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					   MIT Space Systems Laboratory

  SPHERES 0-G Autonomous
Rendezvous and Docking Testbed
              Presented To

           Orbital Express
           December 2000

           David W. Miller
           (617) 253-3288
         MIT, Cambridge MA

                     SPHERES (AFRL-0012) CONCEPT
    —   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.

    —   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
    —   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?
   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.
    —   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

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