Voyager 2 Radio Science Subsystem (RSS) Saturn Radio Occultation, Version 1.0, 0.00001 s Raw Data

* Data Set Overview\n* ================\n\nThis Data Set consists of Raw Data collected during the Saturn Radio Occultation of Voyager 2 on 26 August 1981, Ring Scattering Data collected during the same Time Period, Test and Calibration Data collected about 8 h earlier, and Ancillary Files that might be useful in Analysis of those Data. The Raw Data are sampled Voltage Outputs from Receivers tuned to the Voyager Carrier Frequencies at both S-band and X-band during the Occultation. The Data have been reduced to give Profiles of Temperature and Pressure as a Function of Height in the Atmosphere (Lindal et al., 1985) and to infer Magnetic Field Orientations in the upper Ionosphere (Hinson, 1984).\n\nDuring the Saturn Occultation, the Voyager 2 Spacecraft provided a coherent, dual-frequency Microwave Radio Signal Source. The signal Frequency was derived from a precision, onboard Ultra-Stable Oscillator (USO). The Spacecraft High-Gain Antenna (HGA) beamed that Signal through the Atmosphere and Rings of Saturn. As the Spacecraft moved on its Trajectory, the Radio Signal probed the Atmosphere and Rings at different Radial Positions from the Center of Mass. An Hour later the Signals were received using a 64 m Antenna of the NASA Deep Space Network (DSN) near Canberra (Australia).\n\nTo keep the refracted Radio Beam aimed toward the DSN Antenna during the Atmospheric Occultation, the Spacecraft Attitude was adjusted so that the HGA was pointed at the Virtual Image of the Earth on Limb of Saturn. This ensured that maximum Signal Strength would be available from the deepest Probing. During the deepest Part of the Atmospheric Occultation, the HGA was pointed toward the Rings to determine whether Signals forward scattered by the Ring Particles could be detected on Earth.\n\nRelated Data Sets of possible interest include:\n\n+--------------------------------------------------------------------------------------------------+\n| DATA_SET_ID             | Description                                                            |\n----------------------------------------------------------------------------------------------------\n| VG1-SSA-RSS-1-ROCC-V1.0 | Titan Radio Occultation Raw Data                                       |\n| VG1-S-RSS-1-REDR-V1.0†  | Saturn Voyager 1 Ingress Radio Occultation Raw Data                    |\n| VG1-S-RSS-1-ROCC-V1.0   | Saturn Voyager 1 Egress Radio Occultation and Ring Scattering Raw Data |\n+--------------------------------------------------------------------------------------------------+\n\n†Tentative DATA_SET_ID Assignment\n\n* Parameters\n* ==========\n\nThe Output of each S-band Receiver was a Sinusoidal Carrier Signal embedded in Noise with a Bandwidth approximately 50 kHz and sampled at 300000 samples per second. The X-band Receiver Output was similar; but, because of greater potential for Doppler Drift and Prediction Uncertainty, its Bandwidth was 150 kHz and Sampling Rate was 300000 samples per second. Voltages typically were in the Range of ±10 V, but the absolute Levels were not calibrated. In fact, they are generally not needed since it is the Frequency (or Phase) of the Signal (rather than Amplitude) that is most useful in inferring Properties of a Neutral Atmosphere or Ionosphere, and Amplitude Calibration for Ring Observations can be obtained by referencing Signals to the Background Radiothermal Noise in the Data Stream.\n\nThe Frequency of the USO was known from monitoring during the Jupiter-Saturn Cruise (and from post-Saturn Observations). Doppler Contributions from Motions of the Spacecraft, Earth, Saturn, and other Bodies of the Solar System were determined jointly with the Voyager Navigation Team. Relativistic Doppler Contributions could be estimated from proximity to large Masses. Receiver tuning was recorded in POCA (Programmable Oscillator Control Assembly) Files, which are included with this Archive.\n\n* Processing\n* ==========\n\nNo Processing per se has been carried out on these Data. However, because of the high Sampling Rate, the 8-bit Samples were recorded originally on wide-bandwidth Analog Video Tape. The Analog Tapes were then replayed later at slower Speeds and the Digital Data were extracted and separated onto Computer Compatible Tapes (CCTs) with S-band and X-band Data on different Sets of Tapes. Because the S-band Data had been oversampled originally (300 ksps for a 50 kHz Bandwidth), only one of every three Samples was saved during the Transfer of S-band Data to CCTs. This Process, known as $quot;decimation$quot; meant that 300 s of Data could be stored on an S-band CCT whereas only 100 s of X-band Data would fit.\n\nBecause Analog Recording Technology was required to save the high data rate Digital Samples, there are occasional Dropouts in the Sample Stream. These can be detected by paying special attention to Counter Fields in Data Record Headers.\n\nTwo Analog Recorders (A and B) were available at each DSN Complex. Because a single Recorder could not capture the entire Set of Saturn Occultation Activities, the two were run in parallel with staggered Start/Stop Times. Most Data were collected using Recorder A, but Recorder B was used to capture the Samples while Recorder A was being reloaded.\n\n* Data\n* ====\n\nPrimary Data were delivered to Voyager Radio Science Team Members in the Form of 30 megabyte (MB) CCTs covering 300 s (S-band) or 100 s (X-band). Each Tape had 6000 Records of 5056 bytes (56 bytes of Header Information and 5000 8-bit Samples of Receiver Output Voltage). Tapes were numbered s

Tags: waves-active
Organization: National Aeronautics and Space Administration