Contributions of Italian Spring Accelerometer to Lunar exploration: gravimetry and seismology

1. IX Congresso Nazionale di Planetologia Amalfi Contributions of Italian Spring Accelerometer to Lunarexploration: 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

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

3. Recent and current missions Clementine Lunar Reconnaissance Orbiter KAGUYA - SELENE Lunar Prospector SMART-1 Gruppo di Gravitazione Sperimentale

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

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

6. Moon gravity field Spherical harmonics expansion: Resolution  5458 / l km Gruppo di Gravitazione Sperimentale

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

8. Moon gravity field Degree variance: Compare with Earth! Gruppo di Gravitazione Sperimentale

9. Moon gravity field There is space for improvement! Gruppo di Gravitazione Sperimentale

10. ISA: the accelerometer ISA sensing element ISA pick-up Gruppo di Gravitazione Sperimentale

11. ISA: the accelerometer Gruppo di Gravitazione Sperimentale

12. ISA: the accelerometer GReAT Gradiometer BepiColombo Geostar Gruppo di Gravitazione Sperimentale

13. ISA: the accelerometer Satellite 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 On-ground Gruppo di Gravitazione Sperimentale

14. ISA: the accelerometer Gruppo di Gravitazione Sperimentale

15. ISA: the accelerometer Gruppo di Gravitazione Sperimentale

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

17. The mission MAGIA 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) 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) Gruppo di Gravitazione Sperimentale

18. The mission MAGIA Gruppo di Gravitazione Sperimentale

19. Seismic measurements Teleseismic (free oscillation of Earth) Seismic Noise Solid tide of Earth Gruppo di Gravitazione Sperimentale

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

21. ISA-S: the seismometer Gruppo di Gravitazione Sperimentale

22. Requirements ILN Core Instrument Working group 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. Seismometry New fundamental physics Gruppo di Gravitazione Sperimentale

23. Requirements ILN Core Instrument Working group 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 [0.001-0.1 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. Seismometry New fundamental physics Gruppo di Gravitazione Sperimentale

24. Site selection • 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 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 Gruppo di Gravitazione Sperimentale

25. Thermal issues More than 200 °C range during lunar day  104 m/s2 for the most sensitive (gravimetric) component Need for an adequate thermal control system! http://www.asi.org/adb/02/05/01/surface-temp-chart.html Gruppo di Gravitazione Sperimentale

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

27. Proposals 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 Gruppo di Gravitazione Sperimentale

28. Conclusions • 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 Gruppo di Gravitazione Sperimentale