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Instrument Information

INSTRUMENT_ID RSS-VG1S
INSTRUMENT_NAME RADIO SCIENCE SUBSYSTEM
INSTRUMENT_TYPE RADIO SCIENCE
INSTRUMENT_HOST_ID VG1
INSTRUMENT_DESC
 
    Instrument Overview
    ===================
      Voyager Radio Science investigations at the giant planets
      utilized instrumentation with elements both on the spacecraft
      and at the DSN.  Much of this was shared equipment, being used
      for routine telecommunications as well as for Radio Science.
      The performance and calibration of both the spacecraft and
      tracking stations directly affected the radio science data
      accuracy, and they played a major role in determining the
      quality of the results.  The spacecraft part of the radio
      science instrument is described immediately below; unless
      noted otherwise, the description applies equally well to
      both Voyager 1 and Voyager 2 and it applies throughout the
      Voyager mission.  The description of the DSN (ground) part
      of the instrument follows.  Because the DSN was continually
      changing, that description has been tailored to each Voyager
      encounter.
 
 
    Instrument Specifications - Spacecraft
    ======================================
      The Voyager spacecraft telecommunications subsystem served as
      part of a radio science subsystem for investigations of the
      giant planets.  Many details of the subsystem are unknown; its
      'build date' is taken to be 1977-09-05, the launch date for
      Voyager 1.  Except for hardware failures, noted below, the
      Voyager 1 and Voyager 2 spacecraft subsystems were identical.
 
      Instrument Id                 : RSS-VG1S
      Instrument Host Id            : VG1
      Pi Pds User Id                : UNK
      Instrument Name               : RADIO SCIENCE SUBSYSTEM
      Instrument Type               : RADIO SCIENCE
      Build Date                    : 1977-09-05
      Instrument Mass               : UNK
      Instrument Length             : UNK
      Instrument Width              : UNK
      Instrument Height             : UNK
      Instrument Manufacturer Name  : UNK
 
 
    Instrument Overview - Spacecraft
    ================================
      The spacecraft radio system was constructed around a redundant
      pair of transponders.  Each transponder was equipped with an
      S-band receiver (2115 MHz nominal frequency) and transmitters
      at both S-band (2295 MHz nominal) and X-band (8415 MHz nominal).
      Compared with S-band, X-band is less sensitive to plasma effects
      by a factor of about 10; use of both frequencies coherently on
      the 'downlink' allowed estimation of plasma content along the
      radio path.  Use of X-band also significantly improved the
      quality of radio tracking data for gravity investigations.
 
      The transponder generated downlink signals in either 'coherent'
      or 'non-coherent' modes, also known as 'two-way' and 'one-way,'
      respectively.  When operating in the coherent mode, the
      transmitted carrier frequency was derived coherently from the
      received uplink carrier frequency with a 'turn-around ratio' of
      240/221 at S-band and (11/3)*240/221 at X-band.
 
      In non-coherent mode the transmitted frequency was controlled
      by an on-board oscillator; the X- and S-band remained coherent
      in the ratio 11/3.  A single Ultra-Stable Oscillator (USO) was
      used during radio occultations; it provided stabilities
      several orders of magnitude better than the conventional
      crystal oscillators, which were part of each transponder.
 
      Stability of the Voyager USO was specified in terms of its
      Allan Deviation -- the fractional frequency deviation from
      linear drift [ALLAN1966].  Over 10 minute periods, the Allan
      Deviation ranged from 10^-12 to 4 10^-12 for integrations of
      1-10 sec.  Long-term fractional drift of the oscillator was
      about 5 10^-11 per day.  Although the oscillator was hardened,
      there were discontinuities in the drift when the spacecraft
      passed through the radiation belts of the outer planets.
      Equivalent X-band microwave frequencies for the Voyager 1 USO
      during key events were (multiplying by 3/11 yields the S-band
      frequency):
 
                     8,414,995,272.530 Hz (Titan occultation)
                     8,414,995,272.376 Hz (Saturn occultation)
 
      Traveling wave tube or solid state amplifiers boosted the
      transponder output.  Output powers of 9 and 26  watts could
      be selected at S-band; the choices at X-band were 12 and 22
      watts.
 
      The signals were radiated via a 3.66 m diameter parabolic high
      gain antenna (HGA).  The HGA transmit boresight gain of
      the HGA was 36 dB at S-band and 47 dB at X-band.  The half-power
      half-width of the antenna beam was 0.32 degrees at X-band and
      1.1 degrees at S-band.  Transmit polarization was right-hand
      circular at S-band and either right- or left-hand circular at
      X-band.  A Low-Gain Antenna (LGA) was mounted on the feed
      structure of the HGA and radiated approximately uniformly over
      the hemisphere into which the HGA pointed.  It was used during
      maneuvers, spacecraft anomalies, and at other times when the
      HGA was not appropriate.
 
      For receiving, the S-band HGA gain was 35 dB at 2115 MHz and the
      polarization was right-hand circular.  The receiving system
      noise temperature was approximately 2000K, the carrier tracking
      loop bandwidth was 18 Hz, and the ranging channel noise
      bandwidth was 1.5 MHz.
 
      More information can be found in [ESHLEMANETAL1977].
 
 
    Science Objectives
    ==================
      Science objectives fell into two broad areas of investigation --
      those that could be met using high-precision radiometric data
      (sometimes known as 'tracking' data) and those that could be met
      from studying characteristics of the radio signal after its
      interaction with an atmosphere, plasma, ring particles, or other
      intervening medium.  The tracking data were fundamental to
      inferring the gravitational forces on the spacecraft and
      relativistic effects along the radio path; both the measured
      time delay during a two-way transmission and the Doppler shift
      were used.  Investigators seeking knowledge of atmospheric
      structure, spatial and size distributions of ring particles,
      and velocity of the solar wind measured amplitude, frequency
      (and phase), and polarization of the radio signals which were
      captured by Earth receiving systems.  There are, of course,
      investigations which use both types of data.
 
 
      Gravity Measurements
      --------------------
        The frequency of the downlink carrier signal was precisely
        measured to determine the magnitude of the Doppler shift
        caused by acceleration of the spacecraft as it passed near
        either a single body or a system of bodies.  Since the
        magnitude of the Doppler shift is related to the gravitational
        field strength, the mass of the body (or bodies) can be
        determined.  If the radius of the body is known (as from
        calibrated images), the density can be calculated.
 
        Doppler and range tracking measurements yield accurate
        spacecraft trajectory solutions.  Simultaneously with
        reconstruction of the spacecraft orbit, observation equations
        for the central mass, low order coefficients for the field,
        and a small number of ancillary parameters can be solved.
        Measurements of the gravity field provide significant
        constraints on inferences about the interior structure of
        target bodies.
 
        The Pioneer 10 and 11 spacecraft came closer to Jupiter than
        Voyager, so there was no net improvement in the Jupiter mass
        estimate from Voyager.  But Voyager probed the Galilean
        satellites at closer range, and better mass estimates were
        obtained.  The Voyager encounters with Saturn, in conjunction
        with the close flyby of Pioneer 11, yielded a mass estimate
        comparable to that of Jupiter along with several low-order
        zonal harmonic coefficients.  Voyager 2 was targeted for a
        close encounter with Miranda, an inner satellite of Uranus;
        that, combined with long tracking arcs through the Uranian
        system, yielded the first good estimates of masses for the
        five largest satellites and an improved mass estimate for
        Uranus itself.  The Voyager 2 very close near-polar flyby
        with Neptune yielded estimates for the zonal harmonic
        coefficients J2 and J4 in addition to estimates for the mass
        of both Neptune and Triton.
 
 
      Atmospheric and Ionospheric Radio Occultation Measurements
      ----------------------------------------------------------
        Atmospheric measurements by the method of radio occultation
        contribute to an improved understanding of structure,
        circulation, dynamics, and transport in atmospheres of remote
        planetary bodies.  These results are based on detailed
        analysis of the radio signal received from the spacecraft as
        it enters and exits occultation by the planet.  Three phases
        of an atmospheric investigation may be defined.  The first is
        to obtain vertical profiles of atmospheric structure
        (temperature and pressure in the neutral atmosphere and
        electron density in the ionosphere) with emphasis on large-
        scale phenomena.  During this stage, it is necessary to know
        the mean molecular weight of the atmosphere; for Voyager
        the hydrogen-helium mixing ratio could be determined for each
        planet using the radio data in conjunction with Voyager IRIS
        data.  Second is to investigate absorption at various levels
        in the atmosphere -- such as by methane.  Third is to
        study details of the structure, such as result from
        propagation of buoyancy waves within a neutral atmosphere or
        from alignment of charged particles along magnetic field lines
        in an ionosphere.
 
        Retrieval of atmospheric profiles requires coherent
        samples of the radio signal that has propagated through
        the atmosphere, plus accurate knowledge of the antenna
        pointing and the spacecraft trajectory.  The spatial and
        temporal coverage in radio occultation experiments are
        determined by the observing geometry, including the spacecraft
        trajectory.  For deep atmospheres, changes in antenna pointing
        may be required to compensate for refractive bending by the
        atmosphere.  At Jupiter and Saturn both diametric and grazing
        occultations were obtained using the two Voyager spacecraft;
        measurements were obtained at both equatorial and polar
        latitudes.  Voyager 1 also obtained profiles for Titan.
        Voyager 2 continued to Uranus and Neptune, and also obtained
        occultation profiles at Triton.
 
 
      Radio Measurements on Planetary Rings
      -------------------------------------
        Radio occultation measurements of planetary rings are carried
        out using procedures similar to those employed for atmospheric
        occultations.  Although absorption by ring particles must be
        considered, the dominant effect on strength of the directly
        propagating signal is believed to be conservative scattering--
        that is, scattering which disperses the signal in direction
        without significant absorption.  Profiles of received signal
        strength can be inverted to yield the radial distribution of
        ring material.  Doppler spreading of the signal scattered in
        the near-forward direction can be used to infer the particle
        size distribution, especially when measurements at the two
        Voyager radio wavelengths are combined.
 
        Ring occultations were planned and observed using Voyager 1
        at Saturn and Voyager 2 at Uranus.  Measurements were carried
        out at Neptune using Voyager 2, but no rings or arcs were
        detected using the radio system.  A post-encounter search for
        a radio ring occultation at Jupiter was unsuccessful.
 
        Voyager 2 also carried out an oblique forward scattering
        experiment during its Saturn encounter.  The spacecraft high-
        gain antenna was deflected from the Earth direction so that
        it illuminated the ring system; but no scattered signal was
        detected.
 
 
      Solar Conjunction Experiments
      -----------------------------
        Solar conjunction experiments were conducted to improve
        understanding of the structure and dynamics of the solar
        corona and wind, to improve understanding of relativistic
        effects when radio waves propagate near the Sun, and to test
        the different elements of the radio science subsystem.
        Approximately once per year, each Voyager spacecraft appeared
        to pass behind the solar disk, as seen from Earth.  Radio
        waves propagating between Voyager and Earth stations were
        refracted and scattered (scintillation) by the solar plasma
        [WOO1993].  Intensity fluctuations can be related to
        fluctuations in electron density along the path, while Doppler
        or phase scintillations can be related to both electron
        density fluctuations and also the speed of the solar wind.
        Many plasma effects decrease as the square of the radio
        frequency; plasma effects are about an order of magnitude
        stronger at S-band than X-band.
 
 
      Experimental Relativity
      -----------------------
        The gravitational field of the Sun causes a time delay on
        signals that propagate near the Sun of approximately 300
        microseconds.  Although previous tests had verified the effect
        to an accuracy of a few percent, Voyager measurements could
        be conducted annually and at two frequencies, allowing
        separation of plasma effects.
 
        Gravitational fields of the gas giant planets also affected
        radio signals by causing them to have apparent frequencies
        lower than predicted.  The change in frequency is related to
        the mass of the planet.  By measuring the change in frequency
        as the spacecraft approached the planet, a value for the mass
        could be calculated.  This value could then be compared with
        the mass derived from two-way tracking data.  The spacecraft
        Ultra-Stable Oscillator was used for these measurements;
        two-way transmissions have nearly canceling frequency shifts
        as the signal travels to the spacecraft and then returns.  The
        dual frequencies available from Voyager allowed correction for
        plasma effects along the radio path, but calibration for
        radiation damage to the USO during encounters was more
        difficult.
 
 
    Operational Considerations - Spacecraft
    =======================================
      Descriptions given here are for nominal performance.  The
      spacecraft transponder system comprised redundant units,
      each with slightly different characteristics.  As
      transponder units age, their performance changes slightly.
      More importantly, the performance for radio science depended
      on operational factors such as the modulation state for the
      transmitters, which cannot be predicted in advance.  The
      performance also depended on factors which were not always
      under the control of the Voyager Project.
 
      Spacecraft receivers were designed to lock to the uplink
      signal.  Without locking, Doppler effects -- resulting from
      relative motion of the spacecraft and ground station -- could
      result in loss of the radio link as the frequency of the
      received signal drifted.  Unfortunately, a series of failures
      in the Voyager 2 receivers left that transponder unable to
      track the uplink signal.  Beginning in April 1978, Doppler
      shifts were predicted and the uplink carrier was tuned so
      that Voyager 2 would see what appeared to be a signal at
      constant frequency (to an accuracy of 100 Hz).
 
      During deep occultations by the giant planets, the bending angle
      resulting from refraction exceeded 10 degrees in some cases --
      well beyond the half power beamwidth of the spacecraft antenna.
      In those cases, the pointing of the HGA was adjusted so that
      it followed a 'virtual' Earth and maximum signal strength could
      be sustained.  These 'limb-track' maneuvers were critically
      dependent on accurate timing in the encounter.  To protect
      against Voyager 1 timing errors at Titan (primarily from
      uncertainties in the radius and position of the satellite),
      no limb-track was attempted during ingress, and a fixed
      antenna offset was used during egress.  Fortunately, timing was
      accurate enough that useful data were obtained from each event.
 
      Although the spacecraft radioisotope thermoelectric generators
      were not dependent on solar flux for power, their output decayed
      as the Voyager spacecraft moved outward through the solar
      system.  During encounters with the outer planets, caution was
      required in budgeting power and the high-power mode could not
      be used for the radio transmitters.
 
 
    Calibration Description - Spacecraft
    ====================================
      Prior to and during some encounter sequences, the spacecraft
      was commanded to execute a 'mini-ASCAL' maneuver.  The HGA was
      moved slightly above the Earth line then slightly below the
      Earth line.  The procedure was repeated to the left and right
      of the Earth line so that a 'cross-hair' pattern was mapped
      out.  During the maneuver, the amplitude of the carrier
      signal was measured carefully.  Analysis of the results
      showed whether the HGA was pointed accurately and, if not,
      approximately the error magnitude and direction.
 
      Prior to and after encounters, the spacecraft frequency
      reference was switched to the USO for several hours and the
      carrier signal was monitored using equipment at the DSN.
      These 'USO Tests' were used to calibrate the frequency and
      frequency drift of the USO.  USO tests were particularly
      important before and after the spacecraft entered a severe
      radiation environment since the radiation typically damaged
      the crystal and changed its characteristics slightly.
 
 
    Platform Mounting Descriptions - Spacecraft
    ===========================================
      The centerline of the bus was the roll axis of the
      spacecraft; it also served as the z-axis of the spacecraft
      coordinate system with the high-gain antenna (HGA) boresight
      defining the negative z-direction.  The HGA boresight was
      also defined as cone angle 0 degrees and as azimuth 180
      degrees, elevation 7 degrees.  The Low-Gain Antenna (LGA)
      was mounted on the feed structure of the HGA and radiated
      approximately uniformly over the hemisphere into which the
      HGA pointed.
 
 
    Principal Investigators
    =======================
      The Radio Science Team Leader through the Jupiter encounters
      was Von R. Eshleman.  The Team Leader for the Saturn, Uranus,
      and Neptune encounters was G. Leonard Tyler.
 
 
    Instrument Section / Operating Mode Descriptions - Spacecraft
    =============================================================
      The Voyager radio system consisted of two sections, which
      could be operated in the following modes:
 
      Section      Mode
      -------------------------------------------
      Oscillator   two-way (coherent)
                   one-way (non-coherent)
      RF output    low-gain antenna (no information available)
                   high-gain antenna
 
      Selected parameters describing NASA Standard Transponder (NST)
      performance are listed below:
 
      Oscillator Parameters:                    S-Band     X-Band
         Two-Way Transponder Turnaround Ratio  240/221    880/221
         One-Way Transmit Frequency (MHz)        2296.      8415.
         Nominal Wavelength (cm)                13.06       3.56
 
      RF Output parameters:                     S-Band     X-Band
         RF Power Output (w)                   9 or 26    12 or 22
         Low-Gain Antenna:
           Half-Power Half Beamwidth (deg)        UNK
           Gain (dBi)                             UNK
           EIRP (dBm)                             UNK
           Polarization                         Circular
         High-Gain Antenna:
           Half-Power Half-Beamwidth (deg)        1.1       0.32
           Gain (dBi)                              36        47
           Polarization                           RCP    RCP or LCP
 
 
    Instrument Overview - DSN
    =========================
      Three Deep Space Communications Complexes (DSCCs) (near
      Barstow, CA; Canberra, Australia; and Madrid, Spain) comprise
      the DSN tracking network.  During the Voyager-Saturn era each
      complex was equipped with several antennas (including at least
      one 64-m and and one 26-m antenna), associated electronics,
      and operational systems.  Primary activity at each complex
      was radiation of commands to and reception of telemetry
      data from active spacecraft.  Transmission and reception was
      possible in several radio-frequency bands, the most common
      being S-band (nominally a frequency of 2100-2300 MHz or a
      wavelength of 14.2-13.0 cm) and X-band (7100-8500 MHz or 4.2-
      3.5 cm).  Transmitter output powers up to 400 kw were
      available.
 
      Ground stations have the ability to transmit coded and uncoded
      waveforms which can be echoed by distant spacecraft.  Analysis
      of the received coding allows navigators to determine the
      distance to the spacecraft; analysis of Doppler shift on the
      carrier signal allows estimation of the line-of-sight
      spacecraft velocity.  Range and Doppler measurements are used
      to calculate the spacecraft trajectory and to infer gravity
      fields of objects near the spacecraft.
 
      Ground stations can record spacecraft signals that have
      propagated through or been scattered from target media.
      Measurements of signal parameters after wave interactions with
      surfaces, atmospheres, rings, and plasmas are used to infer
      physical and electrical properties of the target.
 
      The Deep Space Network is managed by the Jet Propulsion
      Laboratory of the California Institute of Technology for the
      U.S.  National Aeronautics and Space Administration.
      Specifications include:
 
      Instrument Id                  : RSS-VG1S
      Instrument Host Id             : DSN
      Pi Pds User Id                 : N/A
      Instrument Name                : RADIO SCIENCE SUBSYSTEM
      Instrument Type                : RADIO SCIENCE
      Build Date                     : N/A
      Instrument Mass                : N/A
      Instrument Length              : N/A
      Instrument Width               : N/A
      Instrument Height              : N/A
      Instrument Manufacturer Name   : N/A
 
      For more information on the Deep Space Network and its use in
      radio science investigations see the reports by
      [ASMAR&RENZETTI1993], [ASMAR&HERRERA1993], and [ASMARETAL1995].
      For design specifications on DSN subsystems see [DSN810-5].
      For an example of use of the DSN for Radio Science see
      [TYLERETAL1992].
 
 
    Subsystems - DSN
    ================
      The Deep Space Communications Complexes (DSCCs) are an integral
      part of the Radio Science instrument, along with other
      receiving stations and the spacecraft Radio Frequency
      Subsystem.  Their system performance directly determines the
      degree of success of Radio Science investigations, and their
      system calibration determines the degree of accuracy in the
      results of the experiments.  The following paragraphs describe
      the functions performed by the individual subsystems of a DSCC.
      This material has been adapted from [ASMAR&HERRERA1993]; for
      additional information, consult [DSN810-5].
 
      Each DSCC includes a set of antennas, signal processing
      equipment, and communication links to the Jet Propulsion
      Laboratory (JPL).  The general configuration is illustrated
      below; antennas (Deep Space Stations, or DSS -- a term carried
      over from earlier times when antennas were individually
      instrumented) are listed in the table.
 
                    --------   --------   --------
                   | DSS 11 | | DSS 12 | | DSS 14 |
                   |  26-m  | |  26-m  | |  64-m  |
                    --------   --------   --------
                        |            |     |
                        |            v     v
                        |         --------------
                         ------->|COMMUNICATIONS|
                                 |    CENTER    |
                                  --------------
                                        |
                                        v
                    ----------      ---------
                   | NETWORK  |    |   JPL   |
                   |OPERATIONS|    | CENTRAL |
                   |   AND    |<-->|   COMM  |
                   | CONTROL  |    | TERMINAL|
                   |  CENTER  |     ---------
                    ----------
 
                          GOLDSTONE     CANBERRA      MADRID
             Antenna      CALIFORNIA    AUSTRALIA     SPAIN
            --------      ----------    ---------    --------
              26-m          DSS 11       DSS 44       DSS 62
              26-m          DSS 12       DSS 42       DSS 61
              64-m          DSS 14       DSS 43       DSS 63
            Developmental   DSS 13
 
 
 
      DSCC Transmitter Subsystem
      --------------------------
        Two transmitters were available at 64-m antennas; output
        power of the first could be adjusted over the range 0.2-20 kW,
        while the second could be adjusted over 10-100 kW.  Nominal
        tuning range was 2100-2120 MHz with the -1 dB points at 2110
        and 2118 MHz.
 
        Only the 0.2-20 kW transmitter was available at 26-m antennas.
        Tuning range was the same.
 
 
 
      Multi-Mission Receiver (MMR)
      ----------------------------
        The Multi-Mission Receiver provided four channels of data for
        occultations studies during the Voyager encounters at Saturn.
        A programmable local oscillator/synthesizer was used to keep
        the signal as close to the center of a 10 MHz IF filter as
        predictions would permit.  The output was sent to the Radio
        Science Subsystem for sampling and recording.  Filter
        bandwidths for S-RCP and S-LCP ring occultations and
        scattering observations were 50 kHz; the corresponding
        bandwidths for X-RCP and X-LCP were 150 kHz.
 
        For signals with narrower spectral ranges, the 10 MHz IF
        output was mixed to 100 kHz where filters as narrow as 100 Hz
        could be applied.
 
 
      DSS Radio Science (DRS) Subsystem
      ---------------------------------
        The Radio Science Subsystem sampled output from the MMR and
        recorded it on high-speed analog video tape for later
        conversion to computer compatible tape (CCT) formats.  Sample
        rates for the Voyager 1 Titan and Saturn encounters were 300
        ksps on all receiver outputs.
 
        Narrower filters and lower sampling rates could be selected
        for special purposes.
 
 
      DSS Frequency and Timing Subsystem
      ----------------------------------
        Frequency and timing were provided by three references: a
        rubidium standard, a hydrogen maser, and a cesium beam
        standard.  Precisions are shown in the tables below:
 
         Reference             Frequency Stability   Integration Time
         -----------------     -------------------   ----------------
         Rubidium Standard      5   parts in 10^12         1 second
                                5   parts in 10^13       100 seconds
                                5   parts in 10^13      1000 seconds
                                5   parts in 10^13        12 hours
                                1   part  in 10^11         1 year
         Hydrogen Maser         3   parts in 10^13         1 second
                                2   parts in 10^14       100 seconds
                                2   parts in 10^14        12 hours
                                2   parts in 10^13         1 year
         Cesium Beam Standard   5   parts in 10^12         1 second
                                8   parts in 10^13       100 seconds
                                2.5 parts in 10^13      1000 seconds
                                8   parts in 10^14     10000 seconds
 
        Station Time relative to the DSN master clock was accurate to
        20 microseconds based on rubidium standard synchronization and
        to 3 milliseconds based on calibration by HF radio.  The DSN
        master clock was accurate to 50 microseconds relative to the
        National Bureau of Standards, based on calibration using a
        portable cesium clock.  The DSS frequency offset relative to
        the DSN master reference frequency was accurate to 1 part in
        10^11 based on rubidium standard or cesium beam standard
        synchronization and to 2 parts in 10^13 based on a hydrogen
        maser.
 
 
    Optics - DSN
    ============
      Performance of DSN ground stations depends primarily on size of
      the antenna and capabilities of electronics.  These are
      summarized in the following set of tables.  Note that 64-m
      antennas were upgraded to 70-m between 1986 and 1989.
      Beamwidth is half-power full angular width.  Polarization is
      circular; L denotes left circular polarization (LCP), and R
      denotes right circular polarization (RCP).
 
                            DSS Antenna Characteristics
 
                                Transmit              Receive
                            ---------------    --------------------
        Quantity             64-m      26-m        64-m       26-m
        --------            -----     -----    ------------   -----
        Frequency (MHz)     2110-     2110-    2270-  8400-   2270-
                             2120      2120     2300   8440    2300
        Wavelength (m)      0.142     0.142    0.131  0.036   0.131
        Gain (dBi)           60.7      51.8     61.7   71.3    53.2
        Beamwidth (deg)      0.15      0.36     0.14  0.038    0.33
        Polarization          RCP       RCP      RCP    RCP     RCP
                              LCP       LCP      LCP    LCP     LCP
                              LIN                LIN            LIN
        CP Ellipticity (dB)   2.2       1.0     0.28    1.0     0.4
        SNT-TWM1-unspec (K)                              25      33
                -diplex (K)                       22
                -orthog (K)                       18
           -TWM2-unspec (K)                                      41
                -diplex (K)                       26
                -orthog (K)                       23
 
         Notes: (1) DSS 14 receive gain was 71.3 dB at X-band; but
                    gain at DSS 43 and DSS 63 was 71.8 dB
                (2) Polarizations available at 64-m antennas were
                    RCP and LCP (simultaneously) or rotatable linear.
                    Polarizations available at 26-m antennas were
                    RCP or LCP or fixed linear.
 
 
    Electronics - DSN
    =================
 
      DSCC Open-Loop Receiver (RIV)
      -----------------------------
        The open loop receiver block diagrams below show the Modified
        Block III Open-Loop Receiver (DSS 14 and 43) and the
        Narrowband Multi-Mission Receiver (MMR) (DSS 63) used during
        early Voyager encounters.  Only the S-band block diagrams are
        shown; expressions for reconstructing both S- and X-band
        signal frequencies (Fs and Fx, respectively) from the
        observed output frequencies (Folr) are given below the
        diagrams.
 
        DSS 14 and 43                                     DSS 63
 
          S-Band                                          S-Band
         2295 MHz                                        2295 MHz
          Input                                            Input
            |                                                |
            v                                                v
           ---     ---                              ---     ---
          | X |<--|x48|<-- ~46 MHz       ~41 MHz-->|x48|-->| X |
           ---     ---                              ---     ---
            |                                                |
          50|                                                |300
         MHz|                                                |MHz
            v                                                v
           ---                                              ---
          | X |<-- 60 MHz                       290 MHz -->| X |
           ---                                              ---
            |                                                |
          10|                                                |10
         MHz|                                                |MHz
            v                                                v
           ---                                              ---
          | X |<-- 10 MHz                        10 MHz -->| X |
           ---                                              ---
            |                                                |
            v                                                v
         Output                                            Output
 
 
        Reconstruction of the antenna frequency from the frequency of
        the signal in the recorded data can be achieved through use
        of one of the following formulas.  Frequency of the
        Programmable Oscillator Control Assembly (Fpoca) is
        approximately 46 MHz at DSS 14 and 43 and approximately
        41 MHz at DSS 63.
 
        DSS 14 and 43
 
          Fs = 48*Fpoca + 50*10^6 - Folr
          Fx = (11/3)*(48*Fpoca + 50*10^6) - Folr
 
        DSS 63
 
          Fs = 48*Fpoca + 300*10^6 + Folr
          Fx = (11/3)*(48*Fpoca + 300*10^6) + Folr
 
 
    Filters - DSN
    =============
 
      DSCC Open-Loop Receiver (RIV)
      -----------------------------
        Filters (usually at the 10 MHz intermediate frequency) could
        be selected by the user to match expected width of the signal
        or uncertainty in its location.  Filters and sampling rates
        used during the Voyager Saturn encounters were:
 
                           DSS 43                DSS 63
                     ------------------    -------------------
                        3 dB     Sample       3 dB     Sample
                     Bandwidth    Rate     Bandwidth    Rate
                     ---------  -------    ---------  --------
          S-band       4.1 kHz  10 ksps      50. kHz  300 ksps
          X-band      15.0 kHz  30 ksps     150. kHz  300 ksps
 
 
 
 
    Detectors - DSN
    ===============
 
      DSCC Open-Loop Receivers
      ------------------------
        Open-loop receiver output is detected in software by the
        radio science investigator.
 
 
      DSCC Closed-Loop Receivers
      --------------------------
        Nominal carrier tracking loop threshold noise bandwidths at
        S- and X-band were 10-12 and 30 Hz, respectively.  Sample
        rates for Doppler were 1-10 per second.
 
 
    Calibration - DSN
    =================
      Calibrations of hardware systems are carried out periodically
      by DSN personnel; these ensure that systems operate at required
      performance levels -- for example, that antenna patterns,
      receiver gain, propagation delays, and Doppler uncertainties
      meet specifications.  No information on specific calibration
      activities is available.  Nominal performance specifications
      are shown in the tables above.  Additional information may be
      available in [DSN810-5].
 
      Prior to each tracking pass, station operators perform a series
      of calibrations to ensure that systems meet specifications for
      that operational period.  Included in these calibrations is
      measurement of receiver system temperature in the configuration
      to be employed during the pass.  Results of these calibrations
      are recorded in (hard copy) Controller's Logs for each pass.
 
      Filters for the Open-Loop Receivers were checked during the
      Test and Calibration period after the Titan and Saturn
      observations concluded.  A test signal was injected at a
      constant frequency, then stepped across the passband to measure
      filter gain at discrete frequencies.
 
 
    Operational Considerations - DSN
    ================================
      The DSN is a complex and dynamic 'instrument.' Its performance
      for Radio Science depends on a number of factors from equipment
      configuration to meteorological conditions.  No specific
      information on 'operational considerations' can be given here.
 
 
    Operational Modes - DSN
    =======================
 
      Closed-Loop vs. Open-Loop Reception
      -----------------------------------
        Radio Science data can be collected in two modes: closed-
        loop, in which a phase-locked loop receiver tracks the
        spacecraft signal, or open-loop, in which a receiver samples
        and records a band within which the desired signal presumably
        resides.  Closed-loop data are collected using Closed-Loop
        Receivers, and open-loop data are collected using Open-Loop
        Receivers in conjunction with the DSCC Spectrum Processing
        Subsystem (DSP).  See the Subsystems section for further
        information.
 
 
      Closed-Loop Receiver AGC Loop
      -----------------------------
        The closed-loop receiver AGC loop can be configured to one of
        three settings: narrow, medium, or wide.  Ordinarily it is
        configured so that expected signal amplitude changes are
        accommodated with minimum distortion.  The loop bandwidth is
        ordinarily configured so that expected phase changes can be
        accommodated while maintaining the best possible loop SNR.
 
 
      Coherent vs. Non-Coherent Operation
      -----------------------------------
        The frequency of the signal transmitted from the spacecraft
        can generally be controlled in two ways -- by locking to a
        signal received from a ground station or by locking to an
        on-board oscillator.  These are known as the coherent (or
        'two-way') and non-coherent ('one-way') modes, respectively.
        Mode selection is made at the spacecraft, based on commands
        received from the ground.  When operating in the coherent
        mode, the transponder carrier frequency is derived from the
        received uplink carrier frequency with a 'turn-around ratio'
        typically of 240/221.  In the non-coherent mode, the
        downlink carrier frequency is derived from the spacecraft
        on-board crystal-controlled oscillator.  Either closed-loop
        or open-loop receivers (or both) can be used with either
        spacecraft frequency reference mode.  Closed-loop reception
        in two-way mode is usually preferred for routine tracking.
        Occasionally the spacecraft operates coherently while two
        ground stations receive the 'downlink' signal; this is
        sometimes known as the 'three-way' mode.
 
 
      Open-Loop Sampling
      ------------------
        The Open-Loop Receiver sampling system can operate in four
        sampling modes with from 1 to 4 input signals.  Input
        channels are assigned to ADC inputs during configuration.
        Modes are summarized in the tables below:
 
        Mode   Analog-to-Digital Operation
        ----   ----------------------------
          1    4 signals, each sampled by a single ADC
          2    1 signal, sampled sequentially by 4 ADCs
          3    2 signals, each sampled sequentially by 2 ADCs
          4    2 signals, the first sampled by ADC #1 and the second
                           sampled sequentially at 3 times the rate
                            by ADCs #2-4
 
 
    Location - DSN
    ==============
      Station locations are documented in [GEO-10REVD].  Geocentric
      coordinates are summarized here.
 
                            Geocentric  Geocentric  Geocentric
      Station              Radius (km) Latitude (N) Longitude (E)
      ---------            ----------- ------------ -------------
      Goldstone
        DSS 12 (26-m STD)  6371.997815  35.1186672   243.1945048
        DSS 13 (develop)   6372.117062  35.0665485   243.2051077
        DSS 14 (64-m)      6371.992867  35.2443514   243.1104584
 
      Canberra
        DSS 42 (26-m STD)  6371.675607 -35.2191850   148.9812546
        DSS 43 (64-m)      6371.688953 -35.2209308   148.9812540
 
      Madrid
        DSS 61 (26-m STD)  6370.027734  40.2388805   355.7509634
        DSS 63 (64-m)      6370.051015  40.2413495   355.7519776
 
 
    Measurement Parameters - DSN
    ============================
 
      Open-Loop System
      ----------------
        Sampled output from the Open-Loop Receivers (OLRs) is a stream
        of 8-bit quantized voltage samples.  The nominal input to
        the Analog-to-Digital Converters (ADCs) is +/-10 volts, but
        the precise scaling between input voltages and output
        digitized samples is usually irrelevant for analysis; the
        digital data are generally referenced to a known noise or
        signal level within the data stream itself -- for example,
        the thermal noise output of the radio receivers which has a
        known system noise temperature (SNT).  Raw samples comprise
        the data block in each data record; a header record
        contains ancillary information such as time tag for the
        first sample in the data block.
 
 
      Closed-Loop System
      ------------------
        Closed-loop data are recorded in Archival Tracking Data Files
        (ATDFs), as well as certain secondary products such as the
        Orbit Data File (ODF).  The ATDF Tracking Logical Record
        contains entries including status information and
        measurements of ranging, Doppler, and signal strength.
 
 
    ACRONYMS AND ABBREVIATIONS - DSN
    ================================
      ACS      Antenna Control System
      ADC      Analog-to-Digital Converter
      AMS      Antenna Microwave System
      APA      Antenna Pointing Assembly
      ARA      Area Routing Assembly
      ATDF     Archival Tracking Data File
      AZ       Azimuth
      CMC      Complex Monitor and Control
      CONSCAN  Conical Scanning (antenna pointing mode)
      CRG      Coherent Reference Generator
      CUL      Clean-up Loop
      DANA     a type of frequency synthesizer
      dB       decibel
      dBi      dB relative to isotropic
      dBm      dB relative to one milliwatt
      DCO      Digitally Controlled Oscillator
      DEC      Declination
      deg      degree
      DMC      DSCC Monitor and Control Subsystem
      DSCC     Deep Space Communications Complex
      DSN      Deep Space Network
      DSP      DSCC Spectrum Processing Subsystem
      DSS      Deep Space Station
      DTK      DSCC Tracking Subsystem
      E        east
      EL       Elevation
      FTS      Frequency and Timing Subsystem
      GCF      Ground Communications Facility
      GPS      Global Positioning System
      HA       Hour Angle
      HEF      High-Efficiency (as in 34-m HEF antennas)
      IF       Intermediate Frequency
      IVC      IF Selection Switch
      JPL      Jet Propulsion Laboratory
      K        Kelvin
      kHz      kilohertz
      km       kilometer
      ksps     kilosamples per second
      kW       kilowatt
      L-band   approximately 1668 MHz
      LAN      Local Area Network
      LCP      Left-Circularly Polarized
      LMC      Link Monitor and Control
      LNA      Low-Noise Amplifier
      LO       Local Oscillator
      m        meters
      MCA      Master Clock Assembly
      MCCC     Mission Control and Computing Center
      MDA      Metric Data Assembly
      MHz      Megahertz
      MMR      Multi-Mission Receiver
      MON      Monitor and Control System
      MSA      Mission Support Area
      N        north
      NAR      Noise Adding Radiometer
      NBOC     Narrow-Band Occultation Converter
      NIST     SPC 10 time relative to UTC
      NIU      Network Interface Unit
      NOCC     Network Operations and Control System
      NSS      NOCC Support System
      OCI      Operator Control Input
      ODF      Orbit Data File
      ODR      Original Data Record
      ODS      Original Data Stream
      OLR      Open Loop Receiver
      POCA     Programmable Oscillator Control Assembly
      PPM      Precision Power Monitor
      RA       Right Ascension
      REC      Receiver-Exciter Controller
      RCP      Right-Circularly Polarized
      RF       Radio Frequency
      RIC      RIV Controller
      RIV      Radio Science IF-VF Converter Assembly
      RMDCT    Radio Metric Data Conditioning Team
      RTLT     Round-Trip Light Time
      S-band   approximately 2100-2300 MHz
      sec      second
      SEC      System Error Correction
      SIM      Simulation
      SLE      Signal Level Estimator
      SNR      Signal-to-Noise Ratio
      SNT      System Noise Temperature
      SOE      Sequence of Events
      SPA      Spectrum Processing Assembly
      SPC      Signal Processing Center
      SRA      Sequential Ranging Assembly
      SRC      Sub-Reflector Controller
      SSI      Spectral Signal Indicator
      STD      Standard (as in 34-m STD antennas)
      TID      Time Insertion and Distribution Assembly
      TSF      Tracking Synthesizer Frequency
      TWM      Traveling Wave Maser
      UNK      unknown
      UTC      Universal Coordinated Time
      VF       Video Frequency
      X-band   approximately 7800-8500 MHz
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Asmar, S.W., and R.G. Herrera, Radio Science Handbook, JPL D-7938, Volume 4,Jet Propulsion Laboratory, Pasadena, CA, 22 January 1993.

Asmar, S.W., and N.A. Renzetti, The Deep Space Network as an Instrument forRadio Science Research, Jet Propulsion Laboratory Publication 80-93, Rev. 1, 15April 1993.

Asmar, S.W., R.G. Herrera, and T. Priest, Radio Science Handbook, JPL D-7938Volume 6, Jet Propulsion Laboratory, Pasadena, CA, 1995.

Deep Space Network / Flight Project Interface Design Book, Document 810-5, JetPropulsion Laboratory, Pasadena, CA.

Eshleman, V.R., G.L. Tyler, J.D. Anderson, G. Fjeldbo, G.E. Wood, and T.A.Croft, Radio Science Investigations with Voyager, Space Science Reviews, 21,207-232, 1977.

DSN Geometry and Spacecraft Visibility, Document 810-5, Rev. D, Vol. 1,DSN/Flight Project Interface Design, Jet Propulsion Laboratory, Pasadena, CA,1987.

Tyler, G.L., G. Balmino, D.P. Hinson, W.L. Sjogren, D.E. Smith, R. Woo, S.W.Asmar, M.J. Connally, C.L. Hamilton, and R.A. Simpson, Radio ScienceInvestigations with Mars Observer, Journal of Geophysical Research, 97,7759-7779, 1992.

Woo, R., Spacecraft Radio Scintillation and Solar System Exploration, WavePropagation in Random Media (Scintillation), Society of Photo-OpticalInstrumentation Engineers, Bellingham, WA, 1993.