Mission Overview
    ================
      The Deep Space Program Science Experiment (DSPSE), first in a
      planned series of technology demonstrations jointly sponsored
      by the Ballistic Missile Defense Organization (BMDO) of the
      DoD and the National Aeronautics and Space Administration
      (NASA ), was launched on 1994-01-25 aboard a Titan IIG rocket
      from Vandenburg Air Force Base in California. The mission
      included two months of systematic lunar mapping (1994-02-26
      through 1994-04-21), which was to have been followed by a flyby
      of the near-Earth asteroid Geographos (1994-08-31).  A software
      error, combined with improbable hardware conditions, on
      1994-05-07 led to accidental spin-up of the spacecraft and loss
      of attitude control gas.  This precluded the flyby of
      Geographos.  The spacecraft itself was affectionately known as
      Clementine since, as in the song of the same name, it would be
      'lost and gone forever' after completing its short mission.
 
      Clementine's primary objective was qualification of light-
      weight imaging sensors and component technologies (including a
      star tracker, inertial measurement unit, reaction wheel, nickel
      hydrogen battery, and solar panel) for the next generation of
      Department of Defense (DoD) spacecraft.  DSPSE represented a
      new class of small, low cost, and highly capable spacecraft
      that fully embraced emerging lightweight technologies to enable
      a series of long-duration deep space missions.  A second
      objective was return of data about the Moon and Geographos to
      the international civilian scientific community.
 
      BMDO assigned responsibility for the Clementine spacecraft
      design, manufacture, integration, and mission execution to the
      Naval Research Laboratory (NRL).  Lawrence Livermore National
      Laboratory (LLNL) provided lightweight imaging sensors
      developed under the sponsorship of BMDO.  Goddard Space Flight
      Center (GSFC) and the Jet Propulsion Laboratory (JPL) provided
      mission design and navigation services.  The Deep Space Network
      (DSN) provided tracking through JPL.  NASA was responsible for
      the scientific return from the mission.
 
      Further information on the Clementine Mission can be found in
      [NOZETTE&GARRETT1994] and [REGEONETAL1994].
 
 
    Mission Phases
    ==============
      Mission phases were defined for significant spacecraft activity
      periods.  During orbital operations a 'cycle' was the time
      required for the Moon to rotate once under the spacecraft
      (about 28 days).  The 'revolution number' refers to an
      observational pass over the moon.  The revolution number was
      incremented by one each time the spacecraft passed over the
      south pole prior to the beginning of data acquisition.
      Revolution number was used in lieu of orbit number because of
      the way the orbit number was defined by the mission.  The orbit
      number was incremented each time the spacecraft passed through
      the equatorial plane on the sunlit side of the Moon.  Thus, the
      orbit number generally changed in the middle of an
      observational pass.  This proved to be awkward in defining the
      data acquired by a single pass over the Moon.
 
 
      PRELAUNCH
      ---------
        Clementine moved from concept to launch in a little over two
        years. Mission milestones included:
 
        1991-11-19   Naval Research Laboratory (NRL) briefed by
                     the Space Defense Initiative Organization
                     (SDIO) on the Clementine concept
        1992-01-12   NRL tasked with 2 month Clementine study
        1992-02-25   NRL tasked by SDIO to be Clementine lead
        1992-03-16   Clementine Concept Definition Review
        1992-04-01   Clementine Concept Definition completed;
                     begin Program Management and System Design
        1992-05-01   Begin Systems Engineering and Testing
        1992-05-13   Clementine System Requirements Review
        1992-06-01   Begin Ground Subsystems Development
        1992-07-30   Preliminary Design Review
        1992-10-20   Launch Range Introduction (Review)
        1992-11-05   Sensor Critical Design Review
        1992-11-16   Spacecraft Vehicle Critical Design Review
        1993-06-01   Begin Spacecraft Integration
        1993-07-01   Begin Ground System Integration and Testing
        1993-10-01   Begin Spacecraft Assembly Testing
        1993-12-01   Begin Launch Operations and Testing
 
        Spacecraft Id                 : CLEM1
        Target Name                   : MOON
        Mission Phase Start Time      : 1991-11-19
        Mission Phase Stop Time       : 1994-01-25
        Spacecraft Operations Type    : ORBITER
 
 
      LAUNCH
      ------
        The Clementine spacecraft was launched on 1994-01-25, from
        Vandenburg Air Force Base in California.  It went into a
        226-km by 259-km geocentric orbit at an inclination of 67
        degrees.
 
        Spacecraft Id                 : CLEM1
        Target Name                   : MOON
        Mission Phase Start Time      : 1994-01-25
        Mission Phase Stop Time       : 1994-01-25
        Spacecraft Operations Type    : ORBITER
 
 
      LOW EARTH ORBIT
      ---------------
        The Low Earth Orbit phase extended from the end of the Launch
        phase until Clementine was spun up to 60 revolutions per
        minute and the kick motor was fired, changing its trajectory
        to a highly elliptical orbit which would encounter the Moon.
        During this Low Earth Orbit phase on-board systems were
        checked out and the spacecraft was three-axis stabilized.
 
        Spacecraft Id                 : CLEM1
        Target Name                   : MOON
        Mission Phase Start Time      : 1994-01-25
        Mission Phase Stop Time       : 1994-02-03
        Spacecraft Operations Type    : ORBITER
 
 
      EARTH PHASING LOOP A
      --------------------
        Earth Phasing Loop A began at the end of the Low Earth Orbit
        phase and lasted until Lunar Orbit Insertion.  This phase
        included two phasing loop orbits, the second of which allowed
        encounter with the Moon.
 
        Spacecraft Id                 : CLEM1
        Target Name                   : MOON
        Mission Phase Start Time      : 1994-02-03
        Mission Phase Stop Time       : 1994-02-19
        Spacecraft Operations Type    : ORBITER
 
 
      LUNAR ORBIT INSERTION
      ---------------------
        The Lunar Orbit Insertion phase extended from the end of
        Earth Phasing Loop A until the beginning of Lunar Mapping.
        During this phase the spacecraft was placed in a lunar orbit
        ranging from 400 to 2940 kilometers above the surface; the
        orbit period was 5 hours.  Lunar Orbit Insertion occurred
        during revolution 0.
 
        Spacecraft Id                 : CLEM1
        Target Name                   : MOON
        Mission Phase Start Time      : 1994-02-19
        Mission Phase Stop Time       : 1994-02-19
        Spacecraft Operations Type    : ORBITER
 
 
      LUNAR MAPPING
      -------------
        Lunar Mapping extended from the end of Lunar Orbit Insertion
        until the beginning of Lunar Departure.  During this phase
        the instruments were checked out, sequences were developed
        and tested for mapping operations, two complete cycles of
        systematic mapping were completed, and the spacecraft was
        prepared for leaving lunar orbit.  The following sub-phases
        can be defined for the Lunar Mapping phase:
 
        Engineering Checkout and Operational Rehearsals
        (revolutions 1-31)
        Systematic Mapping Cycle 1 (revolutions 32-164)
        Systematic Mapping Cycle 2 (revolutions 165-300)
        Post-Systematic Mapping    (revolutions 301-350)
 
        Spacecraft Id                 : CLEM1
        Target Name                   : MOON
        Mission Phase Start Time      : 1994-02-19
        Mission Phase Stop Time       : 1994-05-03
        Spacecraft Operations Type    : ORBITER
 
 
      LUNAR DEPARTURE
      ---------------
        The Lunar Departure Phase extended from the completion of
        Lunar Mapping until the beginning of Earth Phasing Loop B.
        During this phase, the spacecraft was removed from lunar
        orbit.  The burn for Lunar Departure began on 1994-05-04 at
        03:24:15 and lasted 278 seconds; it took place when the
        included parts of revolutions 350-351.
 
        Spacecraft Id                 : CLEM1
        Target Name                   : MOON
        Mission Phase Start Time      : 1994-05-03
        Mission Phase Stop Time       : 1994-05-04
        Spacecraft Operations Type    : ORBITER
 
 
      EARTH PHASING LOOP B
      --------------------
        Earth Phasing Loop B extended from completion of the Lunar
        Departure phase until loss of on-board attitude control on
        1994-05-07.  During this phase the spacecraft was to have
        been checked out in preparation for its flight to Geographos.
 
        Spacecraft Id                 : CLEM1
        Target Name                   : MOON
        Mission Phase Start Time      : 1994-05-04
        Mission Phase Stop Time       : 1994-05-07
        Spacecraft Operations Type    : ORBITER
 
 
    Lunar Orbit Summary
    ===================
      Mapping of 100% of the lunar surface was done in two lunar days
      (two Earth months).  In order to obtain full coverage during
      these two months, the required image overlap for the UVVIS and
      NIR cameras was ~15% in the down track and ~10% in the cross
      track directions.  This required an inclination of the
      orbit at 90 degrees plus-or-minus 1 degree with reference to
      the lunar equator and a periselene of the lunar orbit
      maintained at an altitude of 425 plus-or-minus 25 km.  To
      provide the necessary cross-track separation for the
      alternating imaging strips to cover the entire surface of the
      moon, the orbital period was approximately 5 hours, during
      which the moon rotated approximately 2.7 degrees beneath the
      spacecraft.  Images were taken and recorded only in the region
      of periselene, leaving sufficient time to replay the data to
      Earth.
 
      The best data for lunar mineral mapping is obtained if the
      solar phase angle is less than 30 degrees.  The solar phase
      angle is defined as the angle between the vector to the Sun and
      the vector to the spacecraft from a point on the Moon's
      surface.  To maximize the time period in which the solar phase
      angle is less than 30 degrees the plane of the lunar orbit
      should contain the Moon-Sun line half way through the two-month
      lunar mapping period.  Therefore, insertion into the lunar
      orbit was selected so that, as the Moon-Sun line changes with
      Earth's motion about the Sun, the Moon-Sun line will initially
      close on the orbital plane, and then lie in the orbital plane
      half-way through the mapping mission.  The angle between the
      Moon-Sun line and the orbital plane was close (less than 5
      degrees) for approximately five weeks before becoming zero.
      Table 1 contains a list of Clementine's orbital parameters.
 
 
      Table 1 Clementine Orbital Parameters
      -------------------------------------
        Orbital Period:         4.970 hr < P < 5.003 hr
        Altitude of Periselene: 401 km < radius < 451 km
        Eccentricity:           0.35821 < e < 0.37567
        Right Ascension:        -3 deg < Omega <+3 deg(referred J2000)
        Inclination:            89 deg < i < 91 deg
        Argument of Periselene: -28.4 deg < w < -27.9 deg (1st month)
        29.6 deg < w <  29.2 deg (2nd month)
 
        Orbit determination and monitoring was done on a continuous
        basis throughout the lunar pre-mapping phase.  The
        gravitational potential field of the moon has not been fully
        mapped, and large lunar mass concentrations perturbed the
        orbit, so maintenance burns were required to maintain the
        orbit characteristics.  The number of these burns was
        minimized to avoid unnecessary disruptions to the systematic
        mapping.  To this end, required periapsis burns were
        performed away from periselene in the direction of the near
        pole.
 
        The spacecraft was three-axis stabilized and capable of
        autonomous, open loop inertial pointing with an accuracy of
        0.05 degree, 0.87 milliradian, or better.  This accuracy was
        required to support use of the high resolution camera because
        of its narrow field of view for imaging selected target sites
        during the lunar mapping mission.  Reconstruction of
        spacecraft attitude to 0.03 degree was generally achieved.
 
        To help accomplish attitude determination, the spacecraft had
        two inertial measurement units (IMU) and two star trackers.
        Because of a solar exclusion angle constraint, one of the two
        star trackers had to be covered during lunar orbit.  To meet
        the aforementioned pointing requirements, during lunar orbit
        a star tracker image was processed and the spacecraft
        attitude knowledge was updated at 10 second intervals or
        less.
 
        The spacecraft was able to execute controlled, relative
        pointing motion about a pointing vector for scanning across
        targets over a range of 75 milliradians.
 
        During lunar imaging, the spacecraft had to maintain a NADIR
        pointing attitude.  This required a greater than 180 degree
        rotation over the approximately 1.5-2.0 hour period during
        each lunar orbit.  The spacecraft was also required to
        maintain an angular bias about the X-axis from NADIR to
        permit an imaging groundtrack parallel but offset from the
        NADIR groundtrack.
 
        The spacecraft was required to point to the Earth center, and
        to a specified tracking station site on the Earth, for the
        dumping of data using the high-gain directional antenna.
 
 
      LUNAR ORBITS TYPE A AND B
      -------------------------
        The polar configuration of Clementine's orbit provided
        significant redundant coverage at the poles.  To take
        advantage of the polar convergence, two types of
        observational scenarios, designated type A and B, were
        developed to provide stereo observations at the higher
        latitudes.  Type A orbits (even numbered orbits) made NADIR
        observations from pole to pole.  Type B orbits (odd numbered
        orbits) made NADIR observations for most of the orbit but
        would switch to oblique viewing at the north pole for orbit
        numbers 32-164 and oblique viewing of the south pole for
        orbit numbers 165-300.  The alternating NADIR and oblique
        observations provide stereo coverage.  Oblique viewing was
        achieved at greater than 50 degrees north and 50 degrees
        south latitude down to the poles.