CCSD3ZF0000100000001NJPL3IF0PDS200000001= SFDU_LABEL /* File Format and Length */ PDS_VERSION_ID = PDS3 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 83 FILE_RECORDS = 14491 /* Record Pointer to Major Objects */ ^TABLE = "EPSUMMRY.TAB" /* Description of Objects in File */ DATA_SET_ID = "ICE-C-EPAS-3-RDR-GIACOBIN-ZIN-V1.0" TARGET_NAME = "GIACOBINI-ZINNER" OBSERVATION_ID = "UNK" OBSERVATION_TIME = "UNK" START_TIME = "UNK" NOTE = "ICE EPAS ION INTENSITY SUMMARY DATA" DESCRIPTION = "The Imperial College, London / Space Science Dept. of ESA, Noordwijk / Space Research Laboratory, Utrecht, Energetic Particle Anisotropy Experiment (EPAS) on the International Cometary Explorer [ICE] spacecraft (ISEE-3 experiment designation DFH [NSSDC identification number 78-079A-08], Principal Investigator, Prof. R.J. Hynds of Imperial College) measures the 3-dimensional distribution of energetic ions about the spacecraft. It consists of a system of three identical semi-conductor particle telescopes mounted on the body of the spacecraft and inclined at 30 degrees (Telescope 1), 60 degrees (Telescope 2) and 135 degrees (Telescope 3) to the space- craft spin axis which is maintained perpendicular to the ecliptic plane (to within 1 degree). The spacecraft spin period is 3.04s. Each telescope has a conical field of view of 16 deg. semi-cone angle and a geometrical factor of 0.05 cm2 sr. The telescopes detect ions (electrons being excluded by 'broom' magnets) and measure their total kinetic energy (but not their mass) by each using a stack of two silicon surface barrier detectors. The front detector (A) is 33 micrometers thick while the second (B) is 150 micrometers thick. Particle counts are defined by anticoincidence (A not B), i.e., the ions deposit all their energy in the A detector and do not intercept and trigger the B detector. The amplitude of the signal produced in the A detector is dependent on the energy deposited in the silicon, and hence on the incident ion energy. This signal is fed to pulse height discriminators which define 8 primary energy channels, E1 to E8. In addition, a further channel, E0, monitors the instrument thermal noise but can register ions above the background is the ion flux is sufficiently high. No background noise counting-rate correction is required in any of the primary energy channels, i.e., the counts recorded are actual particle counts. The channel energy ranges depend slightly on ion mass. This is due principally to mass-dependent energy losses when the ions pass through a thin gold electrode on the front surface of the A detector. For protons and water-group ions (such as were observed at comet G-Z), the energy ranges are: Protons Water Group (Noise) E0: 21- 35 keV 35- 65 keV (approx.) E1: 35- 56 keV 65- 95 keV E2: 56- 91 keV 95-140 keV E3: 91- 147 keV 140-205 keV E4: 147- 238 keV 205-310 keV E5: 238- 384 keV 310-480 keV E6: 384- 620 keV E7: 620-1000 keV (From Hynds et al., E8: 1000-1600 keV Science 232, 361, 1986) (The water-group energy rates for channels E6-E8 have not been determined.) In this G-Z dataset, observations for channels E1 to E5 only are included since cometary ions were not detected in the higher energy channels. For each of these channels, particle counts are accumulated in eight azimuthal sectors of 45 deg. width in each telescope. The sectors are numbered from 1 to 8 anticlockwise when viewed from above the ecliptic, with Sector 1 centered on the Sun-Earth line, i.e., it views in the sunward direction and detects ions streaming away from the Sun. At Giacobini-Zinner, a complete 3-dimensional distribution function was obtained at 32 s intervals during the main encounter phase, changing to 64s at greater distances, e.g. after 1830 UT on 12 September outbound. Cometary pick-up ions at large distance (millions of km) from the nucleus are characterized by highly anisotropic distributions, with large fluxes in the sunward viewing sectors (1,2,8). Closer to the comet, within around 500,000 km or 6 hours of closest approach, broader distributions with antisolar streaming are observed. Here enhanced solar wind turbulence excited by cometary ions scatters the ions into near isotropy in the solar wind frame. The observed anisotropy is then due to the ions convecting with the solar wind. Further details of the EPAS instrument can be found in: Balogh et al., IEEE Trans. on Geoscience Electronics, GE-16, No. 3, 176, 1978 and van Rooijen et al., Space Science Instruments, 4, 373, 1979. Preliminary observations from the G-Z encounter are given in Hynds et al., Science, 232, 361, 1986. The instrument configuration is also illustrated in Richardson et al., Planetary and Space Science, 36, 1429, 1988." OBJECT = TABLE NAME = "ION_INTENSITIES" ROWS = 14491 ROW_BYTES = 83 COLUMNS = 12 INTERCHANGE_FORMAT = ASCII DESCRIPTION = "This table contains direction-averaged ion intensities (using 3 telescopes X 8 sectors) for channels E1 to E5, in units of counts/cm**2/s/sr/keV (assuming water group ions) and Channel E1 ion streaming direction, relative to the spacecraft. SAMPLE CALCULATION OF DIRECTION AVERAGED ION INTENSITY 1985 251 0 43 22 Channel 1 ------------------------------------------------------------------------ Tel. Ch. No. of Ion Counts in Sector Total No. No. spins 1 2 3 4 5 6 7 8 counts (N) ------------------------------------------------------------------------- 1 1 10 1. 0. 0. 1. 0. 0. 1. 1. 4 2 1 10 2. 0. 0. 0. 0. 0. 2. 0. 4 3 1 10 0. 2. 0. 1. 1. 2. 0. 1. 7 ------------------------------------------------------------------------- Normalized weighting factors (W) for telescopes: Telescope 1: W(1) = -0.0351 Telescope 2: W(2) = +0.6316 Telescope 3: W(3) = +0.4036 Directional (weighted) average ion counts per telescope for channel 1: N(1)*W(1) + N(2)*W(2) + N(3)*W(3) = 4*-0.0351 + 4*0.6316 + 7*0.4036 = 5.2112 Directional averaged ion counts for channel 1: wtd. avg. ion counts Ion Intensity = --------------------------------------------- geometric factor * integration time * bandwidth geometric factor = 0.05 cm2-sr (for each telescope); integration time = No. of spins * spin period = 10*3.04 = 30.4 s bandwidth = delta-E = 95-65 = 30 keV for channel 1 (water-gp. ions) 5.2112 Ion Intensity = ----------------- = 0.114 ion counts per (cm2-s-sr-keV) 0.05 * 30.4 * 30 " /* Ion intensity columns: */ OBJECT = COLUMN NAME = "YEAR" BYTES = 4 START_BYTE = 1 DATA_TYPE = ASCII_INTEGER FORMAT = "I4" UNIT = "years" DESCRIPTION = "Year of observation" END_OBJECT = COLUMN OBJECT = COLUMN NAME = "DAY_NUMBER" BYTES = 3 START_BYTE = 6 DATA_TYPE = ASCII_INTEGER FORMAT = "I3" UNIT = "days" DESCRIPTION = "Sequential day number of the observation" END_OBJECT = COLUMN OBJECT = COLUMN NAME = "HOUR" BYTES = 2 START_BYTE = 10 DATA_TYPE = ASCII_INTEGER FORMAT = "I2" UNIT = "hours" DESCRIPTION = "Time hour field" END_OBJECT = COLUMN OBJECT = COLUMN NAME = "MINUTE" BYTES = 2 START_BYTE = 13 DATA_TYPE = ASCII_INTEGER FORMAT = "I2" UNIT = "minutes" DESCRIPTION = "Time minute field" END_OBJECT = COLUMN OBJECT = COLUMN NAME = "SECOND" BYTES = 2 START_BYTE = 16 DATA_TYPE = ASCII_INTEGER FORMAT = "I2" UNIT = "S" DESCRIPTION = "Time second field" END_OBJECT = COLUMN OBJECT = COLUMN NAME = "E1_INTENSITY" BYTES = 10 START_BYTE = 18 DATA_TYPE = ASCII_REAL FORMAT = "E10.2" UNIT = "count/cm**2/S/sr/keV" DESCRIPTION = "Direction-averaged ion intensity in E1" END_OBJECT = COLUMN OBJECT = COLUMN NAME = "E2_INTENSITY" BYTES = 10 START_BYTE = 28 DATA_TYPE = ASCII_REAL FORMAT = "E10.2" UNIT = "count/cm**2/S/sr/keV" DESCRIPTION = "Direction-averaged ion intensity in E2" END_OBJECT = COLUMN OBJECT = COLUMN NAME = "E3_INTENSITY" BYTES = 10 START_BYTE = 38 DATA_TYPE = ASCII_REAL FORMAT = "E10.2" UNIT = "count/cm**2/S/sr/keV" DESCRIPTION = "Direction-averaged ion intensity in E3" END_OBJECT = COLUMN OBJECT = COLUMN NAME = "E4_INTENSITY" BYTES = 10 START_BYTE = 48 DATA_TYPE = ASCII_REAL FORMAT = "E10.2" UNIT = "count/cm**2/S/sr/keV" DESCRIPTION = "Direction-averaged ion intensity in E4" END_OBJECT = COLUMN OBJECT = COLUMN NAME = "E5_INTENSITY" BYTES = 10 START_BYTE = 58 DATA_TYPE = ASCII_REAL FORMAT = "E10.2" UNIT = "count/cm**2/S/sr/keV" DESCRIPTION = "Direction-averaged ion intensity in E5" END_OBJECT = COLUMN OBJECT = COLUMN NAME = "THETA" BYTES = 7 START_BYTE = 68 DATA_TYPE = ASCII_REAL FORMAT = "F7.1" UNIT = "degrees" DESCRIPTION = "Channel E1 ion streaming direction component. THETA ranges from 0 degrees (northward streaming) to 180 degrees (southward). Thus, for example, for antisolar streaming in the ecliptic, THETA = 90 deg. and PHI = 180 deg." END_OBJECT = COLUMN OBJECT = COLUMN NAME = "PHI" BYTES = 7 START_BYTE = 75 DATA_TYPE = ASCII_REAL FORMAT = "F7.1" UNIT = "degrees" DESCRIPTION = "Channel E1 ion streaming direction component. PHI = 0 deg. corresponds to sunward streaming and increases anti-clockwise as viewed from above the ecliptic. Thus, for example, for antisolar streaming in the ecliptic, THETA = 90 deg. and PHI = 180 deg." END_OBJECT = COLUMN END_OBJECT = TABLE END