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The Mars Microphone onboard Supercam for the Mars 2020 rover

(1) Universite de Toulouse, ISAE-Supaero, DEOS/SSPA, Toulouse, France (david.mimoun@isae.fr),

(2) IRAP, CNRS, Universite Paul Sabatier, Toulouse, France, (3) LANL, Los Alamos, NM (4) APL

David Mimoun1, Sylvestre Maurice2, Anthony Sournac1, Alexandre Cadu1, Marti Bassas 1, Murdoch Naomi1, Baptiste Chide1, JérémieLasue2, Ralph Lorenz4, Roger Wiens3 and the SuperCam team

A Short History of PlanetaryMicrophones (1/3)

n The short history of the planetary microphones began probably with Grozo2 instrument during the Venera 13 and 14 mission

n First Planetary microphone on Huygensn Successfully retrieved the descent sounds

n

2 June 2011 - 2

(http://mentallandscape.com/V_Venera11.htm)

A Short History of PlanetaryMicrophones (2/3)

n Second opportunity on Mars Polar Landern Mars Microphone Development up to FM

by Greg Delory (UC Berkeley)n Support by the Planetary Societyn Failed landing of MPL

n Third opportunity with Phoenix : soundcoupled with Mardi imager (Not used)

3 June 2011 - 3

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DREAMS Date: 01 03 2011

Pag.: 45/187 ExoMars EDM Science AO 5.2 Accommodation Envelope Taking into account both the sensor and the lander requirements, two possible accommodations are studied and shown in the Figure 19 and Figure 20. For exact dimensions, details, MICD and additional views, please refer to Annex #4.

MicroMETSIS

VISTACamera Cal. Traget

Microphone Sensor

MicroAres

MicroMIMA

MicroMED

Microphone Sensor Elect.

MEtBaro

Camera System

MarsTemMarsWind

CEU

LanderBattery

MicroMETSIS

VISTACamera Cal. Traget

Microphone Sensor

MicroAres

MicroMIMA

MicroMED

Microphone Sensor Elect.

MEtBaro

Camera System

MarsTemMarsWind

CEU

LanderBattery

Camera FoV55°x83°

MicroMIMAFoV 130°

Camera FoV55°x83°

MicroMIMAFoV 130°

Figure 19: DREAMS accommodation #1, CEU and Battery in place of CTPU position.

MicroMETSIS

VISTA

Camera Cal. Traget

MicrophoneSensor

MicroAres

MicroMIMA

MicroMED

Microphone Sensor Elect.

MEtBaro

Camera System

MarsTem MarsWind

CEU

LanderBattery

MicroMETSIS

VISTA

Camera Cal. Traget

MicrophoneSensor

MicroAres

MicroMIMA

MicroMED

Microphone Sensor Elect.

MEtBaro

Camera System

MarsTem MarsWind

CEU

LanderBattery

Camera FoV55°x83° MicroMIMA

FoV 130°

Camera FoV55°x83° MicroMIMA

FoV 130°

Figure 20: DREAMS accommodation #2, CEU and Battery in place of UHF Electronics position.

5.2.1 External unit requirements

Camera system is the sensor imposing the strongest accommodation constraints. MARIE Camera system: Below is the list of specifications relevant to identify MARIE requirements:

1. Focus from 500 mm up to infinite 2. FoV: 55°x83° (100° diagonal) 3. Calibration target to be positioned nominally within focus range (>390-400 mm).

After landing, EDM platform may be tilted up to +/- 40° and centre of the EDM baseplate may lie between 0.25 m and 0.60 m above nominal Martian surface (respectively for a horizontal and a 40° tilted attitude). Considering the above constraints, the following requirements for the camera accommodation have been considered: a) Calibration target shall stay at a minimum distance of 400 mm;

Schiaparelli, w/o heat shield & back cover

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The Mars Microphone sensor was considered a low-risk development, but was judged by the Science panel to lack sufficient scientific justification

A Short History of PlanetaryMicrophones (3/3)

Acoustics on Mars is complicated

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Very strong absorptionWilliams (2001)

102 103 104 105

Frequency (Hz)

0

10

20

30

40

50

60

Soun

d in

tens

ity (d

B)

Sound amplitude as a function of the distance for noise source = 60 dB4 m7 m10 m

Sound amplitude vs. distance on Mars

Increasing distance

Microphone science goals have to be crystal clear

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SuperCam on Mars 2020

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SuperCam is used to study Rocks at distance

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SuperCam is used to study Rocks at distance

Dr. Steven J. Rehse / What is LIBS?

+ soundSpectrum

SuperCam on Mars 2020

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SuperCam is used to study Rocks at distance

Dr. Steven J. Rehse / What is LIBS?

+ soundSpectrum

The science objectives of the Mars Microphone are: 1) To support the LIBS investigation to obtain unique properties of Mars

rocks and soils through their coupling with the LIBS laser.2) To contribute to basic atmospheric science: wind, convective vortices, dust

devils studies at close distance or when interacting with the rover.3) To monitor various artificial sounds.

Microphone science goals

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Microphone will record LIBS impacts up to 4 metersRovers Sounds

1 atm, Air

7.5 mbars, CO2

Freq (Hz) 104102

Pa/√

Hz

4 m

Microphone accommodation

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Mast unit (Interior view)RWEB (External view)

RWEB (External view)

FEE + Cover

Post + Microphone

MTB3-B

MIC + PT1000

MIC-FEE

SuperCam EQM Model

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What can we learn from LIBS acoustics?

The intensity of the acoustic signal acquired as thepeak-to-peak amplitude of acoustic waveformisproportional to the ablated masses (Chaléard et al.,1997; Grad and Mozina 1993)

The mass ablated is obtained from the acoustic signalamplitude.

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velocity of acoustic wave

front

distanceablated mass

peak-to-peak amplitude of acoustic waveform (pressure

gap)

5.2. Waveforms of JSC-1 targets281

The acoustic waveforms for laser impacts onto the compacted JSC1 targets are presented in282

Fig. 15. Although the shape of the waveform is similar to the waveforms produced by impacts283

onto the Aluminium target (see Fig. 6) the peak amplitude is 11.7 ⇥ 10�3 Pa lower for JSC1284

samples than for Aluminium target.285

Figure 15 shows that the peak acoustic amplitude increases with target compaction up to a286

level of compaction of 6 tonnes. For the higher levels, the amplitude remains constant. This287

behaviour follows the variation of the Vickers Hardness indicating that the Vickers Hardness is288

a critical parameter influencing the acoustic signal.289

0 0.2 0.4 0.6 0.8 1 1.2Time (ms)

-0.01

-0.005

0

0.005

0.01

0.015

Pres

sure

(Pa) 2 t

3 t4 t6 t8 t10 t15 t

Figure 15: Waveforms of JSC1 targets at di↵erent levels of compaction as measured by the microphone at 1.5 m fromthe targets. Each line represents the average signal over 10 shots around the 300th shot of the acquisition.

5.3. Analysis of the target craters290

The resulting JSC-1 impact craters were analyzed with a microscope (Olympus GX 71, mag-291

nification factor x100) and the pictures are represented in Fig. 16. The average dimension of292

the crater in the direction of the laser beam is 828 ± 23 µm. There is no significant change in293

resulting crater diameter with the target compaction (< 3 %). Unfortunately, the 45� laser impact294

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The sound peak amplitude increases with the hardnessof the material

Waveforms of JSC1 targets at different levels ofcompaction as measured by the microphone at 1.5 mfrom the targets.

The LIBS acoustic signal constraints the material hardness

(Murdoch et al, 2018, submitted)

Bandwidth of acoustic signals on Mars

n Frequency ranges of the different signals to be calibrated

Aeroacoustics (1 Hz to 500 Hz) for wind speeds < 20 m/s, object sizes > 1 cm

Vortices (10 Hz to 1 kHz) for vortex diameters 1 – 30 m

Dynamic pressure (all frequencies) but drops off rapidly with increasing frequency

Rover activities (1-10 kHz)

Saltation(5-10 kHz)

LIBS acoustics (0.5-5 kHz)

FREQUENCY (Hz)

104103102101100

MICROPHONE BANDWIDTH (100 Hz – 10 kHz)

Nelke and Vary, 2014

Microphone Radiation issues

n Microphone gain had decreased sharply after X-ray inspectionsn All other operations (Shocks, Serialization, retinning) have no impact on

performancen All flight/qualification microphones have been exposed to X-ray

n Need of another lot

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Blue curves (light and dark): no X-ray inspectionOther curves: X-ray inspection

Calibration: End to end

Objectives: n Verify the gains of the instrument in the windy

Martian environmentn Ensure microphone is not saturated by Aeolian

noise

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Test details:n Use of AWTSII 2010 Martian

wind tunnel foreseen (2m x 2m x 0.9m) in Denmark

n LIBS-like sound + MIC operation + Martian atmosphere over a sufficient distance, with wind.

n Target: Spring 2017Arhus wind tunnel, Denmark

Aarhus end-to-end validation tests

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To summarize

n There will be a microphone on Mars 2020 (FM delivered in february 2018, Supercam FM this fall)

n You can hear sounds on Mars (even if it’s tough)n You can do science with it !

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Arm

Wheels

MOXIE

Helicopter+ other engineering noise

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Thanks to : CNESISAE-SUPAEROIRAPLANLJPL