ULYDINST.CAT REVISION HISTORY ---------------------------------------------------------------------------- ---------------------------------------------------------------------------- CHANGES BELOW THIS LINE REFER TO ULYDINST.CAT, REVIEWED 3/6/96 ---------------------------------------------------------------------------- ---------------------------------------------------------------------------- 11/06/98 Added: LABEL_REVISION_NOTE = " 01 Jan 1996 Creation of V1.0 by M. Sykes (SBN) 06 Mar 1996 PDS SBN Peer Review (Tucson, Arizona) 31 Dec 1998 Upgrades and corrections for V2.0 by M. Sykes (SBN) 26 Feb 1999 PDS SBN Peer Review (Heidelberg, Germany)" ---------------------------------------------------------------------------- 12/06/98 INSTRUMENT_HOST_ID = UL -> ULY ---------------------------------------------------------------------------- 12/06/98 INSTRUMENT_NAME = "ULYSSES DUST DETECTOR" -> "ULYSSES DUST DETECTION SYSTEM" ---------------------------------------------------------------------------- 12/06/98 INSTRUMENT_TYPE = "DUST DETECTOR" -> "DUST IMPACT DETECTOR" ---------------------------------------------------------------------------- 12/06/98 In Instrument Overview, "Negative charges (mainly electrons) are collected at the target, the positive charges..." is changed to "Negative charges (mainly electrons) are collected at the target. The positive charges..." and "See [GRUNETAL1992A]..." is changed to "See Gruen et al. (1992b)..." ---------------------------------------------------------------------------- 12/06/98 In Science Objectives Summary, "- To classify particle orbits into bound orbits around the Sun or hyperbolic orbits leaving or entering the solar system. To study the distributions of orbital elements (semi-major axis, eccentricity, inclination ) of particles in bound orbits." is changed to "- To classify particle orbits into bound orbits around the Sun or hyperbolic orbits leaving or entering the solar system. - To study the distributions of orbital elements (semi-major axis, eccentricity, inclination ) of particles in bound orbits." and "on bound orbits" is changed to "in bound orbits" and "on hyperbolic orbits" is changed to "in hyperbolic orbits" and "transiting" is changed to "transversing" and "determine the dust production by collisions" is changed to "determine the amount of dust produced by collisions" and "establish the relationship of these charges with properties" is changed to "establish the relationship of these charges to the properties" ---------------------------------------------------------------------------- 12/06/98 In Science Objectives Summary, the period at the end of each science objective is removed. ---------------------------------------------------------------------------- 12/06/98 In Instrument Measurements, "induce to" is changed to "induce in" ---------------------------------------------------------------------------- 12/06/98 In Detector Description, "induce a charge to" is changed to "induce a charge in" and ( hemisphere) is changed to (hemisphere) and "Some of the ions penetrate the ion collector, which is partly transparent (total transmission approximately 40%), are further accelerated, and hit the entrance cone of an electron multiplier (channeltron)." is changed to "Some of the ions penetrate the ion collector (which is partly transparent - total transmission approximately 40%), are further accelerated, and hit the entrance cone of an electron multiplier (channeltron)." and "A measurement cycle is initiated if either the negative charge Q_e on the hemispherical target, or the positve charge on the ion-collector Q_i, or Q_c exceeds a threshold." is changed to "A measurement cycle is initiated if either the negative charge Q_e on the hemispherical target, or the positive charge Q_i on the ion-collector, or the positive charge Q-c on the channeltron exceeds a threshold." and "... this may cause some interferences for the Q_e measurement. To avoid these interferences during high activity times ..." is changed to "... this may cause some interference for the Q_e measurement. To avoid this interference during high activity times ..." and "distinuguishing" (typo) is changed to "distinguishing" ---------------------------------------------------------------------------- 12/06/98 In Calibration Description, "See [GOLLER&GRUN1989] for more information." is changed to "See Goller and Gruen (1989) for more information." and "(see [GRUNETAL1995C] equation (1))" is changed to "(see Gruen et al., 1995a)" and "Difficulties in accelerating glass and carbon projectiles and the low acceleration rate made it impossible to do more than the tests at one angle." is changed to "Difficulties in accelerating glass and carbon projectiles and the low acceleration rate made it impossible to do tests at more than one angle." and "The particle's flight path inside the detector was obtained as 20 +/- 5 cm." is changed to "The particle's flight path inside the detector was determined to be 20 +/- 5 cm." and "Coulumb" is changed to "coulomb" and % -> percent and 10^14 -> 10**14 ---------------------------------------------------------------------------- 12/06/98 In Instrument Modes, "on-board" is changed to "aboard" ---------------------------------------------------------------------------- 03/25/99 Added: "Onboard Processing ------------------ See Gruen et al, 1992b and 1995c. First, the instrument microprocessor, which controls the experiment measurement cycle, collects the buffered data and processes the data according to its onboard program. This takes about 5 ms. The signal amplitudes and times of a single recorded event (dust impact or noise) are digitized and stored in an Experiment Data Frame (EDF) of 16 bytes (i.e. 128 bits). Supplementary information like event time and instantaneous spim position are collected from the spacecraft and added in each EDF. Dead-time caused by the measurement cycle is 5 ms. The instruments are designed to reliably operate under noisy conditions thereby allowing the reliable extraction of true dust impacts from noise events. True impacts can be detected at rates of as low as one per month. This is achieved by raising the threshold levels of all impact signals individually by telecommand which allows instrument sensitivity to be adapted to the actual noise environment on board the spacecraft. Coincidences between the signals are established which, along with the signal amplitudes, are used to classify each event. Each measured event (noise or impact) is classified according to the strength of its ion signal (IA) into one of six amplitude ranges (AR=1 to 6). Each amplitude range correspond roughly to one decade in electronic charge, Q_I. In addition, each event is categorized into one of four event classes (described by the class number CLN). The event classification scheme, which defines criteria that must be satisfied for each class, is shown: -------------------------------------------------------------------------- Parameters: | CLN=0 | CLN=1 | CLN=2 | CLN=3 -------------------------------------------------------------------------- IA | IA > 0 | IA > 0 | IA > 0 | IA > SP16 -------------| or | or |---------------------------------------- EA | EA > 0 | EA > 0 | EA > 0 | EA > SP14 -------------| or |-------------------------------------------------- CA | CA > 0 | CA > 0 | CA > 0 | CA > SP15 -------------------------------------------------------------------------- ET | | | SP03 <= ET <= SP04 | SP03 <= ET <= SP04 -------------------------------------------------------------------------- IT | | | SP01 <= IT <= SP02 | SP01 <= IT <= SP02 -------------------------------------------------------------------------- EIC | | | EIC = 0 | EIC = 0 -------------------------------------------------------------------------- ICC | | | ICC = 1 | ICC = 1 -------------------------------------------------------------------------- Noise counter| | | | of: | | | | EN | | | | EN <= SP11 IN | | | | IN <= SP09 CN | | | | CN <= SP10 -------------------------------------------------------------------------- Within each class these conditions are connected by logical 'and' except where noted. Class 0 (CLN = 0) includes all events that are not categorized in a higher class (typically noise and unusual impact events - e.g. impacts onto the sensor's internal structure other than the impact target). In classes 1 through 3, the criteria become increasingly restricted so that CLN = 3 generally represents true dust impact events only. Some of the set point values (SP01 to SP15), which can be set by ground command, are used in the classification scheme. The set points are as follows: SP01 = 1 SP02 = 15 SP03 = 1 SP04 = 15 SP09 = 2 SP10 = 8 SP11 = 8 SP14 = 0 SP15 = 0 SP16 = 0 The on board classification can be adapted to the in-flight noise environment by changing the thresholds and classification parameters (set points) or by adjusting the onboard classification program through telecommands. Detailed information on noise is mandatory in order to evaluate the reliability of impact detection for the various event categories, to minimize the effect on dead-time and to optimize memory utilization. The memory is divided into separate ranges in which various data is given priority. The A-range of instrument memory stores the six most recent EDFs - one for each amplitude range regardless of class. The E range, graphically depicted below, stores the last 8 events occurring within class 3. These events satisfy the most stringent constraints and are almost certainly true impacts. The above four classes, together with six amplitude ranges, constitute twenty-four separate categories. Each of these categories has its own 8-bit accumulator: | | Class number (CLN) |Amplitude| IA | Range | 0 1 2 3 ------------------------------------------- 0- 7 | AR = 1 | AC01 | AC11 | AC21 | AC31 8-15 | AR = 2 | AC02 | AC12 | AC22 | AC32 16-23 | AR = 3 | AC03 | AC13 | AC23 | AC33 24-32 | AR = 4 | AC04 | AC14 | AC24 | AC34 48-55 | AR = 5 | AC05 | AC15 | AC25 | AC35 56-63 | AR = 6 | AC06 | AC16 | AC26 | AC36 As long as the respective accumulator does not overflow, each event is counted even if the complete information is not received on ground. Generally, the event rate is so low (even in the low amplitude and low class ranges) that the true increment can be reliably determined. All categories and corresponding accumulators - excluding AC01, AC11 and AC02 - contain primarily impact events. Even in these latter categories, true impacts can be identified and separated from noise events if the complete data set for an event is available (Baguhl et al., 1993). The transmission of seven EDFs consitute an instrument read-out cycle (six A-range events and one of the subcommutated class 3 events as well as all 24 accumulators) which is continuously repeated. The Ulysses mission is designed to provide continuous data coverage even when data transmission to Earth is only possible during one pass of approximately 8 hours per day. Continuous coverage is achieved by storing data from the instruments at a low rate into an on-board memory which is read out at a high rate together with real-time data transmission during a pass. At a spacecraft data transmission rate of 1024 bps, one EDF is sent every 16 seconds. Lower bit rates down to 128 bps during storage or real time transmission periods are possible. Data processing on the ground ----------------------------- After receiving the partially processed data from the spacecraft, the following data processing steps are performed on the ground: (1) instrument health check (2) generation of accumulator histories (3) extraction of discrete events (4) reduction of impact data (5) generation of data products The instrument health check involves inspection of instrument house keeping data such as temperatures, voltages, currents and a check of the test pulse data. If, for example, the temperature readings are too high, the heater power level can be set accordingly. If excessive noise is detected then appropriate measures, such as changing the thresholds or channeltron high voltage by telecommand, can be taken. Occasionally, tests of different instrument modes are performed in order to probe the actual noise environment; the instrument parameters can then be adjusted accordingly. The preparation of data products is the final routine step of dust data processing. A number of separate files are produced which reflect various stages of data processing." ---------------------------------------------------------------------------- 11/06/98 In REFERENCE_KEY_IDs, "GRUNETAL1995A" is changed to "GRUENETAL1995A", "GOLLER&GRUN1989" is changed to "GOLLER&GRUEN1989", and "GRUNETAL1995C" is changed to "GRUENETAL1995C" ---------------------------------------------------------------------------- 03/25/99 Added: OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "GRUENETAL1992B" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "BAGUHLETAL1993" END_OBJECT = INSTRUMENT_REFERENCE_INFO ---------------------------------------------------------------------------- 11/06/98 All REFERENCE_DESC removed. ----------------------------------------------------------------------------