www.DLR.de • Slide 1 “How to build a 10 kg autonomous Asteroid landing package with 3 kg of instruments in 6 years?” - Systems Engineering challenges of a high-density deep space system in the DLR MASCOT project SECESA 2012 17-19 October 2012 Alameda Campus of IST / Technical University of Lisbon, Lisbon, Portugal Caroline Lange Andy Braukhane Ross Findlay Christian Grimm Jan Thimo Grundmann TraMi Ho Lars Witte Tim van Zoest Institute of Space Systems, German Aerospace Center (DLR), Bremen www.DLR.de • Slide 2 Overview • Part #1: MASCOT Project & System • Part #2: Systems Engineering Challenges • Schedule • Interfaces & Requirements • System Design – Science vs. Mass • AIV/AIT • Operational MASCOT Autonomy Manager • Conclusion MASCOT Mobile Asteroid Surface Scout www.DLR.de • Slide 3 Hayabusa-2 • JAXA„s mission to… …A near Earth Object (NEO) called 1999 JU3 • HY-2 is the successor of HY-1, • Launch Dec 2014 • Arrival 2018, stays until 2019 • Uses • Observations • Sample return • Penetrators • Landing modules: Minerva, MASCOT • HY-2 is current design case for MASCOT & MESS HY-2 artists impression (from JAXA) www.DLR.de • Slide 4 MASCOT Major Scientific Goals 1. „Context science‟ by • complementing remote sensing observations • sample analyses ground truth info 2. „Stand-alone science‟ geophysics 3. „Reconnaissance & scouting‟ vehicle • guide HY-2 spacecraft for sampling site selection Global and local sample context and microscopic views of an asteroid sample collected by Japan's Hayabusa probe. Credit: PNAS Highest-resolution image of Itzokawa‘s surface acquired by Hayabusa -1(top) showing grains as small as 6mm. The location of the close-up is indicated on a global image of Itokawa (bottom). Asteroid 1999JU3 (in the yellow circle in the center of the image), imaged by the infrared astronomical satellite AKARI Asteroid 1999JU3: constraints on thermal inertia derived through TPM modeling based on Spitzer observations. (Müller et al., 2011) www.DLR.de • Slide 5 MASCOT System – 1/3 (Reqs) The maximum landing package…: HY-2 –Y Panel with MASCOT integrated • …wet mass shall not exceed 10 kg (incl. HY-2 remaining parts) • …stowed volume shall not exceed a cube volume of 0.3x0.3x0.2m³ The landing package shall… • …be delivered during the main-S/C sampling dress rehearsal maneuver • …operate during two complete asteroid rotations • …perform nominal operations when ground intervention is not possible • should be able to change the surface site MASCOT system (MLI & external foils excluded) Reqs = Requirements; S/C = spacecraft www.DLR.de • Slide 6 MASCOT System – 2/3 (S/S) • Configuration/Structure: • highly integrated carbon-fibre composite structure with: • separate cold P/L- & • warm bus compartment including common E-box for all P/L electronics • Power: Primary battery; redundant supply from H-2 during cruise • Communication: • based on Minerva transceiver, • on MASCOT: omnidirectional, redundant link; one antenna/side • OBC: Redundant, Mascot Autonomy Manager (MAM) • Mechanisms: ”up-righting” & “hopping” motor/drive/excenter • GNC (attitude): proximity sensors (baseline: optical sensors + photocells) • Thermal: ”semi-active”: • Cruise: active (heater power & control from HY-2) • On surface: passive (MLI and coatings) • MESS: physical interface to HY-2 REMAINS @HY-2 S/S = Subsystems; P/L = Payload; OBC = on-board computer; MLI = Multi layer insulation; MESS = Mechanical/Electrical Support Structure www.DLR.de • Slide 7 MASCOT System – 3/3 (P/L) MicrOmega TRL = 6 Heritage from CIVA/MI Infrared hyperspectral microscope ExoMars, Phobos GRUNT, Rosetta / Philae IAS Paris Magnetometer TRL = 9 Heritage from ROMAP on Rosetta Lander (Philae), ESA VEX, Themis Technical University Braunschweig, Radiometer TRL = 8 (5) Heritage from MUPUS-TM on Rosetta Lander (Philae); MERTIS-RAD on BepiColombo DLR PF (Berlin) Camera TRL = 8 Heritage from ExoMars PanCam heads, RosettaROLIS head, ISS-RokViss head DLR PF (Berlin) www.DLR.de • Slide 8 Part # 2:….Schedule Challenges • ~ 6 years of development time – sounds feasible, but…: • extremely prolonged MASCOT Phase A • skipped HY-2 Phase A • shift between MASCOT and HY-2 development schedule • MASCOT was still in Phase A when HY-2 entered Phase B • Same for Phase B (MASCOT) vs. Phase C (HY-2) MASCOT to shorten Phases B & C/D to meet delivery date www.DLR.de • Slide 9 Interfaces: To Hayabusa-2 • To be fixed before reaching appropriate level of system decomposition constrained system design • Examples (during cruise): • Thermal I/F (heater power) • Communication I/F (only RF comms) • Power I/F (restricted power for checkouts) • Mass / Volume constraints Special topic: cultural differences e.g. mass budgeting I/F = Interface; RF = Radio-frequency www.DLR.de • Slide 10 Interfaces: To Instruments 4 Instruments • from 3 Institutes & 2 Countries… • Shall have a high TRL heritage of the P/L to be respected (also: reduced qualification burden) • But need to cope with constraints for overall system (i.e.: volume & mass + I/F with main-S/C) pragmatic approach & intense “two-way communication” between SE & instruments responsible Introduction of a P/L manager (with SE background & tasks) Mutual exchange of requirements and constraints TRL = Technology Readiness Level; I/F = Interface; S/C = spacecraft; P/L = payload; SE = Systems Engineer(ing) www.DLR.de • Slide 11 System Design (Big Science within a Nanosat Mass Budget) • Compromise of standardization & COTS parts/heritage simplification and low mass/volume • E.g. common E-Box with standard electrical & mechanical I/F centralization of thermal control & radiation shielding • Capability driven design approach allows to cope with time and design constraints: • Mixed approach of COTS and dedicated developments what is available & fits to the constraints? after that: matching system capabilities • High importance of accommodation (tight envelope) critical development aspect of such a condensed lander mainly performed on system-level COTS = Commercial of-the-shelf; I/F = Interface; SE = Systems Engineer(ing) www.DLR.de • Slide 12 AIV/AIT challenges • Mix of conventional & tailored model philosophy general system level approach of EM STM QM FM (+ PFC + Drop Tests) • Due to time & programmatic issues: partial break-up of this scheme on subsystem-level, • i.e. subsystem-STM‟s in system QM, • several tests in parallel risk: some QM parts to be procured before STM tests completed High priority to a “test as you fly” approach • Harsh environment requires a full set of qualification tests (thermal, mechanical, radiation on demand, EMC) in a very short timeframe EM = Engineering Model; STM = Structure/Thermal Model; QM = Qualification Model; EMC = Electromagnetic compatibility www.DLR.de • Slide 13 Operational Challenges – MAM – 1/3 During cruise: 4 years of cruise stowed inside HY-2 mostly in hibernation Regular checkouts Separation: During sampling dress rehearsal On the surface: Scientific measurements, up-righting & hopping during 2 days of operation Surface operating conditions hardly predictable & G/S intervention is limited, MASCOT to perform tasks highly autonomously to react & adjust operations sequence. MAM = MASCOT Autonomy Manager; SDL = Separation, Descent & Landing: G/S = Ground Segment www.DLR.de • Slide 14 Operational Challenges – MAM – 2/3 The MAM shall: • be robust with respect to environmental uncertainties (i.e. surface properties for mobility or landing site) MASCOT • regard instrument- & S/Sbehavior after years of cruise (incl. certain FDIR aspects) • be testable in given verification timeframe & project budget Degree of Autonomy Level 0 • Automatic system, i.e. monitoring of parameters and autonomous • Mode switching in failure cases Level 1 • Low level intelligent functions identify errors • Voting mechanism & logic-based function Level 2 … • Flexible, knowledge-based fault diagnosis • Knowledge-based reactive on-board planning & operations optimization Level n From: Eickhoff, J.; Simulating Spacecraft Systems, Springer-Verlag Berlin Heidelberg, 2009 Nominal state machine with state & transition logic running as application on OBC MAM = MASCOT Autonomy Manager; S/S = Subsystem; FDIR = Failure Detection, Isolation & Recovery; OBC = on-board computer www.DLR.de • Slide 15 Operational Challenges – MAM – 3/3 Core decision nodes are: • Decide, if attitude correction is necessary after • touchdown, or • hopping manoeuvre • P/L activation according their pre-defined (nominal) sequence. • Decide, if MASCOT is ready to relocate itself ( hopping) to a different site • Adjust course of action depending on system resources & states (e.g. energy monitoring & -management) Validation approach: • Functional End-to-End Simulation • Hardware-in-the-loop Testing MAM = MASCOT Autonomy Manager; P/L = Payload www.DLR.de • Slide 16 Conclusion • The ‚iron triangle„… • Launch of HY-2 end 2014, Compromise pragmatic definition of mission success • MASCOT delivered to JAXA in February 2014 • Higher Systems to Subsystem Engineer ratio introduced Significantly limited by programmatic constraints Will increase if performance is sacrificed Fixed due to HY-2 launch date & attributed hardware delivery dates • Outlook: lessons learned & knowledge management techniques paper at next SECESA(s) for outcomes www.DLR.de • Slide 17 DLR artist's impression of the Hayabusa-II mission with MASCOT deployed and landed on the asteroids surface (external panels of MASCOT not shown). Thank you!
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