Instrument Information
IDENTIFIER urn:nasa:pds:context:instrument:go.hic::1.1
NAME HEAVY ION COUNTER
TYPE PARTICLE DETECTOR
DESCRIPTION (The following paper has been modified in format from the original andwas spell-checked after transfer to ASCII format. The format forreferences has been changed to be consistent with PDS standards.) Reprinted by permission of Kluwer Academic Publishers, ------------------------------------------------------------------------Space Science Reviews 60: 305-315, 1992.Copyright 1992 Kluwer Academic Publishers. Printed in Belgium.------------------------------------------------------------------------THE GALILEO HEAVY ELEMENT MONITOR T. L. GARRARD(1), N. GEHRELS(2), and E. C. STONE(1) 1 California Institute of Technology, Pasadena, CA 91125, U.S.A2 NASA Goddard Space Flight Center, Greenbelt, MD 20771, U.S.A. Abstract. The Heavy Ion Counter on the Galileo spacecraft will monitorenergetic heavy nuclei of the elements from C to Ni, with energies from~6 to ~200 MeV nucl^-1. The instrument will provide measurements oftrapped heavy ions in the Jovian magnetosphere, including thosehigh-energy heavy ions with the potential for affecting the operation ofthe spacecraft electronic circuitry. We describe the instrument, whichis a modified version of the Voyager CRS instrument. 1. Introduction The Heavy Ion Counter (HIC) is included on the Galileo spacecraftprimarily for the purpose of monitoring the fluxes of energetic heavyions in the inner Jovian magnetosphere and high-energy solar particlesin the outer magnetosphere in order to characterize the ionizingradiation to which electronic circuitry is most sensitive. Themeasurements performed will also be of scientific interest, since theinstrument's large geometry factors and extended energy range willprovide spectral information for ions from 6C to 28Ni with energies of~6 to > ~200 MeV nucl**-1. In this article we will concentrate on Jovianmagnetospheric science. We review here previous scientific resultsconcerning trapped high-energy heavy ions, describe anticipated newfindings with Galileo, and provide a brief instrument description. 2. Previous Results During the Voyager encounters with Jupiter, it was discovered[KRIMIGISETAL1979A], [KRIMIGISETAL1979B], [VOGTETAL1979A],[VOGTETAL1979B] that a major component of the trapped radiation in theinner Jovian magnetosphere is energetic heavy ions. The dominant heavyspecies inside ~ 10 R[J] in the MeV nucl**-1 energy range were found tobe oxygen and sulfur, with sodium also present. The abundances in theinner magnetosphere indicate that the source of the ions is the surfaceor atmosphere of Io. The phase space density of the energetic oxygen and sulfur ions haspositive radial gradient (i.e., increasing outward) in the innermagnetosphere [GEHRELSETAL1981], implying that the diffusive flow atthese energies is inward. On the other hand, the density of the oxygen-and sulfur-rich plasma in the inner magnetosphere is highest at the Ioplasma torus and decreases outward [SISCOEETAL1981]. Barbosa et al.[BARBOSAETAL1984] have proposed that charge exchange in the plasma torusproduces fast neutrals which escape to the outer magnetosphere where ~0.2% are re-ionized by solar ultraviolet or electron impact andrecaptured Some of the newly created ions are subsequently energized bystochastic acceleration caused by magneto- hydrodynamic waves, producingions with large magnetic moments that adiabatically diffuse inward,some attaining energies in excess of 30 MeV nucl**-1 in the innermagnetosphere. As the energetic ions flow inward, they are lost from themagnetosphere, presumably by pitch-angle scattering of themirroring particles into the loss cone (see, e.g., [THORNE1982]). Thestrength of this loss mechanism determines the rate at which the heavyions precipitate into the Jovian atmosphere, exciting ultraviolet andX-ray auroral emissions. At the time of the Voyager encounter in March1979, it appeared losses due to pitch-angle scattering were occurring atnearly the maximum rate, resulting in the precipitation of ~ 10**24 ionss**-1 above ~70 MeV nucl**-1 G**-1, with an extrapolation down to 10 MeVnucl**-1 G**-1 suggesting the possibility of a loss rate of ~10**26 ionss**-1 and an auroral power of ~10**13 W [GEHRELS&STONE1983]. Majorlosses are occurring in the magnetic moment (energy) range appropriateto HIC where the total inward flow rate of oxygen ions with magneticmoments greater than several thresholds is given as a function of radialdistance (L) from Jupiter. The number of inflowing ions first decreasesinside 15 R[J] and falls off sharply inside 10 R[J]. Only a smallfraction of the trapped particles survive to produce the trappedradiation at 5 R[J]. As a result, changes in the rate of pitch-anglescattering can result in significant changes in the flux of particlesreaching 5 R[J]. It is therefore important to better characterize notonly the flux at 5 R[J], but also the nature and any long-termvariability in the loss mechanism operative outside of 5 R[J]. 3. Anticipated New Results The HIC instrument should provide new information on the spectra ofheavy ions at higher energies than previously possible. Fluxes at theseenergies are based on extrapolations of spectra measured at lowerenergies and as a result are very uncertain. Measurements with the HIC instrument will significantly reduce theuncertainty in the high-energy fluxes. The energy of a 3070 MeV nucl**-1G oxygen ion is within the HIC energy range into 5 R[J]. The geometryfactor for E > 20 MeV nucl**-1 oxygen ions (inside 8.5 R[J] for 3070MeV nucl**-1 G**-1 ions) is ~4 cm**2 sr compared with 0.88 cm**2 sr forthe Voyager CRS instrument. More importantly, the livetime for measuring oxygen and sulfur ions with E >= 50 MeV nucl**-1 will be essentially100% because a polling priority system (see instrument descriptionsection) will discriminate against the large fluxes of protons andelectrons that dominate the CRS analysis rate. As a result, a flux ofonly 10**-5 cm**-2 s**-1 sr**-1 should produce 1 analyzed event in10 hours, the time that Galileo is inside 7 R[J]. The oxygen ions which have >= 100 MeV nucl**-1 at 5 R[J] have >= 10MeV nucl**-1 at 10 R[J]. Thus, as Galileo makes repeated orbitalpasses in the vicinity of Europa, it will be possible to monitor thefluxes of particles with M >= 3000 MeV nucl**-1 G**-1 throughout themission. Such long term information is especially important, since thereare a number of reasons why the fluxes might vary. For example, the fluxof high-energy ions could be measurably affected by changes in thedensity of the Io plasma torus which is the source of the escapingneutral atoms and by changes in the solar ultraviolet which re-ionizesthe neutrals in the outer magnetosphere. The HIC instrument will measureany time dependence of the energetic heavy ion fluxes and permitcorrelative studies of any associated changes in auroral emissions ordiffusion processes. The fluxes at 5 R[J] depend strongly on the loss processesoccurring inside of ~15 R[J]. It is postulated that the losses are dueto pitch-angle scattering of the mirroring particles into the loss cone,and that the rate of scattering is close to the strong pitch-anglediffusion limit in the inner magnetosphere ([THORNE1982],[GEHRELS&STONE1983]). At this limit there is sufficient pitch-anglescattering to refill the loss cone as rapidly as particle precipitationempties it, resulting in a nearly isotropic pitch-angle distribution.Since the HIC detectors will view nearly perpendicular to the spacecraftspin axis, essentially complete coverage of the pitch-angle distributionwill be possible. Investigation of any time dependence of the lossprocess will also be possible as Galileo repeatedly passes through theradial range between 15 and 10 R[J] where the radial profiles indicatethat significant losses occur. 4. Instrument Description The Galileo Heavy Ion Counter (HIC) consists of two solid-statedetector telescopes called Low Energy Telescopes or LETs. Use ofthese two telescopes over three energy intervals provides the geometryfactor and energy range necessary to determine the fluxes of the heavy,penetrating radiation to which solid state memories are most sensitive.Heavy collimation and high discrimination thresholds on all detectorsprovide the necessary immunity to accidental coincidences from the largeproton background. Three-parameter analysis provides additionalrejection of background. Two separate telescopes are included in order to cover a wideenergy range while minimizing pulse pile-up through the optimumselection of detector and window thicknesses. The LET E is optimized forthe detection of nuclei with energies as high as 200 MeV nucl^-1,requiring thicker detectors. Thick windows protect this system fromlow-energy proton pile-up, but also exclude lower energy oxygen andsulfur nuclei. The second telescope, LET B, has a substantially thinnerwindow so that it can detect lower energy nuclei (down to ~ 6 MeVnucl^-1), especially in the outer magnetosphere. The properties of thetwo telescopes are indicated in Table I and discussed below. TABLE I Nominal LET parameters------------------------------------------------------------------------Detector Radius Thickness Threshold (cm) (micro-meter) (MeV) ------------------------------------------------------------------------LB1 0.95 32.1 0.3LB2 0.95 29.6 0.4LB3 1.13 421 3.7LB4 1.13 440 2.0LE1 0.95 30.4 9.3(1.4)**aLE2 0.95 33.4 2.0(0.3)**aLE3 1.13 463 25(5.0)**aLE4,5 1.66 ~2000 117(23)**a------------------------------------------------------------------------**a High gain. In the LETB telescope ions which penetrate LB1 and LB2 and stop inthe thicker LB3 detector are analyzed. Detector LB4 is used inanti-coincidence. (If desired, the command system can be used to allowanalysis for ions which penetrate LB1 and stop in LB2, or for ions whichstop in LB1 . Also detector LB4 can be turned off.) Lighter nuclei(especially hydrogen and helium) are rejected by 'slant' discriminationwith a weighted sum of the signals from the front three detectors, SLB = LB1 + 0.42 LB2 + 0.2 LB3 required to be above about 9.6 MeV. The thin window (25 micro-meter Kapton) serves for thermal controland for protection from sunlight. All detectors are surface- barriertype. An important feature is the use of keyhole detectors for LB1 andLB2, which define the event geometry. The active area of these detectors excludes the nonuniform edge of the silicon wafer through the use ofkeyhole- shaped masks during the deposition of the Au and Al contacts. This telescope is an improved version of the Voyager CRS LETs(Stone et al., 1977) which have demonstrated charge (Z) resolutionof 0.1 charge units at oxygen under solar flare conditions (Cook et al.,1980) and 0.2 charge units at ~ 5 R[J], Voyager 1's deepest penetrationof the Jovian magnetosphere [GEHRELS1982]. Additional collimation andthe thicker window decrease the HIC LET's response to background protonsin the Jovian magneto- sphere. The flux of protons in detector L1, forexample, should be reduced by at least a factor of 10 from that observedon Voyager 1. In order to measure the flux of heavy nuclei at higher energies,LE4 and LE5 are each 2000-micro-meter lithium-drifted detectors. Thefront detectors, LE1, LE2, and LE3, are identical to their LET Bcounterparts, providing spectral continuity and overlap. The collimatorhousing is relatively thick to provide background immunity and has alarge opening angle to provide a large geometrical factor. The windowsare 76 micro-meter Kapton and 254 micro-meter Al. As in LET B, lowcharge (low Z) events are recognized and rejected by a slantdiscriminator, SB = LE1 + 0.5 LE2 + 0.1 LE3 + 0.04(LE4 + LE5), where SB must exceed 9.6 MeV to allow analysis. For intermediate energies, a narrow-angle geometry is defined byLE1 and LE2 for particles stopping in either LE2 or LE3. For thehighest energies, where the fluxes are exceedingly small, measurementsare made with the wide- angle geometry defined by LE2, LE3, LE4, and thecollimator. LE1 is not required but its discriminator is recorded as atag bit. LE5 distinguishes stopping and penetrating events. The maximumenergy observed is determined by the LE2 discriminator threshold. Thismaximum is ~185 MeV nucl**-1 for oxygen as noted in Table II. To allowdetection of penetrating galactic cosmic-ray nuclei at higher energiesin the outer magnetosphere, the LET E pre-amplifier gains can beincreased by a factor of 5 to 7 by command. With the exception of spacecraft interface circuitry, all of theelectronics were originally part of the Proof Test Model of the VoyagerCosmic-Ray Science Instrument (CRS), and additional detail may be foundin Stone et al. [STONEETAL1977B] and Stilwell et al. [STILWELLETAL1979B].With the adjustment of amplifier gains and discriminator thresholds andthe incorporation of thicker detectors, collimators, and windows, ithas been possible to develop an instrument which is optimized for themeasurement of high-energy heavy ions trapped in the Jovianmagnetosphere. Minor modifications to the logic allow the instrumentto recognize events of the various types mentioned above, which aresummarized in Table II. Event data are stored in buffers which are read according to apolling scheme which prevents domination of the telemetry by any onetype of event. The buffer polling logic cycles through the five bufferslisted in Table II, reading out one each minor frame (2/3 s) andstepping to the next non-zero buffer on the subsequent minor frame. If aparticular type of event occurs less than 0.3 times per second (i.e., israre) then all of that type will be transmitted regardless of activityin other event types. If a particular type of event occurs more oftenthan 0.3 times per second, it will be readout at least 0.3 times persecond and more of ten if the other event buffers are empty. Telemetry of counting rates and pulse height analyzed events israpid compared to the nominal 3 rpm spin rate of the spacecraft; thuspitch-angle distributions of the trapped radiation can be measured.Both telescopes have their axes oriented near the spin plane for thispurpose. The time resolution of the HIC is in the range from 2/3 to 2 s,implying an angular resolution in the range from 12 deg. to 36 deg.,which is to be compared to the telescope opening angles of 25 deg. innarrow geometry mode and 46 deg. in wide geometry mode. Many of the functions of the coincidence logic and thebuffering/readout scheme can be modified by command to optimize theinstrument for changing environments or partial failures. As notedabove, commands can also be used to change gain on the LET Epre-amplifiers. TABLE II Analysis modes------------------------------------------------------------Name Requirement Geometry Z range factor (cm^2 sr)------------------------------------------------------------ ___LETB LB1.LB2.LB3.LB4 0.44 C to Ni ___DUBL LE1.LE2.LE3 0.44 C to Fe ___TRPL LE1.LE2.LE3.LE4 0.44 C to Ni ___WDSTP LE2.LE3.LE4.LE5 4.0 C to Fe WDPEN LE2.LE3.LE4.LE5 4.0 C to Fe WDPEN LE2.LE3.LE4.LE5.HG 4.0 Li to O(High gain)------------------------------------------------------------ TABLE II cont.-----------------------------------------------------------------Name Oxygen Sulfur Signals Signals energy range energy range telemetered (MeV nucl^-1) (MeV nucl^-1)----------------------------------------------------------------- LETB 6 to 18 9 to 22 LB1,LB2,LB3 DUBL 16 to 17 24 to 25 LE1,LE2 TRPL 17 to 27 25 to 38 LE1,LE2,LE3 WDSTP 26 to 46 37 to 70 LE2,LE3,LE4 WDPEN 49 to ~185 >= 70 LE2,LE3,LE4+LE5 WDPEN 49 to ~500 - LE2,LE3,LE4+LE5(High gain)----------------------------------------------------------------- Acknowledgements A special acknowledgement is due A. W. Schardt, whose untimely deathprevented his co-authorship of this paper. This project was madepossible by the development of the CRS instrument under the leadershipof R. E. Vogt. W. E. Althouse (Caltech) and D. E. Stilwell (GSFC) haveprovided invaluable engineering and programmatic support and advice. Wealso are pleased to acknowledge the contributions of A. C. Cummings atCaltech; M. Beasley, W. D. Davis, J. H. Trainor, and H. Trexel at GSFC:and D. R. Johnson at JPL. This work was supported by a number of NASAcontracts and grants. References Barbosa, D. D., Eviatar, A., and Siscoe, G. L.: 1984, J. Geophys. Res.89, 3789. Cook, W. R., Stone, E. C., and Vogt, R. E.: 1980, Astrophys. J. 238,L97. Gehrels, N.: 1982, 'Energetic Oxygen and Sulfur Ions in the JovianMagnetosphere', CIT Ph.D. Thesis. Gehrels, N. and Stone, E. C.: 1983, J. Geophys. Res. 88, 5537, Gehrels, N., Stone, E. C., and Trainor, J. H.: 1981, J. Geophys. Res.86, 8906. Krimigis, S. M., Armstrong, T. P., Axford, W. I., Bostrom, C. O., Fan,C. Y., Gloeckler, G., Lanzerotti, L. J., Keath, E. P., Zwickl, R. D.,Carbary, J. F., and Hamilton, D. C.: 1979a, Science 204, 998. Krimigis, S. M., Armstrong, T. P., Axford, W. I., Bostrom, C. O., Fan,C. Y., Gloeckler, G., Lanzerotti, L. J., Keath, E. P., Zwickl, R. D.,Carbary, J. F., and Hamilton, D. C.: 1979b, Science 206, 977. Siscoe, G. L., Eviatar, A., Thorne, R. M., Richardson, J. D., Bagenal,F., and Sullivan, J. D.: 1981, J. Geophys. Res. 86, 8480. Stilwell, D. E., Davis, W. D., Joyce, R. M., McDonald, F. B., Trainor,J. H., Althouse, W. E., Cummings, A. C., Garrard, T. L., Stone, E. C.,and Vogt, R. E.: 1979, IEEE Trans. Nuc. Sci. NS-26, 513. Stone, E.C., Vogt, R.E., McDonald, F.B., Teegarden, B.J., Trainor, J.H.,Jokipii, J.R., and Webber, W. R.: 1977, Space Sci. Rev. 21, 355. Thorne, R. M.: 1982, J. Geophys. Res. 87, 8105. Vogt, R. E., Cook, W. R., Cummings, A. C., Garrard, T. L., Gehrels, N.,Stone, E. C., Trainor, J. H., Schardt, A. W., Conlon, T., Lal, N., andMcDonald, F. B.: 1979a, Science 204, 1003. Vogt, R. E., Cummings, A. C., Garrard, T. L., Gehrels, N., Stone, E. C.,Trainor, J. H., Schardt, A. W., Conlon, T. F., and McDonald, F. B.:1979b, Science 206, 984.---------------------------------------------End of Space Science Reviews Article Changes to the instrument in Phase 2A--------------------------------------------- In Phase 2, HIC realtime data are collected by a CDS program for aperiod of time that depends on readout rate: 50 RIM (at 1 bps), 25 RIM(2 bps), or 10 RIM (5 bps), where 1 RIM = 91 minor frames and 1 mf = 2/3sec. At the end of the collection period, another portion of theprogram compresses the data into their output format. The output (before packet headers are added) consists of up to 375 bytesof binary data in two blocks. A dump of simulated data is attached asAppendix A. For details about packet headers, see MOS-GLL-3-310[ECR35559], Flight Software Requirements, Appendix, p. 5-47; and625-610: SIS 2244-05 P2, Instrument Packet File [SIS2244-05]. Thepresent description is of the HIC data only. The first block, of 143 bytes, contains rate data arranged in apredetermined format. There are 57 rate ''words'' of 2 1/2 bytes each,and 1/2 byte of filler (0x0) at block's end. The first byte of eachrate word is a counter of the number of times that rate was read out.The rest of the word (1 1/2 bytes) gives the sum of the rate counts fromthose readouts, in log-compressed form. The compression scheme is thesame as that in the SRD. Several types of rate are subdivided, i.e., have more than one rate wordin the output block. Each successive rate word within a type representsdata taken in a later portion of the collection period. The 57 ratewords appear in the following order: 10 words of DUBL (''A'' rates, for ten successive time divisions) 6 words of TRPL (''B'' rates, for six successive time divisions) 6 words of WDSTP (''C'' rates, for six successive time divisions) 6 words of WDPEN (''D'' rates, for six successive time divisions)10 words of LETB (''E'' rates, for ten successive time divisions) 6 words of LE1 (''G'' rates, for six successive time divisions) 1 word of LE5 (''F'' rates, MUXN=10) 1 word of LE3 (''F'' rates, MUXN=11) 1 word of LE4 (''F'' rates, MUXN=12) 1 word of LE2 (''F'' rates, MUXN=13) 6 words of LB1 (''H'' rates, MUXN=10, for six successive time divisions) 1 word of LB2 (''H'' rates, MUXN=11) 1 word of LB3 (''H'' rates, MUXN=12) 1 word of LB4 (''H'' rates, MUXN=13) (Slant data, from ''F'' and ''H'' rates with MUXN<10 or MUXN>13, arediscarded.) Thus for the longest collection period (50 RIM), we can distinguish~5-min changes in the DUBL and LET B rates and ~9-min changes in thefive rates that have six divisions each. At higher data rates(collection periods of 25 RIM or 10 RIM), the time resolution isproportionally better. The second block, of up to 232 bytes, contains event data arranged in aflexible format. The contents of this block can vary considerablydepending on the number and kind of events that were observed. Eventshave no time divisions. The events are divided into fourteen types and kept, during thecollection period, in fourteen different arrays. Each collection arraycan hold up to 20 or 32 events, depending on type. The array numbersdetermine the order in which events are output. Event types aredistinguished in the output block not by absolute position (as are therates) but by header words. Each string of event information begins with a one-byte header. Thefirst half- byte contains the event array number, i.e., the type. Thesecond half-byte is a counter that gives the number of events in thestring for that type, less one; i.e., counter = counts - 1. If noevents were observed for a given type, no string is output. Each event type has a characteristic word length, so the header alsogives the length of the event string. Each type also has acharacteristic meaning assigned to each bit in its word. For details,see Appendix B. After all the output events comes an event counter array, which consistsof a leading 'f' followed by six numbers of 1 1/2 bytes each. Theseshow the total number of events counted in the collection period foreach of six kinds of event: DUBL, TRPL, WDSTP, WDPEN, LETB, and null(tag word = 0). The fourteen event types are distributed among the five non-null kindsas follows: DUBL, type 9; TRPL, types 5 and 12; WDSTP, types 1, 6,13, and 14; WDPEN, types 7 and 8; and LETB, types 2, 3, 4, 10, and 11.Counts in this array include ''caution'' events, those whose caution bitin the tag word is set. When rates are very low, all observed events are output and the eventblock is very short. When rates are very high, details of some eventswill be lost because of the limited size of the output block: 232 byteswill hold only about 60 events plus the counters. If the event arrays are quite full, the program outputs sixteen eventsfrom each type, starting with number one, until it has no more room.For this situation, only events of types 1-5 will be output in detail;the rest will be lost, as in the Appendix A dump. Since the programoutputs the first sixteen events of each type, events from the beginningof the collection period are favored ever more heavily as rates climb. ------------------------------------------------------------------------Appendix A: hex dump of output block for sparse events (event blockshort) ------------------------------------------------------------------------ Bar = first rate counter of each series, or event type's header. x = filler nybble (always 0x0) octal data*address __0000000 8880 8988 1897 8179 8818 9881 8978 1798 8189 8818 __0000024 9781 7988 18ed 7edf d7fd fd7f dfd7 fdfd 7fdf c7fc __ __0000050 ed73 1fd7 3dfd 73df d73d fd73 dfc7 3ded 76df d77d __0000074 fd77 dfd7 7dfd 77df c77c 8872 a977 3c98 73e9 873e __0000120 9773 c987 3e98 73e9 773c 9873 e987 3eed 6b1f d6bd __ __ __ ___0000144 fd6b dfd6 bdfd 6bdf c6bd 5e76 b5e6 815d 68b5 d697 __ __ ___0000170 0f85 20f8 5210 8601 0860 1086 0108 605e 6b05 d6ba __ x__ __0000214 5d6c 5012 ab9b 9c65 ab9b 9c65 ab9b 9c65 525c 66d5 __0000240 4e5c 66d5 4e5c 66d5 4e62 9cfc f652 9cfc f652 9cfc __ x__ x0000264 f652 72fc a9af ca9a fca9 a082 bcab 5bca b5bc ab50 __ __0000310 924c 24c2 f0fb 794c 24c2 f0fb 794c 24c2 f0fb 79c2 __0000334 3185 a89d 3185 a89d 3185 a89d d217 2670 ca17 2670 __ _0000360 ca17 2670 cae2 19c3 d8a5 19c3 d8a5 19c3 d8a5 f003 x0000404 0060 0c00 6001 17b0 * From Octal Address 0000 to 0216 rate data are provided. Higher addresses contain event data. -------------------------------------Appendix B: event construction------------------------------------- The table below gives details of how each event type is compressed intoits word. The tag word is discarded for all types but #9 since thearray number gives much of the relevant information. The ''maximumnumber of events'' is the highest number that the program will put intothat collection array. A ''small'' event has all zeroes in the first half-byte of each of itsPHA words. Other events are ''big.'' A ''caution'' event is one whosecaution bit (last bit of tag word) is set. Consult the SRD, Table 6 (p.8), for detector correspondence to PHA wordsfor the various event types. Array Word Max # Event Type Bit sourceNo. Len. Evts. PHA3 PHA2 PHA1---------------------------------------------------------------- 1 32 32 big LE1 WDSTP top 11 top 10 top 11 2 8 32 LET B single -- -- top 8 3 20 20 big LETB double -- top 10 top 10 4 32 20 big LETB triple top 10 top 11 top 11 5 32 20 big TRPL top 10 top 11 top 11 6 32 20 big !LE1 WDSTP top 11 top 10 top 11 7 20 20 LE1 WDPEN top 10 top 10 -- 8 20 20 !LE1 WDPEN top 10 top 10 -- 9 48 32 DUBL and ''caution'' all all all plus tag word10 (a) 20 20 small LETB double -- bot 10 bot 1011 (b) 32 20 small LETB triple bot 10 bot 11 bot 1112 (c) 32 20 small TRPL bot 10 bot 11 bot 1113 (d) 32 20 small LE1 WDSTP bot 11 bot 10 bot 1114 (e) 32 20 small !LE1 WDSTP bot 11 bot 10 bot 11 Note that the following pairs of event types have the same construction(there are only 9 different schemes): 1 & 6; 4 & 5; 7 & 8; 11 & 12;13 & 14.
MODEL IDENTIFIER
NAIF INSTRUMENT IDENTIFIER
SERIAL NUMBER not applicable
REFERENCES Barbosa, D.D., A. Eviatar, and G.L. Siscoe, On the Acceleration of Energetic Ions in Jupiter's Magnetosphere, J. Geophys. Res., Vol. 89, p. 3789, 1984.

MOS-GLL-3-310, Flight Software Requirements

Garrard, T.L., N. Gehrels, E.C. Stone, The Galileo Heavy Element Monitor, Space Sci. Rev., 60, 305, 1992.

Gehrels, N., and E.C. Stone, Energetic oxygen and sulfur ions in the Jovian magnetosphere and their contribution to the auroral excitation, J. Geophys. Res., 88, 5537, 1983.

Gehrels, N., Energetic Oxygen and Sulfur Ions in the Jovian Magnetosphere, Ph.D. Thesis, California Inst. of Tech., Pasadena, 1982.

Gehrels, N., E.C. Stone, and J.H. Trainor, Energetic oxygen and sulfur in the Jovian magnetosphere, J. Geophys. Res., 86, 8906, 1981.

Krimigis, S.M., T.P. Armstrong, W.I. Axford, C.O. Bostrom, C.Y. Fan, G. Gloeckler, L.J. Lanzerotti, E.P. Keath, R.D. Zwickl, J.F. Carbary, and D.C. Hamilton, Low-Energy Charged Particle Environment at Jupiter - A First Look, Science, 204, 998, 1979.

Krimigis, S.M., T.P. Armstrong, W.I. Axford, C.O. Bostrom, C.Y. Fan, G. Gloeckler, L.J. Lanzerotti, E.P. Keath, R.D. Zwickl, J.F. Carbary, and D.C. Hamilton, Hot Plasma Environment at Jupiter: Voyager 2 Results, Science, 206, 977, 1979.

SIS 2244-05 P2, Instrument Packet File

Siscoe, G.L., A. Eviatar, R.M. Thorne, J.D. Richardson, F. Bagenal, and J.D. Sullivan, Ring Current Impoundment of the Io Plasma Torus, J. Geophys. Res., 86, 8480, 1981.

Stilwell, D.E., W.D. Davis, R.M. Joyce, F.B. McDonald, J.H. Trainor, W.E. Althouse, A.C. Cummings, T.L. Garrard, E.C. Stone, and R.E. Vogt, The Voyager Cosmic Ray Experiment, IEEE Trans. on Nuclear Science, Vol. 26, p. 513, 1979.

Stone, E.C., R.E. Vogt, F.B. McDonald, B.J. Teegarden, J.H. Trainor, J.R. Jokipii, and W.R. Webber, Cosmic ray investigation for the Voyager missions; energetic particle studies in the outer heliosphere--and beyond, Space Sci. Rev., 12, No. 3, 355-376, Dec. 1977.

Thorne, R.M., Injection and loss mechanisms for energetic ions in the inner Jovian magnetosphere, J. Geophys. Res., 87, 8105, 1982.

Vogt, R.E., W.R. Cook, A.C. Cummings, T.L. Garrard, N. Gehrels, E.C. Stone, J.H. Trainor, A.W. Schardt, T. Conlon, N. Lal, and F.B. McDonald, Voyager 1: Energetic Ions and Electrons in the Jovian Magnetosphere, Science, 204, 1003, 1979.

Vogt, R.E., A.C. Cummings, T.L. Garrard, N. Gehrels, E.C. Stone, J.H. Trainor, A.W. Schardt, T.F. Conlon, and F.B. McDonald, Voyager 2: Energetic Ions and Electrons in the Jovian Magnetosphere, Science, 206, 984, 1979.