MIT Space Systems Laboratory
SPHERES 0-G Autonomous
Rendezvous and Docking Testbed
Presented To
DARPA
Orbital Express
December 2000
David W. Miller
(617) 253-3288
MIT, Cambridge MA
millerd@mit.edu
SPHERES (AFRL-0012) CONCEPT
OBJECTIVE
— Provide a testbed for long duration, micro-
gravity, low risk development of metrology,
autonomy and control technologies in support
of autonomous rendezvous and docking for
DoD and NASA missions.
DESCRIPTION
— Three 0.25 meter diameter, 3.0 kilogram, self-
contained satellites with on-board propulsion,
processing, RF communication and metrology.
— Communicates with Shuttle/ISS ThinkPads
(laptops) for Ku-band (up)downlink access.
— Patterned after MIT MODE (STS-40, 48, 62)
and MACE (STS-67, ISS) controls
laboratories.
— Successfully completed prototype testing on
Air Force, NASA, and MIT funded KC-135
flights in Feb and Mar 2000.
— Manifested on ISS-9a in May 2002
Using ISS to Mature Mission Technologies
SPHERES on ISS is designed to mature algorithmic technologies (metrology,
autonomy and control) for multi-vehicle autonomous rendezvous & docking.
SPHERES has access to long duration m-G that allows 6 DOF per vehicle testing
under large relative motions between vehicles in close proximity.
SPHERES is a unique facility that allows algorithms at low TRL to be matured in
a representative space environment
— Tolerant to risk associated with low TRL since crew can replenish consumables, terminate tests
exhibiting anomalous behavior, etc.
— Fosters technology maturation due to crew observations, video coverage, and uplink of
algorithms and downlink of data within days
R&D has gone to great lengths to simulate the space environment in the
research laboratory. Now, ISS simulates the research laboratory in space.
SPHERES provides a low cost facility in space for developing
& downselecting between algorithms for OE
Current Testing Using SPHERES
Single SPHERE maneuver control Multi-SPHERE rendezvous and
on the KC-135 in February 2000 docking in the SSL 1-G laboratory
Multi-SPHERE formation flight Future upgrades
coordination on the KC-135 — Emulate docking with a target
vehicle in free drift
— Emulate a thruster failure in
resupply vehicle
— Once docked, autonomously
identify new inertia properties and
reconfigure control
— Replace velcro with more
advanced docking capability
Current Testing Using SPHERES
Single and Multiple SPHERES units maneuvers in the KC-135,
February and March 2000
— Testbed Validation
— Initial Formation Flight
Current Testing Using SPHERES
One-g SSL Laboratory Experiment
— Development of 3DOF rendezvous and docking using global coordinates
Relevance to DARPA’s Orbital Express (I)
Orbital Express must demonstrate Orbital Express requires routine
three key features autonomous rendezvous & docking
— (1) fuel transfer, (2) avionics upgrade & — Without human supervision
(3) routine auto. rendezvous & docking — With ability to adapt to low level
— These are essential to replenishment, anomalies
inspection, and repair of existing assets to — That can accommodate cooperative, non-
lengthen life, recover from partial cooperative, and eventually un-
failures, upgrade technologies, and cooperative target vehicles
identify causes
Routine autonomous rendezvous
Fuel transfer demonstrated in & docking is the most immature
Shuttle’s payload bay
Avionics upgrade performed by
astronauts on the Hubble Space
Telescope: human-in-the-loop
Rendezvous and docking
demonstrated in limited forms
— Manual human-in-the-loop with Shuttle
to MIR and ISS
— Automated with human-supervisory-
control of Progress to MIR
Relevance to DARPA’s Orbital Express (II)
Routine autonomous rendezvous & These define a wide design space
docking raises several questions which must be explored before
— How does the problem change as committing these algorithms to OE
different information becomes flight demonstration
available from the two vehicles? The SPHERES Autonomous
— Both vehicles communicate Rendezvous and Docking Testbed
and coordinate their motion can be used to mature these
— Target nulls residual velocities algorithms in an environment that:
while docking vehicle
— Provides long duration micro-G for
performs all maneuvers
close proximity operations
— Docking vehicle must match
— Is risk tolerant by allowing IFM
residual motion of non-
and replenishment of consumables
cooperative target
— Has access to video coverage and
— Can safe mode and recovery logic
Ku-Band (up)downlink facilitating
be developed that requires minimal
iterative algorithm refinement
human intervention?
— Has low cost and high visibility
— Can autonomous close proximity
operations avoid collision and
plume impingement?
SPHERES (AFRL-0012) DETAILED OVERVIEW
FLIGHT SYSTEM PRIORITY
— Flight H/W (fits in 1-1.5 middeck lockers) — DoD SERB rank 15/34
— 3 SPHERES, 4 metrology transmitters, — AF SERB rank 9/14
1 laptop (GFE)
FUNDING NEEDED
— SPHERE satellite contents
— CO2 propulsion tank, RF — Need $900k to transition from high
communication, IR-ultrasonic global fidelity prototype to operation on ISS
metrology, Inertial Measurement Unit
(IMU), AA battery power — Flight hardware fabrication,
STS-ISS integration, operations
— Researcher uplinks algorithms, crew down-
loads from laptop, crew initiates test and — Potential non-DARPA sources include
replenishes consumables, crew downloads and NASA ST-6 proposal & SBIR, and
downlinks data to ground, researcher reviews Lockheed & AFRL
data and refines algorithms, researcher uplinks
refined algorithms. Cycle completed in days.
STATUS
— Currently manifested on ISS-9a in May 2002
for 4-6 months on ISS.
— High fidelity prototype built & operating in
lab & KC-135, Phase 0/1 Safety Package
complete, EMI tests conducted
SPHERES Team Capability
MIT Space Systems Laboratory Payload Systems Incorporated
— David W. Miller — Developer and integrator of
— Formation flight, rendezvous experiments in human-rated space
and docking research in platforms (Shuttle, MIR, ISS)
support of Techsat21, ST-3, The fact that our facilities have
Terrestrial Planet Finder more reflights first flights is
— Design and PI of 0-g dynamics testimony to the versatility of, and
and controls laboratories demand for, our dynamics and
MODE STS-40, 48, 62
controls laboratories
DLS on MIR
MACE STS-67, 106, ISS
— Jonathan P. How
— Formation flight, differential
GPS, robust control
— Brian Williams
— Spacecraft autonomy, remote
agent, Livingstone
autonomous model-based
diagnosis on DS-1