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Contributions of Italian Spring Accelerometer to Lunar exploration: gravimetry and seismology V. Iafolla, E. Fiorenza, C. Lefevre, S. Nozzoli, R. Peron,

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Presentation on theme: "Contributions of Italian Spring Accelerometer to Lunar exploration: gravimetry and seismology V. Iafolla, E. Fiorenza, C. Lefevre, S. Nozzoli, R. Peron,"— Presentation transcript:

1 Contributions of Italian Spring Accelerometer to Lunar exploration: gravimetry and seismology V. Iafolla, E. Fiorenza, C. Lefevre, S. Nozzoli, R. Peron, M. Persichini, A. Reale, F. Santoli Istituto di Fisica dello Spazio Interplanetario (IFSI/INAF), Roma, Italy IX CONGRESSO NAZIONALE DI PLANETOLOGIA AMALFI IX CONGRESSO NAZIONALE DI PLANETOLOGIA AMALFI

2 Renewed interest for the Moon 29/09/2009 Gruppo di Gravitazione Sperimentale 2 Nearest body outside Earth Solar System history Outpost for Solar System settlement Quiet place Fundamental physics Photo Apollo 11

3 Recent and current missions 29/09/2009 Gruppo di Gravitazione Sperimentale 3 Clementine Lunar Prospector SMART-1KAGUYA - SELENE Lunar Reconnaissance Orbiter

4 Lunar Laser Ranging (LLR) 29/09/2009 Gruppo di Gravitazione Sperimentale 4 Three retroreflectors arrays were carried on The Moon by Apollo missions and two by Soviet missions Probably the most important scientific contribution from Apollo missions! Selenodesy Lunar rotation General relativity

5 Moon history 29/09/2009 Gruppo di Gravitazione Sperimentale 5 Constraints on formation, evolution and present state of the Moon come from: Surface composition Magnetic field Gravitational field Selenoseismology Picture NASA Picture ESA

6 Moon gravity field 29/09/2009 Gruppo di Gravitazione Sperimentale 6 Spherical harmonics expansion: Resolution 5458 / l km

7 Moon gravity field 29/09/2009 Gruppo di Gravitazione Sperimentale 7 Konopliv et al. (2001) Mascons

8 Moon gravity field 29/09/2009 Gruppo di Gravitazione Sperimentale 8 Compare with Earth! Degree variance:

9 Moon gravity field 29/09/2009 Gruppo di Gravitazione Sperimentale 9 There is space for improvement!

10 ISA: the accelerometer 29/09/2009 Gruppo di Gravitazione Sperimentale 10 ISA sensing element ISA pick-up

11 ISA: the accelerometer 29/09/2009 Gruppo di Gravitazione Sperimentale 11

12 ISA: the accelerometer 29/09/2009 Gruppo di Gravitazione Sperimentale 12 Geostar Gradiometer GReAT BepiColombo

13 ISA: the accelerometer 29/09/2009 Gruppo di Gravitazione Sperimentale 13 The use of an accelerometer in the lunar environment can be envisaged in at least three ways: Support given to a Radio Science mission (removal of non gravitational perturbations) Gradiometric measurements Selenoseismology Satellite On-ground

14 ISA: the accelerometer 29/09/2009 Gruppo di Gravitazione Sperimentale 14

15 ISA: the accelerometer 29/09/2009 Gruppo di Gravitazione Sperimentale 15

16 The mission MAGIA 29/09/2009 Gruppo di Gravitazione Sperimentale 16 MAGIAMissione Altimetrica Gravimetrica Geochimica lunAre MAGIA (Missione Altimetrica Gravimetrica Geochimica lunAre) is a Moon exploration mission, with Phase A funded by Agenzia Spaziale Italiana Scientific objectives internal structure gravityfigure Detailed study of the internal structure of the Moon through its gravity and figure polar and subpolar regions morphologymineralogy Study of the polar and subpolar regions in terms of their morphology and mineralogy lunar exosphere and radioactive environment Study of the lunar exosphere and radioactive environment gravitational redshift Improved measure of the gravitational redshift measurements from a circumlunar platform position of the seleno-center Determination of the position of the seleno-center ISA contribution

17 The mission MAGIA 29/09/2009 Gruppo di Gravitazione Sperimentale 17 The knowledge of the gravitational field of a celestial body is one of the few ways to constrain its interior structure and composition An analysis of recent lunar gravity field models (from Clementine and Lunar Prospector) shows that their knowledge at high orders can be improved. This implies greater resolution, useful for accurate knowledge of mantle and crust structure and composition The proposed strategy for MAGIA implies use of a GRACE-like configuration with two satellites (the main spacecraft and a subsatellite) optimized for the sougth for spectral range (l 80) rather low orbit Notice that this high resolution implies a rather low orbit for the satellites, thereby enhancing the strength of non-gravitational perturbations like albedo and infrared radiation pressure (and related thermal effects)

18 The mission MAGIA 29/09/2009 Gruppo di Gravitazione Sperimentale 18

19 Seismic measurements 29/09/2009 Gruppo di Gravitazione Sperimentale 19 Solid tide of Earth Teleseismic (free oscillation of Earth) Seismic Noise

20 ISA-S: the seismometer 29/09/2009 Gruppo di Gravitazione Sperimentale 20 acts as a seismometer without any changes The accelerometer, placed on ground, is directly sensitive to seismic disturbances, and therefore acts as a seismometer without any changes The three sensing elements are arranged with their centers of mass along the same axis (the local vertical) tiltmeters gravimeter local vertical

21 ISA-S: the seismometer 29/09/2009 Gruppo di Gravitazione Sperimentale 21 ParameterValueRemarks Measurement Accuracy10 -9 m/s 2 Accuracy required for the acceleration measurements ISA-S intrinsic random noiseS 0 (f) = m/s 2 /Hz 1/2 Level of the total random noise in the ISA measurements process Frequency Range10 -5 – 1 Hz The max resolution is obtained inside the frequency band, but ISA-S can works quite well also at frequency out of the indicated band, increasing the bit rate and taking into account the mechanical transfer function Dynamic range10 6 Set by the acquisition system and converter Frequency readout interval1 s The required data rate is 1 sample/s for the three acceleration components and the three sensing temperatures Resonance frequency3.5 HzFrequency of the mechanical oscillator Quality factor Q10Quality factor of the oscillator Thermal stability x,y m/s 2 /°CISA-S thermal stability for the two tiltmetric components Thermal stability z m/s 2 /°CISA-S thermal stability for the gravimetric component Mass, total5.5 kgISA-S Total mass Dimension300 x 300 x 300 mm Electronic power dissipation6 WISA-S Total power dissipation Data rate (nominal)15 kbit/s Capability of ISA-S/ Capability to recover the local vertical autonomously, in order to operate with two of its elements like tiltmeters and one like gravimeter

22 Requirements 29/09/2009 Gruppo di Gravitazione Sperimentale 22 Science Goal Understand the current seismic state of the Moon, and determine the internal structure of the Moon. 2) Detection of new aggregate states of matter (e.g., strange quark nuggets) Network Requirement Multiple, simultaneously operating sites about the Moon are required to interpret seismic events 2) Multiple, simultaneously operating sites about the Moon are required to interpret seismic events. Science Rationale Seismic waves from lunar tectonic events can be used to determine the structure and composition of the crust, mantle and core. 2) The existence of strange quark nuggets is an important prediction which could also provide a candidate for Dark Matter. Measurement Requirements Measure lunar seismicity using broad-band seismometry at multiple, geographically dispersed, locations. 2) Measure lunar seismic events using broad-band seismometry at no fewer than 5 geographically dispersed locations. SeismometryNew fundamental physics ILN Core Instrument Working group

23 Requirements 29/09/2009 Gruppo di Gravitazione Sperimentale 23 Mission Requirements At least 4 sites simultaneously operating for 6 years. Inter-station timing accuracy: 5ms. Instrument attached to ground and vibrationally isolated from the spacecraft. 2) Detection of strange quark nuggets via epilinear seismic source identification requires at least 5 sites simultaneously operating for as many years as possible. Instrument Requirements Three axis Very Broad Band (VBB) seismometers with: Dynamic Range >24 bits; High Frequency Cutoff about 20 Hz. Sensitivity [ Hz] 10-11m/s [0.1-1 Hz] 2x 10-11m/s [1-20Hz] 10-9m/s. Thermal stability +/_ 5deg with need to thermal blanket ground within 1m if surface deployed. Altitude knowledge. Same. Mass, Power, Thermal Mass 6 kg: Power 2 W(peak), and 1 W(cont.), and 0.2 W (low power). May need additional power for instrument heating. Same.Data 100 Mbits per Earth day; no down link drivers. Same. ILN Core Instrument Working group SeismometryNew fundamental physics

24 Site selection 29/09/2009 Gruppo di Gravitazione Sperimentale 24 Barbara Cohen (SDT Co-chair), The International Lunar Network (ILN) and the US Anchor Nodes mission, Update to the LEAG/ILWEG/SRR, 10/30/08 Strong science desire for farside placement. Due to dependency upon communications satellite, SDT also identified suitable nearside sites. Node 1 must be placed antipodal to a moonquake epicenter known by the Apollo network: -5°S, 75°W is only nearside site Node 2 must be placed within ~30° of the same epicenter, so could also be nearside 2: 30°N, 75°E Nodes 3 and 4 should form a triangle with western node, preferably on the farside Site selection criteria will also involve desires from engineering for DV and comm

25 Thermal issues 29/09/2009 Gruppo di Gravitazione Sperimentale 25 More than 200 °C range during lunar day 10 4 m/s 2 for the most sensitive (gravimetric) component Need for an adequate thermal control system!

26 Thermal issues 29/09/2009 Gruppo di Gravitazione Sperimentale 26 Passive Seismic Experiment Passive Seismic Experiment on Apollo 16 T. A. Sullivan, Catalog of Apollo Experiment Operations, NASA Reference Publication 1317 ISA thermal control system performance

27 Proposals 29/09/2009 Gruppo di Gravitazione Sperimentale 27 Response to REQUEST FOR INFORMATION (RFI) Instruments for U.S. ILN Lunar Missions 19 December 2008 Response to REQUEST FOR INFORMATION (RFI) Instruments for U.S. ILN Lunar Missions 19 December 2008 Response to ESA First Lunar Lander: Request for Information 8 April 2009 Response to ESA First Lunar Lander: Request for Information 8 April 2009

28 Conclusions 29/09/2009 Gruppo di Gravitazione Sperimentale 28 We are seeing a renewal of interest and studies on lunar environment Gravitational physics will play an important role Fundamental physics is always here! ISA accelerometer can support lunar science in many ways


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