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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!