The SEIS experiment on INSIGHT Discovery mission to Mars

IPPW-10, June 18th 2013, San José

Rene Perez, SEIS instrument manager, CNESPh. Lognonné, S. Deraucourt, IPGP

D. Mimoun, ISAEK. Hurst, JPL and the SEIS Team

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A fundamental contribution to understanding the early evolution of the terrestrial planets through investigations of the Mars interior

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Why bother about planetary interiors ?

• The interior of a planet retains the signature of its origin and subsequent evolution.

• The interior structure provides the boundary conditions that can constraint our understanding of both accretion composition and conditions

• The interior structure reveals the signature of early differentiation processes

Crust

Crust

Crust

Crust

MantleMantle

MantleMantle

Core

Core

Core

Crust

Mantle

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Seismology on Mars: a long story...

1976: Viking3 months of (accumulated) seismic data

1996: Mars 96 Failed at launch

2016: Insight Will provide 1 martian year

of data (or more?)

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Scientific objectives:

• Understand the formation and evolution of terrestrial planets through investigation of the interior structure and processes of Mars

• Determine the present level of tectonic activity and impact flux on Mars

Objectives translated in Threshold Science Requirements for SEIS:- Rayleigh wave group velocity dispersion- P and S arrival times- Phobos tide amplitude

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Regional

Global to regional

Globala few/yr

~ 10/yr

~100/yr

M~5.5

M~4.5

M~3.5

3.3 4.6 6Magnitudes

2.6

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The InSight Payload:

Use or disclosure of information contained on this sheet is subject to the restriction on the title page of this document.

SEIS RISE HP3

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3 VBBs-Long period axis (IPGP)

The SEIS experiment overview:

3 SP sensors (IC)short period

LVL: Leveling system (MPS)

E-Box (ETHZ)

WTS: Wind and Thermal shield (JPL)

Tether / Tether box (JPL)

On LanderMars surfaceAPSS: Wind sensors (CAB)Pressure sensors (JPL) and Magnetometer (UCLA)

EarthGround

segmentSEIS

operational (CNES) and data center

(IPGP)SEIS Management (CNES)

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SEIS Operation Concept

• The instrument is always ON and keeps on acquiring raw data• SW (and C&DH) wakes up ~every TBD hours during about ten

of minutes• In routine one daily DSN pass for data downlink

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C&DH t

Wake-up Wake-up Wake-up

TBD hrs TBD hrs

SEIS communication session

E-Box NVmemory usage

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The Sphere VBB (long period sensors)

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Sphere VBB development history:

16 years old...

InSight

PDR

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Performance Validation Plan:

• Phobos tide calibration : – end-to-end performance test done on Earth

• SP performances– end-to-end performance test done on Earth

• VBB performances (S/N): end-to-end test not doable on Earth: – VBBs performance cannot be measured on Earth without a compensation mass (so, not in Mars

configuration)– Only reduced functional tests can be performed on flight VBBs (due to the difference in gravity)– Planning will be incompatible in long term (e.g. ~month) tests in low noise sites with temperature

comparable to Martian condition (e.g. Antarctica)

• Final performance is demonstrated by Tests and Modeling:– Early model (VBB5) extensively tested for performance, providing elements for last tuning of flight models – Measure the instrument self noise, and correct with the Performance Model– Measure sensitivity to external environment parameters– Test in Martian environment when possible (e.g. temperature, pressure capsule noise)– Simulate, when tests are not possible, to derive SEIS performance in Martian environment (Magnetic

field, Pressure)

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SEIS success tree (example)

WTSTh constant

Preliminary- STM

Test - QM

SphereTh. Constant

Preliminary- STM

Test - QM

VBB thermalSensitivity

Test – EMTest - QM

SEIS Thermal Noise

Simulation QM performance plus

temperature profile

Performance Test

Simulation + Tests

Simulation

Validation ofThermal noise allocation

Mars TemperatureModel

+ Sci. Temp.performance

(CNES)

(IPGP)

(CNES)

SP thermalSensitivity

Test – EMTest - QM

(Oxford)

SPTh. Constant

Preliminary- STM

Test - QM

(Oxford)

Ground

Inside/payload skin

Exterior skin

ConvectionModel

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Performances budget:

VBB noise budget (Velocity output):

10-3

10-2

10-1

100

101

102

10-12

10-11

10-10

10-9

10-8

10-7

10-6Subsystems noises input of the instrument, SCIENTIFIC MODE - VELocity output - MARS

Frequency(Hz)

AS

D a

ccel

erat

ion

(m/s

²/sq

rt(H

z))

INSIGHT specificationTotal noise of VBB sensorADC - Velocity Gain = 10Integrator correctorDCSDerivator correctorPhase and Gain correctorOutput gainBrownian Noise

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VBB5 first results …

Thermal environment tests done (and to be continued):• Thermal sensitivity• Behavior under cold environment (recentering, transfer function …)• Full characterization @ cold

Performance Validation:

Early model, but highly representative design under tests.

Ambient Noise@St Maur des Fossés (0.1-1Hz)2013/05/21

M7.4 Earthquake Tonga 2013/05/23@St Maur des Fossés (0.1-1Hz)

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Seismic Vault

VBB (one axis) + reference seismometer installed on the same pillar. Axes in vacuum chamber + µ-metal shieldingRecombine reference seismometer axes to fit VBB’s sensitivity axis, then compare measurements both in time and frequency domain

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Low noise test in low noise site?

• Unique way to detect noise issues at ng/Hz1/2 on fully integrated instrument• This test has been done last summer (BFO) with a previous instrument

configuration (significant gain on the results!)• It’s worth to be repeated with VBB5, but challenging for planning

– Could be attempted in // with ATLO (2015...)?

10-3

10-2

10-1

100

101

10-10

10-9

10-8

10-7

10-6

10-5

10-4

Frequency [Hz]

Acc

eler

atio

n A

SD

[m/s

2/s

qrt(H

z)]

VBB Noise Model

Ambiant seismicity @ BFO

VBB31 noise @ BFO

InSight RequirementsInSight Requirements scaled for Earth

VBB31 self noise model on Earth

Ambiant seismicity @ St Maur

VBB31 noise @ St Maur

BFO or Antartica?...

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Thanks for your attention!