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 Source: NASA - Juno Press Kit |
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Pre-Launch
The Juno Spacecraft has been mated to the launch vehicle at L-10 days. Juno will launch atop an Atlas V rocket from Launch Complex 41 at Cape Canaveral Air Force Station. The actual pre-launch phase begins when the spacecraft is powered up at L-3 days. Final spacecraft configuration and checkouts will be performed at L-45 Minutes. Juno's launch window lasts from Aug. 5 to Aug. 26 with more than 60 minutes of window open time on each of the days. Launch The two main engines of the Atlas V Core Stage ignite 2.7 seconds prior to liftoff. At T-0, the five Solid Rocket Boosters are ignited and the vehicle lifts off. Burnout of the Boosters occurs at T+104 seconds. At first, Boosters 1 and 2 are being jettisoned and 3.4 & 5 follow 1.5 seconds later. The Atlas V will throttle back to maintain 2.5Gs for Payload Fairing Jettison at T+3:24. Until the main engines shut down, an acceleration of 5Gs is maintained by throttling back. After cutoff, the first and second stage separate before the Centaur rocket ignites and fires for about 6 minutes. This burn places Juno into a parking orbit in which it will coast for several minutes . While coasting, the Centaur upper stage moves into the correct orientation for the second burn. The second burn of 9 Minutes will place the spacecraft on the desired departure trajectory. After the burn, the Centaur maneuvers into a separation attitude and initiates a 1.4 RPM Roll. 3.5 Minutes after the burn, Juno will separate from the vehicle by releasing springs.  Photo: NASA/JPL/Caltech Juno - Centaur Separation
Solar Array Deployment 5 Minutes after spacecraft separation, the three massive solar arrays of Juno are going to be deployed. The deployment is being initiated by pyrotechnic charges. Array deployment should take less than three minutes. After the deployment, all spacecraft systems will be checked out before the cruise phase begins.  Photo: NASA/JPL/Caltech Solar Array Deployment
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Cruise Phase
Juno’s path to Jupiter is divided into five portions that will take the vehicle one-and-a-half times around the sun. In total, there are four cruise phases. Thermal requirements will dictate vehicle orientation. Juno’s nominal attitude shows the spacecraft with its high gain antenna pointed to earth to ensure high data rate communications. When the spacecraft passes close to the sun, it has to change its orientation to meet thermal requirements. In that way, the high gain antenna is not pointed directly at earth. It will be used as a heat shield that is pointed at the sun.
Juno’s path to Jupiter is divided into five portions that will take the vehicle one-and-a-half times around the sun. In total, there are four cruise phases. Thermal requirements will dictate vehicle orientation. Juno’s nominal attitude shows the spacecraft with its high gain antenna pointed to earth to ensure high data rate communications. When the spacecraft passes close to the sun, it has to change its orientation to meet thermal requirements. In that way, the high gain antenna is not pointed directly at earth. It will be used as a heat shield that is pointed at the sun.
Inner Cruise Phase 1
This 61-day cruise phase is characterized by initial spacecraft and systems checks, deployment of science instruments such as the Wave sensors and the first trajectory correction maneuver that would occur on August 30 if the vehicle launches on August 5.
Inner Cruise Phase 2
The Inner Cruise 2 is first long phase of the Juno Mission. It lasts from L+63 Days to L+661 Days, it is 1.6 years in length. Two deep space maneuvers will be performed in this phase of the mission. During IC2, the vehicle’s high gain antenna will be used for the first time. The science instruments of the spacecraft will be calibrated and checked during this time.
Inner Cruise Phase 3
This 161-day phase of the mission will include maneuvers to prepare for the Earth Flyby that will boost the vehicle’s velocity. The Flyby occurs when the Juno Spacecraft has completed a full elliptical orbit around the sun. Prior to the Flyby, three course correction burns will be made. The Earth-Flyby will increase Juno’s speed by about 16,300 miles per hour, placing it on its final trajectory to Jupiter. Time of closest approach will be on October 9, 2013 at an altitude of 310 miles. The exact time of closest approach depends on the launch date. Juno will pass through the dark during its earth flyby for about 20 minutes during which it will not receive any sunlight. After Juno passed earth, one additional correction burn will be required to finetune its trajectory.
Quiet Cruise Phase
This is the longest phase of the mission and takes the spacecraft into the vicinity of its destination. This phase lasts for a bit over 26 months and the ground teams will prepare for science operations during that time.
Jupiter Approach Phase
The JAP is the final Cruise Phase of the Juno Mission, it will last 6 months and take the vehicle to a point at which it can enter an orbit around the planet. Initial science observations will begin during this portion of the mission due to the decreasing distance to Jupiter. All Elements will be checked one more time before the most critical part of the flight begins, Jupiter Orbit Insertion. All instruments will be calibrated and tested to verify the vehicle is in a good condition.
This 61-day cruise phase is characterized by initial spacecraft and systems checks, deployment of science instruments such as the Wave sensors and the first trajectory correction maneuver that would occur on August 30 if the vehicle launches on August 5.
Inner Cruise Phase 2
The Inner Cruise 2 is first long phase of the Juno Mission. It lasts from L+63 Days to L+661 Days, it is 1.6 years in length. Two deep space maneuvers will be performed in this phase of the mission. During IC2, the vehicle’s high gain antenna will be used for the first time. The science instruments of the spacecraft will be calibrated and checked during this time.
Inner Cruise Phase 3
This 161-day phase of the mission will include maneuvers to prepare for the Earth Flyby that will boost the vehicle’s velocity. The Flyby occurs when the Juno Spacecraft has completed a full elliptical orbit around the sun. Prior to the Flyby, three course correction burns will be made. The Earth-Flyby will increase Juno’s speed by about 16,300 miles per hour, placing it on its final trajectory to Jupiter. Time of closest approach will be on October 9, 2013 at an altitude of 310 miles. The exact time of closest approach depends on the launch date. Juno will pass through the dark during its earth flyby for about 20 minutes during which it will not receive any sunlight. After Juno passed earth, one additional correction burn will be required to finetune its trajectory.
Quiet Cruise Phase
This is the longest phase of the mission and takes the spacecraft into the vicinity of its destination. This phase lasts for a bit over 26 months and the ground teams will prepare for science operations during that time.
Jupiter Approach Phase
The JAP is the final Cruise Phase of the Juno Mission, it will last 6 months and take the vehicle to a point at which it can enter an orbit around the planet. Initial science observations will begin during this portion of the mission due to the decreasing distance to Jupiter. All Elements will be checked one more time before the most critical part of the flight begins, Jupiter Orbit Insertion. All instruments will be calibrated and tested to verify the vehicle is in a good condition.
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Jupiter Orbit Insertion Phase
This phase begins four days prior to the Jupiter Orbit Insertion Maneuver and ends one hour after the maneuver. Orbit Insertion takes place at the time of closest approach to Jupiter. The engine burn will slow Juno down just enough to be captured in a 107-day orbit around the planet. The burn will last 30 minutes and will be performed in view of earth in order to get telementry data from the spacecraft. Capture Orbit Phase The 107-day capture orbit is flown because it increases propellant savings. A direct insertion into a 11-day orbit would be theoretically possible. During this long orbit, science instruments will gather initial data and undergo checkouts. Approximately 182 hours after capture orbit is achieved, a cleanup burn will be performed to make sure the spacecraft will be in the proper position for the Phase Reduction Maneuver. All instruments will start gathering data at a point about 50 hours after Jupiter Orbit Insertion is complete. The goal is to validate instrument performance for the science orbits of the mission during this first long orbit. |
 Photo: NASA/JPL/Caltech Juno approaches Jupiter
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Period Reduction Maneuver Phase
The PRM will take Juno into its designed 11-day polar orbit around Jupiter. For that, its main engine will be fired for 37 minutes. During this 29-hour phase, no science observations will be made. 11 hours after the burn will have been completed, the initial orbit phase will begin.
Orbits 1-2
The first two orbits of the mission, about 20.5 days in duration, will feature more systems checks and calibrations before science observations begin on orbit 2.
Science Orbits Phase
Orbit 3 through 33 are designated the science orbits phase of the mission. Those orbits will take 336 days. On every orbit, a small jet firing will be performed 4 hours after the vehicle’s closest approach to Jupiter to target the longtitude that is requiered for science observations on the next orbit.
Juno’s orbit around Jupiter will carry it several times over each latitude. Due to Jupiter’s rotation beneath the vehicle, the entire surface can be measured. To get the best science readings, Juno has to fly very close to the Planet’s surface. Closest approach will occur at an altitude of about 3,100 miles above the cloud cover. Mission designers put much effort into designing Juno’s orbit in a way that aviods the strongest radiation belts of the gas giant.
The elliptical orbit also allows the three solar arrays of the vehicle to be exposed to direct sunlight at all times. Constant sun exposure is required to generate enough electricity to power all the instruments. Only a fraction of the sunlight that we have on earth reaches the big gas giant.
The PRM will take Juno into its designed 11-day polar orbit around Jupiter. For that, its main engine will be fired for 37 minutes. During this 29-hour phase, no science observations will be made. 11 hours after the burn will have been completed, the initial orbit phase will begin.
Orbits 1-2
The first two orbits of the mission, about 20.5 days in duration, will feature more systems checks and calibrations before science observations begin on orbit 2.
Science Orbits Phase
Orbit 3 through 33 are designated the science orbits phase of the mission. Those orbits will take 336 days. On every orbit, a small jet firing will be performed 4 hours after the vehicle’s closest approach to Jupiter to target the longtitude that is requiered for science observations on the next orbit.
Juno’s orbit around Jupiter will carry it several times over each latitude. Due to Jupiter’s rotation beneath the vehicle, the entire surface can be measured. To get the best science readings, Juno has to fly very close to the Planet’s surface. Closest approach will occur at an altitude of about 3,100 miles above the cloud cover. Mission designers put much effort into designing Juno’s orbit in a way that aviods the strongest radiation belts of the gas giant.
The elliptical orbit also allows the three solar arrays of the vehicle to be exposed to direct sunlight at all times. Constant sun exposure is required to generate enough electricity to power all the instruments. Only a fraction of the sunlight that we have on earth reaches the big gas giant.
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Deorbit Phase
The deorbit phase begins after orbit 33 of the science mission is complete. This deorbit maneuver was developed to ensure that Juno does not impact Europa, Gannymede or Callisto. The D/O burn will be executed to place the vehicle in to more elliptical orbit. The area of closest approach will then be below Jupiter’s cloud tops enabling the spacecraft to enter Jupiter’s dense atmosphere and burn up. Deorbit is currently set for October 16, 2017. This ends the Juno Mission. Data analysis will continue for several years after the mission has ended. |
 Photo: NASA/JPL/Caltech |
