Dataset Overview
  ================
    This data set contains information on dust the dust environment in
    interplanetary space within the inner solar system, between Jupiter
    and the Sun, and at high polar latitudes of the Sun. Both
    interplanetary and interstellar dust particles have been detected.
    This information is collected with a dust impact experiment, from
    which may be inferred direction of motion, mass, velocity and charge
    (see ULYDINST.CAT). The data presented in this dataset include
    instrumental readouts, inferred metadata, calibration information
    and a calendar of events.  Specifically:
 
    1) ulyddust.tab - data received from the dust detector, the
       spacecraft, and physical properties derived from the detector
       data (Gruen et al., 1995a and Krueger et al., 1999a
       [GRUENETAL1995A], [KRUEGERETAL1999A]).
 
    2) ulydevnt.tab - data received from the dust detector, the
       spacecraft, and physical properties derived from the detector
       data for reliable dust impacts plus noise events.
 
    3) ulydcode.tab - value ranges corresponding to codes found in
       ulyddust.tab.
 
    4) ulydcalb.tab - laboratory calibration data used to relate
       instrument responses to physical properties of the impacting dust
       particles.
 
    5) ulydarea.tab - the area of the dust detector exposed to particles
       as a function of their velocity direction relative to the
       detector axis.
 
    6) ulydstat.tab - time history of the Ulysses mission and dust
       detector configuration, tests and other events.
 
    The data received from the spacecraft are used for determining the
    location and orientation of the spacecraft and instrument. Given are
    the SPACECRAFT-SUN DISTANCE, ECLIPTIC LONGITUDE, ECLIPTIC LATITUDE,
    SPACECRAFT-EARTH DISTANCE, SPACECRAFT-JUPITER DISTANCE, ROTATION
    ANGLE, DETECTOR ECLIPTIC LONGITUDE, and DETECTOR ECLIPTIC LATITUDE.
 
    Data received from the dust detector are given in an integer code
    format.  Some of the integer codes represent a range of values
    within which the data could fall (e.g., ION AMPLITUDE CODE), some
    may represent a specific value (e.g., ION COLLECTOR THRESHOLD), and
    others a classification based upon other integer codes (e.g., EVENT
    CLASS).
 
    The instrument data consist of cataloging information, instrument
    status, instrument readings at time of impact, and classification
    information.  The cataloging information includes the SEQUENCE
    NUMBER (impact number), DATE JULIAN (time of impact), and SECTOR
    (the pointing of the instrument at time of impact).  The instrument
    status data are the threshold levels of the detectors and the
    CHANNELTRON VOLTAGE LEVEL.
 
    The instrument readings include the amplitude codes of the detectors
    aboard the instrument and the integer codes representing the charge
    level rise times of the detectors, the difference in starting times
    of the ion signal and the electron signal, electron and ion signal
    coincidence, and ion and channeltron signal coincidence.
 
    The classification information is used to assist in classifying an
    event into probable impact and non-impact categories.  There are
    three variables used in classification:  EVENT DEFINITION which
    records which detectors begin a measurement cycle; ION AMPLITUDE
    RANGE which is the classification of the ION AMPLITUDE CODE into 6
    subranges (used with EVENT CLASS); and EVENT CLASS which categorizes
    events into a range of probable impacts to probable non-impacts.
 
    The PARTICLE SPEED and PARTICLE MASS and their corresponding error
    factors are determined from the instrument and calibration data
    given in ulyddust.tab and ulydcalb.tab, respectively.
 
 
  Calibration Data
  ================
    ION RISE TIME, ELECTRON RISE TIME, ION CHARGE MASS RATIO, and
    ELECTRON CHARGE MASS RATIO were measured for iron, glass, and carbon
    particles of known mass and impacting at known speeds. Since the
    composition of particles striking the Ulysses spacecraft is unknown,
    logarithmic averages of the above values are used to infer the
    particle speed and mass from the instrumental measurements. See
    Goller (1988) [GOLLER1988].
 
    The data were provided in a private communication to M. Sykes (Jun
    29 03:04 MST 1995) by M. Baguhl. They are the results of these
    experiments for impacts at an angle of 34 degrees from the detector
    axis.
 
 
  Processing Level
  ================
    The data contain different levels of processing.  Some processing
    was done at the time of the impact observation.  This processing
    categorized the detector responses to transmit the data efficiently
    back to Earth.  Data received on Earth is given as an integer code.
    These integer codes can, for example, represent ranges of values, or
    can be a classification determined from other integer codes.  On
    Earth, these integer codes were then fit to calibration curves to
    determine the speed and mass of the impacting particle. See (Goller
    and Gruen 1989; Gruen et al., 1995c [GOLLER&GRUEN1989],
    [GRUENETAL1995C]).
 
    This data set contains the information from the spacecraft
    instrument as received on Earth, information about the location and
    pointing direction of the spacecraft, and the meta-data determined
    from the data analysis.
 
    The calibration data are included as part of this dataset.
 
 
  Sampling Parameters
  ===================
    The occurence of an impact with the instrument begins a measurement
    cycle.  The on-board detectors measure a charge accumulation versus
    time in order to measure the rise time of the accumulation and any
    coincidences between detector readings.  The on-board computer
    converts these measurements to integer codes to minimize the amount
    of data that is transferred back to Earth.  After the conversion,
    the integer codes are categorized to determine if an event is more
    likely to be an impact or noise event.  The data are then stored
    until it is time to transmit to Earth.
 
 
  Data Reduction
  ==============
    Data Reduction - Impact Speed
    -----------------------------
      Impact speed (V) is obtained from the rise-time measurements of
      the ion and electron detectors (IT and ET, respectively) using
      procedures described in part by Gruen et al. (1995c)
      [GRUENETAL1995C] and a private communication to M. Sykes (Jul 22
      03:43 MST 1995) from M. Baguhl. The calibration tables used
      correspond to the mean values obtained for the three different
      projectile materials with which the instruments were calibrated
      (Goller and Gruen 1989; Gruen et al., 1995c) [GOLLER&GRUEN1989],
      [GRUENETAL1995C]. A rise-time measurement is started when the
      respective signal exceeds its threshold and is stopped by a flag
      pulse from the peak-detector. Impact calibration was performed in
      the speed interval from about 2 km/s to 70 km/s, so impact speeds
      derived from rise-time measurements will be limited to this
      range.
 
      Dust accelerator tests as well as experience with flight data have
      shown that (1) the shape of the ion signal is less susceptible to
      noise than the shape of the electron signal and (2) for true
      impacts, ELECTRON AMPLITUDE CODE values (EA) are generally greater
      than the ION AMPLITUDE CODE values (IA) by 2 to 6.  As a
      consequence, the electron rise-time is only used for impact speed
      determination if 2 =< EA-IA =< 6. Since both speed measurements,
      if available, are independent, one obtains two (often different)
      values VIT and VET, respectively. The impact speed is then taken
      to be the geometric mean of VIT and VET.
 
      Determining VIT:
 
         If IA > 16 and IT > 12, then fix IT=14.
         Else, if IA > 16 and IT =< 12, then add 2 to the corresponding
            value of IT.
         VIT is then found in Table 5b of Gruen et al. (1995c)
         [GRUENETAL1995C] or ulydcode.tab.
 
         Note: If IT=0, then VIT is invalid. This differs from
               Gruen et al. (1995c) [GRUENETAL1995C].
 
      Determining VET:
 
         If EA > 16 and ET > 12, then fix ET=14.
         Else, if EA > 16 and ET =< 12, then add 2 to the corresponding
            value of ET.
         VET is then found in Table 5b of Gruen et al. (1995c)
         [GRUENETAL1995C] or ulydcode.tab.
 
         Note: If ET=0, then VET is invalid. This differs from
               Gruen et al. (1995c) [GRUENETAL1995C].
 
      If IA=49, or IA>=60, or IA<3, then IT is not valid, and only VET
      is used to determine impact speed.
 
      If EA=15, or EA>=60, or EA<5, then ET is not valid, and only VIT
      is used to determine impact speed.
 
      If IT is invalid and 6 4*VET, then
 
          VEF=(VIT/VET-4.)/31.*(1.6*sqrt(35.)-1.6)+1.6
 
      If VET > 4*VIT, then
 
          VEF=(VET/VIT-4.)/31.*(1.6*sqrt(35.)-1.6)+1.6
 
      (private communication to M. Sykes from M. Baguhl, Mar  6 03:57
      MST 1996).
 
      If the ratio of both speeds exceeds 4, then the uncertainty can
      increase to about 10 in the calibrated speed range. In any case, a
      speed value with an uncertainty factor VEF>6 should be ignored.
 
    Data Reduction - Impactor Mass
    ------------------------------
      Once a particle's impact speed (V) has been determined, the charge
      to mass ratio can be determined from calibration measurements
      (Figure 3, Gruen et al. (1995c) [GRUENETAL1995C]; ulydcalb.tab).
      The charge to mass ratio for a given impact speed (V) is
      determined by linear interpolation of the calibration table
      (ulydcalb.tab) on a double logarithmic scale, yielding a separate
      value for the ion grid measurement (QIM) and and electron grid
      measurement (QEM).
 
      From these values and the respective impact charges (QI and QE)
      corresponding to IA and EA, respectively (Table 4, Gruen et al.
      (1995c) [GRUENETAL1995C]; ulydcalb.tab), mass values (MQI=QI/QIM
      and MQE=QE/QEM) are determined corresponding to the ion and
      electron grid measurements. When both MQI and MQE are valid, the
      impact particle mass, M, is the geometric mean of these two
      values, or the value corresponding to the valid measurement if the
      other is invalid. If there is no valid impact speed, then there is
      no valid impactor mass.
 
      Note: when V is invalid, M is invalid.
 
      Note: when IA=0, QI is invalid and MQI is invalid.
 
      Note: when EA=0, QE is invalid and MQE is invalid.
 
    Data Reduction - Impactor Mass Error Factor
    ------------------------------------------
      The upper and lower estimate of impactor speed is obtained by
      multiplying and dividing, respectively, the mean particle speed by
      the mass error factor, MEF. If the speed is well determined
      (VEF=1.6) then the mass value can be determined with an
      uncertainty factor MEF=6. Larger speed uncertainties can result in
      mass uncertainty factors greater than 100.
 
      The mass error is calculated from the speed error, keeping in mind
      that mass detection threshold is proportional to speed to the
      3.5th power.  In addition, there is an error factor of 2 from the
      amplitude determination. Added together (logarithmically) these
      yield
 
      MEF=10**(sqrt((3.5*log(VEF))**2+(log(2.))**2))
 
      (Private communication to M. Sykes from M. Baguhl, Mar  6 03:57
      MST 1996.  This differs from the exponent of 3.4 given in Gruen et
      al. (1995a) [GRUENETAL1995A])
 
 
  Coordinate System
  =================
    The coordinates of the spacecraft are given in heliocentric ecliptic
    latitude and longitude (equinox 1950.0), where the pointing
    direction of the sensor is given in spacecraft centered ecliptic
    latitude and longitude (equinox 1950.0).
 
 
  Instrument Status
  =================
    In a private communication to M. Sykes (23 Dec 12:59 MET 1998), H.
    Krueger reported the following:
 
         GRU off         GRU on      GRU configuration complete
 
       91-165 15:04   91-169 16:18       91-169 17:00
       93-045 06:53   93-045 14:23       93-045 22:50
 
    The information found in Tables 2 in Gruen et al. (1995a)
    [GRUENETAL1995A] and Table 1 in Krueger et al. (1999a)
    [KRUEGERETAL1999A] have been modified to correspond to the above.

Confidence Level Overview
  =========================
    Impact times
    ------------
      The impact times are recorded with an accuracy of 2 seconds (Gruen
      et al., 1995c) [GRUENETAL1995C], corresponding to a transmission
      rate above 256 bits per second. In a private communication to M.
      Sykes (Nov 12 08:16 MST 1998), H. Krueger explained that 'for
      longer readout intervals the accuracy is less because the dust
      instrument clock gets reset between two readouts and the time
      information is lost. For example with 128 bps the accuracy is
      896sec, with 64 bps, it is 1792 sec, and so on... . So far, a one
      minute accuracy was sufficient for the Ulysses data.'
 
    Sector
    ------
      In a private communication to M. Sykes (Nov 17 02:25 MST 1998), H.
      Krueger stated that when the ROTATION ANGLE is invalid, SECTOR is
      also invalid. In the data that have been published in the
      literature electronically, prior to 11/98, valid values of SEC are
      reported when ROTATION ANGLE is invalid. This has been corrected.
      See Baguhl (1993) for the relationship between ROTATION ANGLE and
      SECTOR.
 
      In V1.0 of this data set, SECTOR was reported in degrees. In V2.0
      Sector is reported as its original 8-bit word, and has a value
      between 0 and 255 (when valid). Conversion to degrees may be
      accomplished through scaling by 1.40625.
 
    Ion Channeltron Coincidence (ICC)
    ---------------------------------
      The designation ICC is used following Gruen et al. (1995c)
      [GRUENETAL1995C] and Krueger et al. (1999b) [KRUEGERETAL1999B],
      noting that in Gruen et al. (1995a and b) [GRUENETAL1995A],
      [GRUENETAL1995B]and Krueger et al. (1999a) [KRUEGERETAL1999A] the
      designation is IIC.
 
    Entrance Grid Amplitude Code (PA)
    ---------------------------------
      In the data that have been published in the literature and
      electronically, prior to 11/98, there are values of PA which
      exceed 47. In a private communication to M. Sykes (Mar  6 03:57
      MST 1996), Michael Baguhl and Rainer Riemann stated:
 
          'Values of PA greater 47 are caused by a bit flip (caused by a
           timing bug in the sensor electronics) of the MSB. For values
           greater 47, a value of 16 has to be subtracted.'
 
      This correction was made to all PDS DDS files created prior to
      11/98.
 
      As a consequence of subsequent uncertainty about the origin of PA
      values greater than 47, in a private communication to M. Sykes
      (Nov  6 04:07 MST 1998), H. Krueger requested that PA values
      greater than 47 be corrected to '99'. This has been done in
      releases of the DDS data through the PDS after 11/98.
 
    Electron Collector Threshold (ECP)
    ----------------------------------
      For ulydevnt.tab event #85327, ECP=2 while the nominal instrument
      setting is ECP=1. In a private communication to M. Sykes (9 Dec
      1998 13:27:41 MET), H. Krueger stated that this is probably due to
      a bit error since the instrument setting was not changed.
 
    Channeltron Voltage Level (HV)
    ------------------------------
      The nominal high voltage HV=4 (1250V) could not be used because of
      unexpected noise on the channeltron. It is assumed that the nearby
      radioactive thermal generators (RTGs) are to blame, although other
      causes cannot be excluded. During ground tests (without RTGs) no
      such noise was observed. See Gruen et al. (1995a)
      [GRUENETAL1995A].
 
    Impact speed
    ------------
       In a private communication to M. Sykes (Jul 22 03:43 MST 1995),
       M. Baguhl stated that the reason for the exclusion of the values
       IA=49,18 and 0 EA=49,31 is empirical. These values are close to
       the switching points of the amplifier ranges and therefore
       produce incorrect time measurements.  The adjustment of the times
       in amplifier range 2 was made in order to prevent illegal time
       values.
 
 
  Calibration data
  ================
    Instrumental values were extrapolated for particle masses and speeds
    outside the range of those tested, and are so marked. The accuracy
    of these numbers is unknown. For an explication of the experiments
    and data used to generate the calibration file, see Goller (1988)
    [GOLLER1988].
 
    Mission status data
    -------------------
      Noise impacts 104 and 105 report instrument settings at variance
      with that commanded at that time.
                                        -----
 
      In a private communication to M. Sykes (9 Dec 1998 13:27:41 MET),
      H. Krueger stated that values of HV=1 should be HV=2 for mission
      events on 91-037 and 91-169. The incorrect values were published
      in Gruen et al. (1995a) [GRUENETAL1995A].
                                        -----
 
      In a private communication to M. Sykes (23 Dec 1998 12:59:18 MET),
      H. Krueger stated that instrument configuration reported for
      91-330 16:00 Gruen et al. (1995a) [GRUENETAL1995A], Table 2,
      occurred at 91-326 10:14.
 
      In the same message, Krueger corrected additional entries in Gruen
      et al. (1995a) [GRUENETAL1995A], Table 2.:
 
      Old entries:                         New entries:
 
      92-038 18:18  SSEN= 1,0,0,1          92-038 18:56  SSEN= 1, 0, 1, 1
      92-038 19:18                         92-038 19:55
      92-038 20:18                         92-038 20:55
      92-040 02:21                         92-040 02:59
      92-040 03:21                         92-040 03:59
 
                                        -----
 
      The SSEN and HV values for ulydevnt.tab events within a 4 hour
      period from the beginning of a 'GRU noise test' is often
      inconsistent with the procedure reported in the Krueger et al.
      (1999a) [KRUEGERETAL1999A], which may be summarized as:
 
                   At one hour intervals,
 
                       (1) EVD=C,I,E
                       (2) SSEN=0,0,0,0
                       (3) EVD=C,I
                       (4) HV=4
                       (5) HV=3, SSEN=0,0,0,1 (nominal configuration)
 
      In a private communication to M. Sykes (23 Dec 1998 12:59:18 MET),
      H. Krueger stated that the above configuration sequence for the
      noise tests were those requested by the DDS team. It appears that
      the order of some of the command sequences were subsequently
      changed during some noise tests by ground control.