PDS3_DATA_SET_ID = VG1-S-MAG-4-SUMM-HGCOORDS-48.0SEC-V1.0 DATA_SET_NAME = VG1 SAT MAG RESAMPLED HELIOGRAPHIC (RTN) COORDS 48.0SEC V1.0 START_TIME = 1980-11-10T00:00:34.923 STOP_TIME = 1980-11-20T23:59:47.065 ORIGINAL_DATA_SET_RELEASE_DATE = 1996-01-01 PRODUCER_FULL_NAME = Ness, N. F. DATA_SET_SOURCE = "NATIONAL SPACE SCIENCE DATA CENTER" REFERENCES: Acuna, M.H., J.E.P. Connerney, and N.F. Ness, Topology of Saturn's Main Magnetic Field, Nature, 292, 721, 1981. Behannon, K.W., M.H. Acuna, L.F. Burlaga, R.P. Lepping, N.F. Ness, and F.M. Neubauer, Magnetic Field Experiment for Voyagers 1 and 2, Space Sci. Rev., Vol. 21, p. 235, 1977. Behannon, K.W., J.E.P. Connerney, and N.F. Ness, Saturn's Magnetic Tail: Structure and Dynamics, Nature, 292, 753, 1981. Behannon, K.W., R.P. Lepping, and N.F. Ness, Structure and Dynamics of Saturn's Outer Magnetosphere and Boundary Regions, J. Geophys. Res., 88, 8791, 1983. Connerney, J.E.P., M.H. Acuna, and N.F. Ness, Currents in Saturn's Magnetosphere, J. Geophys. Res., 88, 8779, 1983. Lepping, R.P., L.F. Burlaga, and L.W. Klein, Surface Waves on Saturn's Magnetopause, Nature, 292, 750, 1981. Ness, N.F., M.H. Acuna, R.P. Lepping, J.E.P. Connerney, K.W. Behannon, L.F. Burlaga, and F.M. Neubauer, Magnetic Field Studies by Voyager 1 at Saturn: Preliminary Results, Science, 212, 211, 1981. Ness, N.F., M.H. Acuna, K.W. Behannon, L.F. Burlaga, J.E.P. Connerney, R.P. Lepping, and F.M. Neubauer, Magnetic Field Studies by Voyager 2: Preliminary Results at Saturn, Science, 215, 558, 1982. DATA_SET_DESCRIPTION Data Set Overview ================= This data set includes calibrated magnetic field data acquired by the Voyager 1 Low Field Magnetometer (LFM) during the Saturn encounter. Coverage begins in the solar wind inbound to Saturn and continues past the last outbound bowshock crossing. The data are in Heliographic (RTN) coordinates and have been averaged from the 9.6 second summary rate to a 48 second sample rate. All magnetic field measurements are given in nanoTesla (nT). The magnetic field data are calibrated (see the calibration description included in the Voyager 1 Magnetometer instrument catalog file for details). Parameters ========== The full LFM instrument sample rate is 1 sample per 0.06 seconds. Full telemetry resolution 'detail' data must be obtained from the instrument team. For this data set, the data have been resampled to 48 seconds from 9.6 second averages. The 9.6 second data were resampled from 1.92 second averages which were in turn resampled from the detail data. The LFM has eight dynamic ranges. The instrument is designed switch between dynamic ranges automatically depending upon the observed magnetic field magnitude and fluctuations. Instrument digitization uncertainty depends upon dynamic range as indicated in the following table (from [BEHANNONETAL1977]). ----------------------------------------------- LFM Dynamic ranges and quantization uncertainty ----------------------------------------------- Range (nT) Quantization (nT) ----------------------------------------------- 1. +/- 8.8 +/- .0022 2. +/- 26 +/- .0063 3. +/- 79 +/- .019 4. +/- 240 +/- .059 5. +/- 710 +/- .173 6. +/- 2100 +/- .513 7. +/- 6400 +/- 1.56 8. +/- 50,000 +/- 12.2 Processing ========== Voyager EDR's undergo the following processing in order to produce these 48 second averaged summary data: * Read EDR * Unpack header block (rec. id, s/c id, tel. mode, FDS counts, data flags) * Convert selected time tags to integer time (yy/ddd/hh:mm:ss.fff) * Unpack sub-header block (MAG status words, plasma data) * Unpack science block (MAG counts) * Convert counts to gammas * Apply sensor and boom alignment matrices * Rotate (optional) 1.92 second averages while averaging detail gammas to create 1.92 second averages * Average 1.92 second data to 9.6 seconds, then 9.6 second data to 48 seconds * Write Summary record Counts are measured onboard using 12 bit words that may represent values ranging from 0-4096. Integer counts are converted to magnetic field units (gammas) by subtracting a zero offset, from the measured MAG value and multiplying this difference by the sensitivity of the instrument. Data ==== The data files are given in ASCII, fixed field width, comma delimited tables. The record structure is described in the following table: -------------------------------------------------------------------- 48 Second Heliographic (RTN) Coordinates -------------------------------------------------------------------- Column Type Description -------------------------------------------------------------------- time a23 spacecraft event time (UT) of the sample in the format: yyyy-mm-ddThh:mm:ss.sss sclk a12 spacecraft clock in the format: MOD65536:MOD60:FDS-LINE mag_id i1 magnetometer ID (1 = LFM, 2 = HFM) Br f9.3 average of detail magnetic field R component in nT Bt f9.3 average of detail magnetic field T component in nT Bn f9.3 average of detail magnetic field N component in nT Bmag f9.3 magnitude of the averaged magnetic field components in nT avg_Bmag f9.3 average of the magnetic field magnitude over the averaging interval in nT Delta f7.3 spacecraft centered heliographic magnetic field latitude in degrees: Delta = asin(Bn/Bmag) Lambda f7.3 spacecraft centered heliographic magnetic field longitude in degrees: Lambda = atan(Bt/Br) rms_Br f8.3 root-mean-square deviation of Br over the averaging interval in nT rms_Bt f8.3 root-mean-square deviation of Bt over the averaging interval in nT rms_Bn f8.3 root-mean-square deviation of Bn over the averaging interval in nT npts i2 number of detail points in the average dflag a8 8-byte character string which indicates software or spacecraft hardware intervention which reduces confidence in the data [Note that the magnetic field vector descriptions given above are best at lower latitudes, including all latitudes reached by Voyager during the Saturn encounter] Coordinate Systems ================== These data are provided in a heliographic right handed spherical coordinate system known as RTN. RTN coordinates are defined by the following directions: R - radial direction: along the Sun to spacecraft line, positive in the anti-Sunward direction T - tangetial direction: Omega (the Sun's spin axis) X R (parallel to the Solar Equatorial plane) N - normal direction: completes the right handed set CONFIDENCE_LEVEL_NOTE = Review ====== These data have been reviewed by the instrument team and are of the highest quality that can be generated at this time. Science results based on these data have been published in several journals (Science, Nature, JGR, etc.). After submission to the PDS, these data successfully completed the peer review process. Data Coverage and Quality ========================= These data include an 8-byte flag indicating software or spacecraft hardware intervention which reduced confidence in the data. This data flag consists of nulls (spaces) when the data are nominal.