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Systems Engineering. Chad Fish [email protected] 435-797-0469. Presentation Overview. Key System Requirements System Design System Operation Technical Resources and Error Budgets Post-PDR System Changes Technical Risks Technical Coordination Summary Supplementary Material

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Systems engineering

Systems Engineering

Chad Fish

[email protected]

435-797-0469


Presentation overview
Presentation Overview

  • Key System Requirements

  • System Design

  • System Operation

  • Technical Resources and Error Budgets

  • Post-PDR System Changes

  • Technical Risks

  • Technical Coordination

  • Summary

  • Supplementary Material

    • Error Budget Models

    • Level 3 Requirements Compendium



Science objectives
Science Objectives

  • SOFIE will support AIM mission in study of PMCs and the environment in which they form. SOFIE will use differential solar occultation to measure:

    • Five gaseous species (H2O, CO2, O3, CH4, NO)

    • Temperature

    • Particle extinction at 10 wavelengths

  • Each SOFIE channel uses two detectors to make three measurements:

    • Strong band absorption

    • Weak band absorption

    • Difference signal (weak band – strong band = ΔV)

      Remove interference and reduce noise!




System requirements cont1
System Requirements (Cont)

SOF 174 :

Measurement Bands

SOF 183 :

Radiometric SNR





Design description

Instrument Unit

Purpose:

Perform science signal detection & FOV pointing and stabilization control

Contains:

Opto-mechanics

Mirrors, filters, beam splitters, field-stop, chopper

[1.8’ x 6’ Inst FOV; 32º x 24º Glint FOV]

Detector assemblies (includes TECs and PreAmps)

Steering mirror [4º x 4º FOR]

Sun sensor electronics and software [2º x 2º FOV]

Electronics Unit

Purpose:

Perform system command and control, communication, signal conditioning, and power conditioning

Contains:

Command and data handling electronics and system software

Position and stabilization control electronics and software

Communication, signal conditioning, and mechanisms control electronics and software

Thermal sensor, TEC thermal control, and housekeeping electronics

Power conditioning electronics

Design Description




Instrument unit
Instrument Unit

Radiator

Pin pullers

Aperture cover

Steering mirror

Alignment cubes

N2 Purge

Witness Mirrors (x4)

Circular connector interfaces

Dynamic Envelope: 16.2 x 26.3 x 29.5 inches

SC Isolator Feet (eff 14° wedge)


Sofie instrument unit cont
SOFIE Instrument Unit (cont)

POINTING AND

STABILIZATION CONTROL

Sun Sensor

SIGNAL DETECTION

Channel Separation Module


Sofie electronics unit
SOFIE Electronics Unit

Electronics PCBs

Top Connectors and Cabling

SC Radiator Panel

Power Conditioning

Dynamic Envelope: 16.2 x 26.3 x 29.5 inches







Science mode cont1
Science Mode (cont)

Maximum science measurement duration (AQR, DATA) = 155 seconds





Solar Scanning and Maneuvering

Vertical Scanning

FOV

Azimuthal Offsetting

(bore sighting)


Science Data Products

2

1

1

1

El

Az




Technical resources
Technical Resources

Resource margin and reserve managed by mission








Changes since pdr
Changes since PDR

SMA Caging Mechanism Removed

Wedge Removed

Radiator Reshaped

Cable Ports Relocated


Changes since pdr cont
Changes since PDR (cont)

Repositioned in SC and Radiator Removed

Electronics Power Conditioning

Redesigned

Detector Packages now

Non-hermetic



Technical risks
Technical Risks

RISK ID = SOFIE_RISK_4

SOFIE depends upon an active pointing system to provide the required sun pointing accuracy and precision. The active pointing and control system algorithm may be unable to provide the required sun pointing accuracy and precision and the science capability would be degraded.

CRITICALITY

Green

MITIGATION

Extensive prototype and protoflight testing will be conducted.



Technical coordination sdl design processes
Technical Coordination – SDL Design Processes

  • Engineering Design and Development

    • System Design

      • QP0401

    • Software Design

      • QP0406

  • Document Control and Configuration Management

    • Document Control

      • QP0501

    • Software Configuration Management

      • QP0403, SOFIE Software Configuration Management Plan

    • SDL to maintain up-down information flow

  • Waivers, Problem Failure Reports (PFR)

    • QP1301


Technical coordination internal peer review
Technical Coordination – Internal Peer Review

  • Review follows Breadboard/Prototype design phase

    • Includes SDL members both internal and external to SOFIE

    • System and component level

  • Following review, design placed in configuration control




Se summary

Designs are mature and provide margin on system requirements

Technical resources are being managed and tracked

Error budgets are being managed

SE Summary



Radiometric system requirements
Radiometric System Requirements

SOF 174 :

Measurement Bands

SOF 183 :

Radiometric SNR


Radiometric model error budget
Radiometric Model Error Budget

Optical Input Path


Radiometric model error budget cont
Radiometric Model Error Budget (cont)

Optical Math Model Transfer Function


Radiometric model error budget cont1
Radiometric Model Error Budget (cont)

Electronics Path

Effective Sync Rect Q = 500




Pointing model error budget cont
Pointing Model Error Budget (cont)

  • 2D derived by hand, includes 1 mode in mirror and 1 mode in structure (4 plant states)

  • Integrates OSC’s latest S/C model (from AIM Bus CDR) and SSG’s latest SMA model




Alignment Knowledge Error Budget – SOFIE FOV to ROS

Spacecraft Pointing Knowledge Requirements


Alignment knowledge error budget slow thermal dynamic
Alignment Knowledge Error Budget – Slow Thermal Dynamic

Simulation of Hot Case Conditions

  • Assumptions

    • Hot case thermal loads considered

    • Restrained temperatures:

      • CSM Assembly – 37 F to 48 F

      • Radiator Interface – 24.5 F

      • Aft Optics Deck – 30 F to 37 F

      • Fore Optics Deck – 25 F to 32 F

      • Bottom Deck – 32 F to 35 F

      • Sun Sensor – 39 F to 43 F

      • Mid Optics – 39 F

      • M1 and Hub – 34 F

      • M2 and Mount – 52 F

      • Isolator interface at S/C – 86 F

    • Only conduction heat transfer considered

    • Steady-state temperature predicted

    • Displacements from 70 F

    • Displacements relative to Field Stop


Alignment knowledge error budget slow thermal dynamic1
Alignment Knowledge Error Budget – Slow Thermal Dynamic

Simulation of Cold Case Conditions

  • Assumptions

    • Hot case thermal loads considered

    • Restrained temperatures:

      • CSM Assembly – -27 F

      • Radiator Interface – -35 F

      • Aft Optics Deck – -26 F

      • Fore Optics Deck – -31 F

      • Bottom Deck – -30 F

      • Sun Sensor – -27 F

      • Mid Optics – -25 F

      • M1 and Hub – -28 F

      • M2 and Mount – -26 F

      • Isolator interface at S/C – -4 F

    • Only conduction heat transfer considered

    • Steady-state temperature predicted

    • Displacements from 70 F

    • Displacement relative to Field Stop


Alignment knowledge error budget slow thermal dynamic2
Alignment Knowledge Error Budget – Slow Thermal Dynamic

Simulation of SOFIE to SC Deflections

Node in center of Aperture Cover (SOFIE FEM coordinate system)

Hot Case:       Tx:        3.03e-4 in

                        Ty:        -6.05e-3 in

                        Tz:        -8.46e-3 in

                        Rx:       -2.14e-4 degrees

                        Ry:       5.39e-5 degrees

                        Rz:       -4.41e-5 degrees

Cold Case:       Tx:        6.00e-4 in

                        Ty:        -1.82e-2 in

                        Tz:        -1.99e-2 in

                        Rx:       -6.77e-4 degrees

                        Ry:       6.92e-5 degrees

                        Rz:       -3.87e-5 degrees


Pointing budget sofie to sc accuracy
Pointing Budget – SOFIE to SC Accuracy

SOFIE Science FOV Boresight to Sun Center

(SYS755)

Required 60

RSS

SOFIE Science FOV Boresight to ROS Error

CBE 0.4

SOFIE ROS to S/C Deck I/F Plane Error

(SOF231)

Required 30

S/C Deck I/F Plane to MRC Error (SYS837)

Required 2

MRC Pointing Accuracy (SYS844)

Required 17

SOFIE ROS to S/C Deck I/F Plane Static Error

CBE 1

SOFIE ROS to S/C Deck I/F Plane Slow Dynamic Error

CBE 2

SOFIE ROS to S/C Deck I/F Plane Launch Shift

CBE 2

ACS Accuracy (BUS272)

Required 5

Ephemeris Error (SYS844)

Required 36

RSS = 3 Arcminutes (3 Sigma)


GFOV Clearance

9.53in.

Science FOV

Glint FOV

0.69in.




Level 3 Requirements Management

  • Requirements will be utilized as the main method for defining the functionality, performance, design constraints, and interfaces for the AIM program

  • Requirements will be used throughout all phases of the program to guide design, development, integration, and test

  • Requirements tracking and compliance assurance will be an integral part of peer, design, integration, and test reviews to insure that the system development is proceeding in accordance with the systems engineering and management process

  • After initial completion, the requirements and interfaces will baselined and change tracking will occur:

    • Access control will allow those teams and individuals with responsibility for portions of the requirements to propose changes to those requirements.

    • The system engineering team will work with the necessary engineers and management personnel to access the impact of requirements changes on the remainder of the system.


Level 3 Requirements Management (cont)

AIM Requirements Traceability & Specification Tree (from AIM SEMP)


Level 3 Requirements Management (cont)

AIM Requirements Development Approach and Guidelines (from AIM SEMP)


Level 3 & 4 Requirements Management (cont)

  • SOFIE Level 3 requirements derived from AIM Level 1 & 2 requirements

    • Level 3 requirements report (DOORS) created in accordance with WBS

    • Approved by AIM Mission systems engineer and Deputy SE

  • Level 3 requirements managed by SOFIE systems engineer

    • Level 3 requirements assigned to appropriate discipline leads

  • Level 4 requirements derived from Level 3 requirements by systems engineer and discipline leads

    • Subcontractors requirements are also managed as Level 4

  • Level 3 and Level 4 requirements derivation includes source traceability and verification process information

    • Serves as Verification Matrix

  • SOFIE Instrument Specifications and SOFIE Flight Software Specifications captured in SDL/04-004 and SDL/04-003, respectively








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