Mission Overview
  ================
    The Mars Exploration Rover (MER) mission consisted of two
    spacecraft, MER-2 hardware which included the Spirit rover,
    and MER-1 hardware, which included the Opportunity rover
    [CRISPETAL2003, GARVINETAL2003].  Spirit was launched June 10,
    2003, on a Delta II 7925 launch vehicle.  Opportunity followed
    3 weeks later, launching July 7, 2003 on a Delta II 7925 Heavy
    vehicle.  Each spacecraft followed a Type I trajectory from
    Earth to Mars, with Spirit landing in Gusev Crater on January 4,
    2004 UTC and Opportunity landing in Meridiani Planum on January
    25, 2004 UTC.  The Earth-Mars range was 170.2 million km at the
    time of Spirit's landing and 198.7 million km at the time of
    Opportunity's landing.
 
    The spacecraft design was based on the Mars Pathfinder configuration
    for cruise and entry, descent, and landing.  Each MER spacecraft
    contained a rover which was carried to Mars inside a lander.  The
    lander was packed inside a heatshield and backshell attached to a
    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 trajectory at a velocity of
    5.4 km/s.  The lander velocity was reduced from this high entry
    speed by the application of aerodynamic braking by a parachute and
    aeroshell, propulsive deceleration using small solid rocket motors,
    and inflated airbags to reduce the remaining vertical and horizontal
    velocity components at surface impact (involving significant
    bouncing).  Key engineering status information was collected and
    returned in near real time to the extent possible during entry and
    descent.  In addition, all engineering data obtained during the
    critical entry, descent, and landing phase were recorded for later
    playback during the first week of landed operations.
 
    The two landing sites were selected because of their science
    potential and safety characteristics [GOLOMBEKETAL2003].  The two
    sites exhibited different types of evidence suggesting past
    liquid-water activity. For Gusev, the evidence was primarily
    geomorphologic (possible crater lake) and for Meridiani, it was
    primarily mineralogic (gray coarse-grained hematite).  The
    navigation team determined the location of the landing sites in
    inertial space, by fitting direct-to-Earth (DTE) two-way X-band
    Doppler and two passes of UHF two-way Doppler between each rover
    and Mars Odyssey.  Translated to the MOLA IAU 2000 frame
    [SEIDELMANNETAL2002] these inertial positions are 14.571892
    degrees S latitude and 175.47848 degrees E longitude for Spirit,
    and 1.948282 degrees S latitude, 354.47417 degrees E longitude for
    Opportunity.  The location of the landing sites, with respect to
    surface features in maps produced in the MOLA IAU 2000 cartographic
    reference frame, are 14.5692 degrees S latitude, 175.4729 degrees
    E longitude for Spirit and 1.9462 degrees S latitude, 354.4734
    degrees E longitude for Opportunity.
 
    Each of the identical rovers was equipped with a science payload
    consisting of two remote sensing instruments (Pancam and the
    Miniature Thermal Emission Spectrometer) at the top of a rotatable
    mast to survey the surrounding terrain, a robotic arm capable of
    placing three instruments (Alpha Particle X-Ray Spectrometer,
    Moessbauer Spectrometer, and Microscopic Imager) and a rock
    abrasion tool (RAT) on selected rock and soil samples, and
    several on-board magnets and calibration targets.  Engineering
    sensors and other components on the rovers useful for science
    investigations included stereo navigation cameras (Navcam) on the
    top of the mast, stereo hazard cameras in front and rear under the
    solar panels (Hazcams), wheel motors, the wheels themselves
    for digging, gyros, accelerometers, and reference solar cells.
    Mission operations allowed commanding of the rover each martian day,
    or sol, on the basis of the previous sol's data.  Over the 90-sol
    prime mission lifetime and several mission extensions, the
    rovers carried out field geology investigations, exploration,
    and atmospheric characterization.
 
    Many extended missions followed the 90-sol primary mission.
    Brief summaries of the activities in each mission phase are
    described below. The mission has been described in many papers,
    including a pre-landing set of papers in the December 2003 special
    section of Journal of Geophysical Research - Planets, and post-
    landing special issues of Science in 2004 for Spirit rover (volume
    305, number 5685) and Opportunity rover (volume 306, number 5702).
    Additional special issues were published in 2005 for Earth and
    Planetary Science Letters (volume 240, number 1) and Nature (volume
    436, number 7047).  In 2006, the science team published several
    papers on the Spirit rover in Journal of Geophysical Research -
    Planets (volume 111, number E02). Another JGR special issue was
    published in 2008 (volume 113, number E06), and a 2010 update is
    in press as of this writing.
 
 
  Mission Phases
  ==============
 
    DEVELOPMENT
    -----------
      The development phase began with the start of mission funding in
      May, 2000. During this phase, the science and technology
      requirements were developed and analyzed, and the spacecraft and
      mission were designed.  The instruments and spacecraft were
      fabricated and tested before delivery to Kennedy Space Center.
      The design of the spacecraft trajectory and mission operations
      were also determined during this period.
 
      Spacecraft Id : MER2
      Target Name : MARS
      Mission Phase Start Time : 2000-05-08
      Mission Phase Stop Time : 2003-06-10
      Spacecraft Operations Type : LANDER
 
      Spacecraft Id : MER1
      Target Name : MARS
      Mission Phase Start Time : 2000-05-08
      Mission Phase Stop Time : 2003-07-07
      Spacecraft Operations Type : LANDER
 
 
    LAUNCH
    ------
      The launch phase for each vehicle began at the final countdown
      through spacecraft separation from the upper stage.  Spirit
      (MER-2 hardware) was launched June 10, 2003, at 1759 UTC
      (1359 EDT) from launch complex 17A at Cape Canaveral Air Force
      Station, Florida.  The launch azimuth was 93 degrees.  The boost
      portion of the launch vehicle trajectory took approximately 10
      minutes, and was followed by a short coast phase in a parking
      orbit for approximately 15 minutes.  After third stage burnout,
      the upper stage despun the stack using a yo-yo despin system.
      Separation of the third stage occurred approximately 36 minutes
      after launch.
 
      Opportunity (MER-1 hardware) was launched July 8, 2003, at
      0318 UTC (July 7, 2003, 2318 EDT) from launch complex 17B at
      Cape Canaveral Air Force Station, Florida. The launch azimuth
      was 99 degrees.  The boost portion of the launch vehicle
      trajectory took approximately 9 minutes, and was followed by
      a long coast phase of approximately 60 minutes in a parking
      orbit.  After third stage burnout, the upper stage despun the
      stack using a yo-yo despin system.  Separation of the third
      stage occurred approximately 83 minutes after launch.
 
      Spacecraft Id : MER2
      Target Name : MARS
      Mission Phase Start Time : 2003-06-10
      Mission Phase Stop Time : 2003-06-10
      Spacecraft Operations Type : LANDER
 
      Spacecraft Id : MER1
      Target Name : MARS
      Mission Phase Start Time : 2003-07-07
      Mission Phase Stop Time : 2003-07-07
      Spacecraft Operations Type : LANDER
 
 
    CRUISE
    ------
      The cruise phase for each spacecraft began soon after separation
      from the third stage and ended 45 days before entry into the Mars
      atmosphere. The duration of cruise phase was 162 days for Spirit
      and 156 days for Opportunity.  The major activities during this
      phase included: checkout and maintenance of the spacecraft in its
      flight configuration, monitoring, characterization and calibration
      of the spacecraft and payload systems, software parameter updates,
      attitude correction turns, navigation activities for determining
      and correcting the vehicle's flight path, and preparation for EDL
      and surface operations, including EDL X-band communication tests.
      No science investigations were conducted during cruise, except for
      instrument health checkouts.
 
      Spacecraft Id : MER2
      Target Name : MARS
      Mission Phase Start Time : 2003-06-10
      Mission Phase Stop Time : 2003-11-19
      Spacecraft Operations Type : LANDER
 
      Spacecraft Id : MER1
      Target Name : MARS
      Mission Phase Start Time : 2003-07-07
      Mission Phase Stop Time : 2003-12-10
      Spacecraft Operations Type : LANDER
 
 
    APPROACH
    --------
      The approach phase was dedicated to the activities necessary to
      ensure a successful Entry, Descent, and Landing for each
      spacecraft, beginning 45 days before entry into the Martian
      atmosphere and ending at the atmospheric entry interface point
      3522.2 km from the center of Mars.  The main activities during
      this phase were: acquisition and processing of navigation data to
      support development of the final trajectory correction maneuvers
      and activities leading up to the final turn to the entry attitude
      70 minutes before entry and separation from the cruise stage 15
      minutes before entry.
 
      Spacecraft Id : MER2
      Target Name : MARS
      Mission Phase Start Time : 2003-11-19
      Mission Phase Stop Time : 2004-01-03
      Spacecraft Operations Type : LANDER
 
      Spacecraft Id : MER1
      Target Name : MARS
      Mission Phase Start Time : 2003-12-10
      Mission Phase Stop Time : 2004-01-24
      Spacecraft Operations Type : LANDER
 
 
    ENTRY, DESCENT, AND LANDING
    ---------------------------
      The entry, descent, and landing (EDL) phase for each spacecraft
      started six minutes prior to landing.  Approximately 20 seconds
      after parachute deploy, the heatshield separated from each
      spacecraft, followed approximately 10 seconds later by lander
      separation on a bridle.  This was followed by radar acquisition
      of the ground, acquisition of three images by the DIMES (Descent
      Image Motion Estimation System), airbag inflation, RAD/TIRS
      rocket firing, bridle cut (6.5 m above the surface for Spirit,
      8.5 m for Opportunity), and landing.  The landing (first impact)
      occurred at 04:26 UTC on January 4, 2004 for Spirit (1425 Mars
      local solar time, solar longitude Ls = 327.66) and 04:55 UTC on
      January 25, 2004 for Opportunity (1323 Mars local solar time,
      solar longitude Ls = 339.10).  Spirit bounced 28 times
      before coming to rest on the base petal of the lander.
      After retraction of the airbags and opening of the petals, the
      base petal was oriented at a tilt of 2 degrees.  Opportunity
      bounced 26 times before coming to rest on a side petal (+Y petal)
      of the lander. After retraction of the airbags and opening of
      the petals, the base petal was oriented at a tilt of 5 degrees,
      with the base petal down on the surface.  The entry, descent,
      and landing phase for each spacecraft was completed once the
      rover solar panels were opened and the lander was on the
      surface of Mars in a thermally stable, positive energy balance,
      in a commandable configuration.
 
      Spacecraft Id : MER2
      Target Name : MARS
      Mission Phase Start Time : 2004-01-04
      Mission Phase Stop Time : 2004-01-04
      Spacecraft Operations Type : LANDER
 
      Spacecraft Id : MER1
      Target Name : MARS
      Mission Phase Start Time : 2004-01-25
      Mission Phase Stop Time : 2004-01-25
      Spacecraft Operations Type : LANDER
 
 
    POST-LANDING THROUGH EGRESS
    ---------------------------
      The post-landing through egress phase of each mission began after
      the lander petals and rover solar panels had been opened.  This
      phase ended 12 Martian sols (each sol being 24.66 hours) after
      landing for Spirit, and 7 Martian sols for Opportunity, when
      each rover drove off of the lander directly onto the surface of
      Mars.  Data confirming the egress event for Spirit were received
      at 01:53 PST January 15, 2004 (09:53, January 15, UTC).  Engineers
      received confirmation that Opportunity's six wheels successfully
      rolled off the lander and onto martian soil at 03:01 PST,
      January 31, 2004 (11:01 January 31, UTC).
 
      Spacecraft Id : MER2
      Target Name : MARS
      Mission Phase Start Time : 2004-01-04
      Mission Phase Stop Time : 2004-01-15
      Spacecraft Operations Type : LANDER
 
      Spacecraft Id : MER1
      Target Name : MARS
      Mission Phase Start Time : 2004-01-25
      Mission Phase Stop Time : 2004-01-31
      Spacecraft Operations Type : LANDER
 
 
    PRIMARY MISSION
    ---------------
      Spirit and Opportunity's primary missions each lasted for 90
      Martian sols from time of landing.  During this phase and the
      extended mission phase, a wealth of science and engineering
      information was collected from the rover and instrument payload.
      During Spirit's mission, the rover traveled in a primarily
      northeast direction from its landing site to the 210-meter
      diameter crater informally called 'Bonneville,' and then headed
      southeast towards the hills nicknamed 'Columbia Hills,' covering
      a distance travelled of 635 meters.  During that time, Spirit
      acquired 23810 Pancam images, 2886 Navcam images, 3980 Hazcam
      images, and 1872 Microscopic Imager images (these image counts
      include full frames, subsampled frames, downsampled frames, and
      thumbnails). During Opportunity's prime mission, the rover
      spent the first two months investigating the surrounding area
      where it landed, which was a 20-meter diameter crater nicknamed
      'Eagle.' After the study of 'Eagle,' it headed east towards the
      130-meter diameter crater nicknamed 'Endurance,' covering a
      distance travelled of 772 meters.  During the prime mission,
      Opportunity acquired 22503 Pancam images, 2343 Navcam images,
      4421 Hazcam images, and 1395 Microscopic Imager images.
 
 
      Spacecraft Id : MER2
      Target Name : MARS
      Mission Phase Start Time : 2004-01-11
      Mission Phase Stop Time : 2004-04-06
      Spacecraft Operations Type : LANDER
 
      Spacecraft Id : MER1
      Target Name : MARS
      Mission Phase Start Time : 2004-02-01
      Mission Phase Stop Time : 2004-04-27
      Spacecraft Operations Type : LANDER
 
 
    EXTENDED MISSION 1
    ------------------
      The rovers' extended missions have not yet ended.  Objectives
      for each of the extended missions are described in the next
      section.
 
      Spacecraft Id : MER2
      Target Name : MARS
      Mission Phase Start Time : 2004-04-06
      Sol Start Time: 91
      Mission Phase Stop Time : 2004-09-30
      Sol Stop Time: 264
      Spacecraft Operations Type : LANDER
 
      Spacecraft Id : MER1
      Target Name : MARS
      Mission Phase Start Time : 2004-04-27
      Sol Start Time: 91
      Mission Phase Stop Time : 2004-09-30
      Sol Stop Time: 243
      Spacecraft Operations Type : LANDER
 
    EXTENDED MISSION 2
    ------------------
 
      Spacecraft Id : MER2
      Target Name : MARS
      Mission Phase Start Time : 2004-10-01
      Sol Start Time: 265
      Mission Phase Stop Time : 2005-03-31
      Sol Stop Time: 441
      Spacecraft Operations Type : LANDER
 
      Spacecraft Id : MER1
      Target Name : MARS
      Mission Phase Start Time : 2004-10-01
      Sol Start Time: 244
      Mission Phase Stop Time : 2005-03-31
      Sol Stop Time: 420
      Spacecraft Operations Type : LANDER
 
    EXTENDED MISSION 3
    ------------------
 
      Spacecraft Id : MER2
      Target Name : MARS
      Mission Phase Start Time : 2005-04-01
      Sol Start Time: 442
      Mission Phase Stop Time : 2006-09-30
      Sol Stop Time: 974
      Spacecraft Operations Type : LANDER
 
      Spacecraft Id : MER1
      Target Name : MARS
      Mission Phase Start Time : 2005-04-01
      Sol Start Time: 421
      Mission Phase Stop Time : 2006-09-30
      Sol Stop Time: 954
      Spacecraft Operations Type : LANDER
 
    EXTENDED MISSION 4
    ------------------
 
      Spacecraft Id : MER2
      Target Name : MARS
      Mission Phase Start Time : 2006-10-01
      Sol Start Time: 975
      Mission Phase Stop Time : 2007-09-28
      Sol Stop Time: 1328
      Spacecraft Operations Type : LANDER
 
      Spacecraft Id : MER1
      Target Name : MARS
      Mission Phase Start Time : 2006-10-01
      Sol Start Time: 955
      Mission Phase Stop Time : 2007-09-28
      Sol Stop Time: 1307
      Spacecraft Operations Type : LANDER
 
    EXTENDED MISSION 5
    ------------------
 
      Spacecraft Id : MER2
      Target Name : MARS
      Mission Phase Start Time : 2007-09-29
      Sol Start Time: 1329
      Mission Phase Stop Time : 2008-09-28
      Sol Stop Time: 1684
      Spacecraft Operations Type : LANDER
 
      Spacecraft Id : MER1
      Target Name : MARS
      Mission Phase Start Time : 2007-09-29
      Sol Start Time: 1308
      Mission Phase Stop Time : 2008-09-28
      Sol Stop Time: 1663
      Spacecraft Operations Type : LANDER
 
    EXTENDED MISSION 6
    ------------------
 
      Spacecraft Id : MER2
      Target Name : MARS
      Mission Phase Start Time : 2008-09-29
      Sol Start Time: 1685
      Mission Phase Stop Time : 2010-09-26
      Sol Stop Time: 2393
      Spacecraft Operations Type : LANDER
 
      Spacecraft Id : MER1
      Target Name : MARS
      Mission Phase Start Time : 2008-09-29
      Sol Start Time: 1664
      Mission Phase Stop Time : 2010-09-26
      Sol Stop Time: 2372
      Spacecraft Operations Type : LANDER
 
    EXTENDED MISSION 7
    ------------------
 
      Spacecraft Id : MER2
      Target Name : MARS
      Mission Phase Start Time : 2010-09-27
      Sol Start Time: 2394
      Mission Phase Stop Time : 2012-09-30
      Sol Stop Time: 3108
      Spacecraft Operations Type : LANDER
 
      Spacecraft Id : MER1
      Target Name : MARS
      Mission Phase Start Time : 2010-09-27
      Sol Start Time: 2373
      Mission Phase Stop Time : 2012-09-30
      Sol Stop Time: 3087
      Spacecraft Operations Type : LANDER