WIXLIB

Mission OverviewTo accomplish its science objectives, Juno orbits overJupiter’s poles and passes very close to the planet.Juno needs to get extremely close to Jupiter to makethe very precise measurements the mission is after. Thisorbital path carries the spacecraft repeatedly throughhazardous radiation belts — but avoids the most powerful radiation belts. Jupiter’s radiation belts are analogousto Earth’s Van Allen belts — but far more deadly.The Juno spacecraft is scheduled to launch aboard anAtlas V551 rocket from Cape Canaveral, Fla., in Aug.2011, reaching Jupiter in July 2016.Following launch from Cape Canaveral Air Force Station,Fla., the Juno spacecraft is scheduled to use its mainrocket motor twice (for an Aug. 5 launch, it would beused on Aug. 30, and Sept. 3, 2012) to modify itstrajectory towards Jupiter. During cruise, there are also13 planned trajectory correction maneuvers to refine itsorbital path. An Earth flyby 26 months after launch willprovide a boost of spacecraft velocity, placing it on atrajectory for Jupiter. The transit time to Jupiter followingthe Earth flyby is about three years, including the periodof the initial capture orbit. The 30-minute orbit insertionburn will place Juno in orbit around Jupiter in early July2016.Juno LaunchThe spacecraft will orbit Jupiter 33 times, skimming towithin 3,100 miles (5,000 kilometers) above the planet’scloud tops every 11 days, for approximately one year.9Press Kit

Mission PhasesPre-Launch PhaseThirteen mission phases have been definedto describe the different periods of activityduring Juno’s travels.These phases are:Pre-Launch, Launch,Inner Cruise 1, InnerCruise 2, Inner Cruise3, Quiet Cruise, JupiterApproach, JupiterOrbit Insertion, CaptureOrbit, Period ReductionManeuver, Orbit 1-2,Science Orbits andDeorbit.The Flight System is mated to the launch vehicle atL-10 days. Juno uses Space Launch Complex 41(SLC-41) at Cape Canaveral Air Force Station, thesame launch pad used by NASA’s New Horizons mission and other Atlas V launch vehicles.The Pre-Launch mission phase lasts from spacecraftpower-up at L-3 days to final spacecraft configurationat L-45 minutes. Juno’s launch period lasts 22 days(Aug. 5–26, 2011) with a launch window at least 60minutes in duration every day of the launch period. Thelaunch period has been optimized to maximize injectedmass into Jupiter science orbits.JunoSpacecraftLaunch VehicleThe Atlas V551 is a twostage launch vehicle thatuses a standard Atlasbooster with five solidrocket boosters in the firststage and a Centaur upperstage for the second. TheCentaur upper stage hasa restartable engine andis three-axis stabilized.Guidance and navigationare provided by the Centaurfollowing launch. The Junospacecraft is enclosed forthe flight through Earth’satmosphere in the Atlas’s16.4-foot (5-meter) diameter, 68-foot (20.7-meter)long payload fairing.Forward LoadReactor (FLR)RL 10A CentaurEngineAtlas V BoosterCentaurSolid AdapterRD-180EngineJuno InterstageAdapterLaunch vehicle10Press Kit

The launch vehicle is throttled to maintain 2.5 g’s forPayload Fairing Jettison, which occurs a little underthree-and-a-half minutes after launch. Following jettison of the payload fairing, acceleration is maintainedat 5.0 g’s until booster engine cutoff. The Atlas/Centaurseparation occurs approximately six seconds afterbooster engine cutoff. The first burn of the second stageof the Centaur rocket begins 10 seconds after the separation. The first Centaur burn lasts about six minutesand completes when the vehicle has achieved its targetparking orbit.Boost Profile and InjectionThe boost phase begins with the ignition of the boosterengine system. Liftoff occurs when the Atlas’s five solidrocket boosters are ignited.Upon burnout of the solid rocket boosters (at approximately 104 seconds after launch) they are staggerjettisoned: first solids 1 and 2, then 1.5 seconds later,solids 3, 4 and 5.Launch profileJuno Launch11Press Kit

Following the completion of its second burn, theCentaur turns to a pre-planned separation attitude andinitiates a 1.4 revolutions per minute roll rate. The Junospacecraft is scheduled to separate from its Centaurbooster about three-and-a-half minutes after theCentaur completes its burn. At the time of separation,a clampband releases and push-off springs push theJuno spacecraft from the Centaur.During the parking orbit coast period (approximately30 minutes in length), the Centaur turns itself and thespacecraft to the required attitude for the start of itssecond burn. The Centaur’s second burn (approximately nine minutes in length) places Juno on the desireddeparture trajectory.Solar Array DeploymentTransition to the Cruise mission phase is expected tooccur three days after launch.Juno’s massive solar arrays are scheduled to begin deployment about five minutes following separation. Thelength of time it takes for deployment is expected to beless than three minutes.Solar array deployment sequenceCruise PhasesJuno’s trajectory to Jupiter consists of five phases overfive years and one-and-a-half loops of the sun.There are four cruise phases: Inner Cruise 1 (61 days),Inner Cruise 2 (598 days), Inner Cruise 3 (161 days), andQuiet Cruise (791 days).During cruise, the spacecraft is usually oriented so thatits high-gain antenna is Earth-pointed. However, closeto the sun there are times where thermal and powerrequirements do not allow for Earth-pointing of the antenna. At these times the spacecraft is pointed off-sunin such a way that thermal requirements can be met.Inner Cruise Phase 1The Inner Cruise 1 phase spans the interval from L 3 toL 63 days. It is characterized by initial spacecraft andinstrument checkouts, deployment of the Waves instrument antenna, Juno’s first trajectory correction maneuver, and the location of the spacecraft far enough fromthe sun to allow Earth-pointing instead of sun-pointing.Juno LaunchEarth–Jupiter trajectory12Press Kit

phase ends at Jupiter Orbit Insertion minus four days,which is the start of the critical sequence that will resultin the spacecraft orbiting Jupiter.Inner Cruise Phase 2The Inner Cruise 2 phase spans the period from L 63days until L 661 days (1.6 years in length). The mission’s two deep space maneuvers occur during thisphase, prior to the spacecraft’s one Earth flyby. Otherspacecraft activities during the Inner Cruise 2 phase include calibrations and alignments associated with usingthe high-gain antenna for the first time. The spacecraft’sscience instruments are also checked out again.This phase is characterized by instrument checkouts aswell as initial science observations of Jupiter. Calibrationsand science observations performed during this phasego a long way toward validating instrument performancein the Jupiter environment, testing the data processingpipeline, and preparing the team for successfully returning baseline Jupiter science data starting in Orbit 3.Inner Cruise Phase 3Jupiter Orbit Insertion PhaseThe Inner Cruise 3 phase spans the interval from L 661days to L 822 days. During this time, the Juno flightteam is focused on performing the required maneuvers,as well as an integrated operations exercise aroundEarth flyby.The Jupiter Orbit Insertion phase begins four daysbefore the start of the orbit insertion maneuver and endsone hour after the start of the insertion maneuver. JupiterOrbit Insertion occurs at closest approach to Jupiter,and slows the spacecraft enough to let it be captured byJupiter into a 107-day-long orbit. The insertion maneuver also sets up the orbital geometry for future 11-dayscience orbits.The Earth flyby occurs as the spacecraft is completingone elliptical orbit around the sun. It will boost Juno’svelocity by 16,330 miles per hour (about 7.3 kilometersper second), placing the spacecraft on its final trajectoryfor Jupiter. Closest approach to Earth occurs on Oct. 9,2013, at an altitude of 310 miles (500 kilometers). Theexact time of closest approach will vary by about eighthours on this date, depending on launch date.The Jupiter Orbit Insertion burn is performed on themain engine (the third large main engine burn of themission). The burn will last 30 minutes and is designedto be performed in view of Earth. After the burn, thespacecraft is in a polar orbit around Jupiter.During the flyby, Juno will pass behind Earth as seenfrom the sun, causing an interval when Earth blocks thesun’s rays from reaching the spacecraft’s solar panels,The time in eclipse is about 20 minutes, and representsthe only time after Launch Phase when Juno will notreceive direct sunlight.Capture Orbit PhaseThe Capture Orbit phase starts at Jupiter Orbit Insertionplus one hour and ends 18 hours before the PeriodReduction Maneuver 106 days later. The 107-dayCapture Orbit provides substantial propellant savingswith respect to a direct Jupiter Orbit Insertion entry intoan 11-day orbit.Three trajectory correction maneuvers are planned before and one after Earth flyby to refine Juno’s trajectory.A cleanup maneuver 7.6 days after the beginning ofthis phase is performed to ensure the timing of the largeburn in the upcoming phase. Instruments are on formost of the Capture Orbit, and there are routine checkouts and science observations.Quiet Cruise PhaseThe Quiet Cruise phase lasts from L 822 days untilthe start of Jupiter Approach at L 1,613 days. Duringthe tail end of the Quiet Cruise phase, which lasts for26 months, the Juno project team will be staffed up tolevels anticipated as needed for upcoming operationsaround Jupiter.The Capture Orbit is an opportunity to gain valuableearly orbital operations experience with the spacecraftas well as the instruments. The team plans to have allthe instruments on and taking data beginning 50 hoursafter Jupiter Orbit Insertion.Jupiter Approach PhaseThe Jupiter Approach phase lasts the final six monthsof cruise (178 days) before Jupiter Orbit Insertion. TheJuno Launch13Press Kit

As with Jupiter Approach observations, calibrations andscience observations performed during the CaptureOrbit go a long way toward validating instrument performance in the Jupiter Environment.Juno’s Highly Elliptical Polar OrbitsOrbiting Jupiter around the poles carries Juno repeatedly over every latitude. As the planet rotates beneath thespacecraft, the entire surface can be covered by Juno’ssuite of instruments.Period Reduction Maneuver PhaseDuring the Period Reduction Maneuver phase, Junotransitions from an orbit that takes 107 days to circumnavigate Jupiter to one that takes only 11 days.The phase starts 18 hours before the maneuver andconcludes 11 hours after the maneuver is complete.The rocket firing that takes place during this maneuveris a larger burn in duration (37 minutes) than the JupiterOrbit Insertion burn. The Period Reduction Maneuverburn is performed on the main engine (the fourth andlast large main engine burn of the mission). No scienceobservations are planned during this phase.For many of the instruments to do their job, the spacecraft has to get closer to Jupiter than any previous mission. To avoid the highest levels of radiation in the beltssurrounding Jupiter, mission navigators have designeda highly elongated orbit that approaches the gas giantfrom the north. Flying south, the spacecraft’s point ofclosest approach will be about 3,100 miles (5,000 kilometers) above the cloud tops. As Juno exits over thesouth pole, its orbit carries it far beyond even the Jovianmoon Callisto’s orbit.Juno’s elliptical orbit around Jupiter has another benefit.It allows the spacecraft’s three massive solar panels tobe constantly bathed in sunlight. This is important because the amount of sunlight that reaches Jupiter is only1/25th that which reaches Earth. To keep the spacecraft’s instruments and operating systems poweredrequires the solar panels to have an almost constantexposure to the available sunlight.Orbits 1–2 PhaseThe Orbits 1–2 phase starts 11 hours after the PeriodReduction Maneuver burn — near the beginning of thefirst 11-day orbit. This phase ends 20 days later withthe commencement of the mission’s first science orbit.Orbit 2 and Planned ScienceDeorbit PhaseIn addition to calibrations and other instrument preparations for the science orbits, preliminary Orbit 2 scienceplans include: remote sensing movies and atmosphericdynamics measurements, water abundance observations and fields and particles observations like thoseplanned for the science orbits.The Deorbit phase occurs during the final orbit of themission. The 5.5-day phase starts several days after theOrbit 33 science pass and ends with impact into Jupiterduring the following orbit.The deorbit maneuver was designed to satisfy NASA’splanetary protection requirements and ensure that Junodoes not impact Europa (as well as Ganymede andCallisto).Science Orbits PhaseThe Science Orbits phase includes Orbit 3 throughOrbit 33 and lasts 336 days. Small orbital trim maneuvers are planned about four hours after each set ofperijove (closest approach to Jupiter) science observations. These maneuvers target the longitude requiredfor science observations in the next orbit.Juno LaunchBy orbit 34, a deorbit burn will be executed, placing thespacecraft on a trajectory that will reset its point of closest approach to the planet to an altitude that is belowthe cloud tops at 34 degrees North Jupiter latitude onOct. 16, 2017. Juno is not designed to operate insidean atmosphere and will burn up.14Press Kit

SpacecraftJuno uses a spinning, solar-powered spacecraft in ahighly elliptical polar orbit that avoids most of Jupiter’shigh-radiation regions. The designs of the individualinstruments are straightforward and the mission did notrequire the development of any new technologies.The 12 reaction control system thrusters are mountedon four rocket engine modules. They allow translationand rotation about three axes. They are also used formost trajectory correction maneuvers.Command and Data HandlingWhy A Rotating Spacecraft?Command and data handling includes a RAD750 flightprocessor with 256 megabytes of flash memory and128 megabytes of DRAM local memory. It provides100 Mbps total instrument throughput, more thanenough for payload requirements.For Juno, like NASA’s earlier Pioneer spacecraft, spinning makes the spacecraft’s pointing extremely stableand easy to control. Just after launch, and before itssolar arrays are deployed, Juno will be spun-up byrocket motors on its still-attached second-stage rocketbooster. Juno’s planned spin rate varies during the mission: 1 RPM for cruise, 2 RPM for science operationsand 5 RPM for main engine maneuvers.Electronics VaultTo protect sensitive spacecraft electronics, Juno willcarry the first-of-its-kind radiation shielded electronicsvault, a critical feature for enabling sustained explorationin such a heavy radiation environment. Each of the titanium cube’s eight sides measures nearly a square meter(nearly 9 square feet) in area, about a third of an inch(1 centimeter) in thickness, and 4 pounds (18 kilograms)in mass. This titanium box — about the size of an SUV’strunk — encloses Juno’s command and data handlingbox (the spacecraft’s brain), power and data distributionunit (its heart) and about 20 other electronic assemblies.The whole vault weighs about 500 pounds (200 kilograms).To simplify and decrease weight, all instruments arefixed. While in orbit at Jupiter, the spinning spacecraftwill sweep the fields of view of its instruments throughspace once for each rotation. At two rotations per minute, the instruments’ fields of view sweep across Jupiterabout 400 times in the two hours it takes Juno to flyfrom pole to pole.StructureThe spacecraft’s main body measures 11.5 feet(3.5 meters) tall and 11.5 feet (3.5 meters) in diameter.The spacecraft’s hexagonal two-deck structure usescomposite panel and clip construction for decks, centralcylinder and gusset panels. Polar mounted off-centerspherical tanks provide spinning spacecraft designs withhigh stability.PowerJuno’s Electrical Power Subsystem manages the spacecraft power bus and distribution of power to payloads,propulsion, heaters and avionics. The power distributionand drive unit monitors and manages the spacecraftpower bus, manages the available solar array power tomeet the spacecraft load and battery state of charge,and provides controlled power distribution.Propulsion SystemFor weight savings and redundancy, Juno uses a dualmode propulsion subsystem, with a bi-propellant mainengine and mono-propellant reaction control systemthrusters.Power generation is provided by three solar arraysconsisting of 11 solar panels and one MAG boom. Two55 amp-hour lithium-ion batteries provide power whenJuno is off-sun or in eclipse, and are tolerant of theJupiter radiation environment. The power modes duringscience orbits are sized for either data collection duringan orbit emphasizing microwave radiometry or gravityscience.The Leros-1b main engine is a 645-Newton bi-propellant thruster using hydrazine–nitrogen tetroxide.Its engine bell is enclosed in a micrometeoroid shieldthat opens for engine burns. The engine is fixed to thespacecraft body firing aft and is used for major maneuvers and flushing burns.Juno Launch15Press Kit

Solar PowerThermal ControlJupiter’s orbit is five times farther from the sun thanEarth’s, so the giant planet receives 25 times lesssunlight than Earth. Juno will be the first solar-poweredspacecraft designed to operate at such a great distancefrom the sun, thus the surface area of solar panels required to generate adequate power is quite large.Juno’s thermal control subsystem uses a passive design with heaters and louvers. The main component ofthe thermal control subsystem consists of an insulated,louvered electronics vault atop an insulated, heated propulsion module. This design accommodates all missionthermal environments from Earth orbit to Jupiter orbitaloperations. During cruise, while the spacecraft is closeto the sun, the high-gain antenna is used as a heatshield to protect the vault avionics.Juno benefits from advances in solar cell design withmodern cells that are 50 percent more efficient andradiation-tolerant than silicon cells available for spacemissions 20 years ago. The mission’s power needs aremodest. Juno has energy-efficient science instruments.Solar power is possible on Juno due to the energyefficient instruments and spacecraft, a mission designthat can avoid Jupiter’s shadow and a polar orbit thatminimizes the total radiation.Most instrument electronics are contained within theradiation vault a

1,740 million miles (2,800 million kilometers) End of mission (deorbit): October 16, 2017 Distance traveled in orbit around Jupiter: 348 million miles (560 million kilometers) Total distance, launch through Jupiter impact: 2,106 mil-lion miles (3,390 million kilometers) Program The Juno mi