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PDS_VERSION_ID                    = PDS3
LABEL_REVISION_NOTE               = "
      2002-11-26 R. SIMPSON adapted from VG2J file using JPL D-2652;
      2003-11-05 M.R. SHOWALTER fixed a few typos."
RECORD_TYPE                       = STREAM

OBJECT                            = INSTRUMENT
  INSTRUMENT_HOST_ID               = VG2
  INSTRUMENT_ID                    = "RSS-VG2U"

  OBJECT                           = INSTRUMENT_INFORMATION

   INSTRUMENT_TYPE                 = "RADIO SCIENCE"
   INSTRUMENT_DESC                 = "

     Instrument Overview
       Voyager Radio Science investigations at the giant planets
       utilized instrumentation with elements both on the spacecraft
       and at the NASA Deep Space Network (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

     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 1977-08-20, the launch date for
       Voyager 2.  Except for hardware failures, noted below, the
       Voyager 1 and Voyager 2 spacecraft subsystems were identical.

       Instrument Id                 : RSS-VG2U
       Instrument Host Id            : VG2
       Pi Pds User Id                : UNK
       Instrument Name               : RADIO SCIENCE SUBSYSTEM
       Instrument Type               : RADIO SCIENCE
       Build Date                    : 1977-08-20
       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

       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 2 USO
       during key events were (multiplying by 3/11 yields the S-band

                      8,420,430,593.447 Hz (Jupiter occultation)
                      8,420,430,462.000 Hz (Saturn occultation)
                      8,420,430,456.100 Hz (Uranus occultation)
                      8,420,430,398.420 Hz (Neptune 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

       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 plasma properties (such as velocity of the solar wind and
       structure of the Io plasma torus) 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.

       For an overview of the pre-launch science goals see
       [ESHLEMANETAL1977].  The preliminary science results were
       published as follows:
               Jupiter      [ESHLEMANETAL1979B]
               Saturn       [TYLERETAL1982]
               Uranus       [TYLERETAL1986]
               Neptune      [TYLERETAL1989]

       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

         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 [ANDERSONETAL1987A].  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 [LINDALETAL1981] and Saturn
         [LINDALETAL1985] 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 [LINDALETAL1983].  Voyager 2
         continued to Uranus [LINDALETAL1987] and Neptune
         [LINDALETAL1990], and also obtained occultation profiles at
         Triton [GURROLA1995].

       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

         Ring occultations were planned and observed using Voyager 1
         at Saturn [MAROUF&TYLER1985] and Voyager 2 at Uranus
         [GRESHETAL1989].  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 [TYLERETAL1981B].

         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

       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
         [ANDERSONETAL1987B] [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.

       Io Plasma Torus Experiment
         Both before and after the Voyager 1 occultation by Jupiter,
         the radio signal to Earth passed through the Io Plasma Torus.
         Using Earth satellites to provide measurements of the
         terrestrial ionosphere, [LEVYETAL1981] determined the
         electron density within the torus from differential phase
         shift between the S- and X-band signals.

       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 [KRISHERETAL1990].

     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.

       Members of the Voyager Radio Science Team and their primary
       interests for the Uranus encounter  were:

       J.D. Anderson Jet Propulsion Lab   Gravity, Relativity
       V.R. Eshleman Stanford University  Atmospheres
       G.F. Lindal   Jet Propulsion Lab   Atmospheres, Methodology
       G.L. Tyler    Stanford University  Experiment Technique/Design

     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-Uranus era each
       complex was equipped with several antennas (including at least
       one 64-m 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

       Ground stations had the ability to transmit coded and uncoded
       waveforms which could be echoed by distant spacecraft.
       Analysis of the received coding allowed navigators to determine
       the distance to the spacecraft; analysis of Doppler shift on
       the carrier signal allowed estimation of the line-of-sight
       spacecraft velocity.  Range and Doppler measurements were used
       to calculate the spacecraft trajectory and to infer gravity
       fields of objects near the spacecraft.

       Ground stations could record spacecraft signals that had
       propagated through or been scattered from target media.
       Measurements of signal parameters after wave interactions with
       surfaces, atmospheres, rings, and plasmas were used to infer
       physical and electrical properties of the target.

       The Deep Space Network was managed by the Jet Propulsion
       Laboratory of the California Institute of Technology for the
       U.S.  National Aeronautics and Space Administration.
       Specifications included:

       Instrument Id                  : RSS-VG2U
       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

     Subsystems - DSN
       The Deep Space Communications Complexes (DSCCs) were an
       integral part of the Radio Science instrument, along with other
       receiving stations and the spacecraft Radio Frequency
       Subsystem.  Their system performance directly determined the
       degree of success of Radio Science investigations, and their
       system calibration determined 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] with
       adjustments for the situation during the Voyager-Jupiter time
       frame.  For additional information, consult [DSN810-5].

       Each DSCC included 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) are listed in
       the table.

                     --------   --------   --------
                    | DSS 11 | | DSS 12 | | DSS 14 |
                    |  26-m  | |  26-m  | |  64-m  |
                     --------   --------   --------
                         |            |     |
                         |            v     v
                         |         --------------
                                  |    CENTER    |
                     ----------      ---------
                    | 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.

       Open-Loop Receivers
         Multi-Mission Receivers provided as many as four channels of
         data for occultation studies during Voyager encounters.  For
         the Uranus encounter at Canberra, these were assigned as
         follows:  DSS-43 S-RCP, DSS-42 S-RCP, DSS 45 X-RCP, and DSS
         42 X-RCP.  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 then
         sampled and recorded.  Filter bandwidths for S-RCP and X-RCP
         were 20 kHz.  The samples were recorded for later analysis.

         For signals with narrower spectral ranges, the 10 MHz IF
         could be mixed to 100 kHz where filters as narrow as 100 Hz
         could be applied.

       DSS Frequency and Timing Subsystem
         Frequency and timing were provided by a hydrogen maser.
         Precisions are shown in the tables below:

          Reference             Frequency Stability   Integration Time
          -----------------     -------------------   ----------------
          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

     Optics - DSN
       Performance of DSN ground stations depended primarily on size
       of the antenna and capabilities of electronics.  These are
       summarized in the following set of tables.  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 (MMR)
         The open loop receiver block diagram shown below is for the
         Multi-Mission Receiver (MMR) system at Canberra during the
         Voyager Uranus encounter.  Based on a tuning prediction file,
         the POCA controlled the DANA synthesizer, the output of which
         (after multiplication) mixed input signals at both S- and
         X-band to fixed intermediate frequencies for amplification.
         These signals in turn were down converted and passed through
         additional filters until they yielded Output with bandwidths
         up to 45 kHz.  The Output was digitally sampled and either
         written to magnetic tape or electronically transferred for
         further analysis.

            S-Band                                          X-Band
           2295 MHz                                        8415 MHz
            Input                         800 MHz            Input
              |                              |                 |
              v                              v      8115       v
             ---        1995 MHz            ---      MHz      ---
            | X |<-------------            | X |------------| X |
             ---               |            ---               ---
              |                |             |                 |
              |               ---           ---                |
              |              |x 3|         |x11|               |
              |               ---  approx   ---                |
              |                |   665 MHz   |                 |
              |                 -------------                  |
           300|                       |                        |300
           MHz|                      ---                       |MHz
              |                     | X |<--600 MHz            |
              v                      ---                       v
             ---                      ^                       ---
            | X |<--290 MHz           |            290 MHz--| X |
             ---                    -----                     ---
              |        9.9         |x 1.5|          9.9        |
              |        MHz          -----           MHz        |
              |         |             ^              |         |
            10|         v             |              v         |10
           MHz|        ---       -----------        ---        |MHz
              |-------| X |     |   DANA    |      | X |<------|
              |        ---      |Synthesizer|       ---        |
              |         |        -----------         |         |
              v         v             ^              v         v
           -------   -------          |           -------   -------
          |Filters| |Filters|    ----------      |Filters| |Filters|
          |  4-8  | |  1-3  |   |   POCA   |     |  1-3  | |  4-8  |
           -------   -------    |Controller|      -------   -------
              |         |        ----------          |         |
            10|         |0.1                      0.1|         |10
           MHz|         |MHz                      MHz|         |MHz
              v         v                            v         v
             ---       ---                          ---       ---
  10 MHz ---| X |     | X |<------ 0.1 MHz --------| X |     | X |<-
             ---       ---                          ---       ---   |
              |         |                            |         |10 MHz
              v         v                            v         v
           Output     Output                      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.  Filters are defined below.

         FSant = (9/2)*SYN+2100*10^6-Fsamp+Frec    (Filters 1,2,3,8)
               = (9/2)*SYN+2100*10^6+Frec          (Filters 4,5,6,7)

         FXant = (33/2)*SYN+7700*10^6-3*Fsamp+Frec (Filters 1,2,3,8)
               = (33/2)*SYN+7700*10^6+Frec         (Filters 4,5,6,7)

          FSant,FXant  are the antenna frequencies of the incoming
                        signals at S and X bands, respectively,
          SYN          is the output frequency of the DANA
                        synthesizer, commonly labeled the readback
                        POCA frequency on data tapes,
          Fsamp        is the effective sampling rate of the digital
                        samples, and
          Frec         is the apparent signal frequency in a spectrum
                        reconstructed from the digital samples.

     Filters - DSN

       DSCC Open-Loop Receiver (MMR)
         MMR filters and recommended sampling rates included the

                             S-Band                    X-Band
                   ------------------------  -------------------------
                   Output   3 dB Recommended Output   3 dB     Rec'ded
          Filter   Center   Band   Sampling  Center   Band    Sampling
                    Freq    Width    Rate*   Freq     Width     Rate*
                    (Hz)    (Hz)     (sps)   (Hz)     (Hz)      (sps)
          ------   ------  ------  --------  ------  ------   --------
             1        150     100       200     550     100        200
             2        750     500      1000    2750     500       1000
             3       1500    1000      2000    5500    1000       2000
             4        409     818      2000    1500    3000       6000
             5       1023    2045      5000    3750    7500      15000
             6       2045    4091     10000    7500   15000      30000
             7       4091    8182     20000   15000   30000      60000
             8      37500   20000     50000  137500   20000      50000

           * Sampling rates depend on resolution of samples and number
             of analog-to-digital converters assigned to each channel;
             see discussion of modes under 'DSCC Spectrum Processing
             Subsystem' below.  The rates at which single A/D
             converters can operate with the MMR include:

               8-bit samples:      12-bit samples:     16-bit samples:
                     200                  200                1250
                     250                 1000
                     400                 1250
                     500                 2000
                    1000                 5000
                    1250                10000

     Detectors - DSN

       DSCC Open-Loop Receivers
         Open-loop receiver output was detected in software by the
         radio science investigators.

       DSCC Closed-Loop Receivers
         Nominal carrier tracking loop threshold noise bandwidths at
         S- and X-band were 10-12 and 30-48 Hz, respectively.  Sample
         rates for Doppler were nominally 1 per 5 seconds at Uranus.

     Calibration - DSN
       Calibrations of hardware systems were carried out periodically
       by DSN personnel; these ensured that systems operated at
       required performance levels -- for example, that antenna
       patterns, receiver gain, propagation delays, and Doppler
       uncertainties met specifications.  No information on specific
       calibration activities is available.  Nominal performance
       specifications are shown in the tables above.  Additional
       information may be available in versions of [DSN810-5] or

       equivalent documents applicable to the Uranus encounter time

       Prior to each tracking pass, station operators performed a
       series of calibrations to ensure that systems met
       specifications for that operational period.  Included in
       those calibrations was measurement of receiver system
       temperature in the configuration to be employed during the
       pass.  Results of the calibrations were recorded in (hard
       copy) Controller's Logs for each pass.

     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 could be collected in two modes: closed-
         loop, in which a phase-locked loop receiver tracked the
         spacecraft signal, or open-loop, in which a receiver sampled
         and recorded a band within which the desired signal
         presumably resided.  Closed-loop data were collected using
         Closed-Loop Receivers, and open-loop data were 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 could be configured to one
         of three settings: narrow, medium, or wide.  Ordinarily it
         was configured so that expected signal amplitude changes were
         accommodated with minimum distortion.  The loop bandwidth was
         ordinarily configured so that expected phase changes could be
         accommodated while maintaining the best possible loop SNR.
         For Uranus the nominal setting was narrow.

       Coherent vs. Non-Coherent Operation
         The frequency of the signal transmitted from the spacecraft
         could 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 were known as the coherent (or
         'two-way') and non-coherent ('one-way') modes, respectively.
         Mode selection was made at the spacecraft, based on commands
         received from the ground.  When operating in the coherent
         mode, the transponder carrier frequency was 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 was derived from the spacecraft
         on-board crystal-controlled oscillator.  Either closed-loop
         or open-loop receivers (or both) could be used with either
         spacecraft frequency reference mode.  Closed-loop reception
         in two-way mode was usually preferred for routine tracking.
         Occasionally the spacecraft operated coherently while two
         ground stations received the 'downlink' signal; this was
         sometimes known as the 'three-way' mode.

       Open-Loop Sampling
         The Open-Loop Receiver sampling system could operate in four
         sampling modes with from 1 to 4 input signals.  Input
         channels were assigned to ADC inputs during configuration.
         Modes were 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

         Open loop data from the Uranus encounter were sampled
         using Mode 1.

     Location - DSN
       Station locations are documented in [GEO-10REVD].  Geocentric
       coordinates are summarized here.

                             Geocentric  Geocentric  Geocentric
       Station              Radius (km) Latitude (N) Longitude (E)
       ---------            ----------- ------------ -------------
         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

         DSS 42 (26-m STD)  6371.675607 -35.2191850   148.9812546
         DSS 43 (64-m)      6371.688953 -35.2209308   148.9812540

         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) was a
         stream of 8-bit two's complement voltage samples packed into
         the most significant half of 16-bit data words.  The nominal
         input to the Analog-to-Digital Converters (ADCs) was
         +/-10 volts, but the precise scaling between input voltages
         and output digitized samples was usually irrelevant for
         analysis; the digital data were 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 had a known system noise temperature (SNT).  Raw
         samples comprised the data block in each data record; header
         and trailer records contained ancillary information such as a
         time tag for the first sample in the data block.

       Closed-Loop System
         Closed-loop data were 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
         contained entries such as status information and measurements
         of ranging, Doppler, and signal strength.

       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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