The majority of the text in this file was extracted from the Juno
Mission Plan Document, S. Stephens, 2012. [JPL D-35556]
Instrument Host Overview
For most Juno experiments, data were collected by instruments on
the spacecraft then relayed via the orbiter telemetry system to stations of
the NASA Deep Space Network (DSN). Radio Science required the DSN for its
data acquisition on the ground. The following sections provide an
overview, first of the orbiter, then the science instruments, and
finally the DSN ground system.
Instrument Host Overview - Spacecraft
Juno launched on August 5, 2011. The spacecraft used a delta V - EGA
trajectory consisting of deep space maneuvers on August 30, and September
14, 2012 followed by an Earth gravity assist on 9 October 2013 at an
altitude of ~500 km. Juno arrived at Jupiter in July 2016 using a 53.5-day
capture orbit prior to commencing operations for a prime mission comprising
32 high inclination, high eccentricity orbits of Jupiter. The orbit is
polar (~90deg inclination) with a periapsis altitude of ~4,500 km and a
semi-major axis of ~57 RJ giving an orbital period of about 53 days.
Data were not acquired during Jupiter Orbit Insertion (Perijove 0) nor
during Perijove 2. See MISSION.CAT for details of the mission.
Juno is a spin-stabilized spacecraft equipped for 10 diverse science
investigations plus a camera included for education and public outreach.
The spacecraft includes one high gain (HGA), two low gain antennas (LGAs),
a toroidal medium gain antenna, a large set of solar arrays in three
'wings', a main engine, and attitude thrusters. In this description
Juno will frequently be called 'the spacecraft.'
Juno is a spin-stabilized with a large spin-to-transverse moment of
inertia ratio. It is solar powered with 3 large, deployable rigid-panel
wings that can be moved to adjust the spin axis to the HGA boresight.
The solar panels are spaced at 120 deg. intervals around a basic
6-sided structure. Juno utilizes high energy density Li ion
batteries for battery-regulated bus voltage. Basic radiation
protection for sensitive electronics is afforded by a titanium-
walled vault. Juno has a dual-mode propulsion system with a
deployable micrometeoroid sheild for the main engine. Attitude
control thrusters are used for re-orienting the spin axis and for
smaller trajectory/orbit corrections, and spin-up/down manuevers. The
thermal design uses a cold-biased passive design with software-
controlled heaters. Attitude control is provided using Inertial
Measurement Units, Stellar Reference Units, Spinning Sun Sensors, and
active (thrusters) and passive (fluid-filled loop) nutation damping.
Telecom is achieved with X-band uplink and downlink coupled with five
antennas for completed coverage and including tones capability for
critical low-link margin telemetry. Ka-band telecom is included for
improved Doppler measurement performance. Essential systems are
redundantt and cross-strapped. The z-axis of the spacecraft coordinate
system is co-aligned with the HGA axis, hence, nominally points toward
Earth. The spacecraft x-axis is in the direction of the solar panel which
includes the MAG boom at the end. The y-axis completes a right-hand
The spacecraft comprised several subsystems, which are described briefly
below. For more detailed information, see JPLD-5564.
Structures and Mechanisms Subsystem
The spacecraft structure uses heritage composite panel and clip
construction for decks, central cylinder, and gusset panels.
Polar mounted off-center spherical tanks are consistent with a spinning
spacecraft design with a high, stable inertia ratio. The central
cylinder has high torsional stiffness. Six gussets provide stiffness
for the solar arrays. Components are located such that they meet all
mechanical requirements, including mass, field of view, magnetics, and
alignments. The radiation vault uses titanium panels that provide
structure as well as shielding. Assembly, Test, and Launch Operations
(ATLO) access is easily available through 3 removable panels (top and 2
sides). The Telecom subassembly is contained on one panel. Louvers
on the outside reject heat during Inner Cruise. The vault also serves
as a Faraday cage. Spacecraft mechanisms include solar array
articulation, providing up to 4.5 deg. of wing tilt, and allowing
approximately 1.9 deg. of principal axis adjustment. A main engine
cover must open and close for each of 4 main engine burns as well as
main engine flushing burns, and also provides micrometeoroid protection.
Solar array wings consist of 11 solar panels and 1 MAG boom. They use
heritage designs for (a) spring driven and viscously damped deployment,
and (b) a multi-panel retention and release.
The Gravity Science and Telecom Subsystem provides X-band command uplink
and engineering telemetry and science data downlink for the entire post-
launch, cruise, and Jupiter orbital operations at Earth ranges up to 6.5
AU. The subsystem also provides for dual-band (X- and Ka-band) Doppler
tracking for Gravity Science at Jupiter (concurrent X-band telemetry
during Gravity Sciences passes also contributes to data return
requirements). The subsystem is designed, built, and tested at JPL
prior to delivery to Lockheed Martin.
The non-science part of the subsystem is fully redundant. The Ka-band
uplink for Gravity Science is single-string as is the Ka-band power
amplifier. The subsystem is designed to provide a minimum 2-sigma
margin on all links. Juno will normally use NASA's Deep Space Network
(DSN) 34-m subnet for communications. The 70-m subnet will be used
for critical event coverage post launch, reception of tones during
main engine maneuvers (DSMs, JOI, and PRM), enhanced data return
during selected orbits at Jupiter, and for safe mode telecom.
The telecom design is sized to provide a minimum science downlink rate
of 18 kbps into a 34-m DSN station at max range (6.46 AU) during
orbital operations, and 12 kbps during Gravity Science perijove passes.
Higher data rates will be used at shorter ranges or with a 70-m DSN
station. The design also supports sending tone modulation during DSMs,
JOI, and PRM burns when the spacecraft spin axis is nearly normal to
the Earth line.
Telecom equipment includes two Small Deep Space Transponders (SDSTs),
both with X/X and one with additional X/Ka capability. The X/X/Ka
capability serves as a partial backup for Gravity Science. There are
two 25-W X-band Traveling Wave Tube Amplifiers (TWTAs), 5 Waveguide
Transfer Switches (WTSes), 2 X-band diplexers, filters, microwave
components, waveguide, and cabling. These are all used to feed 5
separate antennas. The high-gain antenna (HGA) is a 2.5-m, shaped,
axially symmetric, Gregorian, dual-reflector antenna fed by a
dual-band, coaxial, corrugated feed. The HGA supports uplink and
downlink at both X and (carrier-only) Ka-band. There is an X-band
medium-gain antenna (MGA or F-MGA), foreward and aft low-gain
antennas (LGAs, specifically F-LGA and A-LGA), and toroidal
antenna (T-LGA) that provides coverage during the DSMs, JOI, and PRM
burns. The toroidal antenna is also used briefly during cruise when
the Sun-Probe-Earth (SPE) angle is near 90 deg.
All antennas except the toroidal antenna are aligned with the
spacecraft Z axis, which will be aligned with the spin axis shortly
after launch using the adjustable solar array wing actuators. The HGA,
MGA, and foreward LGA are nearly co-boresighted (the MGA and LGAs are
slightly offset from the spin vector). The aft LGA is used when
the spacecraft's trajectory goes inside of the Earth's orbit and the
SPE angle is greater than 110 deg.
The Ka-band Translator Subsystem (KaTS) receives a Ka-band uplink
through the HGA from the DSN (DSS-25) and coherently generates a
Ka-band downlink carrier signal and then amplifies the signal. The
signal is then guided to the Ka-band feed of the HGA for the Gravity
Science two-way Ka-band Doppler signal. The KaTS is provided by the
Italian Space Agency.
Juno uses a dual-mode Propulsion Subsystem, with a biprop main engine
(ME) and monoprop Reaction Control System (RCS) thrusters. The 12
thrusters are mounted on 4 Rocket Engine Modules (REMs), allow
translation and rotation about 3 axes, and provide some redundancy.
There are 8 lateral thrusters, canted away from X by 5 deg. along Y
and by 12.5 deg. along Z, and 4 axial thrusters, canted away from Z
by 10 deg. along Y. 6 equal-sized spherical propellant tanks contain
fuel (4 tanks) and oxidizer (2). Biprop mode (N2O4/hydrazine) is
used for major maneuvers and flushing burns, and monoprop mode
(blowdown hydrazine) is used for spin-up and -down, precession,
active nutation damping, and most TCMs and OTMs. The Leros-1b main
engine is well-characterized, and is fixed on the Z axis, pointing
aft. Isolation valve ladders included in the pressurization system
eliminate propellant mixing concerns. RCS thrusters are located to
minimize plume interactions. The propellant tanks are sized
consistent with the planned delta-V budget, for the maximum
spacecraft mass that can be lifted by an Atlas V 551 to the required C3.
Electrical Power Subsystem (EPS)
Juno's redundant, single fault tolerant Electrical Power Subsystem
manages the spacecraft power bus and distribution of power to payloads,
propulsion, heaters, mechanism motor actuators, NASA Standard Initiators
(NSIs), and avionics. The Power Distribution and Drive Unit (PDDU)
monitors and manages the spacecraft power bus, manages the available
solar array power to meet the spacecraft load and battery state of
charge (SOC), and provides controlled power distribution. The Pyro
Initiator Unit (PIU) includes a redundant, dual fault tolerant
Pyrotechnic Initiator Module (PIM). Power generation is provided
by 3 solar arrays using current generation UTJ solar cells. Two 55
A-hr Li ion batteries provide power when Juno is off-Sun or in
eclipse, and are tolerant of the Jupiter radiation environment. The
power modes during Science Orbits are sized for either an MWR or a
GRAV orbit, and provide sufficient margin given the expected loads
during perijove science passes as well as DSN telecom passes.
Sufficient power and energy margins have also been demonstrated for
the Launch, DSMs, JOI, PRM, and deorbit burn mission events, as well
as safe mode near EOM.
Command and Data Handling Subsystem (C&DH)
The C&DH is based on two redundant, single fault tolerant boxes
developed for MRO. Each C&DH box includes a cPCI bus interconnected
to 3U cards (except the DTCI card which uses 6U format) and a
RAD750 flight processor with 256 MBytes of NVM flash memory and 128
MBytes of SFC DRAM local memory. It provides 100 Mbps total
instrument throughput, more than enough for payload requirements.
32 Gbits (base 2, EOL) of science data storage (plus 8 Gbits for
EDAC) are available on the DTCI card, which has been demonstrated
to be sufficient for minimum and maximum science orbit downlink data
requirements, and representative stress cases that account for data
retransmission and prioritization.
Guidance, Naviation, and Control Subsystem (GN&C)
The Juno GN&C Subsystem uses spin-stabilized control. The launch
spin rate of 1.4 RPM is initiated by the launch vehicle upper stage
(and adjusted by the spacecraft after solar array deployment). The
planned spin rate varies during the mission: 1 RPM for cruise, 2 RPM
for science operations, and 5 RPM for main engine maneuvers. MWR and
GRAV orbits at Jupiter use 2 different spacecraft attitudes: spin
axis parallel to orbit normal for MWR orbits, and HGA Earth-pointed
for GRAV orbits. Precession and spin control use balanced mode for
minimum delta-V, and are capable of unbalanced mode for lower fuel
use (although not planned to be used). Active nutation damping
requires the Inertial Measurement Units (IMUs). Delta-V maneuvers
using the RCS thrusters can be either turn-burn-turn (TBT), which
requires precession to turn to the desired attitude, or vector-mode
(Vect), in which thrust is provided in both axial and lateral
directions. Main engine maneuvers require precession to point the
engine in the desired direction. One of two Stellar Reference
Units (SRUs) and one of two Spinning Sun Sensors (SSSes) are
continuously powered (the SRU is turned off for ME burns, and both
SSSes are powered on during safe mode). One of two IMUs is powered
for delta-V maneuvers, large precessions (larger than ~2.5 deg.),
active nutation damping, and spin control.
Temperature Control Subsystem (TCS)
Juno's Thermal Control Subsystem uses a passive cold biased design
with heaters and louvers. The core TCS consists of an insulated,
louvered electronics vault atop an insulated, heated propulsion module.
This design accommodates all mission thermal environments from
perihelion to orbital operations. During cruise, while the spacecraft
is close to the Sun, the HGA is used as a heat shield to protect the
vault avionics. Outside ~1.4 AU, the spacecraft pointing is
unrestricted, while inside ~1.4 AU Sun-pointing and off-Sun-pointing
are required. Most instrument electronics are contained within the
radiation vault and are thermally managed as part of the vault TCS.
Science sensors are externally mounted to the deck and are individually
blanketed and heated to maintain individual temperature limits.
JUNO SCIENCE INSTRUMENTS
Juno's instrument complement includes Gravity Science using the X and Ka bands
to determine the structure of Jupiter's interior; magnetometer investigation
(MAG) to study the magnetic dynamo and interior of Jupiter as well as to
explore the polar magnetosphere; and a microwave radiometer (MWR) experiment
covering 6 wavelengths between 1.3 and 50 cm to perform deep atmospheric
sounding and composition measurements. The instrument complement also
includes a suite of fields and particle instruments to study the polar
magnetosphere and Jupiter's aurora. This suite includes an energetic particle
detector (JEDI), a Jovian auroral (plasma) distributions experiment (JADE), a
radio and plasma wave instrument (Waves), an ultraviolet spectrometer (UVS),
and an Jupiter infrared auroral mapping instrument (JIRAM). The JunoCam is a
camera included for education and public outreach. While this is not a
science instrument, we plan to capture the data and archive them in the PDS
along with the other mission data. The MAG investigation consists of
redundant flux gate magnetometers (FGM) and co-located advanced stellar
compasses (ASC). The ASCs are provided by the Danish Technical University
under an effort led by John Jorgenson. The SRU is used for low-light remote
sensing at visible wavelengths and as an in situ particle detector for high
Scott Bolton is the Juno Principal Investigator. The Science Team members
responsible for the delivery and operation of the instruments are listed
Instrument Acronym Lead Co-I
---------------------------------------------- -------- ---------
Gravity Science GRAV Park
Magnetometer MAG Connerney
Microwave Radiometer MWR Levin
Jupiter Energetic Particle Detector Instrument JEDI Mauk
Jovian Auroral Distributions Experiment JADE Allegrini
Radio and plasma wave instrument WAVES Kurth
Ultraviolet Imaging Spectrograph UVS Gladstone
Jovian Infrared Auroral Mapper JIRAM Mura
Juno color, visible-light camera JUNOCAM Hansen
Stellar Reference Unit SRU Becker
Advanced Stellar Compass ASC Joergensen
Gravity Science (GRAV): The Gravity Science investigation was designed to
map Jupiter's graviational field.
- Determine normalized gravity coefficients J4, J6, and J8 - J14
Magnetometer (MAG): The Magnetometer investigation was designed to map
Jupiter's magnetic field.
- Derive a spherical harmonic model of Jupiter's main magnetic
field through degree and order 14
Microwave Radiometer (MWR): The Microwave Radiometer was designed to
characterize Jupiter's atmosphere.
- Determine the global O/H ration (water abundance) in Jupiter's
- Measure latitudinal variations in Jupiter's deep atmosphere
(composition, temperature, cloud opacity, and dynamics)
- Measure the microwave brightness temperatures of Jupiter over all
latitudes at wavelengths that fully sample the atmospheric thermal
emission at all altitude levels from the ammonia cloud-forming
region to below the water cloud-forming region
Jupiter Energetic Particle Detector Instrument (JEDI): The Jupiter
Energetic Particle Detector Instrument was designed to characterize
Jupiter's polar magnetosphere.
- Measure the pitch angle and energy distribution of electrons
across auroral features
Jovian Auroral Distributions Experiment (JADE): The Jovian Auroral
Distributions Experiment was designed to characterize Jupiter's
- Measure three dimensional time variable, pitch angle, energy and
composition distribution of ions
- Measure ion composition to differentiate between H+, H2+, H3+,
O+, and S+.
Radio and Plasma Wave Instrument (Waves): The Waves instrument was
designed to characterize Jupitter's polar magnetosphere.
- Measure radio and plasma wave emissions associated with
auroral phenomena in the polar magnetosphere
Ultraviolet Imaging Spectrograph (UVS): The Ultraviolet Imaging
Spectrograph was designed to characterize Jupiter's polar
- Characterize the UV auroral emissions
Jovian Infrared Auroral Mapper (JIRAM): The Jovian Infrared Auroral
Mapper was designed to characterize Jupiter's atmosphere.
Juno color, visible-light camera (JUNOCAM): The Juno color, visible-
light camera was designed to engage the public and educate students.
Advanced Stellar Compasses (ASC): These are four low-light cameras
that provide quaternions for the two fluxgate magnetometer assemblies
on the magnetometer boom. They also may provide science images of
non-stellar objects and for dust studies.
Stellar Reference Unit (SRU): The Stellar Reference Unit (SRU) is
operated as a broadband visible (450-1100 nm) science imager for the
purpose of studying low-light features and phenomena of the Jovian
system, such as Jupiter's faint dust ring and lightning. It is also
used as an in situ particle detector for studying the high energy
radiation environment at Jupiter.
Instrument Host Overview - DSN
Radio Science investigations 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 Deep Space Network was a telecommunications facility managed by
the Jet Propulsion Laboratory of the California Institute of
Technology for the U.S. National Aeronautics and Space
The primary function of the DSN was to provide two-way communications
between the Earth and spacecraft exploring the solar system. To carry
out this function the DSN was equipped with high-power transmitters,
low-noise amplifiers and receivers, and appropriate monitoring and
The DSN consisted of three complexes situated at approximately equally
spaced longitudinal intervals around the globe at Goldstone (near
Barstow, California), Robledo (near Madrid, Spain), and Tidbinbilla
(near Canberra, Australia). Two of the complexes were located in the
northern hemisphere while the third was in the southern hemisphere.
The network comprised four subnets, each of which included one antenna
at each complex. The four subnets were defined according to the
properties of their respective antennas: 70-m diameter, standard 34-m
diameter, high-efficiency 34-m diameter, and 26-m diameter.
These DSN complexes, in conjunction with telecommunications subsystems
onboard planetary spacecraft, constituted the major elements of
instrumentation for radio science investigations.
For more information see [ASMAR&RENZETTI1993]