Microscope : A scientific Microsatellite development

Transcription

1 Microscope : A scientific Microsatellite development V. CIPOLLA, Y. ANDRE, P.Y. GUIDOTTI, A.ROBERT B. POUILLOUX, P. PRIEUR, L.PERRAUD Centre National d Etudes Spatiales 18 av. Edouard Belin Toulouse France 9 th August 2016

2 Microscope = Microsatellite à traînée compensée pour l observation du principe d équivalence 2 Micro-satellite dedicated to fundamental physic experience. The scientific objective of the mission consists in a test of the Equivalence Principle (EP) between gravitational mass and inertial mass with a relative accuracy of (i.e. a hundred time better than accuracy of experiences made on Earth) Mission main scientific objective To test in space the (Weak) Equivalence Principle a.k.a. universality of free fall Mass could be defined in two different ways : Inertial mass m i : proportional term between the force acting on a body and its acceleration F m i Gravitational mass m g : proportional term between the gravity forces acting on a body submitted to a gravitation field and the gravitation field itself F g m G g r M m G M 2 r Both masses are identical (i.e. different bodies have the same ratio) always experimentally verified m m 1g 1i m m 2g 2i 2 g g g m g g

3 Mission rationale and principle To perform a free-fall of two different masses in space Control of 2 masses of different composition Gravitational Source : the Earth Inertial Acceleration : Orbital Motion Several quantum gravity theories predict a violation of EP? Violation is found Defining the limit of the validity of the General Relativity theory Evidence of new particle and/or new interaction New physic validation : strings.. Violation isn t found (@ ) Help theoretical physicians to eliminate some theories of fundamental forces unification 3

4 Microscope project organization CNES : responsible for System, Ground Segment (except CMSM), Satellite & Launch interface CNES is Satellite responsible (No industrial Prime Contractor) : CNES is responsible for the Equipment procurement CNES is responsible for the Payload integration CNES is responsible for Bus and Satellite AIT (in CST facilities) ONERA is responsible for the T-SAGE instrument and for the CMSM (Scientific Mission Center) OCA (French Riviera Observatory) : Scientific Data Processing ESA : Micro Propulsion System (a part of Cold Gas Propulsion System) Funding and procuring MPS (based on GAIA one design) ESA contribution to the mission Germany (DLR funding) : PTB : Proof Masses delivery ZARM/Bremen University : Drop Tower for free fall tests (for instrument validation) Performances Group : CNES-ONERA-OCA-ZARM Steering committee ESA-CNES-DLR-ONERA-INSU-OCA-ZARM 4

5 Mission main characteristic Mission main characteristic Measurement principle Need to modulate the gravity field seen by the proof masses at the frequency ƒ EP Measurement performed on several orbits to reduce noise effects Need of specific calibration session to characterize and tune the payload Sun Synchronous Orbit Altitude = 700 km -30/+70 LTAN = 6 h or 18h Lifetime : 2 years + 1 year extension Myriade product line platform Main Satellite requirement Attitude control requirement Angular velocity stability < 10-9 rad/s Angular acceleration < rad/s 2 Thermal requirement Thermal stability of Sensor Unit < 2 mk at ƒ EP Thermal stability of Payloads front end units < 20 mk at ƒ EP Drag free requirement 5 S/C acceleration induced by non gravity forces shall be < m/s2 at ƒ EP

6 Microscope satellite description Microscope developed in the Frame of Myriade product line Myriade microsatellite Myriade development started in 1999 under lead of CNES Target :150 Kg, 200 W and 2 years class micro satellite Design based on a Platform with generic functional chain : Structure (customizable) Power : PCDU, Battery, harness AOCS : Sun Sensor, MAG, MTB, STR, RW On board data management : OBC Communication : S-band antennas, RxTx Propulsion (option) Generic multi-mission ground segment Generic development, validation and AIT tools Payload Myriade Back ground 17 satellites launched including Microscope 3 satellites in development Plateform 6

7 Payload description T-SAGE : Twin Space Acceleration for Gravity Experiment Designed, developed and integrated by ONERA DMPH Châtillon (Fr) Composed by 2 Sensor Units (SU) Each SU composed by 2 concentric electrostatic 6-axis inertial sensors SU 1 : different materials (Pt, Ti) SU 2 ; same materials (Pt) 2 Front End Electronics Units Capacitive detection DAC I/F Control Unit ICUME SUs control loops I/F with the S/C 7

8 CGPS main characteristic Microscope Specificity CGPS = Cold Gas Propulsion System Developed by CNES and ESA Composed by two identical submodules Propellant : 8.25 kg of N 2 each HP section MEOP : C LP section MEOP : 4 45 C Design based on from the shelf components and equipment Except for electronic module and some specific fluidic item (Plenum) Propulsion system requirement Response time < 250 ms (1 ) Thrust range : [1:300] µn Thrust resolution : 0.1 µn Thrust noise : < 3.22 µn in [0.001:10] Hz bandwidth 8

9 Satellite description Attitude and Acceleration Control System : Drag-free Control design 6 Control Loops (1 each 4 Hz 8 Control Loops (1 each 50 Hz 24 Control Loops (6 each 1027 Hz 9

10 Microscope Specific subsystem IDEAS passive deorbiting system Developed by CNES Introduced to respect French Space Operation Law (Best effort to re-entry before 25 years EoL) Composed by 3 module SEG : inflating subsystem (ALAT) Wing (x2) : braking subsystem (AD&S) Gossamer arm, Sails, HDRM BTCU : electronic I/F module (EREMS) Main characteristic No moving masses (mission constraint) 10 Propellant : 0.13 kg of N 2 HP section MEOP : C LP section MEOP : 0.45 bars Increase the mean drag surface : 2.09 m² à 5.44 m² Decrease of mean re-entry time : 70 years 27 years (at 707 km)

11 Microscope Specific subsystem GNSS Rx Myriade ground orbit determination tool (Doppler ranging) does not fit with Microscope mission requirement (Orbit position knowledge < 7 m at ƒ EP ) Microscope used a new Low cost software Galileo/GPS receiver developed by Syrlinks GPS mono-frequency (Galileo soon) Continuous mode + sleep mode Masse = 1 kg Power budget = 4 W nominal / 2,5 W sleep Volume = 180 x 140 x 40 mm 3 EEE Commercial Components less than class 3 11

12 Microscope satellite overview Myriade standard equipement and payload SAS (x3) BCU (Payload Module) PCDU RW OHS (x2) ICUME MTB (x3) RxTx (x2) µdpu Pyrsoft (x6) OBC Battery S-band antenna (x2) 12

13 Microscope satellite overview Microscope specific development IDEAS Tank (x6) L-band antenna (x2) PRM (x2) ECM (x2) Rx GNSS MT (x8) 13

14 Satellite development A phase : start in 2000 B Phase start in 2003 C/D Phase start in 2012 Launch date Oct-04 Satellite budget Mass : 120 Kg Power : 80 W Propulsion system : Field Emission Electric Propulsion (FEEP), same than LPF (under development) Launch date Oct-09 Satellite budget Mass : 190 Kg Power : 187 W Decision taken in 2009 to give up FEEP (under development) and to switch to Cold Gas propulsion (qualified) Launch date April-16 Satellite budget Mass : 317 Kg Power : 125 W Satellite integration started in May 2014 P/F AIT : May-14 Dec-14 P/L AIT : Sep-14 Jun-15 Propulsion AIT : July-15 14

15 Satellite qualification EMC; Electrical compatibility September 2015 Thermal Vacuum October 2015 MCI November 2015 Mechanical qualification December 2015 SA deployment December 2015 R/F autocompatibility December

16 Launch & First Operation Launched the 25th April 2016 on VS14 from Centre Spatial Guyanais Launched as auxiliary passenger of Sentinel 1B flight Additional Auxiliary passenger Flight Your Satellite! (3 CubeSat) In Orbit commissioning plan 16 1 st phase : from April to end of June 2016 To validate in flight all the equipment and subsystem To go trough all satellite mode To characterize the behavior of P/L for each kind of scientific session 2 nd phase : from end of August to end of October 2016 To validate the optimization introduced in payload control (following the analysis of 1 st phase results)

17 In Orbit commissioning In Orbit commissioning results Electrical subsystem huge margins SA gives more power than expected (+4%) Battery have a better capacity than expected (+10%) Power budget better than expected (-10%) Thermal subsystem Compliant to prediction Maximum difference w.r.t. prediction : 6 C 83% of thermistor are within 4 C w.r.t. prediction Heating power less than expected GNSS subsystem Better than expected PVT availability : 99.5% Position error (1 ) : [12; 8; 4] m (Radial, Normal, Tangential) Propulsion subsystem MT behavior have been validated for all thrust domain Gas consumption better than expected External perturbation less than expected (Low solar activity) Satellite performances better than expected (Magnetic perturbation, MCI, Thruster alignment) 17

18 In Orbit commissioning Attitude and Acceleration Control System results Non-mission modes No issue All the Myriade equipment have been validated Mission mode Compliant to prediction Star Tracker Stray light problem solved by SW modification (clipping) Harmonic Error less than expected T-SAGE Linear and Angular bias have bee characterized Response time and High Frequency noise conform to prediction 1 st Drag-Free performed the 9 th of June : Results are better than requirement : << ƒ EP Requirement STR noise T-SAGE noise 18

19 Conclusion Development phase lessons Microscope accuracy goals oblige to rethink our way to work To take into account neglected phenomena (MLI clanks, induced gravity gradients) Order of magnitude of several parameters overpass experimental characterization Satellite could not be end-to-end tested on ground mission is operated as a in orbit commissioning Microscope development frame Satellite developed in the frame of Myriade product line : Great advantage to belong to Myriade validation method and team running smoothly New development reduced to strictly necessary Need to fit to Sentinel-1B launch date (only launch oppurtunity identified) constrained our AIT In orbit commissioning phase lessons As expected, the operations were very intense due to the number and complexity of the s/s By the end of the commissioning, software upload will be performed on almost every computer except for central OBC : to improve performance and correct anomalies A break during commissioning was initially scheduled. It proved to be very useful, we extended it to give more time to data analysis before engaging scientific sessions Data analysis is extremely complex due to the number of control loops, degrees of freedom, and sensitivity of the accelerometers: necessity to have big and well prepared teams Challenging missions on Microsatellite are possible 19