Data Set Overview
  =================
    This data set contains information on 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, Krueger et al., 1999a, and Krueger et al. 2009b).
 
     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.
 
    In addition, the subdirectory 'sounder' contains the on and off times of
    the URAP sounder, which is known to increase the noise rate of the dust
    instrument (Krueger et al. 2006b).  The on-off times are given in one file
    for each year of operation.  For years with no corresponding sounder
    on-off file, the sounder was off for the duration of that year.  A
    document describing the effect of the sounder sequence on the dust
    instrument is included in the document directory.
 
     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.  Full
    spacecraft ephemeris and orbit/attitude data (SPICE) are available at the
    PDS Planetary Plasma Interactions (PPI) Node, at http://ppi.pds.nasa.gov.
 
     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.
 
    In 2010 it was discovered that the julian dates provided in the files
    ulyddust.tab and ulydevnt.tab had been calculated incorrectly from the UT
    times.  The julian dates were recalculated and the data set was
    incremented from version 3.0 to version 3.1.
 
    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).
 
     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).
 
     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 occurrence 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 - 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) 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). 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) or ulydcode.tab.
 
        Note: If IT=0, then VIT is invalid. This differs from
              Gruen et al. (1995c).
 
     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) or ulydcode.tab.
 
        Note: If ET=0, then VET is invalid. This differs from
              Gruen et al. (1995c).
 
     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); 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);
    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))
 
 
    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) and Table 1 in
    Krueger et al. (1999a) have been modified to correspond to the above.
 
    On-off times and download times
    -------------------------------
 
    Data were downloaded for all times that the GRU was on.  The GRU on-off
    times are listed in the status table (ulydstat.tab).

Confidence Level Overview
  =========================
    Impact times
    ------------
 
     The impact times are recorded with an accuracy of 2 seconds (Gruen et
    al., 1995c), 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.  When SECTOR and
    ROTATION ANGLE are invalid, detector ecliptic latitude and longitude are
    also invalid and represented by a null value.
 
    In V1.0 of this data set, SECTOR was reported in degrees. In V2.0 and
    V3.0, 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) and Krueger et
    al. (1999b), noting that in Gruen et al. (1995a and b) and Krueger et al.
    (1999a) 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).
 
    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).
 
    Effect of URAP Sounder on UDDS
    ------------------------------
 
    The URAP sounder is known to increase the noise rate of the dust
    instrument (Krueger et al. 2006b).  For this reason, the on and off times
    of the URAP sounder are included in this data set in the directory
    data/sounder.  A flag has also been added to the two data files
    ulyddust.tab and ulydevnt.tab indicating whether the sounder was on or off
    for each event.  The effect of the sounder on the UDDS signal has been
    investigated by Robert McDowell and Roger Hess and the results are given
    in the document urapsoundersequencepdf.pdf in the document directory of
    this volume.
 
    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).
 
                                      -----
 
    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), Table 2, occurred at 91-326 10:14.
 
    In the same message, Krueger corrected additional entries in
    Gruen et al. (1995a), 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
 
    (SSEN is the list of the values of detection thresholds ICP, CCP, ECP,
    PCP.)
                                      -----
 
    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), 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.