to meet its performance requirements in the presence of ripple voltages specified in the CS101 and CS114 requirements in paragraphs 8.4.2.2 and 8.4.2.3, respectively.

4.3.1.4 Voltage Transients

The TWTA shall be designed to meet its performance requirements in the presence of transient voltages specified in the CS106 requirements in paragraph 8.4.2.4.

4.3.1.5 Sudden Removal of Power

The TWTA shall meet its performance requirements without degradation after exposure to an abrupt, unannounced removal of power.

4.3.1.6 Polarity Reversal Protection

The TWTA shall should have built-in protection to prevent damage due to polarity reversal at the power inputs (up to -35V), where feasible.

4.3.1.7 Over-Current Protection

The TWTA shall not use non-resetting over-current protection (i.e., fuses) internal to the unit, but if they are required by the contractor to isolate an internal fault, prior approval shall be obtained from the COR.

4.3.1.8 Primary Power Return Ground

TWTA shall provide a dedicated Primary Power return in the same connector as the primary power.

4.3.1.9 Power Wiring Redundancy

The TWTA shall utilize redundant power wiring.

Load Induced Noise Requirements

4.3.2.1 Turn-on Current Transients

The amplitude and duration of TWTA in-rush currents, at both initial application of prime power and subsequent component turn-on, shall be per the following:

<10 microseconds: not to exceed 10 times max steady state or 10A, whichever is larger

Between 10 microseconds and 10 milliseconds: not to exceed 3 times max steady state or

3A, whichever is larger

>10 milliseconds: not to exceed max steady state.

4.3.2.2 Operational Current Transients

The TWTA operational current transients shall be less than or equal to 5A above the steady state current for a period of less than 1 millisecond.

The rate of change of the current shall be less than or equal to 20 milliamperes/microsecond.

4.3.2.3 Repetitive Transients

Any repetitive current transients, in the frequency range between 1 Hz to 200 Hz, shall not exceed 0.2 A peak-to-peak.

This measurement will be performed with an oscilloscope current probe in time domain.

4.4 ELECTRICAL GROUNDING

Primary Power DC Isolation

At the TWTA primary power interfaces, primary power and primary power returns shall be isolated from signal grounds and from the component chassis by a DC resistance of greater than or equal to 1 MΩ.

Internally Generated Secondary Returns

Secondary returns (power and signal grounds) shall be referenced to the component chassis ground by connecting them at one or more places.

Internally Generated Secondary to Primary DC Isolation

Secondary power (or signal) inputs shall be isolated from primary power by a DC resistance of greater than 1 MΩ.

Mechanical Contact Resistance

The DC resistance of the mechanical contact between two conductive mating surfaces (internal to the component, and at the spacecraft interface) shall be less than or equal to 2.5 mΩ DC resistance.

Mating Method

The primary mating method for a PACE component is metal-to-metal contact between component mounting feet (or base plate) and the spacecraft structure. When the use of this method is not possible, as determined by the Mechanical Interface Control Document (MICD), the use of a ground strap is necessary.

Ground Strap, Non-Conductive Surface

The TWTA shall contain provisions for a grounding strap to be attached from the component chassis for connection to the spacecraft conductive structure.

4.4.6.1 Ground Lug Contact Area

The grounding lug location on the TWTA chassis or the tie points in contact with the ground strap shall have a minimum contact area of 80 mm². The ground lug contact area must remain free of any material finish that may affect the reliability of the ground connection and be shown in the MICD.

Reserved

Connector DC Resistance

Component connectors shall be electrically connected to chassis with a DC resistance less than or equal to 2.5 mΩ.

4.5 SIGNAL AND DATA INTERFACES

The TWTA will have three types of telemetry interfaces: (1) active analog and (2) passive analog readings and (3) digital status indicators.

All telemetry interfaces shall be redundant to accommodate spacecraft redundancy

Active Analog Telemetry

4.5.1.1 Active Analog Telemetry

As a minimum, the following active analog telemetry lines shall be provided from the TWTA for assessing the "health" of the TWTA:

Anode Voltage

Helix Current

DC Power Consumption

At least one dedicated Return Line, connected to the EPC chassis, shall be provided at the

TWTA/SC interface for the Active Analog Telemetry.

4.5.1.2 Active Analog Telemetry Short Circuit Protected

The sources of active analog signals shall be short circuit protected.

4.5.1.3 Active Analog Telemetry Source and Load Resistance

The source and load resistances (at the source and destination, respectively) shall be documented in the component Electrical Interface Control Document (EICD) such that the overall system compatibility of the telemetry signal is reviewed and controlled.

4.5.1.4 Anode Voltage, Helix Current, and DC Power Telemetry Characteristics

The output range of anode voltage, helix current, and DC power consumption shall be nominally

0 to +5.0V full scale. The nominal calibration of the telemetry reading is:

Anode Voltage: 1Volt per 100-200 Volts (TBR)

Helix Current: 1Volt per milliAmp (V/mA)

DC Power Consumption: As agreed by vendor and COR

The accuracy of the analog telemetry shall be within ±5% of full scale at any temperature within the specified TWTA operating temperature range.

Each signal output shall have an output impedance of 5±1 kilo ohms (kohms) resistive.

4.5.1.5 TWTA RF Power Output Telemetry

Calibration curves shall be provided such that RF output power level may be determined as a function of a measurable TWTA parameter, such as DC power consumption.

Calibration curves shall be generated for the temperatures -10°C, 25°C, and 50°C.

Passive Analog Telemetry

4.5.2.1 Passive Analog Telemetry Interface

If the TWTA is supplied with passive internal temperature sensors, they shall be #311P18-

02A101 thermistor parts, with a resistance of 2252 ohms at 25 degrees C.

4.5.2.2 Passive Linearizing Resistor

The linearizing resistor for the thermistors will be located with the temperature sensor conditioning circuit in the Spacecraft Bus avionics.

4.5.2.3 Thermistor Resistor Conditioning

Temperature sensors will be conditioned to provide a voltage range which represents a temperature range that includes a margin of greater than or equal to 5 degrees C beyond the unit qualification or non-operational survival limit, whichever is worse.

Digital Telemetry

4.5.3.1 Digital Status Telemetry

At a minimum, the following digital status indicators shall be provided by the TWTA so that the

TWTA state can be determined given that the state of the external relay that switches the SC bus voltage to the TWTA is known:

a. TWTA ON/OFF: Indicates the ON/OFF state of the TWTA.

b. High Voltage (HV) ON/OFF: Indicates the ON/OFF state of the HV from the EPC to the

TWT.

c. Spurious Shutoff (Auto Restart Event) ON/OFF: Indicates whether a spurious shutoff/auto restart event occurred.

4.5.3.2 Digital Telemetry Voltage Range

The digital telemetry voltage range shall be within 0 to +5 VDC.

4.5.3.3 Digital Telemetry Short Circuit Protected

The sources of digital telemetry signals shall be short circuit protected.

4.5.3.4 Digital Telemetry Source and Load Resistance

The source and load resistances (at the source and destination, respectively) for digital telemetry signals shall be such that the intended logic levels from the source are not violated.

4.5.3.5 Digital Status Max Voltage

The unit shall be able to withstand a 12 VDC on open contact on a fault condition where the maximum voltage is driven by the C&DH.

4.5.3.6 Digital Status Return Line

At least one dedicated Return Line, connected to the EPC chassis, shall be provided at the

TWTA/SC interface for the Digital Status Telemetry.

Reserved

Pulse Commands

All TWTA command interfaces shall be redundant to accommodate spacecraft redundancy

The pulse applied to the TWTA command line shall have the following characteristics:

Pulse Amplitude: 24-35 Volts (31-32V nominal)

Pulse Duration: 20 milliseconds ±10%; Pulse Current: <100 milliamps; Source

Impedance: <1 Ohm

Each pulse input shall have a dedicated return wire.

The TWTA command line and command return line shall be DC isolated from the TWTA primary and secondary returns and TWTA chassis by 1 Mega ohm (Mohm) minimum.

RF Signals

4.5.6.1 Reserved

4.5.6.2 Multipaction

The TWTA shall not exhibit multipaction breakdown at any internal pressure from sea level to less than 10-5 Torr. A 6 dB margin above the maximum power specified in Section 4.1.3 shall be demonstrated by test, or alternatively, a 10 dB margin shall be verified by analysis.

If 10 dB of analytical margin can be demonstrated, vacuum testing shall be performed at 0 dB above the operating power for no less than 8 Hours at 25°C.

4.6 OPERATING MODES

TWTA States

The TWTA shall have four basic states:

OFF: SC bus voltage is removed from the TWTA.

IDLE: SC bus voltage is applied to TWTA but EPC and TWT are both in an OFF state.

STANDBY: The EPC is ON but only filament power is supplied to the TWT (high voltages are OFF).

ON: The TWTA is ON with high voltages applied to the TWT (i.e. Cathode Beam

ON). In this state the TWTA is fully functional.

Note: SC bus voltage is applied to the TWTA by an external switch, which is not part of the

TWTA. The SC controls this switch.

4.7 COMMAND AND DATA SERVICES

Commands and ON/OFF Sequences

To command the TWTA ON and OFF, the SC provides redundant sets of two command (CMD) lines and a command return to the TWTA. A voltage pulse (pulse command) is applied to these lines to transition the TWTA to the desired state. The pulse commands and a normal ON and

OFF sequence shall be as follows:

A. TWTA ON Sequence: This sequence assumes that SC bus voltage has been applied to the TWTA through the external switch, resulting in the IDLE state.

CMD Line 1: TWTA ON: Causes the TWTA to turn ON from the IDLE or STANDBY state. If initially in the IDLE state, the command shall cause the EPC to turn ON and supply filament voltage to the TWT. The result is the STANDBY state. An internal timer controls when high voltages should be applied to the TWT, allowing sufficient warm-up time for proper operation of the TWT. The EPC then automatically supplies high voltages to the TWT, resulting in the ON state.

B. TWTA OFF Sequence: This sequence assumes that the TWTA is in the ON state defined above.

CMD Line 2: TWTA OFF: Causes the TWTA to turn itself OFF in the proper sequence and the result is the IDLE state.

The SC bus voltage is removed from the TWTA to complete the OFF sequence.

If the TWTA ON command is executed without the SC bus voltage applied to the

EPC, the TWTA shall not be damaged or degraded.

The TWTA ON sequence shall only be executed when the TWTA ON command is generated with SC bus voltage applied. If the ON command is generated without spacecraft voltage, the

TWTA shall remain in the OFF state.

The TWTA OFF state can be achieved in several ways but the preferred method is as listed above. Other sequences to the OFF state, (e.g. removing the SC bus voltage from the TWTA without first turning the TWT and EPC OFF when the TWTA is in the ON state), shall not be damaging to the TWTA.

If the input RF drive is turned off with the TWTA ON, the TWTA shall not be damaged or degraded.

5.0 PHYSICAL REQUIREMENTS

5.1 INTERFACE DOCUMENTATION

The contractor shall use metric units when interfacing with NASA GSFC including any drawings, documents, models, except for the following cases:

Heritage Hardware: Hardware that has been previously qualified, or of similar design heritage, may be specified in English units where use of metric equivalents would lead to additional cost to the program.

Fasteners: Although bolt circles will be defined using metric dimensioning, use of

English fasteners is permitted.

Angular Measurement: Angular measurement may be expressed in degree of arc or in an appropriate subdivision of degree of arc such as second of arc (arc-sec) when advantageous to application.

Mechanical Interface

The mounting interface shall be defined in the Mechanical Interface Control Document (MICD), which will be developed between the contractor and NASA GSFC.

Electrical Interface

The electrical interface shall be defined in the Electrical Interface Control Document (EICD), which will be developed between the contractor and NASA GSFC.

5.2 MASS PROPERTIES

Component Masses

The EPC mass shall be ≤ 1600 grams.

The TWT mass shall be ≤ 1400 grams.

Center of Mass Location

The contractor shall define the center of mass in the Mechanical ICD.

Center of Mass Accuracy

The center of mass shall be determined to within ±6 mm relative to an external reference.

Determination of Moments and Products of Inertia

The final moments and products of inertia of the TWTA shall be calculated to within 10%.

5.3 PHYSICAL ENVELOPE

The EPC external dimensions, including mounting provisions, shall be less than the envelope of

25 cm x 10 cm x 15 cm (LWH) including connectors and mounting flanges, as defined in the

Mechanical ICD.

The TWT external dimensions, including mounting provisions, shall be less than the envelope

40 cm x 15 cm x 10 cm (LWH), including connectors and mounting flanges, as defined in the

Mechanical ICD.

High voltage interconnect cable shall be TBD cm, as defined in the Mechanical ICD.

5.4 MOUNTING

Mounting interface flatness, and co-planarity requirements for the component side of the interface (including brackets, if any, and shims) shall be as defined in the MICD.

The TWTA shall have a flatness of 0.25 mm from any 2 points on the mounting interface for a component <0.3 m2 and 0.50 mm from any 2 points on the mounting interface for a component

>0.3 m2 and <0.6 m2.

Connector locations names, and orientations shall be defined in the mechanical drawings and

MICD to be supplied.

6.0 ENVIRONMENTAL REQUIREMENTS

Environmental design requirements for the spacecraft components are specified in this section.

The PACE spacecraft components will be capable of meeting their performance requirements after exposure to the environments specified in this section.

6.1 MECHANICAL FACTORS OF SAFETY

The TWTA shall demonstrate positive Margins of Safety under limit loads for all yield and ultimate failures using the Factors of Safety (FS) defined in Table 6-1. Margin of Safety (MS) is defined as follows:

MS = (Allowable Stress (or Load) / (Applied Limit Stress (or Load) x FS)) -1

Table 6-1 Factors of Safety

Primary and secondary structure comprised of composite materials, Beryllium, bonded joints and/or bonded inserts shall be proof tested to 1.25 x Limit Load; qualification by analysis only is not acceptable. Actual flight component testing is preferred, but testing of representative sets of hardware with a similarity qualification argument can be used if approved by the COR.

6.2 QUASI-STATIC ACCELERATION

Quasi-static acceleration represents the combination of steady-state accelerations and the low frequency mechanically transmitted dynamic accelerations that occur during launch.

The TWTA shall be designed to withstand the quasi-static design limit loads defined in the mass-acceleration curve (MAC) shown in Table 6-2 without damage or degradation of performance. The design loads shown below will be updated based on the results of coupled loads analysis.

Linear interpolation should be used between breakpoints to determine the appropriate limit load as a function of TWTA weight. Note that these design limit loads are intended to cover only the low frequency launch environment and must be used in conjunction with the random vibration environments to assess structural margins.

Table 6-2 TWTA Design Limit Loads

6.3 FREQUENCY REQUIREMENT

Fundamental Launch Frequencies

The TWTA shall have a fundamental frequency greater than 100 Hz when hard mounted at its

S/C interface. Any component, which fails to meet the specified fundamental frequency, must supply a finite element model, correlated to modal survey test results up to 50 Hz, to be used in coupled loads analyses. Requirements for the submitted finite element model are in the SOW and discussed in Section 11.5.4.

6.4 VIBRATION

Sinusoidal Vibration

The TWTA shall undergo qualification, protoflight or acceptance (level depends on qualification status of unit) sine vibration testing on all three axes at the levels shown in Table 6-3. Stiff components showing a first mode greater than 150Hz can be exempted from sine vibration testing upon approval by the COR. A generic sine vibration specification is provided for both

Protoflight (PFT), Qualification (QT) and Acceptance (AT) levels applied at the PACE to

TWTA interface. See Section 11.4.1 for definitions of Protoflight, Qualification, and

Acceptance.

Table 6-3 TWTA Sine Vibration Environment

Frequency Protoflight, Qual Level Flight, Acceptance Level

5-20 Hz 0.63 in (double amplitude) 0.50 in (double amplitude)

20-100 Hz 12.5 G 10.0 G

Figure 6-1 Sine Vibration Environment

Levels may be notched to not exceed 1.25 times the design limit load outlined in section 6.2.

Peak levels at the low end of the frequency range (5 – 20 Hz typically) may be ramped up as needed to accommodate shaker table displacement limitations.

Random Vibration

The TWTA shall demonstrate its ability to meet its performance requirements after being subjected to the random vibration environment in Table 6-4.

Table 6-4 TWTA Random Vibration Environment

Frequency ASD Level (g2/Hz)

(Hz) Qualification Acceptance

20-50

50-800

800-2000

0.026

+6 dB/oct

0.16

-6 dB/oct

0.026

0.013

+6 dB/oct

0.08

-6 dB/oct

0.013

Overall 14.1 Grms 10.0 Grms

Table 6-5 Reserved

Figure 6-2 Reserved

The contractor shall perform random vibration analysis along with static loads analysis. Please see NASA-HDBK-7005 and NASA-STD-7001 for more information.

During the test, the test input level will be reduced (notched) at critical frequencies, if required, to limit the random vibration loads and/or acceleration responses to 3 dB above design limit levels.

Notching shall be limited to -12 dB of the original input and to a bandwidth of less than 100 Hz to limit the random vibration responses to 3dB above design limit levels. Notching beyond these limits will require PACE project approval.

6.5 SHOCK

The TWTA shall be designed to meet its performance requirements after being subjected to the shock environment in )

Table 6-6, applied at the TWTA interface to the PACE spacecraft structure.

(Note that the enveloped levels shown below are driven by WFIRST below 1000Hz and PACE above 1000 Hz.)

Table 6-6 Qualification Level Shock Response Spectrum

Freq (Hz) SRS (G)

100 100

500 1300

1400 1600

10000 1600

A shock susceptibility and attenuation assessment shall be performed on all Spacecraft components. If the flight shock environment as shown on a Shock Response Spectra (SRS) plot

(Q=10) is enveloped by the curve shown below (Figure 6-3), then the shock environment can be considered benign and there is low risk in deferring the shock test to the Observatory level.

Figure 6-3 Shock Envelope

Analysis supporting this conclusion (i.e. deferral of shock testing) shall be provided to the PACE

Project for review.

Any component determined to be susceptible to the shock environment (e.g., shock levels are above the curve) shall have shock testing performed at the component level (preferably on a qualification unit).

Component self-induced shock testing shall be accomplished by two actuations at the component level for each self-induced shock source (in order to account for the scatter associated with the actuation of the device) for the first flight unit, and a single actuation on subsequent units.

6.6 RESERVED

6.7 TRANSPORTATION

In addition to the launch loads shown above, the TWTA shall also be designed to withstand the maximum transportation loads shown in Table 6-7 without damage or degradation of performance.

Table 6-7 Transportation Loads

Transportation Cleanliness

Materials and enclosure used for transportation and storage shall not generate molecular or particle contaminants or degrade the surface cleanliness of the item or adjacent items

6.8 PRESSURE

Operating Pressure Range

The TWTA shall be designed to meet all performance requirements while operating over a pressure range of 1.08 x 105 N/m2 (813 Torr) to 1.3 x 10-12 N/m2 (1 x 10-14 Torr).

Maximum Depressurization Rate

The TWTA shall be designed to meet all performance requirements after exposure to a maximum depressurization rate of -50 mbar/sec (-0.72 psi/sec) experienced during launch and ascent.

The TWTA shall be vented such that internal pressure is equal to external pressure within 30 minutes after launch.

6.9 RESERVED

6.10 GROUND ENVIRONMENTS

The TWTA shall meet all of their performance requirements during exposure to air temperature between +5 and +30 degrees C and relative humidity between 30% and 70%.

After powered “OFF” and exposed to air temperatures of +5 to +30 degrees C and relative humidity of 0 to 70%, the TWTA shall meet all of their performance requirements.

6.11 THERMAL REQUIREMENTS

Flight Interface Design Temperature Limits

When powered “OFF”, the TWTA shall be capable of surviving indefinitely when its temperatures are within the survival limits shown in Table 6-8 without damage or permanent performance degradation.

The TWTA shall also survive indefinitely, without damage or permanent performance degradation, if powered “ON” anywhere within the Operational and Protoflight/Qualification limits shown in Table 6-8.

The TWTA shall demonstrate turn on at the Minimum and Maximum Protoflight/Qualification limits shown in Table 6-8.

Table 6-8 Temperature Limits at Box Mounting Interface

Minimum Temperature

(ºC)

Maximum Temperature

(ºC)

Operational (In Spec) -10 +50

Protoflight/Qualification

(In Spec)

-20 +60

Survival (Unpowered) -25 +65

Thermal dissipation at saturation over the operating band shall be:

≤ 80 W for TWT

≤ 15 W for EPC

The thermal dissipation mode shall be conduction only.

Thermal dissipation in no-drive mode shall be ≤ 95 W.

6.12 CHARGED PARTICLE RADIATION REQUIREMENTS

Components containing electronic parts will be exposed to a natural space radiation environment that consists of: (1) trapped particles which include electrons, protons, and heavier ions; (2) particles from solar events (coronal mass ejections and flares); and (3) galactic cosmic ray particles.

Definitions

Total Ionizing Dose (TID) - the mean energy deposited by ionizing radiation in a device region divided by the mass of the region. This is often given in units of rad(Si), where 1 rad(Si) = 100 erg deposited per gram of silicon.

Enhanced Low Dose Rate Sensitivity (ELDRS) - used to refer to a part that shows enhanced radiation-induced damage at dose rates below 50 rad(Si)/s. The enhancement is the result of true dose rate effects.

Displacement Damage Dose (DDD) - the mean energy deposited by ionizing radiation in a device region that goes into atomic displacements divided by the mass of the region. There is no official unit for DDD. One such unit is MeV/g.

Single Event Effect (SEE) - any measurable effect to a circuit due to an ion strike. This includes, but is not limited to, single event upsets (SEUs), single event transients (SETs), single hard errors (SHEs), single event latchups (SELs), single event functional interrupts (SEFIs), single event burnouts (SEBs), single event gate ruptures (SEGRs), and single event dielectric ruptures

(SEDRs).

Single Event Upset (SEU) - a change of state or transient induced by an energetic particle such as a cosmic ray or proton in a device. This may occur in digital or analog, circuits and may have effects in surrounding interface circuitry (a subset known as SETs). These are “soft” errors in that a reset or rewriting of the device will usually return the device to normal behavior thereafter.

The general goal for non-destructive events such as SEUs or SETs is not to avoid them completely, but to manage their impact through robust circuit design, automatic correction, and/or operational activities based on knowledge from ground radiation tests and circuit/system analysis.

Single Event Latchup (SEL) - a condition that may cause device failure due to a single event induced high current state. A SEL may or may not cause permanent device damage, but requires power cycling of the device to resume normal device operations. In addition, susceptible devices have the concern for latent damage (device does not fail from the immediate single particle event, but reliability is degraded and premature failure may occur).

Linear Energy Transfer (LET) - a measure of the energy deposited per unit length as an energetic particle travels through a material. The common LET unit is MeV*cm2/milligram (mg) of material.

Threshold LET (LETth) - the maximum LET at which no SEE is observed at a particle fluence of

107 ions/cm2.

Total Ionizing Dose

6.12.2.1 Minimum TID Tolerance for EEE Parts and Materials

The top-level total ionizing dose requirement (“WFIRST”) is shown in Figure 6-4. The dose values are calculated as a function of aluminum shield thickness in units of krad in silicon. For a nominal

100 mils (2.54 mm) of equivalent aluminum shielding and a 6-year mission life, the expected dose is 25.5 krad-Si at the 95% confidence level.

EEE parts and materials shall be selected according to the level of shielding and 95% confidence level curve in Figure 6-4

Figure 6-4 Total Ionizing Dose-Depth Curves (“WFIRST”)

6.12.2.2 ELDR Evaluation

Linear bipolar and BiCMOS device types that are known to be, or potentially susceptible to

Enhanced Low Dose Rate Sensitivity (ELDRS) for TID, shall be evaluated using test data at a low dose rate not to exceed 0.01 rad(Si)/sec in accordance with the latest version of MIL-STD-883, Test Method 1019 for all bias cases to be used in the Spacecraft Observatory equipment (i.e., biased and unbiased), unless existing data shows that a lower dose rate is required to manifest the

ELDRS effect.

Displacement Damage Dose

The displacement damage dose or non-ionizing dose is the mean energy deposited in a material that goes into atomic displacements divided by the mass of the material. It is analogous to the ionizing dose except that the energy considered produces displacements in a semiconductor lattice.

Parts sensitive to displacement damage degradation (e.g., optical detectors, precision bipolar integrated circuits, crystal oscillators, and power devices) shall be able to tolerate a minimum

DDD of 6.67 x 108 MeV/g (or a 10 MeV equivalent proton fluence of 8.45×1010 cm-2) and 5.50 x

108 MeV/g (or a 10 MeV equivalent proton fluence of 8.35×1010 cm-2), respectively.

This meets the DDD exposure for a 6-year mission with orbit about the Sun-Earth second

Lagrange point, L2, at the 95% confidence level and nominal 100 mils of aluminum shielding.

Single Event Effects

The TWTA shall be designed to avoid or tolerate errors due to non-destructive Single Event

Upsets.

6.12.4.1 Destructive Events (SELs)

All devices shall have a single-event latchup (SEL) LET threshold greater than 37 MeV-cm2/mg.

Latch-up susceptibility will be evaluated using test data obtained on at least three samples at maximum specified device operating temperature and maximum specified device operating voltage(s) and using at least 107 ions/cm2 with ions of sufficient energy to meet the linear energy transfer requirement throughout the active charge-collection depth of the device.

For devices with SEL LET thresholds between 37 and 75 MeV-cm2/mg, an evaluation of the probability and impact of destructive events shall be conducted to determine acceptability.

Circumvention techniques shall be evaluated to ensure that no latent damages are induced by an…