Data Set Information
DATA_SET_NAME GIOTTO PARTICLE IMPACT ANALYZER DUST MASS SPECTRA V1.0
DATA_SET_ID GIO-C-PIA-3-RDR-HALLEY-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview: The PIA data was acquired in four modes of data compression, termed mode 0 (the least compressed), and modes 1, 2, and 3, each with increasing degrees of compression. With each spectrum are a PIA assigned sequence number and event numbers, a unique ID-number, instrument settings, and the relative approach time. The PIA time is a 16-bit counter that starts with zero after switch-on. As the Spacecraft Time Signal (STS) is used to reset the internal PIA time counter, the TIM highest possible value is 48960 counts. STS-pulses are given after the transimssion of 256 formats. This results for format F1/F2 and high bitrate (46080 bps) in 5802.67 s. (: 256 formats * 64 frames * 2040 bytes * 8 bit/byte/46080 bps) The time resolution is DTIM : 1/ (138240 HZ /2**14 ) : 0.1185 s. Each STS defines the time for an event with TIM : 0. Therefore, SCET : GRT(STS) + (TIM * DTIM) - propogation delay (8:00.1 sec). where SCET : Spacecraft Event Time, GRT : Ground Reception Time. The table below lists important GRT for the Encounter (Mar 13-14). GRT TIM Remarks 19:23:46.81 switch-on 19:23:47.97 00000 calculated GRT for TIM:0 (reset for TIM) 19:23:49.15 34797 start of transmission (events 1-11 are old) 19:23:49.75 00015 first event after switch-on 12039 last event before STS 19:47:34.81 STS 00006 first event after STS 48959 last event before next STS 21:24:17.51 STS 00021 first event after STS 48960 last event before next STS 23:01:00.20 STS 00005 first event after STS 35388 event before TIM-reset 00000 add 35388 to TIM 00007 event before TIM-reset 00000 add 35396 to TIM 00004 event before TIM-reset 00:11:01 closest approach 00035 add 35566 to TIM 13394 last event before next STS 00:37:42.90 STS 00004 first event after STS 48956 last event before next STS 02:14:25.81 STS 00000 first event after STS 48144 last event before switch-off 03:49:42 PIA OFF The data for these files were received as a series of FITS files, each of which consisted of spectra of a single mode. Amplitude-triggered samples in the spectra were indicated by an 'X' following the sample. The files have been regrouped according to Mode and presented as a binary array with a separate ASCII index table. Reformatting at SBN The following changes were made to the data: o Flagged amplitudes, followed by an 'X' in the text file, were indicated in the binary file as a additional byte set equal to 1 for flagged amplitudes, 0 otherwise. This is the same system used for the IKI VEGA submissions. Known Anomalies/Problems: o In the received FITS file numbered 40, the final spectrum in the file (sequence number 2991, event number 46698, time 48110) was truncated. It is not clear if only this last spectrum was lost or if other spectra might have followed since the NAXIS1 and NAXIS2 values from the header indicate more data. The incomplete spectrum was omitted entirely from the binary table. o Two mode 1 spectra were found which contained an odd number of bytes in the spectrum. In mode 1 the number of bytes should be even, as each sample in the spectrum consists of a time sample byte and an amplitude sample byte. In these cases the single byte was assumed to be a time value and a null amplitude byte was appended to the spectrum. o In working with these files it was noted that many spectra exhibited strange features, including: - parameter values but no spectrum bytes (i.e., zero-length spectra) - repeating time values of 255 (the maximum possible time) - repeating amplitude values of 127 (the maximum possible) - repeating values of 32 (ASCII code for blank) o There was a failure in the instrument during the fly-by. The following is taken directly from the FITS file header which was attached to the text files: During the actual flyby two out of six multiplier-amplifiers failed, yielding incorrect amplitude information in the mass spectra channel; to obtain partial correction for amplitude, use F(a), where F(0) : 0 F(20) : 49 F(1...4) : a*2 + 21 F(21) : 52 F(5...8) : a + 25 F(22) : 57 F(9...14) : a + 26 F(23...25) : 3*(a-23) + 62 F(15,16) : a + 27 F(26...83) : a + 4a F(17...19) : a + 2b F(84...127) : 128 NOTE: Despite this correction the amplitude ranges 1...22 and around 51...65 are incomplete.
DATA_SET_RELEASE_DATE 3000-01-01T00:00:00.000Z
START_TIME 1986-03-13T07:15:48.710Z
STOP_TIME 1986-03-14T03:41:00.000Z
MISSION_NAME GIOTTO
MISSION_START_DATE 1985-07-02T12:00:00.000Z
MISSION_STOP_DATE 1992-07-10T12:00:00.000Z
TARGET_NAME HALLEY
TARGET_TYPE COMET
INSTRUMENT_HOST_ID GIO
INSTRUMENT_NAME PARTICULATE IMPACT ANALYZER
INSTRUMENT_ID PIA
INSTRUMENT_TYPE DUST DETECTOR
NODE_NAME Small Bodies
ARCHIVE_STATUS ARCHIVED
CONFIDENCE_LEVEL_NOTE Confidence Level Overview: N/A
CITATION_DESCRIPTION Kissel, J., and A.C. Raugh, GIOTTO PARTICLE IMPACT ANALYZER DUST MASS SPECTRA V1.0, GIO-C-PIA-3-RDR-HALLEY-V1.0, NASA Planetary Data System, 1990.
ABSTRACT_TEXT The PIA data was acquired in four modes of data compression, termed mode 0 (the least compressed), and modes 1, 2, and 3, each with increasing degrees of compression. With each spectrum are a PIA assigned sequence number and event numbers, a unique ID-number, instrument settings, and the relative approach time. The PIA time is a 16-bit counter that starts with zero after switch-on. As the Spacecraft Time Signal (STS) is used to reset the internal PIA time counter, the TIM highest possible value is 48960 counts. STS-pulses are given after the transimssion of 256 formats. This results for format F1/F2 and high bitrate (46080 bps) in 5802.67 s. (: 256 formats * 64 frames * 2040 bytes * 8 bit/byte/46080 bps) The time resolution is DTIM : 1/ (138240 HZ /2**14 ) : 0.1185 s. Each STS defines the time for an event with TIM : 0. Therefore, SCET : GRT(STS) + (TIM * DTIM) - propogation delay (8:00.1 sec). where SCET : Spacecraft Event Time, GRT : Ground Reception Time.
PRODUCER_FULL_NAME INTERNATIONAL HALLEY WATCH
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