PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = "Mark B. Vincent, June 1999" RECORD_TYPE = STREAM OBJECT = TEXT INTERCHANGE_FORMAT = ASCII PUBLICATION_DATE = 1998-01-16 PRODUCER_FULL_NAME = "DAVID COLBURN" NOTE = "ASCII description of NEP files" END_OBJECT = TEXT END Description of nephelometer files in the data bank: This file describes the data obtained by the Galileo Probe Nephelometer during the descent into the Jupiter atmosphere on December 7, 1995. The total time of data acquisition was less than two hours before the destruction of the probe in the Jupiter atmosphere. The Nephelometer measured light scattering at 900 nm wavelength at five angles in order to determine properties of aerosol particles and clouds encountered during descent. References describing the instrument include 1. Ragent, B., C. A. Privette, P. Avrin, J. G. Waring, C. E. Carlston, T. C. D. Knight and J. P. Martin, Galileo Probe Nephelometer Experiment, Space Science Reviews, 60, 179-201, 1992. 2. Ragent, B., D. S. Colburn, P. Avrin and K. A. Rages, Results of the Galileo Probe Nephelometer Experiment, Science, 272, 854-856, 1996 3. Ragent, B., D. S. Colburn, K. A. Rages, T. C. D. Knight, P. Avrin, G. S. Orton and G. W. Grams, The Clouds of Jupiter: Results of the Galileo Jupiter Mission Probe Nephelometer Experiment, to appear in Journal of Geophysical Research, Planets, 1998. The data are in tabular form in ASCII format, and thus can be read easily by FORTRAN (or similar) programs. There are 21 files. Each starts out with a header in ASCII which describes the content of the columns and which a FORTRAN program should skip over before reading the data. The following are the 24 data files in the volume: File 1 - raw.dat Raw data. This is the hexadecimal information from the probe. A description of this file follows this table of contents. File 2 - ptz.dat Probe Descent Data. Pressure, temperature and altitude. File 3 - elecoffs.dat Electronic Offsets, Counts. An offset measurement made periodically. File 4 - srcalign.dat Source Monitors and Alignment Detector Readings, Counts. File 5 - tempvolt.dat Forward, Backward and Electronics Temperature Sensor Readings, in Degrees C, and Voltage Monitor, in Counts. File 6 - gain.dat Gain of 16 Degree Channel Electronics. File 7 - contam.dat Contamination Channel Readings, Counts. File 8 - scatter.dat Scatter Data, Counts. File 9 - fittemp.dat Fitted Temperature Profiles, Fitted to a Ninth Order Polynomial File 10 - xsec11.dat Cross Sections with No Adjustment of Baseline and Using Pre-Launch Calibration Data Extrapolated to Cover Out-of-Range Temperatures. File 11 - xsec12.dat Cross Sections with No Adjustment of Baseline and Using Both Pre-Launch Calibration Data and Post-Encounter Test Data to Cover Out-of-Range Temperatures Experienced during Probe Descent. File 12 - xsec21.dat Cross Sections with Adjustment of Baseline to Zero at Measurement Number 14 (p = 0.510 bars) and Using Pre-Launch Calibration Data Extrapolated to Cover Out- of-Range Temperatures Experienced during Probe Descent. File 13 - xsec22.dat Cross Sections with Adjustment of Baseline to Zero at Measurement Number N=14 (p=0.510 bars) and Using Both Pre-Launch Calibration Data and Post-Encounter Test Data to Cover Out-of-Range Temperatures Experienced during Probe Descent. File 14 - xsec31.dat Cross Sections with Adjustment of Baseline to Zero at Measurement Number 24 (p = 0.627 bars) and Using Pre-Launch Calibration Data Extrapolated to Cover Out- of-Range Temperatures Experienced during Probe Descent. File 15 - xsec32.dat Cross Sections with Adjustment of Baseline to Zero at Measurement Number N=24 (p=0.627 bars) and Using Both Pre-Launch Calibration Data and Post-Encounter Test Data to Cover Out-of-Range Temperatures Experienced during Probe Descent. File 16 - xsec41.dat Cross Sections with Adjustment of Baseline to Zero at Measurement Number 60 (p = 1.345 bars) and Using Pre-Launch Calibration Data Extrapolated to Cover Out-of-Range Temperatures Experienced during Probe Descent. File 17 - xsec42.dat Cross Sections with Adjustment of Baseline to Zero at Measurement Number N=60 (p=1.345 bars) and Using Both Pre-Launch Calibration Data and Post-Encounter Test Data to Cover Out-of-Range Temperatures Experienced during Probe Descent. File 18 - xsec51.dat Cross Sections with Adjustment of Baseline to Zero at Measurement Number 69 (p = 1.621 bars) and Using Pre-Launch Calibration Data Extrapolated to Cover Out-of-Range Temperatures Experienced during Probe Descent. File 19 - xsec52.dat Cross Sections with Adjustment of Baseline to Zero Both at Measurement Number N=69 (p=1.621 bars) and Using Pre-Launch Calibration Data and Post-Encounter Data Test to Cover Out-of-Range Temperatures Experienced during Probe Descent. File 20 - xsec61.dat Cross Sections with Adjustment of Baseline to Zero at Measurement Number 117 (p = 3.603 bars) and Using Pre-Launch Calibration Data Extrapolated to Cover Out-of-Range Temperatures Experienced during Probe Descent. File 21 - xsec62.dat Cross Sections with Adjustment of Baseline to Zero at Measurement Number N=117 (p=3.603 bars) and Using Both Pre-Launch Calibration Data and Post-Encounter Test Data to Cover Out-of-Range Temperatures Experienced during Probe Descent. File 22 - senstemp1.dat Sensitivities for each scatter channel, normalized to 1.000 at 15C, and extrapolated from pre-launch tests on the Flight Unit. File 23 - senstemp2.dat Sensitivities from pre-launch tests on the Flight Unit, normalized to 1.000 at 15 C, and modified using post-encounter data. File 24 - baseoffs.dat Baseline offsets versus temperature measured with the flight unit in the laboratory. File 1 contains all of the Nephelometer data transmitted back during the encounter, in hexadecimal form. They were taken directly from the file NEP0701A.SDM, sent from the project office in July 1996. Column 1 has the line number. Each nephelometer frame is identified by a block of 20 lines beginning with the sync word EB 90 followed by the nephelometer frame number in hexadecimal format. Since a nephelometer frame is composed of data from 20 consecutive spacecraft frames, frame number zero contains data from lines 1 through 20, and the frame number for later data is obtained by the integer division of ( line number - 1 ) by 20. Useful data ended at line number 878, and two lines of zeros have been added to complete nephelometer frame 43. As an aid to understanding hexadecimal format, the following examples are shown: Hexadecimal frame numbers 9, A, F, 10, 1A, and 20 have the decimal equivalent 9, 10, 15, 16, 26, and 32. Column 3 contains the number 5 for A string data and 6 for B string data. The file NEP0701A.SDM contains both, and where they overlap, the data is identical, except for a few lines where it is obvious which choice should be made. This data set contains only A string data, because it is a complete set and where B string data exists there is no reason for preferring it over the A string data. Column 2 shows in decimal notation the probe minor frame number transmitted by the probe, cycling from 0 through 63. The minor frame number, and the date and time of transmission, are not essential to interpreting the nephelometer data, since the timing of the measurements is asynchronous with the time of transmission. The first minor frame with nephelometer data is minor frame number 1. Columns 5 through 10 are the Universal Time and date assigned to each minor frame. Columns 5 and 6 represent December 7, 1995. Columns 7 and 8 give the minute and hour, in that order, so that for example the numbers 7, 16 represent 2207 U.T. Columns 9 and 10 give the seconds and milliseconds. The first digit of column 10 generally increases by 1 for each line because the minor frames were transmitted at intervals of very nearly 4 seconds. After every 15 lines, column 7 is expected to increase by one, representing an addition of one minute. The remaining columns (11 through 15) contain the nephelometer data. Every twenty lines contains one nephelometer frame, the start of which is identified by a code word EB 90. The next two digits comprise the nephelometer frame number, supplied by the nephelometer clock, beginning with frame 0 at startup and ending at frame 43 (hexadecimal notation 2B). Since the data set is complete, the frame numbers are found where the index is 1, 21, 41, etc., with the frame number equaling (index - 1)/20. The first several words comprise the engineering data for the frame and they are followed by the words for the nephelometer measurements. In the hexadecimal printout, a frame contains 100 words of 8 bit length. To unpack the data, we have strung the words together to recover the original group of 800 binary bits, and then extracted the 10 bit nephelometer words along with the 8 and 2 bit housekeeping data. Rollover corrections had to be applied to some of the housekeeping data when the analog signals representing temperature, etc., exceeded the expected range of the analog to digital converter. The unpacked data, in counts, are shown in Files 3 through 8. File 2 relates the time of each measurement to the atmospheric pressure and temperature and the probe altitude as determined by the ASI experiment. Thus the data in the remaining files are labelled by atmospheric pressure in order to relate nephelometer findings to the atmospheric environment. Files 9 through 21 are cross sections computed according to the parameters described in the headings. (See reference 3) Files 22 are the sensitivities for each scatter channel, normalized to 1.000 at 15 C, and extrapolated from pre-launch tests on the Flight Unit (tests performed from -20 C to + 50 C), versus T1, the temperature for the forward scatter channels, or T2, the temperature for the backscatter channel. Both the temperatures and the sensitivities have been fitted by a 9th order polynomial, fit to the measured data. Files 23 are the sensitivities from pre-launch tests on the Flight Unit (tests performed from -20 C to + 50 C), normalized to 1.000 at 15 C, and modified outside of these laboratory test temperature limits by insights obtained from tests of the Spare Flight Unit performed after probe encounter with Jupiter, versus T1, the temperature for the forward scatter channels, or T2, the temperature for the backscatter channel. Both the temperatures and the sensitivities have been fitted by a 9th order polynomial, fit to the laboratory measured data. Files 24 are the baseline offsets versus temperature were measured for the flight unit in the laboratory at temperatures from about -20 to 50 C and are extrapolated to the values listed here. Since baseline offsets are principally believed to be due to induced ground currents, the value of offset may have been strongly affected by the final configuration of the instrument in the vehicle. Therefore the values in this file must be judiciously employed for the actual flight case data, for which the instrument was mounted on the probe and deployed during encounter. Although the data in this file are included for completeness, for alternative procedures the user is referred to Ragent et al., The clouds of Jupiter: Results of the Galileo Jupiter Mission Probe Nephelometer Experiment, J. Geophys Res., 103, 22891-22909, 1998.