Voyager RSS VG2UINST.CAT
Return to RSS data set page.
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_NAME = "RADIO SCIENCE SUBSYSTEM"
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
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 1977-08-20, 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
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 2 USO
during key events were (multiplying by 3/11 yields the S-band
frequency):
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
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 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
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 [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
combined.
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
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
[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
available.
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
[TYLERETAL1992].
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
| --------------
--------|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.
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)
where
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
following:
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
2000
2500
3125
4000
5000
6250
10000
12500
15625
20000
25000
31250
50000
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
frame.
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)
--------- ----------- ------------ -------------
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) 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.
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"
END_OBJECT = INSTRUMENT_INFORMATION
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "ALLAN1966"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "ANDERSONETAL1987A"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "ANDERSONETAL1987B"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "ASMAR&HERRERA1993"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "ASMAR&RENZETTI1993"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "ASMARETAL1995"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "DSN810-5"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "ESHLEMANETAL1977"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "ESHLEMANETAL1979B"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "GEO-10REVD"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "GRESHETAL1989"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "GURROLA1995"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "KRISHERETAL1990"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "LEVYETAL1981"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "LINDALETAL1981"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "LINDALETAL1983"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "LINDALETAL1985"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "LINDALETAL1987"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "LINDALETAL1990"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "MAROUF&TYLER1985"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "TYLERETAL1981B"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "TYLERETAL1982"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "TYLERETAL1986"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "TYLERETAL1989"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "TYLERETAL1992"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "WOO1993"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
END_OBJECT = INSTRUMENT
END
Return to RSS data set page.