PRELIMINARY DESIGN OF A CUBESAT FOR PLUME SAMPLING AND IMAGING AT EUROPA

Transcription

1 PRELIMINARY DESIGN OF A CUBESAT FOR PLUME SAMPLING AND IMAGING AT EUROPA David GAUDIN (1), N. André (1), M. Blanc (1), D. Mimoun (2) (1) IRAP/CNRS-UPS, Toulouse, France (2) ISAE-SUPAERO, Toulouse, France

2 1. JOINT EUROPA MISSION (ESA Cosmic Vision M5, 2016) 12U Multi-Mission Platform designed by Students from Supaero Designed for missions on earth environment : Altitude 100km HESTIA (ONERA + SUPAERO) : Urban heat observation SPIRou (IRAP + SUPAERO) : Exoplanets detection Understand ATISE (CSUG Europa Grenoble) as : Polar a complex aurora observation system responding to Jupiter system forcing, characterize the habitability of its potential biosphere, and search for life. Different configurations considered : <15km EPIC: Europa Plume Investigation by Cubesat 2

3 2. EPIC SCIENCE TRACEABILITY MATRIX JEM Carrier/Orbiter Study the Europa System at a global scale Interior, Subsurface, Surface, Exosphere, Magnetosphere Habitability - Magnetometer, Radio Science - Laser Altimeter - ELS/IMS, INMS, Dust analyzers - Navigation Camera, Radiation Monitor Science objectives EPIC Direct sampling of Europa Plumes Study the moon-magnetosphere interactions, locally Enabling instrumentation Imaging plume sources on the surface of Europa - Option: EPICom Magnetometer + Electrostatic Analyzer - Option: EPICam Magnetometer + INMS + Camera Constraints on platforms Environment & Mission Constraints 1. Propulsion 2. Power 3. Radiation - 3D Coverage of Europa - Low altitude km, near polar circular orbit - Spatial resolution of 10 s km horizontally - AOCS for orbit and attitude control - Low periapsis <15km, elliptical orbit - Use JEM as relay - Survivability during eclipses 4. Thermal 3

4 3. EPICom SCIENCE TRACEABILITY MATRIX Goal Objectives Investigation Study the charged particles environment of plumes around Europa Detect plumes activities at the surface of Europa Determine the composition of charged particles within the plumes Detail the interaction between Europa plumes and Jupiter magnetic and gravity fields Caracterise the charged particle environment of Europa from a multipoint perspective. Measurement requirements Instrumentation focused Instrument Mission Design requirements Automatic release of the cubesat if the Determine the location of plume plumes are very short time events. and their sources, and select the Mapping the surface of Europa and Selection of the Targeted plume on on Wide angle camera (on Orbiter) best charged plume to target (Geophysics, particle searching for composition plumes. for habitability earth and potential controlled release of! the surface/subsurface) Determine the Mass And Energy of charged particles (Habitability) Determine how the charged particles within Europa plumes interact with Jupiter's magnetic field (Environment/Magnetosphere) Caracterise the charged particles Environment from a multipoint perspective (Environment/Plasma) Caracterise the magnetosphere from a multipoint perspective (Environment/Magnetosphere) Crossing of the selected plume. Measurements of particle masses from 1u to 60u. Measurements of particle energies from 10eV to 10KeV. Measurement of charged particles distribution in the Europa environment. Identification of ion cyclotron waves. Measurement of magnetic field vector and magnitude up to 8000nT with a resolution of at least 0.5 nt. Measurement of charged particles during several orbits. Measurements of particle masses from 1u to 60u. Measurements of particle energies from 10eV to 10KeV. Miniaturized Electrostatic analyzer (on CubeSat) Miniaturized Magnetometer, Miniaturized Electrostatic Analyzer (on CubeSat) Miniaturized Electrostatic Analyzer (on CubeSat and Orbiter) Measurement of magnetic field Miniaturized Magnetometer (on during several orbits. Measurement CubeSat and Orbiter) of 800nT and variations of tens nt. cubesat otherwise. Responsiveness to Plume detection. Orbit with low periapsis (0-15Km) for at least one crossing of the targeted plume. Sampling at the same altitude around Europa to discriminate particles from the plumes and those from others origins. Measurements of the magnetic field and charged particles during most of an orbit when a plume is crossed and during a complete orbit of Europa around Jupiter. Measurements of charged particles at an altitude different from JEM Measurements of magnetic field at an altitude different from JEM 4

5 4. STRAWMAN PAYLOAD TAILORED FOR EPIC EPICom EPICam 5

6 5. EPIC MISSION SCENARIO Mission profile : JEM tracking and determination of interesting plumes via a wide angle camera (max 3,5 days) Ejection of the CubeSat the nearest possible of an identified plume (max 1,8 days) Maneuver to reach the plume at the periapsides of the orbits (15Km, and lower) Transmission of the data to JEM thanks to a S-Band transmitter Max 4,4 Mission operations Mission duration: 3,5 days (1 complete coverage of Europa s orbit around Jupiter) with a possible extension of a maximum of 10 Days after deployment - Thrust Mode - Guidance Mode - Com Mode - CAM+INMS+MAG - INMS+MAG - JEM Orbit 6

7 6. EPIC PROPULSION NEEDS Maneuvers for EPIC: Plan change maneuver in order to go through a selected plume Orbit form change maneuver to a low periapsides elliptical synchronous orbit with JEM Cost in Delta-V : up to 75m/s in worst case Orbit maintenance : Jupiter powerful gravitational field disturbs orbits near Europa. A Delta-V of 0,55 m/s per Day is required for corrections. Total Needs : 3,5 Days -> 79m/s 10 Days -> 82m/s Electric propulsion Tile High ISP : 1500s - High Delta-V capacity : 243m/s (for 20Kg) - Dry Mass : 1,4Kg - Size : 1U 10*10*12,5 - Low Thrust : 1,5mN - Power cons. : 25W Chemical propulsion MPS High Thrust : 1,25N - High Delta-V capacity : 49m/s (for 24Kg) - Mass : 1,66Kg - Size : 1U 10*10*11,35 - Temperature : 5-50 C - Low IPS : 235s 7

8 7. TRADE-OFF POWER SOURCE Thrust Mode (11,5-23,2W) Guidance Mode (8,9) Com Mode (6,9W) CAM + INMS + MAG (15,6W) INMS+MAG (7,4W) Kg Primary Batteries Solar Panels Around 6 Days W Solar 20W Battery 15W Solar 15W Battery 10W Solar 10W Battery Days Solar Panel + Secondary Batteries Primary Batteries 3,5 Day nominal mission Power 10 Day extended mission Capacity ehawk Solar Array (MMA Design) 4,4W/kg Gomspace BP4 (GomSpace) 38,50 W.h Efficiency charge/discharge 0,9 Batteries LTC SL-760 (Tadiran) Specific energy Max continous discharge curent Weight Around 500 Wh/Kg 100 ma 18g Primary Batteries possible On Solar panels + Secondary Batteries 8

9 8. RADIATION ISSUES Context : Dose for EPIC Duration Dose behind 2,5mm Al (Krad) min max min max Interplanetery trip 4,9 Y 0 0 JOI + PRM 6,5 M 0 0 With JEM Jovian Tour 9,5 M EIO + Ejection to relay orbit 0 0 Lander Relay 34 D 41 D Relay to LEO 1 D 3 D Tracking of plumes 1,8 D 3,6 D 18,3 36,6 Subtotal with JEM 513,3 629,6 Manœuvre 0 D < 1,8 D 0 18,3 Released LEOperation Days 3,5 D 10 D Subtotal Released ,3 Total EPIC (Krad)

10 9. RADIATION MITIGATION Expected Radiation dose (behind 2,5mm of Al) is 750 Krad for 10 day mission Radiation inside CubeSat and Vault Admissible Radiation Dose 160 Vault CubeSat < 150Krad in the CubeSat < 50Krad in the Vault Three layers of shielding The deployer protects the cubesat until an interresting plume is detected (10 mm) The external structure of the cubesat (3mm) Vaults protect more sensitive component of the cubesat (6mm) Launch of JEM Deployment of the CubeSat 46.9 CubeSat opération 10

11 10. REQUIRED PLATFORM Europa Environment Constraints 1. Propulsion 2. Power 12U CubeSat Mass : 24Kg Max Size : 218*238*365mm3 3. Radiation 4. Thermal 11

12 14. EPICom / EPICam PRELIMINARY DESIGN Thrusters 3,5 Day Nominal Mission with Primary Batteries 3,5 Day Nominal Mission with Primary Batteries Aluminium Vault Star Tracker Bloc SCAO MAG Avionic 10 Day Extended Mission with Solar Panels 10 Day Extended Mission with Solar Panels MAG CAM INMS PASTELS 12

13 12. MASS BUDGET EPICom 22,173 Kg Total Mass CubeSat Margin Mass (Kg) 1,827 Margin Mass Ratio 8,23% Total Mass CubeSat + Deployer > 32 Kg Strong constraints for JEM but: Provides unique Science Returns Gives opportunity to sample a plume freshly ejected Relaxes risks for JEM EPICom 3,5 Day Nominal Mission With Primary Batteries Margin Structure 30% Propulsion system 30% Sub-system CubeSat MONA 12U Supaéro Mass (g) 2445 Internal Shielding x MPS 130 Aerojet RocketDyne (1U) AOCS Block XACT 910 SCAO Micropopulsion Vacco 1245 Sun Sensor 30% 5 x Sun Sensor FSS 15 Support Supports 150 Power Supply card Gomspace P S-Band 425 AV Command Data Handling System 30% Ninano (Steel electronics) 85 Interface 100 Supports and rodes 415 Battery pack 30% 150 x LTC SL760 AA 2700,0 RF S-Band 30% 2 x Syrlinks EWC Charged Particles PASTELS 2860 Spectrometer Payload 30% Magnetometer MAG Boom BOOM MAG 13120

14 To Be Continued SCAO : EPICam -> XACT + Micropropulsion + Star Trackers EPICom -> XACT + Micropropulsion Avionics Mission Profile In search of information Solar Panels : Multi-deployable Radiation Mitigation Mass optimized structure Thermal Regulation : Need of a hot Box? Need of MLI, surface coating? Deployer for 12U CubeSat 14

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16 I-] Block Diagram Aluminium Vault Propulsion 12V 8V INMS CAM MAGIC 3,3V 5V 3,3V 3,3V 5V 12V 16

17 II-] EPICom PHASE POWER NEEDS Mode Safe Mode Guidance Desaturation Mission mode Com Pre-thrust Mode Thrusters Bloc AOCS Idle 1 1 0,3 0,5 0 1 Micropropulsion Sun Sensor Ninano S band Thrust Mode Payload 0 Idle Idle PASTEL + MAG Idle Idle Idle Total Power Needs with system margin 6,1 8,9 21,7 12,0 6,9 23,2 11,5 System Margin 30,00% 17

18 III-] SOLAR PANEL STUDY Solar flow at Jupiter (W/m²) 51,5 Size of a solar cell (cm²) 40,15mm x 80,15mm Weight of a cell (g) 3,56 Efficiency of Solar Panel 0,3 Coefficient deterioration due to radiation 0,9 Surface area required (m²) 1,198 Nomber of cells 398 Mass of Solar Cells (Kg) 1,42 Question : AOCS powerfull enough? 18

19 IV-] AOCS EPICom EPICam 19