Artist's rendering of the Juno spacecraft bus
|Mission type||Jupiter orbiter|
|Mission duration||6 years total
Cruise: 5 years
Science phase: 1 year
|BOL mass||3,625 kg (7,992 lb)|
|Power||400 W; two 55-ampere-hour lithium-ion batteries|
|Start of mission|
|Launch date||August 5, 2011UTC
(4 years, 2 months and 3 days ago)
|Rocket||Atlas V 551 (AV-029)|
|Launch site||Space Launch Complex 41
Cape Canaveral Air Force Station, Florida, United States
|Flyby of Earth|
|Closest approach||October 9, 2013
(1 year, 11 months and 29 days ago)
|Distance||559 km (347 mi)|
|Orbital insertion||4 July 2016|
|JIRAM||Jovian Infrared Auroral Mapper|
|JADE||Jovian Auroral Distribution Experiment|
|JEDI||Jovian Energetic Particle Detector Instrument|
|Waves||Radio and Plasma Wave Sensor|
|UVS||Ultraviolet Imaging Spectrograph|
Juno is a NASA New Frontiers mission to the planet Jupiter. Juno was launched from Cape Canaveral Air Force Station on August 5, 2011 and will arrive on July 4, 2016. The spacecraft is to be placed in a polar orbit to study Jupiter's composition, gravity field, magnetic field, and polar magnetosphere. Juno will also search for clues about how the planet formed, including whether it has a rocky core, the amount of water present within the deep atmosphere, how its mass is distributed, and its deep winds, which can reach speeds of 618 kilometers per hour (384 mph).
The Juno spacecraft is going to Jupiter powered by an electrical source deployed in deep space: solar arrays. Commonly used by satellites orbiting Earth and working in the inner Solar System, solar panels are typically set aside for missions beyond the asteroid belt in favor of generators powered by radioisotope thermoelectric generators. For Juno, however, three solar array wings, the largest ever deployed on a planetary probe, will play an integral role in stabilizing the spacecraft and generating power.
The spacecraft's name comes from Greco-Roman mythology. The god Jupiter drew a veil of clouds around himself to hide his mischief, but his wife, the goddess Juno, was able to peer through the clouds and see Jupiter's true nature.
- 1 Overview
- 2 Scientific instruments
- 3 Operational components
- 4 Galileo's plaque and Lego figurines
- 5 Timeline
- 6 See also
- 7 References
- 8 External links
Juno requires a five-year cruise to Jupiter, arriving around July 4, 2016. The spacecraft will travel over a total distance of roughly 2.8 billion kilometers (18.7 AU; 1.74 billion miles). The spacecraft will orbit Jupiter 37 times over the course of 20 months. Juno's trajectory used a gravity assist speed boost from Earth, accomplished through an Earth flyby two years (October 2013) after its August 5, 2011 launch. Shortly after the flyby of Earth, Juno entered briefly into safe mode twice during October 2013. Nevertheless, it remains on track for its encounter with Jupiter. In August 2016, the spacecraft will perform an orbit insertion burn to slow the spacecraft enough to allow capture into a 14-day polar orbit.
Once Juno is inserted into a polar orbit, infrared and microwave instruments will begin to measure the thermal radiation emanating from deep within Jupiter's atmosphere. These observations will complement previous studies of its composition by assessing the abundance and distribution of water, and therefore oxygen. By filling missing pieces of the puzzle of Jupiter's composition, this data will also provide insight into Jupiter's origins. Juno will also investigate the convection that drives general circulation patterns in Jupiter's atmosphere. Other instruments aboard Juno will gather data about its gravitational field and polar magnetosphere. The Juno mission is set to conclude in February 2018, after completing 37 orbits around Jupiter, when the probe will be de-orbited to burn up in Jupiter's outer atmosphere, so as to avoid any possibility of it impacting on one of its moons.
The Atlas V (AV-029) using a Russian-designed RD-180 main engine, powered by kerosene and liquid oxygen, was started and underwent checkout 3.8 seconds prior to the ignition of five strap-on solid rocket boosters (SRBs). Following SRB burnout, approximately 1 minute 33 seconds into the flight, two of the spent boosters fell away from the vehicle followed 1.5 seconds later by the remaining three. When heating levels had dropped below predetermined limits, the payload fairing that protected Juno during transit through the thickest part of the atmosphere separated, about 3 minutes 24 seconds into the flight. The Atlas V main engine cut off 4 minutes 26 seconds after liftoff. 16 seconds later, the Centaur second stage ignited and burned for approximately 6 minutes, putting the satellite into an initial parking orbit.
The vehicle coasted for approximately 30 minutes, and then the Centaur was re-ignited for a second firing of 9 minutes, putting the spacecraft on an Earth escape trajectory.
Prior to separation the Centaur stage used onboard reaction engines to spin Juno up to 1.4 RPM. About 54 minutes after launch, the spacecraft separated from the Centaur and began to extend its solar panels. Following the full deployment and locking of the solar panels, Juno 's batteries began to recharge. Successful deployment of the solar panels reduced Juno 's spin rate by two-thirds. The probe is spun to ensure stability during the voyage and so that all instruments on the probe are able to observe Jupiter.
The voyage to Jupiter will take five years, which included an Earth flyby on October 10, 2013. On 12 August 2013 Juno had traveled half of its journey to Jupiter. When it reaches the Jovian system, Juno will have traveled approximately 19 AU.
Scott Bolton of the Southwest Research Institute in San Antonio, Texas is the principal investigator and is responsible for all aspects of the mission. The Jet Propulsion Laboratory in California manages the mission and the Lockheed Martin Corporation was responsible for the spacecraft development and construction. The mission is being carried out with the participation of several institutional partners. Co-investigators include Toby Owen of the University of Hawaii, Andrew Ingersoll of California Institute of Technology, Fran Bagenal of the University of Colorado at Boulder, and Candy Hansen of the Planetary Science Institute. Jack Connerney of the Goddard Space Flight Center served as instrument lead.
Juno was originally proposed at a cost of approximately US$700 million (FY03) for a June 2009 launch. NASA budgetary restrictions resulted in postponement until August 2011, and a launch on board an Atlas V rocket in the 551 configuration. As of June 2011[update], the mission was projected to cost $1.1 billion over its life.
The Juno spacecraft's suite of science instruments will:
- Determine the ratio of oxygen to hydrogen, effectively measuring the abundance of water in Jupiter, which will help distinguish among prevailing theories linking the gas giant's formation to the Solar System.
- Obtain a better estimate of Jupiter's core mass, which will also help distinguish among prevailing theories linking the gas giant's formation to the Solar System.
- Precisely map Jupiter's gravitational field to assess the distribution of mass in Jupiter's interior, including properties of its structure and dynamics.
- Precisely map Jupiter's magnetic field to assess the origin and structure of the field and how deep in Jupiter the magnetic field is created. This experiment will also help scientists understand the fundamental physics of dynamo theory.
- Map the variation in atmospheric composition, temperature, structure, cloud opacity and dynamics to pressures far greater than 100 bars (10 MPa; 1450 pound/sq inch) at all latitudes.
- Characterize and explore the three-dimensional structure of Jupiter's polar magnetosphere and its auroras.
- Measure the orbital frame-dragging, known also as Lense–Thirring precession caused by the angular momentum of Jupiter, and possibly a new test of general relativity effects connected with the Jovian rotation.
After traveling for two years, Juno returned to Earth in October 2013. It used Earth’s gravity to help propel itself toward the Jovian system in a maneuver called Gravitational slingshot. The spacecraft received a boost in speed of more than 8,800 mph (3.9 km/s) and was set on a direct course to Jupiter. The flyby was also used as a rehearsal for the Juno science team to test the instruments, like the cameras, and practice certain procedures before the arrival to Jupiter.
Other spacecraft like New Horizons took a straight path to Jupiter after launch. Juno, on the other hand, did not have enough momentum for a direct trip when launched, and was pulled back by the Sun's gravity and needed Earth's gravity assist. That is due to the fact that when Juno was due to launch there was not an available rocket powerful enough to send such a heavy spacecraft directly to Jupiter, so the flyby maneuver was an essential part of the mission. The Atlas V rocket provided half of the boost Juno needs to reach Jupiter, and the Earth flyby provided the rest.
Several instruments were active during the flyby, including Juno's Advanced Stellar Compass (ASC). Originally designed to track faint stars for deep space orientation, the ASC captured low-resolution images of the Earth–Moon system during its final encounter, giving a starship-like view of the world.
Orbit and environment
Juno's planned polar orbit is highly ellipitical and takes it close to the poles—within 4,300 kilometers (2,672 mi)—but then far beyond even Callisto's orbit. Each orbit takes 14 days and the spacecraft is expected to complete 37 orbits until the end of the mission.
This type of orbit helps the craft avoid any long-term contact with Jupiter's radiation belts, which can cause damage to spacecraft electronics and solar panels. The "Juno Radiation Vault", with 1-centimeter-thick titanium walls, will also aid in protecting and shielding Juno's electronics. However, the radiation is so destructive that the instruments JunoCam and Jovian Infrared Auroral Mapper (JIRAM) are expected to last only through the eighth orbit. The microwave radiometer is planned to last 11 orbits.
To better understand the Juno orbit parameters, one must take into account what was learned about radiation in the Jovian system with the Galileo mission. The Galileo probe to Jupiter, which was in an equatorial orbit, had to endure over 20 radiation anomalies, exceeding its design limit by at least a factor of three. In comparative terms, Juno will receive much less high levels of radiation than the Galileo orbiter.
||The primary goal of the radiometer is to probe the deep atmosphere of Jupiter at radio wavelengths ranging from 1.3 cm to 50 cm using six separate radiometers to measure Jupiter's thermal emissions. (Principal investigator: Mike Janssen, Jet Propulsion Laboratory)|
||The primary goal of JIRAM is to probe the upper layers of Jupiter's atmosphere down to pressures of 5–7 bars (72–102 pound/square inch) at infrared wavelengths in the 2–5 μm interval using an imager and a spectrometer. (Principal investigator: Angioletta Coradini, Italian National Institute for Astrophysics)|
||The magnetic field investigation has three goals: mapping of the magnetic field, determining the dynamics of Jupiter's interior, and determination of the three-dimensional structure of the polar magnetosphere. The magnetometer experiment consists of the Flux Gate Magnetometer (FGM), which will measure the strength and direction of the magnetic field lines, and the Advanced Stellar Compass (ASC), which will monitor the orientation of the magnetometer sensors. (Principal investigator: Jack Connerney, NASA's Goddard Space Flight Center)|
||The Gravity Science Investigation will probe the mass properties of Jupiter by using the communication subsystem to perform Doppler tracking. Gravity Science is a distributed instrument. It includes the X-Band and Ka-Band transponders on the spacecraft and the 34-meter Deep Space Network antenna at Goldstone, California.(Principal investigator: John AndersonJet Propulsion Laboratory. Principal investigator (Juno's Ka-band Translator KaT): Luciano Iess, Sapienza University of Rome)|
||JADE will resolve the plasma structure of the Jovian aurora by measuring the angular, energy and compositional distributions of particles in the polar magnetosphere of Jupiter.(Principal investigator: David McComas, Southwest Research Institute)|
||JEDI will measure the energy and angular distribution of hydrogen, helium, oxygen, sulfur and other ions in the polar magnetosphere of Jupiter.(Principal investigator: Barry Mauk, Applied Physics Laboratory)|
||This instrument will identify the regions of auroral currents that define Jovian radio emissions and acceleration of the auroral particles by measuring the radio and plasma spectra in the auroral region.(Principal investigator: William Kurth, University of Iowa)|
||UVS will record the wavelength, position and arrival time of detected ultraviolet photons during the time when the spectrograph slit views Jupiter during each turn of the spacecraft. Using a 1024 × 256 micro channel plate (MCP) detector, it will provide spectral images of the UV auroral emissions in the polar magnetosphere. (Principal investigator: G. Randall Gladstone, Southwest Research Institute)|
||A visible light camera/telescope, included in the payload to facilitate education and public outreach. It will operate for only seven orbits around Jupiter because of the planet's damaging radiation and magnetic field. (Principal investigator: Michael C. Malin, Malin Space Science Systems)|
Juno is the first mission to Jupiter to use solar panels instead of the radioisotope thermoelectric generators (RTGs) used by Pioneer 10, Pioneer 11, the Voyager program, Ulysses, Cassini–Huygens, New Horizons, and the Galileo orbiter. It is also the farthest solar powered trip in the history of space exploration. Once in orbit around Jupiter, Juno will receive 4% as much sunlight as it would on Earth, but the global shortage of Pu-238, as well as advances made in both solar-cell technology and efficiency over the past several decades, makes it economically preferable to use solar panels of practical size to provide power at a distance of 5 AU from the Sun.
The Juno spacecraft uses three solar arrays symmetrically arranged around the spacecraft, which were stowed against the sides of the spacecraft for launch. Shortly after the spacecraft cleared Earth's atmosphere the arrays were deployed. Two of the arrays have four hinged segments each, and the third array has three segments with a magnetometer in place of the fourth segment. Each panel, or array, is 2.7 meters (8.9 ft), by 8.9 meters (29 ft) long, the biggest on any NASA deep-space probe.
If the arrays were optimized to operate at Earth, they would produce 12 to 14 kilowatts of power. The combined mass of the three arrays is nearly 750 pounds (340 kg). Only about 486 W will be generated when Juno arrives at Jupiter, declining to near 420 W as radiation degrades the cells. The solar panels will remain in sunlight continuously from launch through to the end of the mission, except for short periods during the operation of the main engine.
In general, once we’re out at Jupiter, we need 405 watts, which is not really enough to even run your hair dryer. Of those 405 watts, about half of them go toward keeping the spacecraft warm. So, the other half, somewhere in the 250 range, is to run all of the instruments and all of the avionics.— Russ Gehling, the solar array subsystem's lead engineer
A central power distribution and drive unit monitors the power that is generated by the solar arrays, distributes it to instruments, heaters and experiment sensors as well as batteries that are charged when excess power is available. Two 55-amp-hour lithium-ion batteries that are able to withstand the radiation environment of Jupiter will provide power when Juno passes through eclipse.
Juno 's telecommunication systems have more in common with that of New Horizons than that of Cassini. Juno supports tone-fault signalling for cruise-mode operations, but it is expected to be used less often. Communications are via the 70-meter antennae of the Deep Space Network (DSN) utilizing an X-band direct link. The command and data processing of the Juno spacecraft includes a flight computer capable of providing ~50 Mbit/s of instrument throughput. Gravity science subsystems use the X-band and Ka-band doppler tracking and autoranging.
Juno uses a bipropellant LEROS 1b main engine, manufactured by AMPAC-ISP in Westcott, UK. It uses hydrazine and nitrogen tetroxide for propulsion and provides a thrust of 645 newtons. The engine bell is enclosed in a debris shield fixed to the spacecraft body, and is used for major burns. For control of the vehicle's orientation (attitude control) and to perform trajectory correction maneuvers, Juno utilizes a monopropellant reaction control system (RCS) consisting of twelve small thrusters that are mounted on four engine modules.
Galileo's plaque and Lego figurines
Juno carries a plaque to Jupiter dedicated to Galileo Galilei. The plaque was provided by the Italian Space Agency and measures 2.8 by 2 inches (7.1 by 5.1 cm). It is made of flight-grade aluminum and weighs 6 grams (0.21 oz). The plaque depicts a portrait of Galileo and a text in Galileo's own hand, penned in January 1610, while observing what would later be known to be the Galilean moons. The text translates as:
On the 11th it was in this formation, and the star closest to Jupiter was half the size than the other and very close to the other so that during the previous nights all of the three observed stars looked of the same dimension and among them equally afar; so that it is evident that around Jupiter there are three moving stars invisible till this time to everyone.
The spacecraft also carries three Lego figurines representing Galileo, the Roman god Jupiter and his wife Juno. In Roman mythology, Jupiter drew a veil of clouds around himself to hide his mischief. From Mount Olympus, Juno was able to look into the clouds and reveal her husband's real nature. Juno holds a magnifying glass as a sign for searching for the truth and her husband holds a lightning bolt. The third Lego crew member, Galileo Galilei, has his telescope with him on the journey.
Although most Lego toys are made of plastic, Lego made these figures of aluminum to endure the extreme conditions of space flight.
|August 2012||Two deep space maneuvers ||Completed|
|October 2013||Earth flyby for speed boost||Completed|
|4 July 2016||Arrival to Jupiter and polar orbit insertion|
|Science phase: 37 orbits planned over 24 months|
|February 2018||spacecraft disposal in the form of a controlled deorbit into Jupiter|
- Atmosphere of Jupiter
- Comet Shoemaker–Levy 9
- Exploration of Jupiter
- Moons of Jupiter
- Jupiter Icy Moon Explorer
- Europa Multiple-Flyby Mission
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|Wikimedia Commons has media related to Juno.|
- Official website on NASA.gov
- Juno mission web site on South West Research Institute
- Juno Mission Profile by NASA's Solar System Exploration
- NASA Selects New Frontiers Concept Study: Juno Mission to Jupiter at NASA Jet Propulsion Laboratory
- The Juno Mission to Jupiter at Space.com
- NASA 360 New Worlds New Discoveries 1/2. Retrieved June 30, 2011.
- Juno Instruments (includes link to make paper scale model here)
- Why With Nye - features legendary educator and entertainer Bill Nye demystifying the cutting edge science behind NASA's groundbreaking Juno mission to Jupiter