OBJECT = DATA_SET DATA_SET_ID = ICE-C-MAG-3-RDR-GIACOBIN-ZIN-V1.0" OBJECT = DATA_SET_INFORMATION DATA_SET_NAME = "ICE MAGNETOMETER DATA V1.0" DATA_SET_COLLECTION_MEMBER_FLG = Y START_TIME = 1985-09-10T10:00:00.040Z STOP_TIME = 1985-09-14T20:51:14.500Z DATA_SET_RELEASE_DATE = UNK PRODUCER_FULL_NAME = "INTERNATIONAL HALLEY WATCH" DETAILED_CATALOG_FLAG = N DATA_SET_DESC =" \v Data Set Overview ================= \v These data were obtained from the JPL magnetometer experiment on ICE (Principal Investigator: E.J. Smith; data provided by J. Wolf). The instrument produces three, high-accuracy, triaxial measurements per second of the magnetic field strength in 8 ranges, i.e., +/-4 nT (lowest full range), 14, 42, 144, 640, 4000, 22000, and 140000 nT (highest full range) and a sensitivity of 1/256 of each full range, in a 0-3 Hz pass band. During the G-Z encounter the instrument range was switched automatically between the 4 lowest ranges depending on the field intensity, giving sensitivities of 0.015, 0.051, 0.17 and 0.57 nT respectively. The time resolution is 1/3 sec from the start of Day 253 (September 10, 1985) until Day 255 (September 12, 1985), 18:38. At that time the bit rate dropped from 1024 to 512 bps, and the time resolution decreased to 2/3 sec. The coordinate system for the magnetic field components is the I,S coordinate system, defined by the JPL group before launch. I is the unit vector in the direction of the ICE spin axis (positive in the northward direction), and S is the unit vector from the spacecraft to the Sun. The z-axis is equal to I, the y-axis to the normalized cross-product I x S, and the x-axis to Y x Z. The I,S coordinate system is approximately the same as the Solar Ecliptic (SE) system since the spacecraft z-axis is maintained within half a degree of perpendicular to the Ecliptic plane. (SE is defined the same way as GSE, but with the spacecraft [point of observation] substituted for Earth). While the JPL reduction program eliminates most noise spikes, there is a small number that do appear in these data. JPL does not hand-edit the high resolution data, since there is such a volume of it. Users should check for noise spikes when doing averaging or other analyses. There is no special flag for 'bad' or missing data. A scan of the 5 days of high resolution data at JPL revealed the following noise spikes: Time Field magnitude ---- --------------- Day 253, 10:11:59.84 47.25 Day 254, 03:51:28.21 59.17 04:05:17.84 56.19 10:10:55.31 59.68 11:06:13.15 128.07 12:04:23.92 62.73 Day 255, 09:07:17.48 57.75 09:07:17.82 185.49 Day 256, 07:35:54.94 57.58 21:08:09.00 23.83 23:01:15.94 35.20 Day 257, 10:08:07.77 46.06 20:03:15.75 51.07 The following information (and the table of noise spikes given above) has been provided by J. Wolf (JPL), after examining plots of the magnetic field data during the comet encounter: The highest legitimate value of Bmagnitude is 59.21 at 11:01:01.29 on Day 254, at the time of closest approach to the comet. On Day 254, one should eliminate points with Bmagnitude greater than 40 from 09:00 to 11:00 and from 11:10 to 13:00. During the interval 11:00 to 11:10, points with Bmagnitude greater than 60 should be eliminated. For the rest of this 5 day interval, one should eliminate points with Bmagnitude greater than 20 nT. " CONFIDENCE_LEVEL_NOTE = " \v Confience Level Overview ======================== \v N/A" END_OBJECT = DATA_SET_INFORMATION OBJECT = DATA_SET_TARGET TARGET_NAME = "GIACOBINI-ZINNER" END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_HOST INSTRUMENT_HOST_ID = ICE INSTRUMENT_ID = MAG END_OBJECT = DATA_SET_HOST OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "ESA SP-1066" END_OBJECT = DATA_SET_REFERENCE_INFORMATION END_OBJECT = DATA_SET