Mission Overview
  ================
    The Mars Pathfinder Project was one of the first of the NASA
    Discovery class missions.  Discovery Program missions are defined
    as low cost missions, (with a $150M FY'92 development cost cap),
    and a fast schedule (less than 3 years development period).  They
    have focused, but significant, science objectives.
 
    Mars Pathfinder placed a single vehicle on the surface of Mars,
    the Mars Pathfinder Lander, which then deployed a microrover,
    called variously 'Sojourner', the 'Microrover Flight Experiment',
    or the 'Mars Pathfinder Rover'.  Several instruments were
    included on the two spacecraft.  The Sojourner carried three
    cameras, (two black & white cameras on the front and one color
    camera in the rear), and the Alpha Proton X-Ray Spectrometer
    (APXS).  Sojourner's mobility provided the capability of 'ground
    truthing' a landing area over hundreds of square meters on Mars.
    The Lander investigated the surface of Mars with two additional
    science instruments, a stereoscopic imager with spectral filters
    on an extensible mast (Imager for Mars Pathfinder or IMP), and
    the Atmospheric Structure Instrument / Meteorology package
    (ASI/MET).  Mars Pathfinder paved the way for a cost effective
    implementation of future Mars lander missions as part of a
    comprehensive Mars exploration program augmented by additional
    Discovery Program missions.
 
    The launch occurred December 4, 1996 on a McDonnell Douglas Delta
    II 7925 launch vehicle.  The Earth-Mars trajectory was a Type 1
    transfer with a Mars arrival date of July 4, 1997.  The landing
    site for Mars Pathfinder was in the Ares Vallis region of Chryse
    Planitia at 19.17 degrees North latitude, 33.21 degrees West
    longitude.  (See [GOLOMBEKETAL1997B] or the DATASET.CAT file on
    this CD-ROM for specifics.) The Earth elevation angle at landing
    was 11 degrees and rising, and the Sun was 30 degrees below the
    local horizon and rising.  The Earth-Mars range at arrival was
    191,000,000 km (and increasing).
 
    Required guidance, navigation, attitude control, telemetry, and
    power generation functions during the 7 month cruise were
    provided by the cruise stage.  At Mars arrival, the cruise stage
    was jettisoned from the entry capsule.  The entry capsule entered
    the Martian atmosphere directly from the Earth-Mars transfer
    orbit at a velocity of 7.6 km/s.  The lander velocity was reduced
    from this high entry speed through the sequential application of
    aerodynamic braking by a Viking heritage aeroshell and parachute,
    propulsive deceleration using small solid tractor rockets, and
    airbags to nullify the remaining vertical and horizontal velocity
    components at surface impact.  Key engineering status information
    was collected and returned in near real time to the extent
    possible during entry and descent.  In addition, all engineering
    and science data obtained during the critical entry, descent, and
    landing phase were recorded for playback at the initiation of
    lander surface operations.
 
    The principle surface operations activities were return of
    engineering data characterizing the performance of the lander
    system in the Martian environment, return of science data
    obtained from the imaging, meteorology, and spectroscopy
    instruments, and operation of the rover to deploy instruments and
    conduct science and technology experiments.
 
    Seven mission phases, including the extended phase, were defined
    to describe the periods of activity during the mission.  Brief
    summaries of the activities in each phase are described below.
 
    The mission has been described in many papers including a
    February, 1997 special issue of the Journal of Geophysical
    Research and a December, 1997 special issue of Science.  Sometime
    in the latter half of 1998 there will be another special issue of
    the JGR discussing the results of the mission.
 
 
  Mission Phases
  ==============
 
    DEVELOPMENT
    -----------
      The development phase began with the start of mission funding
      in 1993.  During this phase, the science and technology
      requirements were analyzed and the spacecraft and its
      components were designed.  The instruments and spacecraft were
      fabricated and tested before delivery to the Eastern Test
      Range.  The spacecraft trajectory and mission operations were
      also determined during this period.
 
      Spacecraft Id                 : MPFL
      Target Name                   : MARS
      Mission Phase Start Time      : 1993-11-01
      Mission Phase Stop Time       : 1996-08-12
      Spacecraft Operations Type    : LANDER
 
 
    PRELAUNCH
    ---------
      The prelaunch phase extended from delivery of the spacecraft to
      the Eastern Test Range (ETR) until initiation of the terminal
      countdown three hours prior to launch.  Principle activities
      performed during this phase included final assembly and
      checkout of the spacecraft, mating with the Payload Assist
      Module-D (PAM-D), propellant loading, and integration of the
      spacecraft/PAM-D stack on the Delta.  In addition, there was an
      extensive review cycle required prior to launch.
 
      Spacecraft Id                 : MPFL
      Target Name                   : MARS
      Mission Phase Start Time      : 1996-08-12
      Mission Phase Stop Time       : 1996-12-04
      Spacecraft Operations Type    : LANDER
 
 
    LAUNCH
    ------
      The launch phase extended from the initiation of the terminal
      countdown through spacecraft separation from the upper stage.
      Mars Pathfinder was launched December 4, 1996, at 6:58 am UTC
      (1:58 am EST) from launch complex 17B at Cape Canaveral, FL.
      The launch azimuth was 95 degrees.  The boost portion of the
      launch vehicle trajectory took approximately 10 minutes.
      Injection occurred about one hour later after an extended coast
      phase.  After third stage burnout, the upper stage despun the
      stack using a yo-yo despin system.  Separation occurred
      approximately 75 minutes after launch.
 
      Spacecraft Id                 : MPFL
      Target Name                   : MARS
      Mission Phase Start Time      : 1996-12-04
      Mission Phase Stop Time       : 1996-12-04
      Spacecraft Operations Type    : LANDER
 
 
    CRUISE
    ------
      The cruise phase started when the spacecraft separated from the
      upper stage and ended twelve hours prior to entry.  The cruise
      phase was subdivided into three subphases: near Earth,
      Earth-Mars transfer, and Mars approach.  The near Earth
      subphase started at separation and ended the day after the
      first Trajectory Correction Maneuver (TCM), which occurred on
      January 10, 1997.  Major activities performed in this subphase
      were initial link acquisition, initiation of the nominal cruise
      attitude profile, checkout of the spacecraft engineering
      functions, rover and instrument health checks, and TCM-1.  The
      Earth-Mars transfer subphase started at the end of the
      near-Earth subphase and extended through May 20, 1997 (45 days
      prior to arrival).  Activities carried out during this subphase
      included routine spacecraft health and performance monitoring,
      tracking data acquisition for navigation, and the second and
      third TCM's (performed on February 3 and May 7, respectively).
      The Mars approach subphase started on May 21, 1997 and ended
      twelve hours prior to entry on July 4, 1997.  TCM-4 (on June
      25), the entry attitude turn (where the spacecraft was placed
      into the desired entry attitude), and preparations for Mars
      atmospheric entry were completed during this subphase.
 
      Because the instruments were all enclosed within the folded-up
      lander, no science investigations were conducted during cruise,
      except for instrument health checkouts.
 
      Spacecraft Id                 : MPFL
      Target Name                   : MARS
      Mission Phase Start Time      : 1996-12-04
      Mission Phase Stop Time       : 1997-07-04
      Spacecraft Operations Type    : LANDER
 
 
    ENTRY, DESCENT, AND LANDING
    ---------------------------
      The entry, descent and landing (EDL) phase of the mission
      started 12 hours prior to entry.  The spacecraft was in the
      autonomous EDL control mode during this period.  This phase
      ended when the airbags were fully retracted, the petals were
      deployed, and the lander transitioned from the EDL mode to
      sequence control.  This occurred 87 minutes after landing.  The
      EDL phase was divided into three subphases: entry, terminal
      descent, and EDL surface.
 
      The entry subphase extended from the start of the EDL phase
      through parachute deployment.  The exact time of parachute
      deployment was calculated from on-board accelerometer
      measurements, and occurred at 4:54:41 pm UTC (9:54:41 am PDT)
      on July 4, 1997.  Activities in this period included cruise
      stage separation, peak aerodynamic heating and deceleration,
      acquisition of engineering and science accelerometer data, and
      parachute deployment.
 
      The terminal descent subphase started at parachute deployment
      and ended when the lander rolled to a stop on the surface of
      Mars.  The landing occurred at 4:56:55 pm UTC (9:56:55 am PDT)
      July 4, 1997; the true local time at the landing site on Mars
      was 2:58 am.  The lander rolled for about two minutes before
      finally coming to rest about 12 miles southwest of its targeted
      landing spot.  It rested on the surface at a very slight tilt
      of about 2.5 degrees.  Heatshield separation, bridle
      deployment, radar altimeter data acquisition, airbag inflation,
      RAD (rocket assisted descent) motor ignition, and impact were
      the key activities of this subphase.
 
      The EDL surface subphase covered the time period required for
      the deflation and retraction of the airbags and deployment of
      the lander petals.  The spacecraft landed on its base petal,
      obviating the need for righting itself.  At 6:24 pm UTC (11:24
      am PDT), engineering data indicated that Pathfinder had fully
      deployed its petals and was awaiting sunrise on Mars to power
      up.
 
      Spacecraft Id                 : MPFL
      Target Name                   : MARS
      Mission Phase Start Time      : 1997-07-04
      Mission Phase Stop Time       : 1997-07-04
      Spacecraft Operations Type    : LANDER
 
 
    LANDER SURFACE MISSION
    ----------------------
      Mars Pathfinder's surface, or primary, mission phase began when
      its lander petals were fully unfolded and the lander switched
      to a sequence of computer commands that controlled its
      functions.  This phase ended 30 Martian 'sols' (each sol being
      24.6 hours) after landing.  During this and the extended
      phases, a wealth of engineering and science information was
      collected from the lander and the instrument packages mounted
      on it.  The IMP camera alone acquired 16,661 images.
 
      Spacecraft Id                 : MPFL
      Target Name                   : MARS
      Mission Phase Start Time      : 1997-07-04
      Mission Phase Stop Time       : 1997-08-03
      Spacecraft Operations Type    : LANDER
 
 
    ROVER SURFACE MISSION
    ---------------------
      The Rover's primary mission lasted for seven Martian 'sols'
      from the time of landing.  One of the lander's airbags did not
      fully retract, and was initially draped over the edge of the
      rover's petal.  The petal had to be partially closed and then
      reopened.  This resulted in a slight delay in the deployment of
      the rover, which occurred at 5:37 am, July 6, 1997 UTC, (10:37
      pm, July 5, PDT).  During the Rover's primary and extended
      mission phases, the Rover traveled in a clockwise direction
      around the lander.  It acquired over 600 images and deployed
      the APXS instrument at a number of rock and soil sites.
 
      Spacecraft Id                 : MPFR
      Target Name                   : MARS
      Mission Phase Start Time      : 1997-07-04
      Mission Phase Stop Time       : 1997-07-11
      Spacecraft Operations Type    : ROVER
 
 
    LANDER EXTENDED MISSION
    -----------------------
      The Lander's extended mission ended with the last receipt of
      science data from the surface on September 27, 1997.  It is
      believed that a combination of a dead battery and the
      increasing cold of approaching Martian winter crippled the
      spacecraft's ability to communicate with Earth.
 
      Spacecraft Id                 : MPFL
      Target Name                   : MARS
      Mission Phase Start Time      : 1997-08-03
      Mission Phase Stop Time       : 1997-09-27
      Spacecraft Operations Type    : LANDER
 
 
    ROVER EXTENDED MISSION
    ----------------------
      The Sojourner rover was continuing to function at the time the
      Lander ceased communicating with Earth.  Upon loss of
      communication, the Rover presumably acted on its stored
      commands, which directed it to return to the Lander.
 
      Spacecraft Id                 : MPFR
      Target Name                   : MARS
      Mission Phase Start Time      : 1997-07-11
      Mission Phase Stop Time       : 1997-09-27
      Spacecraft Operations Type    : ROVER