PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM DATA_SET_ID = "GO-J-PLS-3-RDR-FULLRES-V1.0" PRODUCT_ID = "PLSCALIB.TXT" PRODUCT_TYPE = "CALIBRATION" PRODUCT_CREATION_DATE = 2000-11-21 OBJECT = TEXT PUBLICATION_DATE = 2000-03-17 NOTE = "PLS calibration information." END_OBJECT = TEXT END To convert PLS counts per second to differential flux the count rate is multiplied by a factor, CHI, which is a function of sensor and energy. The complete set of 64 values of CHI for each of the 20 sensors are contained in the files: CALIB_1.TAB (E: 1,3,5,7) CALIB_2.TAB (P: 1,3,5,7, M2i, M2d) CALIB_3.TAB (E: 2,4,6) CALIB_4.TAB (P: 2,4,6, M1i,M1d,M3i,M3d) The values for CHI may be thought of as a dimensioned array of the form CHI( DetId, E-Step ) where DetId is in the range 1-20, and E-Step is in the range 0-63. The energies for each detector step are summarized in the files E_STEP_1.TAB (E: 1,3,5,7) E_STEP_2.TAB (P: 1,3,5,7, M2i, M2d) E_STEP_3.TAB (E: 2,4,6) E_STEP_4.TAB (P: 2,4,6, M1i,M1d,M3i,M3d) If an individual RDR record is read into the following variable names TIME, SCLK, RATE, DETID, E-STEP, M-STEP, SECTOR, SAMPLE, ACCUM then the differential flux may be computed by: DJDE = RATE * CHI(DETID,E-STEP) The value of the AACS rotor spin angle at the start of the individual measurement is contained in the variable SECTOR. A discussion of this item follows later in this text. Transformation routines are available in the Galileo SPICE data to convert the angles to Jovicentric coordinate systems of interest. The PLS sensors respond to ambient plasma and to very high energy radiation which penetrates the walls and shielding in the instrument. Removal of this background cannot be done in an automated fashion. Extensive work must be done on a spectrum by spectrum basis. This has not been performed on the RDR data set. Similarly, corrections to the measurements due to spacecraft charging cannot be done automatically and have not been done for these data. The statistical characteristics of individual measurements are associated with the number of counts obtained in the original sample time and with the effects of the onboard data compression performed on all PLS sensor data. The number of raw counts may be obtained by multiplying the RATE by ACCUM, the sensor accumulation time obtained from the RDR record. The statistical uncertainty then is the square-root of the number of counts. Each PLS sensor has a 17-bit accumulator associated with it. The lower 16-bits function as a normal counter, while the 17th bit is a latched overflow flag. Each 17-bit accumulation is operated on by a quasi-logarithmic compression algorithm in the PLS data system. This algorithm compresses the 17-bit number to an 8-bit code for inclusion in the PLS telemetry stream. The details of this quasi-logarithmic compression are detailed below. All RDR data have been decompressed. PLS SENSOR DATA LOGARITHMIC COMPRESSION out in out in out in out in out in out in out in 00- 0 20- 32 40-128 60- 512 80-2048 A0- 8192 C0- 32768 01- 1 21- 34 41-136 61- 544 81-2176 A1- 8704 C1- 34816 02- 2 22- 36 42-144 62- 576 82-2304 A2- 9216 C2- 36864 03- 3 23- 38 43-152 63- 608 83-2432 A3- 9728 C3- 38912 04- 4 24- 40 44-160 64- 640 84-2560 A4-10240 C4- 40960 05- 5 25- 42 45-168 65- 672 85-2688 A5-10752 C5- 43008 06- 6 26- 44 46-176 66- 704 86-2816 A6-11264 C6- 45056 07- 7 27- 46 47-184 67- 736 87-2944 A7-11776 C7- 47104 08- 8 28- 48 48-192 68- 768 88-3072 A8-12288 C8- 49152 09- 9 29- 50 49-200 69- 800 89-3200 A9-12800 C9- 51200 0A-10 2A- 52 4A-208 6A- 832 8A-3328 AA-13312 CA- 53248 0B-11 2B- 54 4B-216 6B- 864 8B-3456 AB-13824 CB- 55296 0C-12 2C- 56 4C-224 6C- 896 8C-3584 AC-14336 CC- 57344 0D-13 2D- 58 4D-232 6D- 928 8D-3712 AD-14848 CD- 59392 0E-14 2E- 60 4E-240 6E- 960 8E-3840 AE-15360 CE- 61440 0F-15 2F- 62 4F-248 6F- 992 8F-3968 AF-15872 CF- 63488 10-16 30- 64 50-256 70-1024 90-4096 B0-16384 *D0- 65536 11-17 31- 68 51-272 71-1088 91-4352 B1-17408 *D1- 69632 12-18 32- 72 52-288 72-1152 92-4608 B2-18432 *D2- 73728 13-19 33- 76 53-304 73-1216 93-4864 B3-19456 *D3- 77824 14-20 34- 80 54-320 74-1280 94-5120 B4-20480 *D4- 81920 15-21 35- 84 55-336 75-1344 95-5376 B5-21504 *D5- 86016 16-22 36- 88 56-352 76-1408 96-5632 B6-22528 *D6- 90112 17-23 37- 92 57-368 77-1472 97-5888 B7-23552 *D7- 94208 18-24 38- 96 58-384 78-1536 98-6144 B8-24576 *D8- 98304 19-25 39-100 59-400 79-1600 99-6400 B9-25600 *D9-102400 1A-26 3A-104 5A-416 7A-1664 9A-6656 BA-26624 *DA-106496 1B-27 3B-108 5B-432 7B-1728 9B-6912 BB-27648 *DB-110592 1C-28 3C-112 5C-448 7C-1792 9C-7168 BC-28672 *DC-114688 1D-29 3D-116 5D-464 7D-1856 9D-7424 BD-29696 *DD-118784 1E-30 3E-120 5E-480 7E-1920 9E-7680 BE-30720 *DE-122880 1F-31 3F-124 5F-496 7F-1984 9F-7936 BF-31744 *DF-126976 * indicates accumulator overflow (D0-DF) Note: input is in decimal counts output is encoded in hexadecimal (base 16) NOTES ON DIFFERENTIAL M/Q CALIBRATION TABLES: DIFMQ tables provide the connection between energy step, mass step, and M/Q values for the three differential mass spectrometer sensors. Each table is for a different value of M/Q. Each table gives the three mass steps that correspond to that M/Q for each energy step. For example, M/Q=1 particles at 2.9 ev will be seen in energy step 6, mass steps 2, 3, and 4. The three-step mass range is determined in prelaunch calibrations, and bracket the mass peak. NOTES ON INTEGRAL M/Q CALIBRATION TABLES: INTMQ tables provide the connection between energy step, mass step, and M/Q values for the three integral mass spectrometer sensors. Each table is for a different value of M/Q. The table gives the location of the "knee" in a plot of response vs mass step at a given energy. At this location the specified M/Q component will be swept away from the sensor causing a decrease in the count rate. NOTES ON THE PLASMA SCIENCE EXPERIMENT SECTORS The AACS rotor spin angle is an integer number in the range 0-255. It is zero when the spacecraft X-axis is pointed at (or near) the south ecliptic pole and increases as the spacecraft rotates. The rotor spin angle may be converted to an angle in the range 0-360 degrees with the equation: angle = (AACS rotor spin angle) * (360/256) The fields-of-view of the PLS detectors are offset by 45 degrees from the spacecraft X-axis in the X-Y plane. So when the rotor spin angle is zero (0) the fields-of-view are making a +45 degree angle with respect to the X-axis in the X-Y plane. This 45 degree offset is not included in the AACS rotor spin angle provided in the RDR data files. To compute the rotational angle from the north ecliptic pole to the velocity vector of the plasma particles entering the PLS field-of-view: velocity angle = 45 + [ (AACS rotor spin angle) * (360/256) ] A significant challenge to the PLS flight software was decoupling data collection from data transmission. Plasma measurements need strong control of, and repeatability in, the angular sampling. A very conscious trade was made by the PLS team to relax the time knowledge in favor of tightening the angular knowledge. This means that the PLS data can not be directly compared to the spacecraft attitude (AACS) data set based solely on the time word. PLS uses the AACS CLOCK data distributed onboard the spacecraft to determine when to begin accumulating sensor data. Depending on the modes of operation PLS may begin, for example, on quadrant or octant sector boundaries. Within each sector the instrument uses a fixed accumulation time for each sample. Thus within each sector successive samples (successive energy steps) start at successively larger angles as the spacecraft rotates at ~18.9 degrees/second. Sectoring mode AACS Sector values -------------------- ------------------------------------- Quadrants (4/spin) 0, 64, 128, 192 Octants (8/spin) 0, 32, 64, 96, 128, 160, 192, 224 The time assigned to each measurement in an RDR file is the time that data collection was initiated for that particular mode. Thus, data collected over approximately one spin of the spacecraft will all have the same SCLK time in the file. And since the actual data collection begins on a sector boundary, the actual time of the first data may be up to one sector later than the initiation time. PLS DETECTORS Detector ID Detector Name ----------- -------------------------------- 1 Mass Spectrometer 1 Integral 2 Mass Spectrometer 1 Differential 3 1 Positive Ion 4 2 Positive Ion 5 3 Positive Ion 6 Mass Spectrometer 2 Integral 7 Mass Spectrometer 2 Differential 8 4 Positive Ion 9 5 Positive Ion 10 6 Positive Ion 11 7 Positive Ion 12 Mass Spectrometer 3 Integral 13 Mass Spectrometer 3 Differential 14 1 Electron 15 2 Electron 16 3 Electron 17 4 Electron 18 5 Electron 19 6 Electron 20 7 Electron