# Presentation: 328299

## SNAP Systems EngineeringWBS 1.3

**David Pankow**
**Space Sciences Laboratory,**
***and***** Mechanical Engineering Department,**
**University of California Berkeley**
**November 2003**

## SNAP Engineering Overview

- Observatory Overview
- Optical Telescope Assembly (OTA)
- Telescope (TMA-63) Packaging
- Instrument (Camera) Packaging
- Outer Stray Light Baffle
- Active Mechanism Concerns
- Spacecraft Overview
- Sub-systems Summary
- Market Survey (e.g. RSDO Catalog)
- Mission Profile - Launch Vehicle and Orbit Selection
- Ground Segment
- Systems Engineering
- Design and Trade Studies Status
- Documentation & Configuration Control
- R & D Tasks, Manpower, & Schedule
- Summary

## SNAP’s DESIGN EVOLUTION

**Passive Cold Biased Bus & Baffle / Warm Optics**
- Active Coolers are not Mature, Cryogen's are Short Lived
- High Earth Orbit allows Passive Cooling and Stable Pointing
- Build, Test, and Fly Warm Optics
- Cold Optics are a Significant Cost & Schedule Driver *(NGST)*
- Compact Telescope with the Longest Light Baffle that can be Fit !
**Generic *****and*****  Rigid Spacecraft**
- One Mission Thermal Attitude   ...near Sun Line Normal Viewing
- No Flexible Appendages and Minimal Mechanisms
- On Board Momentum Control & Management
- Structural Noise Isolation at the Sources
- RSDO generic spacecraft with Identified Upgrades

## OBSERVATORY Cross Section

- Main Baffle Assembly

- Door Assembly

- Primary Solar Array

- Secondary Mirror, Hexapod
- and “Lampshade” Light Baffle

- Secondary Metering Structure

- Primary Mirror

- Optical Bench

- Tertiary Mirror

- Fold-Flat
- Mirror

- Spacecraft

- Instrument Dewar

- Instrument Thermal Radiator

**OBSERVATORY Cross Section**

- Spectrograph

- Focal Plane

- ‘Stovepipe’ Baffle

## TELESCOPE OPTICS DESIGN (TMA-63)

**TELESCOPE OPTICS DESIGN (TMA-63)**

- Annular Field Three Mirror Anastigmat (TMA)
-  Folded Light Path Permits Very Compact Telescope Design
-  2 meter Primary in 3.3m long package with 20.66m Focal Length
-  *Allows anti-sunward Thermal Radiator for Instrument *
-  Obstructing Secondary causes Annular Field of View
-  Single *(Flat)* Focal Plane Array of Detectors
*(Often called the Fully Integrated Detector Option (FIDO)*
-  36 - CCD’s
-  36 - IR Sensors
-  Spectrograph *(fully redundant)*
-  Common 140K remains Adequate
- 130K Spectrograph bias is viable

## Corning ULE Ultra-Low Expansion Glass
Face Sheets Bonded to Water-Jetted Honeycomb Core
180 mm thick Core with 2.5mm Ribs Typical
Achieves 85-90% Light weighting
Extensive Manufacturing History

Schott Zerodur Glass/Ceramic Material
Solid Blank, Mass Reduced by Machining Backside
190 mm Pockets with 5mm Ribs Typical
Open Back is Lowest Fabrication Risk
Semi-Closed Back for Greater Rigidity
Achieves 70-85% Light weighting
Extensive Manufacturing History

All Approaches are Viable for SNAP

- Face Sheets Bonded to Water-Jetted Honeycomb Core
- 180 mm thick Core with 2.5mm Ribs Typical
- Achieves 85-90% Light weighting
- Extensive Manufacturing History
**Schott Zerodur Glass/Ceramic Material**
- Solid Blank, Mass Reduced by Machining Backside
- 190 mm Pockets with 5mm Ribs Typical
- Open Back is Lowest Fabrication Risk
- Semi-Closed Back for Greater Rigidity
- Achieves 70-85% Light weighting
- Extensive Manufacturing History
**All Approaches are Viable for SNAP**

**TELESCOPE MIRROR OPTIONS**

## TELESCOPE STRUCTURE

**TELESCOPE STRUCTURE**

*SECONDARY MIRROR SUPPORT STRUCTURE*

*OPTICS “COFFIN” BELOW*

*PRIMARY OPTICAL BENCH*

**COMPOSITE TELESCOPE STRUCTURE***(driven by the required 1 ppm Optics Stability)*- Standard M-55J Graphite Fibers are Adequate        *for the Needed ppm / K Stability*-  Quasi-Isotropic Lay Up: *CTE < -0.12 ppm /**** C*- On Orbit Temperature Control:  ***T < **± **2 **** C*- Cyanate Ester Matrix       *provides low CME (moisture)*- ***These are Today’s Technology !***

*OPTICS, THERMAL, AND GEOMETRIC DEFINITIONS ARE COMPLETE**DETAILED DESIGN AND FEM ANALYSES ARE MATURE*

***...******with Three STIFF Metering Beams***

## TELESCOPE OVERVIEW

**TMA-63 TELESCOPE DESIGN IS PROGRESSING RAPIDLY**
**OPTICAL TELESCOPE (OTA)**** - Implementation *****(TMA-63 is very mature !)***
**Open Back Zerodur vs Closed Back ULE (LBL - Sagem-Reosc) studies complete**
**No Zerodur “show-stoppers” – Increased glass mass, perhaps shorter schedule**
**Critical end to end  ****“*****Hubble*****”**** *****(Reflex)***** Test definition results are promising**
**FEM results suggest Std. 1/20****th**** wave optics 1G validation appears viable**
**64 Support Fingers needed to Reduce Gravity Sag in Primary Mirror**

## INSTRUMENT and THERMAL

**INSTRUMENT and THERMAL**

**PASSIVE GIGA-CAM 140K DEWAR THERMAL BUDGET**
**  ****45 w ****	****Radiating Capacity from 2m****2**** unobstructed 130K Radiator to Space**
**< 4w>****	****Radiator Thermal Isolation Mounts & MLI behind**
- 		**RADIANT COUPLING LOSSES**
**< 6w>****	****CONICAL Cosmic Ray Shield - MLI outside (********** ************ *****~ 1%)**
**<17w>****	****Open End CONE Blackbody Loss to warm Coffin Cavity**
- 		**CONDUCTIVE COUPLING LOSSES**
**< 1w>****	****Giga-Cam Thermal Isolation Mounts**
**< 2w>****	****Dewar Thermal Isolation Mounts and Cold Plate Gaskets**
**< 1w>****	****Electrical “Flex-Print” (TBD traces)**
**< 8w>****	****Average Electrical Power for HgCdTe & CCD’s**
** ****~ 6w** 	**CURRENT MARGIN**
**~10°C ****	****Gradient allocated for Cold Plate, Radiator, and Flex-Links**

*130K PASSIVE*
*RADIATOR*

*FOCAL PLANE*

*DEWAR*

*SHUTTERS*

***NOTE:**** Thermal and Contamination Close Outs ****NOT SHOWN**** for Clarity*

*Spectrograph*

## INSTRUMENT THERMAL NOTES

**HESSI COLD PLATE ASSEMBLY**
**Supports Germanium Detector Assembly under Vacuum**

**HESSI DETECTORS**
**Extensive Thermal Isolation**
**Only ~3W of Active Cooling**

|  | HESSI | SNAP |
| --- | --- | --- |
| Detector Temperature | 73 K | 140 K |
| Cooling Budget | 3 W active | 20 W passive |
| Detector (Cold) Mass | 38 kg | est. 32 kg |
| Orbit | LEO | HEO |
| “Focal Plane” Precision | mm | microns |

**INSTRUMENT THERMAL NOTES**

## STRAY LIGHT BAFFLE DESIGN

**STRAY LIGHT BAFFLE DESIGN**

**FUNDAMENTAL BAFFLE DESIGN CONSIDERATIONS**
-  Top Cut Angle Chosen to Block Sunlight in All Science Attitudes
-  Earth-Lit Region must be Well Baffled
-  Baffle–Lamp Shade–Stove Pipe diffraction line dictates the “Hat Size”
**Trades Indicate an Ordinary Aluminum Shell Construction is Adequate !**
***Detailed ASAP (software) Stray Light analysis are now underway !***

## TELESCOPE THERMAL

**OPTICS: Build,Test, & Fly Warm**

**High Earth orbit (HEO) to minimize Earth-glow Loading**
** ****GaAs - OSR Striping of the (warm) Solar Array Panels**
** ****Front surface heat rejection Only**
** ****Optical Solar Reflectors are back silvered Quartz tiles (*********** *****~ 8%, *********** *****~ 80%)**
** ****Low emissivity Silvered Mirrors**
** ****Thermal Isolation mounting and ****	****Extensive MLI blanketing**
** ****Cool Light Baffle and **
**	****Actively Heated Telescope**

## SNAP OBSERVATORY STRUCTURES

**“****Coffee Table” Spacecraft Bus**

**GFRP Composite Telescope Structure**

**Telescope Light Baffle Structure**

**PRIMARY STRUCTURES**
**Total, or Integrated Observatory Design & Finite Element Model (FEM) is done**
**Baffle, Door, Telescope, & Optics Design Studies Posted - Stout Bus defined**
**17 Hz -1****st**** Mode exceeds 10 Hz Delta IV req’mt, with 20% Launch Mass Margin**

**17 Hz First Mode**

## ACTIVE MECHANISM CONCERNS

***Our Guess at Reviewers Likely First Reactions !***

## SNAP’s ELECTRICAL DIAGRAM OVERVIEW

**INSTRUMENT FUNCTIONS**

**SPACECRAFT FUNCTIONS**

***HIGH SPEED DATA PORTS***

**MIL-STD**
**1553**
**BUS**
**Interfaces**

## MOSTLY GENERIC SUBSYSYEMS
EPS (electrical), C&DH (command & data handling), TCS (bus thermal)

MISSION UNIQUE SUBSYSTEMS
ACS (attitude control), SMS (structure & mechanisms), RF (Communications)

THE “CLEAN INTERFACE” EXCEPTIONS
Telescope mounts to the Spacecraft “Coffee Table”, or ANY FLAT SURFACE
Load Path expands from (66”) PAF to 2.5m Baffle & Telescope Bipod Ring
Stiffness & Strength Requirements must be imposed on Primary Structure

Star Trackers, Gyro (IRU), and Solar Arrays mount on the Instrument
Observatory Control Unit & Memory mount on the Spacecraft

IMDC’s (GSFC) Risk Assessment & New Technologies Comments
Risk on spacecraft bus is generally low, with well-understood technologies and readily available components
No significant technology development required for bus 

Higher risk is on the instrument side...

**EPS (electrical), C&DH (command & data handling), TCS (bus thermal)**
**MISSION UNIQUE SUBSYSTEMS**
**ACS (attitude control), SMS (structure & mechanisms), RF (Communications)**
**THE “CLEAN INTERFACE” EXCEPTIONS**
**Telescope mounts to the Spacecraft “Coffee Table”, or *****ANY FLAT SURFACE***
***Load Path expands from (66”) PAF to 2.5m Baffle & Telescope Bipod Ring***
***Stiffness & Strength Requirements must be imposed on Primary Structure***
**Star Trackers, Gyro (IRU), and Solar Arrays mount on the Instrument**
**Observatory Control Unit & Memory mount on the Spacecraft**
**IMDC’s (GSFC) Risk Assessment & New Technologies Comments**
***Risk on spacecraft bus is generally low, with well-understood technologies and readily available components***
***No significant technology development required for bus ***
***Higher risk is on the instrument side...***

**SNAP SPACECRAFT OVERVIEW**

## SNAP Mission Profile

**SNAP Mission Profile**

**Delta IV M+ (4240) Launch from KSC**
- 2.6 x 25 Re Injection to Final 28 Inclination Orbit
- Phased for near Ecliptic Plane Orbit
- Our Plus: *The perigee is Stable Over Berkeley !*
**Commissioning Phase - several overlapping weeks**
- Spacecraft Turn On Activities
- Structured Cool Down of the Telescope
- Slow Roll, or Auxiliary (rear) Solar Arrays
- Degassing & Dry Out Period
- Optics Turn On – Open Cover, Focus, Cal., etc.
**Mission / Science Operations *****(Routine Survey)***
- Alternate near N/S Ecliptic Pole Observing
- Observing is Suspended below 9 Re (radiation issues)
- Onboard Storage and High Speed Data Down-Link

***Delta IV fairing***

## SNAP GROUND DATA SYSTEM

**SNAP GROUND DATA SYSTEM**

## SNAP GROUND DATA SYSTEM

- NRAO’s ALMA project - 12m Ka Band *VERTEX RSI*  dish *(Jan ’03 1st Light)*

- SSL’s Berkeley Ground Station (BGS) - 11m S-Band Dish
-  3rd Year of mostly Automated Operation
-  MOC & SOC Infrastructure for FAST / RHESSI / CHIPS
-  BGS dish is S&X-Band Capable *(but not Ka-Band)*

## SNAP S.E. Resources Allocation

**MASS ALLOCATION (~21% margin) *****2020 kg Direct to Orbit Launch Capacity***

**MISSION REQUIREMENTS: **Complete Document is Posted at ***snap.lbl.gov***

## SNAP S.E. Resources Allocation

**ELECTRICAL POWER REQUIREMENTS**

**MISSION REQUIREMENTS: **Complete Document is Posted at ***snap.lbl.gov***

## SYSTEMS ENGINEERING DOCUMENTS

**TOP LEVEL SNAP PLANNING DOCUMENTS**
- “Mission Definition and Requirements Document” (MDRD) Describes our Negotiated Level 1 Science Requirements – version 1d is posted.
- “Integrated Requirements Database”is the evolving Flow Down of Requirements to the Level 2, 3 & 4 Requirements and is posted.
- Work Breakdown Structure (WBS) is in Place and Being Used for all SNAP Planning and Budgeting Efforts.
- Draft Observatory I&T Plan is under Active Review and Discussion
- Solid Works and PDM is Networked, and the Maturing SNAP Solid Model is under Configuration Control *(15**th** release now posted)*.
** **IGES export issues to structural and thermal models are being examined
- Instrument, Telescope & Spacecraft ICD’s will be developed as designs mature

## SYSTEMS ENGINEERING DOCUMENTS

**SNAP’s EVOLVING CONTROLLED DOCUMENTS DATABASE**

## STRUCTURES – 1st Generation NASTRAN Model Complete
Baffle Trades, Telescope Trades, Optical Element Trades, Bus defined
End to end 1G Optics verification plan is progressing 

THERMAL DESIGN
Excel & Matlab Lumped Node Telescope & Camera Models allow cross checks

TELESCOPE & OPTICS
Optics Tolerancing Submitted, and detailed Stray Light Studies are underway
Draft Telescope & Primary Mirror Specification Documents under Review

ATTITUDE CONTROL SYSTEM 
Image Jitter based Modeling and Simulation Studies are Show Promise
Parallel Physical and State Models allow interactive cross checking

COMMAND & DATA HANDLING
Industry std. “fully redundant & cross strapped 1553” avionics bus defined
High speed “selectively redundant” Instrument data bus architecture defined

MISSION INTEGRATION & TEST
End to End Telescope I&T Plans are Progressing Rapidly
Sequences, Test Options, and Schedules are being Traded

**Baffle Trades, Telescope Trades, Optical Element Trades, Bus defined**
**End to end 1G Optics verification plan is progressing **
**THERMAL DESIGN**
**Excel & Matlab Lumped Node Telescope & Camera Models allow cross checks**
**TELESCOPE & OPTICS**
**Optics Tolerancing Submitted, and detailed Stray Light Studies are underway**
**Draft Telescope & Primary Mirror Specification Documents under Review**
**ATTITUDE CONTROL SYSTEM **
**Image Jitter based Modeling and Simulation Studies are Show Promise**
**Parallel Physical and State Models allow interactive cross checking**
**COMMAND & DATA HANDLING**
**Industry std. “fully redundant & cross strapped 1553” avionics bus defined**
**High speed “selectively redundant” Instrument data bus architecture defined**
**MISSION INTEGRATION & TEST**
**End to End Telescope I&T Plans are Progressing Rapidly**
**Sequences, Test Options, and Schedules are being Traded**

**SYSTEMS ENGINEERING STUDIES**

## SYSTEMS ENGINEERING REVIEWS

**SNAP MISSION LEVEL REVIEWS**
**’****01 IMDC & ISAL Mission and Instrument Design Reviews at GSFC**
***Extremely useful for Refining the Mission Concepts***
**’****02 Independent Lehman R&D Review**
**SNAP team received many complements for a thorough presentation**
**’****02 “Team X” Mission Design Review at JPL**
***Mission Implementation refined, No New Mission concerns raised***
**NASA’s “BEYOND EINSTEIN” Announcement of Opportunity**
***Type 1 & Type 2 proposal outcomes are not yet fully known***
**ISSUES & CONCERNS**
**Critical Path (Optics) Procurement Options are being pursued**

## SYSTEMS ENGINEERING STATUS

** ****TELESCOPE **packaging options and requirements are well defined
-  Several Light-weighting Options are Actively being Considered
-  Our team’s desire is to maintain technology and vendor flexibility
** *****OPTICS PROCUREMENT IS OUR CRITICAL PATH ITEM***
** ****INSTRUMENT **needs and viable approaches are known & actively pursued
-  Sensor Packaging & Electrical Packaging Trades are In Progress
-  Thermal management calls for continuing vigilance
** **
** ****SPACECRAFT **can be a generic *(& interagency)*** RSDO** procurement
-   Instrument - ACS interactions calls for studies & tracking
** ****LAUNCH VEHICLE **– Track the Options and New Development Maturity

## Systems: R&D Schedule

## SUMMARY & COMMENTS

**Build, Test, & Fly Warm is both Proven and Cost Effective**
**Passive Thermal Approach Remains Viable for the Instrument **
**SNAP has Several Lightweight, Low CTE Mirror Options**
**Composite Telescope Structures Are Well Understood, and this Technology Continues to Mature**
**Spacecraft Bus has several concerns, but No New Technology **
**Healthy Competition in the ‘Heavy Lifter’ Launch Business**
** **Delta IV: (3 for 3) *EUTELSAT, DSCS-A3, DSCS-B6*
-  Atlas V: (3 for 3) *Hotbird 6, Hellas-Sat, Rainbow 1 (...or Atlas IIIB)*
-  Sea-Launch: (9 for 10) ...*but International Partnership is a concern*