{"id":15401,"date":"2016-07-01T00:34:07","date_gmt":"2016-06-30T16:34:07","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/juno-switched-to-autopilot-mode-for-jupiter-final-approach\/"},"modified":"2016-07-01T00:34:07","modified_gmt":"2016-06-30T16:34:07","slug":"juno-switched-to-autopilot-mode-for-jupiter-final-approach","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/juno-switched-to-autopilot-mode-for-jupiter-final-approach\/","title":{"rendered":"Juno switched to autopilot mode for Jupiter final approach"},"content":{"rendered":"
\"Artist's
Artist\u2019s concept of the Juno spacecraft at Jupiter. Credit: NASA\/JPL-Caltech<\/figcaption><\/figure>\n

Four days out from arriving at the solar system\u2019s biggest planet, NASA\u2019s Juno spacecraft received a final uplink of commands Thursday governing the robotic probe\u2019s high-velocity braking maneuver Monday to steer into orbit around Jupiter.<\/p>\n

Juno will run on autopilot for the rest of its approach, counting down to a series of tightly-choreographed maneuvers Monday leading to ignition of the craft\u2019s main engine to slow its speed by 1,212 mph (541.7 meters per second), just enough to be captured in orbit by the firm grasp of Jupiter\u2019s gravity.<\/p>\n

Before uploading the final command sequence, ground controllers stationed at NASA\u2019s Jet Propulsion Laboratory and at a control center run by Lockheed Martin, the spacecraft\u2019s builder and operator, prepared the engine for Monday\u2019s critical burn.<\/p>\n

\u201cTen days ago, we opened the main engine cover so that the engine would be ready to fire when we get to July 4, and a couple of days ago we pressurized the whole system, so that the engine is ready to go, (and) all the propulsion, all the pipes and valves are all ready to fire,\u201d said Ed Hirst, Juno mission manager at JPL.<\/p>\n

Engineers transmitted the final command file, dubbed \u201cji4040,\u201d to Juno around 3:15 p.m. EDT (1915 GMT) Thursday via an antenna in NASA\u2019s Deep Space Network located in Goldstone, California.<\/p>\n

\u201cOnce those commands are sent, it will be hands-off from the team here on the ground,\u201d Hirst told reporters Thursday before sending the order for Juno to launch its Jupiter arrival sequence. \u201cWe\u2019ll continue to monitor the spacecraft and make sure everything is executing as we expect it to execute, but the spacecraft is on its own, and it\u2019s designed to take care of itself with all the command sequences that we\u2019ve sent it.\u201d<\/p>\n

Scott Bolton, an astrophysicist from the Southwest Research Institute in San Antonio who leads the Juno science team, said Thursday he has mixed emotions as the spacecraft zips toward Jupiter on the tail end of a 1.7 billion-mile (2.8 billion-kilometer) journey.<\/p>\n

\u201cYeah, I\u2019m nervous,\u201d Bolton said.<\/p>\n

Bolton\u2019s team proposed the $1.1 billion Juno mission to NASA in February 2004, and it beat out a competing concept to return samples from South Pole-Aitken basin on the far side of the moon, winning the space agency\u2019s backing in June 2005.<\/p>\n

Juno launched Aug. 5, 2011, from Cape Canaveral on top of the most powerful version of United Launch Alliance\u2019s Atlas 5 rocket, and the probe returned to Earth\u2019s vicinity in October 2013 for a gravity assist, slingshotting it toward Jupiter.<\/p>\n

\u201cI\u2019m excited with anticipation, of course, because we\u2019re finally arriving, but I also have tension and nervousness because there\u2019s a lot riding on what happens July 4,\u201d Bolton said.<\/p>\n

\"Artist's
Artist\u2019s concept of Juno\u2019s Leros 1b main engine during the orbit insertion burn. Credit: NASA\/JPL-Caltech<\/figcaption><\/figure>\n

Engineers expect to receive confirmation that Juno\u2019s main engine, burning a mix of liquid hydrazine and nitrogen tetroxide propellants, has started its 35-minute burn at 11:18 p.m. EDT Monday (0318 GMT Tuesday).<\/p>\n

Radio tones broadcast by Juno will be picked up by an array of huge dish antennas on the ground. Each tone comes in at a slightly different frequency, indicating when Juno accomplishes one of the many steps during the arrival sequence.<\/p>\n

Juno\u2019s high-gain antenna will not be pointed toward Earth during the insertion burn, eliminating any chance engineers will receive detailed telemetry on the progress of the engine firing.<\/p>\n

Instead, controllers will listen for tones at the start and end of the burn, and watch for a subtle fluctuation in the radio signal coming from Juno caused by the Doppler shift, a variation in the frequency of the spacecraft\u2019s transmission as its velocity changes.<\/p>\n

The Doppler effect is similar to the change in pitch of an emergency siren as an ambulance passes.<\/p>\n

Heading for a point 2,900 miles (4,667 kilometers) above Jupiter, Juno will configure itself for the make-or-break engine firing beginning shortly after 9 p.m. EDT Monday (0100 GMT Tuesday), when the spacecraft will begin turning to face the right direction for the burn.<\/p>\n

The pointing maneuver will turn Juno\u2019s three huge solar array wings, each stretching nearly 30 feet (9 meters) long, away from the sun, forcing the probe to drain power from its batteries. Juno is the first spacecraft to travel to Jupiter\u2019s distance, where the sun is 25 times dimmer than it is at Earth, and rely solely on solar power.<\/p>\n

Built with lean power requirements in mind, the power-efficient space probe can run all its systems and scientific instruments on enough juice to power five 100-watt light bulbs.<\/p>\n

About 22 minutes before ignition, Juno\u2019s smaller pointing thrusters will increase the craft\u2019s spin rate from 2 rpm to 5 rpm for added stability during the main engine burn.<\/p>\n

\"The
The JunoCam instrument aboard NASA\u2019s Juno spacecraft recorded this view of Jupiter and three of its moons Tuesday at a range of 3.9 million miles (6.2 million kilometers). JunoCam, like Juno\u2019s other instruments, was turned off Wednesday. Credit: NASA\/JPL-Caltech\/SwRI\/MSSS<\/figcaption><\/figure>\n

At the time of Juno\u2019s engine firing, Jupiter\u2019s gravity will exert a tight tug on the spacecraft, accelerating it to approximately 150,000 mph (about 250,000 kilometers per hour), making Juno one of the fastest human-made objects in history.<\/p>\n

Soon after the insertion maneuver is complete, Juno will spin down back to its standard two revolutions per minute, then turn back toward the sun to start recharging its batteries and beam telemetry to engineers on Earth.<\/p>\n

Check out a detailed timeline of the major events Monday.<\/p>\n

Juno\u2019s Leros 1b engine, supplied by Moog-ISP in the United Kingdom, needs to fire for at least 20 minutes for the probe to reach a safe orbit around Jupiter, according to Rick Nybakken, the mission\u2019s project manager at JPL.<\/p>\n

Otherwise, Jupiter\u2019s gravity will bend Juno\u2019s trajectory and send it speeding back into interplanetary space, missing the planet entirely.<\/p>\n

Software programmers installed safeguards to raise the probability of a good insertion burn, including an \u201cauto restart\u201d feature to allow the engine to quickly resume the burn if a computer fault or another anomaly interrupts it.<\/p>\n

Monday\u2019s engine burn, assuming it operates for all 35 minutes, will place Juno in an elongated orbit that takes the spacecraft around Jupiter\u2019s poles once every 53-and-a-half days. A follow-up engine burn is scheduled for Oct. 19 to lower the high end of Juno\u2019s orbit, placing the robot on a course around the planet that takes it as close as 3,100 miles (5,000 kilometers) over Jupiter\u2019s cloud tops every two weeks.<\/p>\n

During each close flyby of Jupiter, the body-mounted instruments aboard Juno will take turns looking at the planet\u2019s clouds, measuring plasma, and quantifying the giant world\u2019s gravitational and magnetic fields as the orbiter spins on its axis once every 30 seconds.<\/p>\n

Ground controllers powered off Juno\u2019s extensive science payload Thursday ahead of the July 4 arrival, but the instruments detected the probe\u2019s crossing into the Jovian magnetosphere last week, registering a change in the environment around the spacecraft as it moved out of the solar wind and into a region dominated by Jupiter.<\/p>\n