“How to build a 10 kg autonomous Asteroid landing

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
Jan Thimo
TraMi Ho
Tim van
Institute of Space
Systems, German
Aerospace Center
(DLR), Bremen
www.DLR.de • Slide 2
• Part #1: MASCOT Project & System
• Part #2: Systems Engineering Challenges
• Schedule
• Interfaces & Requirements
• System Design – Science vs. Mass
• Operational  MASCOT Autonomy Manager
• Conclusion
MASCOT  Mobile Asteroid Surface Scout
www.DLR.de • Slide 3
• 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
Asteroid 1999JU3 (in the
yellow circle in the center of
the image), imaged by the
infrared astronomical satellite
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
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
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)
TRL = 6
Heritage from CIVA/MI
Infrared hyperspectral
ExoMars, Phobos GRUNT,
Rosetta / Philae
IAS Paris
TRL = 9
Heritage from ROMAP on
Rosetta Lander (Philae), ESA
VEX, Themis
Technical University
TRL = 8 (5)
Heritage from MUPUS-TM on
Rosetta Lander (Philae);
MERTIS-RAD on BepiColombo
DLR PF (Berlin)
TRL = 8
Heritage from ExoMars
PanCam heads, RosettaROLIS head, ISS-RokViss
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
• 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
• 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
During sampling dress
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)
• 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
• Voting mechanism & logic-based function
Level 2
• Flexible, knowledge-based fault
• 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
• 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
• The ‚iron triangle„…
• Launch of HY-2 end 2014,
 pragmatic definition of
mission success
• MASCOT delivered to JAXA in
February 2014
• Higher Systems to Subsystem
Engineer ratio introduced
Significantly limited
by programmatic
Will increase if
performance is
Fixed due to HY-2
launch date &
attributed hardware
delivery dates
• Outlook: lessons learned &
knowledge management
 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!