PDS_VERSION_ID = PDS3
LABEL_REVISION_NOTE = "
01 Jan 1996 Creation of V1.0 by M. Sykes (SBN)
Jan 1999 Final data updates and new data deliveries (through 1996)
to PDS SBN by DDS Science Team (H. Krueger, MPI Heidelberg);
Upgrades and corrections for V2.0 by M. Sykes (SBN);
06 Aug 2002 Added terse description - B. Harris (PPI);
18 Aug 2003 Updated reference style to PDS standard format by S.Joy (PPI);
01 Feb 2004 Updated for Version 3.0 - B. Harris (PPI);"
OBJECT = DATA_SET
DATA_SET_ID = "GO-D-GDDS-5-DUST-V3.0"
OBJECT = DATA_SET_INFORMATION
DATA_SET_NAME = "GALILEO DUST DETECTION SYSTEM V3.0"
DATA_SET_COLLECTION_MEMBER_FLG = "N"
DATA_OBJECT_TYPE = TABLE
START_TIME = 1989-12-28T17:20
STOP_TIME = 2001-12-31T11:54
DATA_SET_RELEASE_DATE = 2003-08-12
PRODUCER_FULL_NAME = "MARK V. SYKES"
DETAILED_CATALOG_FLAG = "N"
ARCHIVE_STATUS = "LOCALLY ARCHIVED"
CITATION_DESC = "Krueger, H., E. Gruen, A. Grapps,
D. Bindeschadler, M. Baghul, S. Dermott, N. Divine, H. Fechtig,
B.A. Gustafson, D.P. Hamilton, M.S. Hanner, M. Horanyi, J. Kissel,
B.-A. Lindblad, D. Linkert, G. Linkert, I. Mann, J.A.M. McDonnell,
G.E. Morfill, C. Polanskey, R. Riemann, G. Schwehm, N. Siddique,
P. Staubach, R. Srama, and H.A. Zook.,
GALILEO DUST DETECTION SYSTEM V3.0. GO-D-GDDS-5-DUST-V3.0,
NASA Planetary Data System, 2003."
ABSTRACT_DESC =" Detector responses and derived
quantities from the Galileo dust detector as well as spacecraft geometry
information for reliable impacts from launch through 2001. See
Gruen et al. (Plan. Sp. Sci. 43, 953-969, 1995) and Krueger et al.
(Plan. Sp. Sci. 47, 85-106, 1999; Plan. Sp. Sci. 49, 1285-1301, 2001)
for more information."
DATA_SET_TERSE_DESC = "
This data set contains all Dust Detector data submitted by the DDS team.
All data from spacecraft launch through the Io 31 Orbit is supplied."
DATA_SET_DESC = "
Dataset Overview
================
This data set contains information on the dust environment in
interplanetary space within the inner solar system and in the Jupiter
system, within and without the Jovian magnetosphere and around the
Galilean satellites. This information is collected with a dust impact
experiment, DDS, from which may be inferred direction of motion, mass,
velocity and charge (see GO_DDS_INST.CAT). The data presented in this
dataset include instrumental readouts, inferred metadata, calibration
information and a calendar of events. Specifically:
1) galddust.tab - data received from the dust detector, the spacecraft,
and physical properties derived from the detector data for reliable
dust impacts (Gruen et al. 1995b and Krueger et al. 1999b).
2) galdevnt.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) galdcode.tab - value ranges corresponding to codes found in
galddust.tab.
4) galdcalb.tab - laboratory calibration data used to relate instrument
responses to physical properties of the impacting dust particles.
5) galdsen*.tab - the area of the dust detector exposed to particles as a
function of their velocity direction relative to the detector axis.
6) galdstat.tab - time history of Galileo 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, 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 consists of cataloging information, instrument
status, instrument readings at time of impact, and classification
information. The cataloging information includes the SEQUENCE NUMBER
(impact number), JULIAN DATE (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
galddust.tab and galdcalb.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 Galileo spacecraft is unknown, logarithmic
averages of the above values are used to infer the particle speed and
mass from the instrumental measurements. See [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 ([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 physical properties 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 in [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&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 5a of Gruen et al. (1995c) or galdcode.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 5a of Gruen et al. (1995c) or galdcode.tab.
Note: If ET=0, then VET is invalid. This differs from
Gruen et al. (1995c).
If IA=49, or IA=18, or IA<3, then IT is not valid, and only VET is used
to determine impact speed.
If EA=49, or EA=31, or EA<5, then ET is not valid, and only VIT is used
to determine impact speed.
If IT is invalid and 6<EA-IA or EA-IA<2, then there is no valid impact
speed.
If neither IT nor ET is valid, then there is no valid impact speed.
Data Reduction - Impact Speed Error Factor
==========================================
The upper and lower estimates of impactor speed are obtained by
multiplying and dividing, respectively, the mean particle speed by the
velocity error factor, VEF. If only one speed is measured, and is from
the electron detector, the minimum uncertainty is VEF=2. If only one
speed is measured, and is from the ion detector, the minimum uncertainty
is VEF=1.9. It is assumed that minimum error of 1.6 is achieved if both
individual speeds agree to within a factor of 4. This error corresponds
to the logarithmic mean of the minimum errors in the two cases when only
a single speed is valid.
Since these are all 1-sigma errors, it may happen that VIT or VET fall
outside the error bar given for the mean impact speed, V. In order to
avoid this, the error factor is 'stretched' to contain the values:
If VIT > 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,
[GRUENETAL1995C]); galdcalb.tab). The charge to mass ratio for a given
impact speed (V) is determined by linear interpolation of the calibration
table (galdcalb.tab) on a double logarithmic scale, yielding a separate
value for the ion grid measurement (QIM) 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);
galdcalb.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 [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).
"
CONFIDENCE_LEVEL_NOTE = "
Impact times
============
The impact times during the Cruise phase of the mission were recorded
with an accuracy of 1.1 hours. After June 25, 1990, inclusive, the
accuracy was 4.3 hours (this value has been set in order to bridge gaps
in the data transmission as long as one month) ([GRUENETAL1995B];
[KRUEGERETAL1999B]). There were also periods in which more frequent
memory reads resulted in a time resolution of 2/3 seconds.
Time Error Value (TEV)
======================
Prior to 1993, data were not released with individual TEV values. Time
resolutions given by [GRUENETAL1995B] and applied retrospectively
to data prior to 1993 yields the following distribution of TEV across
those impact and noise events:
galddust galdevnt
IMPACT SEQUENCE NUMBER | TEV EVENT SEQUENCE NUMBER | TEV
------------------------------ -----------------------------
001-099 | 66 0001-0607 | 0
100-138 | 259 0608-1099 | 66
139-147 | 0 1100-1218 | 259
148-344 | 259 1219-1851 | 0
345-352 | 0 1852-3244 | 259
353-359 | 259 3245-4627 | 0
4628-5446 | 259
These values were confirmed in a private communication to M. Sykes
(Dec 9 05:06 MST 1998) by H. Krueger.
Based on information in [KRUEGERETAL1999B], TEV values were changed
for the following events to the values below:
IMPACT SEQUENCE NUMBER | TEV EVENT SEQUENCE NUMBER | TEV
------------------------------ -----------------------------
2762-2767 | 70 8991-8996 | 70
2768-2837 | 2 8997-9069 | 2
2848-2851 | 33 9080-9083 | 33
2852-2869 | 2 9084-9101 | 2
NOTE: In the current (1998) PDS release, the Galileo DDS Status File
(galdstat.tab) extends only through the end of 1995. Thus, Time
Error Factors for 1996 and 1997 impact and event data cannot be checked
against the sampling mode of the DDS until the release of the updated
status file.
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 [GRUENETAL1995B] and
[KRUEGERETAL1999B], noting that in [GRUENETAL1995A] and [GRUENETAL1995C],
and [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 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.
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 [GRUENETAL1995B].
Spacecraft Earth distance
=========================
The value for the same impact event in galddust.tab and galdevnt.tab
is different, but less than 7500 km.
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 and EA=15 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. An explication of the experiments and data
used to generate the calibration may be found in [GOLLER1988].
"
END_OBJECT = DATA_SET_INFORMATION
OBJECT = DATA_SET_TARGET
TARGET_NAME = "DUST"
END_OBJECT = DATA_SET_TARGET
OBJECT = DATA_SET_HOST
INSTRUMENT_HOST_ID = GO
INSTRUMENT_ID = GDDS
END_OBJECT = DATA_SET_HOST
OBJECT = DATA_SET_REFERENCE_INFORMATION
REFERENCE_KEY_ID = "GOLLER1988"
END_OBJECT = DATA_SET_REFERENCE_INFORMATION
OBJECT = DATA_SET_REFERENCE_INFORMATION
REFERENCE_KEY_ID = "GOLLER&GRUEN1989"
END_OBJECT = DATA_SET_REFERENCE_INFORMATION
OBJECT = DATA_SET_REFERENCE_INFORMATION
REFERENCE_KEY_ID = "GRUENETAL1995A"
END_OBJECT = DATA_SET_REFERENCE_INFORMATION
OBJECT = DATA_SET_REFERENCE_INFORMATION
REFERENCE_KEY_ID = "GRUENETAL1995B"
END_OBJECT = DATA_SET_REFERENCE_INFORMATION
OBJECT = DATA_SET_REFERENCE_INFORMATION
REFERENCE_KEY_ID = "GRUENETAL1995C"
END_OBJECT = DATA_SET_REFERENCE_INFORMATION
OBJECT = DATA_SET_REFERENCE_INFORMATION
REFERENCE_KEY_ID = "KRUEGERETAL1999A"
END_OBJECT = DATA_SET_REFERENCE_INFORMATION
OBJECT = DATA_SET_REFERENCE_INFORMATION
REFERENCE_KEY_ID = "KRUEGERETAL1999B"
END_OBJECT = DATA_SET_REFERENCE_INFORMATION
END_OBJECT = DATA_SET
END