NASA’s Gravitational-Wave - PowerPoint Presentation

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NASA’s Gravitational-Wave Mission Concept Study

Robin Stebbins, Study ScientistNinth LISA SymposiumParis, 22 May 2012

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OutlineGoalsElements of the studyContext of the study

Responses to the Request-For-Information (RFI)Science performance analysisAssessment of architecturesRiskCost2This document contains no ITAR-controlled information and is suitable for public release.

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Goals of the StudyDevelop mission concepts that will accomplish some or all of the LISA science objectives at lower cost points

.Explore how mission architecture choices impact science, cost and risk.Big QuestionsAre there concepts at $300M, $600M or $1B?What is the lowest cost GW mission?Is there a game-changing technology that hasn't been adequately considered?3This document contains no ITAR-controlled information and is suitable for public release.

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Elements of the StudyRequest for Information (RFI) – due Nov. 10

th.Core Team – ~25 GSFC, JPL & university scientists and engineers critically reviewing RFI responsesScience task force – ~15 volunteer scientists evaluating science performance of conceptsCommunity Science Team (CST) – 10 scientists, Rai Weiss, Ned Wright co-chairsPublic workshop – December 20-21st Concurrent engineering studies by JPL’s Team-X in March and AprilFinal Report to NASA Headquarters – July 6thPresentation to the Committee on Astronomy and Astrophysics (CAA) of the National Research Council (NRC)This document contains no ITAR-controlled information and is suitable for public release. 4

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Context of the Study – A Brief History of LISA

1974 - A dinner conversation: Weiss, Bender, Misner and Pound1985 – LAGOS Concept (Faller, Bender, Hall, Hils and Vincent)1993 – LISAG - ESA M3 study: six S/C LISA & Sagittarius1997 - JPL Team-X Study: 3 S/C LISA 2001-2015 - LISA Pathfinder and ST-7 DRS2001 – NASA/ESA project began2003 – TRIP Review2005 – GSFC AETD Review2007 – NRC BEPAC Review2009 – Astro2010 Review2011 – NASA/ESA partnership ended2011 – Next Generation Gravitational-Wave Observatory (NGO) started2012 – ESA L1 downselect5

This document contains no ITAR-controlled information and is suitable for public release.

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Context of the Study – Activities in Europe

LISA PathfinderDemonstration of space-based GW technology, in late stages of I&T2014 launchTechnology developmentInertial sensor electronics, charge controlOptical systemLaser systemPointing and point-ahead mechanismsNGOHighly developed concept with extensive science case and technical detail6This document contains no ITAR-controlled information and is suitable for public release.

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Context of the Study in the U.S.Next major mission in Astrophysics starts after 2018.

The Astrophysics Division anticipates that a “probe-class” mission could be started ~2017.The Division will not commit to a ‘large’ mission until after Astro2020. ‘Commit’ means the Confirmation Review at the end of Phase B.A partnership with ESA seems highly likely. That would require:Rebuilding a partnershipReliably coordinating two agencies’ programs7

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RFI Responses

8

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RFI Responses17 responses total12 for mission concepts, several with options

3 for instrument concepts2 for technologiesFour natural groupsNo-drag-free concepts (2)Geocentric orbits (4)LISA-like (5)Other (2)9

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What constitutes “LISA-like?”Drag-free controlFree-falling test mass

Precision stationkeepingContinuous laser rangingHeliocentric orbitsConstellation in stable equilateral triangleNo orbital maintenanceMillion-kilometer long armsLaser frequency noise subtraction (TDI)Emulate Michelson’s white-light fringe condition through post-processing10

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No-Drag-Free Concepts

11

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No-Drag-Free ConceptsRely on either very long arms (50X LISA) or geometry (100X reduction) to compensate for using the spacecraft as the test mass.

Disturbances are solar radiation pressure variability, solar wind, interplanetary magnetic fieldMeasure, model and correct for spurious forces (102 - 104 X)Displacement noise from motions of the spacecraft CG, owing to, say, thermoelastic effectsConcerns about measuring solar wind and modeling/testing other disturbance (e.g., Pioneer effect)12

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Geocentric Concepts

13

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Geocentric ConceptsNoise concerns

Thermal environment: moving sub-Sun point, eclipsesSun in the telescopeVarying Earth albedoGeosynchronous may have interesting modulation properties. (McWilliams’ talk Thursday afternoon)LAGRANGE/Conklin described by Buchman Tuesday afternoon.A big cost question: can you do this for a factor of 4 less by employing nanosat technology, lower reliability standards, standard bus, a different way of doing business, … a different business model?14

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LISA-like Concepts

15

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LISA-like ConceptsHow far can the LISA architecture be descoped

?No technical or performance issuesScience performance falls off much faster than cost Found the bottom!See Jeff Livas’s talk Tuesday afternoon in LISA-NGO Technology session.16

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Other Concepts

17

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Other ConceptsThe superconductor idea doesn’t work.

Atom InterferometryAtoms clouds as test massesAtom interferometer as a phasemeterSee John Baker’s talk Thursday afternoon in Other Experiments and Alternative Design sessionInSpRLMost aggressive design conceptInvoked ‘superclocks’ and resonanceSeems to require a few orders of magnitude improvement in several key performance parametersLacks enough definition to evaluateYu concept doesn’t promise to be cheaper.Digital Interferometry is interesting.18

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Science Performance

Analysis19

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Science Performance

20Volume of the Universe exploredDetection numbers for source populations (Massive BHs, EMRIs, Galactic Binaries)Discovery spaceParameter resolutionAll work done by Neil Cornish and the Science Task Force. See Cornish talk, Friday morning.

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Sensitivity Curves – All 15 Concepts

21

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Massive Black Hole Horizons

22

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Massive Black Hole Horizons – No-Drag-Free

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Massive Black Hole Horizons – Geocentric

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Massive Black Hole Horizons – Geosynchronous

25

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Massive Black Hole Horizons – LISA-Like

26

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Detection Rates – Large Seed Models (/yr)

27

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Detection Rates – Small Seed Models (/yr)

28

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EMRI Horizons

29

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EMRI Detections

3010 M⊙ compact object, eccentricity 0.5 at 2 yrs to plunge, spin 0.5 central BH, SNR=15

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WD-WD Detection Numbers

31

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Parameter Estimation – LISA-like Concepts

32Similar detection numbers, but each descope x 3-10 loss in resolution

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Architecture Choices

33

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Architecture Choices – Mission DesignHeliocentric – fixed, drift-away, in-line, L2/leading/trailing, 1 AU

Geocentric – OMEGA, geosync, L3/L4/L5, LEOCompare delta-v, constellation stability, propellant, thermal, modulation of science signal, comm34

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Architecture Choices – Inertial ReferenceProof mass – cubical, parallelepiped or spherical free-

falling, or torsion pendulumSpacecraft center-of-gravity (aka no-drag-free) with modeled correctionsAtom interferometry - atoms as proof masses, atoms as secondary inertial referencePayload as separated spacecraft35

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Architecture Choices – Measurement StrategiesLaser interferometry with laser heterodyne phase comparison – free-space or digital

interferometryLaser interferometry with atom interferometer phase comparisonLaser and clock frequency noise correction – 3 spacecraft & TDI, or very much better phase reference (AI)36

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Implementation Strategies

37

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Implementation Strategies

38ParameterSGO MidLAGRANGEOMEGAMass Margin53%

53%

53%

Payload mass (kg), power (W) CBE

216.5 kg, 233 W

99.7 kg, 99.3 W

Option 1:

64.3 kg, 80W;

Option 2:

55 kg, 54W

Mass rack-up

Science-craft type 1

Science-craft type 2

Propulsion Module type 1 + Prop

Propulsion module type 2 + Prop

LV Adapter

Launch Mass Wet

717

kg (3)

 

661 + 139 (3)

 

?

4553 kg

531

kg (2)

586 kg (1)

224 + 174 (2)

591 + 114 (1)

32 kg

3182 kg

147

kg (6)

 

374 + 465.5 (1)

 

28 kg

2347 kg

Launch Vehicle

Atlas V 551;

6075

kg

Atlas V 511;

3285

kg

Falcon 9 Block

2;

2490 kg

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Risk

39SGO-Mid/HighLAGRANGEOMEGAThese are a combination of Team-X and Core Team risks.Risk rises rapidly with modest (<10%) cost reductions.This assessment is not complete.

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CostTeam-X is very conservative.

Cost estimates range from $1.2B to 2.1B.Per science year costsSGO-hi $450M/yr SGO-mid/Lagrange ~$800-900/yrOmega ~$1,300M/yrImportant cost driversNon-recurring costs (NRE) and recurring costs (RE) are important.Design validationSerial vs parallel construction of multiple units (~$150M/yr)40

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SummaryThe CST prefers SGO-Mid (3 arms, LISA-like, 1 Mkm

, drift-away).Big QuestionsWe found no concepts at $300M, $600M or $1B.The lowest cost GW mission is ~$1.4B (±0.2).We found no game-changing technology that hasn't been adequately considered.Heliocentric is a better choice than geocentric.Three dual-string spacecraft appear to be more robust than six single-string spacecraft.No-drag-free achieves only modest savings while incurring substantial risk. [Cost model is uncertain.]Three arms has lower risk and mediating cost factors relative to two arms.41

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Backup Slides

42

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FeedstockWhitepapers (17x~15 pages = 235)

Workshop Presentations (~20 x 30 charts = 600)Core Team Work (~200 pages)Team-X inputPresentations (4 x ~60 charts = 240)Master Equipment ListsFunctional Interface DiagramsCAD filesOrbit analysesTeam-X outputViewgraphs (~3 x 280 = 840)Team-X reports (~3 x 10-20 = 45)CST Work (~50 pages)Total: north of 2230 pages43

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Mission Design Review 1/2

44 FeatureSGO-MidLagrangeOmega 1. Trajectory Phase DV

[174, 153, 200]

m/s



Stack ~ 120 m/s to L2

[SC1,

3

]: [460, 300

]



[206, 328, 450] + 4 m/s

vs.

3



210 m/s if 3 PMs

Significance: Prop module size(s), Total mass, Launch

vehicle

2. Trajectory

Phase

D

t

17 months

27 months



12 months (

vs. ~ 7

)



Significance: Cost/complexity of trajectory phase operations (FDF & Ops)

3. Lunar Flybys Used

No

Yes



No

Significance: Cost/complexity/risk of trajectory phase operations (FDF & Ops)

4. Mission Phase

D

t

2 yr / extendable

2 yr /

not

extendable

1 yr / extendable

Significance: Cost of science operations, Amount of science, Constellation

Stability

5.

Const. Stability

D

L/L,

Da

,

Dn

, (

Dg

||

,

Dg

+

)

±0.007, ±0.6



, ±1.5

Mhz

,

±(0.008, 1.0)

m

rad



±0.1, ±0.12



, ±94

Mhz

,

±(0.8, 0.32)

m

rad



±0.025, ±2.2



, ±60

Mhz

,

±(0.17, 0.15)

m

rad



Significance: Cost of additional mechanisms and electronics

6.

Mission Phase

D

V

No

Yes (SC2)



No

Significance: Cost/sophistication of

mN

-thruster system (~ 10 m/s/yr)

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Mission Design Review 2/2

45 FeatureSGO-MidLagrangeOmega 7. Distance to Earth /

HGA, ISC

req

?

24 to 55



10

6

km /

HGA

[21, 1.5,

21

]



10

6

km

HGA/LGA,

ISC/LGA

0.6



10

6

km

LGA



Significance: Cost/complexity of communications;

ISC = inter-spacecraft comm.

8.

GeoEcliptic

Orbit

No

No

Yes



Significance: (a) Sun direction variation

(thermal stability)

(b) Sun in telescope aperture (thermal, optical interference)

(c) Earth eclipses (thermal, science interruptions)

Feature

SGO-Mid

Lagrange

Omega

9.

Launch Vehicle C3

+0.27 (km/s)

2

-0.3 (km/s)

2

-0.05 (km/s)

2

Significance: Launch vehicle selection

10.

Single Prop Option

No

(

?

)

Yes (but not necessary)

Yes (but not necessary)

Significance: Input to possible trade for single prop module cost savings (?)

11.

“FDF” Ops Cost

$ 18

M



$ 27

M



$ 23

M

(?

if 3 PMs

)

Cost Drivers: Trajectory and mission phase durations, trajectory complexity