July 4, 2016 – After nearly a five-year journey through space, the Lockheed Martin-built Juno spacecraft will arrive at Jupiter on the evening of July 4. During Juno’s approach, the planet’s gravity will tug at the spacecraft, accelerating it to speeds of over 250,000 kilometers per hour (150,000 mile per hour) relative to Earth – making it one of the fastest human-made objects ever. When Juno arrives at Jupiter, it will slam on the brakes, fire its main engine in reverse, and slow down to enter Jupiter’s orbit.
Key Moments Tonight:
After traveling nearly 1,740 million miles (2,800 million kilometers) Juno’s Jupiter Orbit Insertion is a critical event and is performed as part of a carefully designed sequence.
The Juno spacecraft was launched atop a United Launch Alliance Atlas V on August 5, 2011, from Cape Canaveral, Florida. An Earth flyby 26 months after launch provided a boost of spacecraft velocity, placing it on a trajectory for Jupiter.
Prior to June 16, 2016, the Juno team executed two deep space maneuvers using Juno’s main engine, and seven trajectory correction maneuvers, which used the spacecraft’s altitude control system to provide its propulsive thrust. These planned burns refined the spacecraft’s trajectory.
On June 28, Juno’s propulsion system was pressurized and the following day, all of the instrumentation not geared toward the successful insertion event was turned off. All science instruments (including the cameras), will be off until roughly two days after achieving orbit.
“If it doesn’t help us get into orbit, it is shut down,” said Scott Bolton, Juno’s principal investigator from the Southwest Research Institute in San Antonio. “That is how critical this rocket burn is.”
To increase the probability that the main engine burn will take place as planned, certain features of the onboard computer’s fault protection are also disabled. This decreases the likelihood of a computer restart or other anomaly during the sequence, which would interrupt the burn. In the event of such an interruption, the commands are designed to quickly reboot the system and continue the sequence in order to complete the critical burn.
Tonight, the spacecraft will perform a series of steps in preparation for the main engine burn that will guide the spacecraft into orbit:
At 7:16 p.m. MDT, Juno will begin to turn slowly away from the sun and toward its orbit insertion attitude. Then 72 minutes later, it will make a faster turn into the orbit-insertion attitude.
At 8:41 p.m. MDT, Juno switches to its low-gain antenna. Fine-tune adjustments are then made to the spacecraft’s attitude.
Twenty-two minutes before the main engine burn, at 8:56 p.m. MDT, the spacecraft spins up from 2 to 5 revolutions per minute (RPM) to help stabilize it for the orbit insertion burn.
At 9:18 p.m. MDT, Juno’s 35-minute main engine burn will begin. The main engine burn will slow the spacecraft by about 1,212 miles per hour (542 meters per second) so it can be captured into the gas giant’s orbit. The burn occurs at the spacecraft’s closest approach to Jupiter, and slows it enough to be captured by the giant planet’s gravity. Jupiter will be roughly 540 million miles (860 million kilometers) from Earth at the time of the burn.
After the main engine burn, Juno will spin down from 5 to 2 RPM, turn back toward the sun, and ultimately transmit telemetry via its high-gain antenna. The total time off sun-point is 103 minutes.
The Deep Space Network is providing continuous coverage during Juno’s Orbit Insertion Phase. The main engine burn is performed in view of Earth, allowing the spacecraft’s progress to be monitored by mission teams at NASA JPL and Lockheed Martin Space Systems. Goldstone, California will be the prime Deep Space Network station receiving Juno’s signals tonight, on 5 dishes, with 4 dishes at Canberra, Australia serving as a backup.
Juno will start its tour of Jupiter in a 53.5-day orbit. The spacecraft will save fuel by executing a burn that places it into this capture orbit instead of going directly to the 14-day orbit that will occur during the mission’s primary science collection period. It also allows the Juno team time to calibrate and validate instrument performance in the extreme Jupiter environment, test the data processing pipeline, and prepare for the successful acquisition of science data during the first planned science orbit – Orbit 3.
JunoCam images are expected to be returned from the spacecraft for processing and release to the public beginning in late August or early September.
The science orbit phase will start on October 19, after the final main engine burn of the mission. For nearly a year and a half, the spacecraft will execute a close flyby above the planet’s cloud tops every 14 days. On each orbit, Juno will cross over Jupiter’s poles and pass very close to the gas giant. This type of orbit has never been attempted at Jupiter and will give us an entirely new perspective of the planet and its orbiting moons.
Jupiter spins every 10 hours, and mission planners have designed the flight plan so the spacecraft passes over a different section of Jupiter on each orbit. After completing its 33 planned science orbits, Juno will have covered the entire planet, and will de-orbit into Jupiter.
JPL manages the Juno mission for NASA. The mission’s principal investigator is Scott Bolton of Southwest Research Institute in San Antonio. The mission is part of NASA’s New Frontiers Program, managed at the agency’s Marshall Space Flight Center in Huntsville, Alabama. Lockheed Martin Space Systems in Littleton, Colorado built the spacecraft and is on the flight operations team with JPL.
Watch tonight’s events online at NASA TV.