ULYSSES DUST DETECTION SYSTEM (Data Set Description)

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).

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.

                                                                               
       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 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 If neither IT nor ET is valid, then there is no valid impact speed.

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.

CONFIDENCE_LEVEL_NOTE

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.

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                           
                                                                               
				     

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 conmfiguration)