The Martian Radiation Experiment, or MARIE was designed to measure the radiation environment of Mars using an energetic particle spectrometer as part of the science mission of the 2001 Mars Odyssey spacecraft (launched on April 7, 2001). It was led by NASA's Johnson Space Center and the science investigation was designed to characterize aspects of the radiation environment both on the way to Mars and while it was in the Martian orbit.

MARIE ICD, JPL Document MSP01-98-0016, June 23, 1999, Jet Propulsion
                   Laboratory, Pasadena, CA, 1999.

Scientific Objectives and Overview
  ==================================
    Mars is substantially exposed to the harshest elements of space
    weather. Unlike Earth, which sits inside a protective magnetic field
    called the magnetosphere, Mars does not have a global magnetic field
    to shield it from solar flares and cosmic rays. Another factor is
    the lack of atmosphere. Mars' atmosphere is less than 1% as thick as
    Earth. These two factors make Mars vulnerable to space radiation.
    The Marie instrument was designed to measure the amount of harmful
    radiation in the Mars environment.
 
    The particles which are thought to be most harmful to humans fall
    mostly in the energy range of 30 MeV to thousands of MeV per
    nucleon.  These are the particles with enough energy to damage human
    DNA. The MARIE instrument is designed to measure particles in the
    range of 15 MeV to 500 MeV/n. The data gathered in several detector
    elements is combined to identify the species of the incident
    particles and their energies in this range. The MARIE Instrument was
    developed by NASA Johnson Space Center. The development process was
    a coordinated effort of NASA/JSC, Lockheed-Martin and Battelle.
    Battelle developed the CPU, power boards, A detector, B detector and
    C detector boards.  Lockheed was tasked with development of the
    position sensor devices (PSD), the instrument packaging, system
    integration, software development and certifying the instrument for
    flight. NASA/JSC provided the project management and coordination of
    the contractors.
 
    If a particle enters the MARIE detector telescope within the 60
    degree cone defined by the A1 and A2 detectors, and has enough
    energy to reach the A2 detector, it is considered a coincident
    event. On coincident events, all detector boards are polled by the
    CPU and the data for this event is recorded. The readout for each
    detector records a pulse height that is proportional to the amount
    of energy deposited in the detector. The PSD's also record the
    position of the strike within the detector.
 
    The minimum proton energy required to form an A1A2 coincidence
    corresponds to a proton with range greater than the sum of the
    thickness of A1, PSD1, PSD2, and a minuscule part of the A2
    thickness. This adds up to 0.374 g/cm2 of Si and corresponds to a
    proton energy of 19.8 MeV. So protons above this energy will be
    recorded by the telescope; more energy per nucleon is required for
    higher-charged particles. If one takes into account the thin
    aluminum case that surrounds MARIE, the minimum proton energy is 30
    MeV.  The angular response functions are calculated for those
    particles that give an A1A2 coincidence and also pass through PSD1
    and PSD2 detectors, since they are the only particles that can
    provide the incidence angle of the charged particle. Note that not
    all particles that give rise to A1A2 coincidence pass through PSD1
    and PSD2 because the position sensitive detector are slightly
    smaller in size. A new particle identification algorithm is being
    developed to determine incident angles for particles that miss the
    PSDs or have their positions mis-reported by the PSDs. (The latter
    are common, owing to spurious detector noise.)
 
    If a particle hits only one of the A-detectors, the event is
    discarded because the angle of impact and energy loss in the other
    detector boards is not known. Also, any particle entering the bottom
    of the telescope will not register an event on the C-detector due to
    the directional properties of the C-detector.
 
    The chassis box of MARIE is made from machined aluminum with an
    alodine coating. The exterior surfaces are painted white. Input
    voltage to MARIE is 28 VDC and power requirements are 3 watts for
    survival mode and 7 watts for nominal operation.There are no
    external controls. All control is from the orbiter through an RS-422
    interface.
 
 
  Calibration
  ===========
    Data obtained during the cruise phase of the 2001 Mars Odyssey
    mission have been used to calibrate the data. Pulse height spectra
    in the range 0 to 4096 have been scaled to yield distributions of
    apparent charge, Z. Calibration factors for each detector were
    determined by forcing the obvious high-energy proton peak in each
    distribution to have its center at Z = 1.
 
 
  Operational Considerations
  ==========================
    During Odyssey's daily DSN session, MARIE is off for 1-2 hours,
    causing small gaps in coverage. When the recorded data volume
    approaches the capacity of MARIE's local storage, data acquisition
    is halted until the next download opportunity. When all data have
    been downloaded, the storage area is erased and the instrument
    reset. This sequence of events causes relatively long outages, on
    the order of 1 to 2 days.
 
 
  Detectors
  =========
    Each of the two A detector assemblies contains a 25.4 x 25.4 x 1 mm
    ion-implanted silicon solid state detector, detector signal
    amplifiers, detector high voltage supply and the interface circuitry
    between the detector and the MARIE CPU. The MARIE CPU controls the
    interface circuitry including high voltage control, collecting
    digitized signal amplitude data and controlling signal coincidence
    timing sources. The two A-detectors are used to define a coincidence
    event. These detectors are operated near 160 V.
 
    Each of the four B-detector assemblies contains a 5 mm thick
    lithium-drifted silicon solid state detector, detector signal
    amplifiers, detector high voltage supply and the interface circuitry
    between the detector and the MARIE CPU. The MARIE CPU controls the
    interface circuitry including high voltage control and collecting
    digitized signal amplitude data. These detectors are operated near
    350 V.
 
    The C detector consists of a Schott-glass Cherenkov detector and a
    Hamamatsu photo multiplier tube (PMT). When a charged particle with
    a velocity greater than [velocity of light / glass refractive index]
    hits the Cherenkov detector, the detector releases a photon light
    burst proportional to the energy of the particle which struck it.
    The photo multiplier tube receives the light pulse and translates it
    into an electronic pulse which is amplified by the tube and read by
    the electronics on the C-detector board. The C-detector assembly
    contains the PMT, detector signal amplifiers, detector high voltage
    supply and the interface circuitry between the detector and the
    MARIE CPU. The MARIE CPU controls the interface circuitry including
    high voltage control and collecting digitized signal amplitude data.
 
    Each of the two position sensitive detector (PSD) assemblies
    contains 25.4 X 25.4 mm position sensitive detector. These are
    double-sided silicon strip detectors with 24 strips on each side,
    with a 1 mm pitch. The strips on one side are oriented so as to be
    orthogonal to the strips on the other side. The active area of these
    detectors is 24 mm x 24 mm. Hits from all four strip planes define
    the particle's incident angle.
 
    From the front of the device, particles entering the detector pass
    through detector A1, PSD1, PSD2, A2, B1, B2, B3, B4, and C.
    Depending on the angle of incidence and scattering within the
    detector, some of the downstream detectors (B's and C) may be missed
    on any given event.
 
 
  Electronics
  ===========
    The Central Processing Unit (CPU) board has an Intel 80C188
    microprocessor, detector interface circuitry and data communication
    hardware for transferring data to the spacecraft from the 80 MB
    flash memory. The flash memory holds the program code and any data
    which has not been transferred to the spacecraft. The power from the
    spacecraft is nominally 28 volts. The Marie instrument has
    Interpoint DC-DC converters to convert the power to a usable level.
 
    Each detector has its own card, with all of the electronics
    associated with the detector on it, including a 12 bit
    analog-to-digital (ADC) converter, and Field Programmable Gate
    Array (FPGA)
 
    The power, mode control and data download of the MARIE instrument
    are controlled by the Odyssey spacecraft. Commands are sent from the
    ground to the spacecraft central processing unit (CPU) to power on
    MARIE and to change modes.
 
 
  Location
  ========
    The MARIE instrument frame is illustrated by this diagram:
 
                       _______________ HGA
                       \             /
                   ..   `._________.'
    Science        || ._______________.Science deck
     Orbit         || |       ^+Xsc   |
    Velocity       || |       |       |
      ^.           || |       |      ^+Xmarie .'   MARIE FOV
        `.         || |       |+Zsc /||     .'   (68 deg cone)
          `.       ||@| <-----o ..'._|_.  .'
                   || +Ysc     /   | | |.'
                   || |     _.' <----o o-------->  MARIE FOV
                   || |  _.'  +Ymarie _.`.         boresight
            Solar  || ..'_____________.   `.
            Array  ..       Bottom Deck     `.
                                              `.
                         /
                        /                            -------->
                       /                            Aerobraking
                      V Nadir                        Velocity
 
 
    Actual keywords defining MARIE instrument frame and incorporating
    MARIE mounting alignment information are provided in reference [1].
 
    The MARIE FOV (field of view), as defined in [2], is a 68-degree
    cone centered around the -Y axis of the MARIE instrument frame.
 
    The set of keywords in the data section above defines MARIE FOV
    as a circle with a half-angle of 34 degrees and boresight direction
    along the -Y axis of the MARIE instrument frame.
 
    The following data for the FOV geometry were extracted from the
    SPICE instrument kernel for MARIE, provided by the NAIF Node of
    the Planetary Data System [3].  (The text of this section also was
    adapted from that SPICE kernel.)  These data are included here for
    the benefit of those familiar with the use of SPICE kernels.
 
      INS-53040_FOV_FRAME             = 'M01_MARIE'
      INS-53040_FOV_SHAPE             = 'CIRCLE'
      INS-53040_BORESIGHT             = (
                                          0.0000000000000000
                                         -1.0000000000000000
                                          0.0000000000000000
                                        )
 
      INS-53040_FOV_BOUNDARY_CORNERS  = (
                                          0.0000000000000000
                                         -0.8290375725550400
                                         +0.5591929034707500
                                         )
 
 
  Operational Modes
  =================
    The instrument has only two modes, Science Mode and Survival Mode.
 
    Science Mode: When placed in Science mode, the MARIE acts as an
       autonomous data acquisition device. Data is collected until the
       spacecraft issues a mode change command to move to survival mode.
 
    Survival Mode: From survival mode, the spacecraft can issue commands
       to download data, change parameters, power down or return to
       Science Mode. During the data download, the spacecraft controls
       the download process and downlinks the data to the ground.
 
 
  Measured Parameters
  ===================
    The detector is composed primarily of three types of silicon
    detectors: the A detectors, which are square in cross-section (25.4
    mm on a side) and 1 mm in depth; the B detectors, circular, 63.5 mm
    diameter and 5 mm thick; and the PSDs, or position-sensitive
    detectors. The PSDs are square double-sided strip detectors with 24
    1 mm strips on each side (the strips on one side are orthogonal to
    those on the other side), and have a thickness of 0.3 mm. There are
    two A detectors, A1 and A2; sandwiched in between them are PSD1 and
    PSD2; behind A2, there are the B detectors, B1 through B4.
    Downstream of B4 is a circular piece of quartz, 10 mm thick, that
    radiates photons (Cerenkov radiation) generated by the passage of
    high-velocity particles through it. The photons are reflected by a
    45 deg mirror into a photo multiplier tube that sits out of the path
    of particles that hit the detectors.
 
    MARIE is triggered by a coincidence of hits in detectors A1 and
    A2. Once triggered, the data acquisition system records 12-bit
    digitized outputs which are proportional to the energies deposited
    in the A and B detectors. A two-byte data word is stored for each of
    these channels. The pulse height from the phototube is similarly
    digitized in 12 bits and stored.
 
    Readout of the PSDs is more complex. Each PSD has two orthogonal
    sides, referred to as columns and rows. The following description
    applies to each side of each detector. Onboard hardware analyzes the
    signals from each of the 24 strips and finds the two largest pulse
    heights. For each, the pulse height is digitized in 8 bits (256
    channels) and stored, along with the strip number. The largest pulse
    height and position are referred to as 'event1', the second-largest
    as 'event2.' The event2 data are usually noise. Four quantities are
    stored for each side of each detector, so that a total of sixteen
    words (thirty-two bytes) of PSD data are stored on each event. The
    eight-bit pulse heights are referred to as 'magnitudes', the
    positions are valid only when in the range 1 to 24.
 
 
  References
  ==========
    1. M'01 Frames Definition Kernel (FK), latest version as of March 6,
       2001
    2. 'MARIE ICD', MSP01-98-0016, June 23, 1999
    3. MARIE Instrument Kernel (TI), March 6, 2001

extracted metadata from PDS3 catalog and
                    modified to comply with PDS4 Information Model

Mars Odyssey Radiation Environment Experiment

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