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Tuesday, June 21, 2016

SPACECRAFT APPROACHES JUPITER!

JUNO MISSION

Juno launched from Cape Canaveral Air Force Station on Aug. 5, 2011.   Its set to enter Jupiter's orbit in less than two weeks on July 4th, 2016!

While ten other spacecraft have flown in Jupiter's neighborhood in decades past, part of what makes Juno stand apart is its ability to generate solar power from Jupiter's neighborhood. - See more at: http://www.space.com/32742-juno-spacecraft.html#sthash.sS1NgqoE.dpuf



Mission Time line
  • Launch: 5 August 2011
  • Deep Space Maneuvers: - August/September 2012
  • Earth flyby gravity assist: - October 2013
  • Jupiter arrival: 4 July 2016
  • Spacecraft will orbit Jupiter for 20 months (37 orbits)
End of mission (deorbit into Jupiter): February 2018


Long-term stay at Jupiter
  • On December 7, 1995, the Galileo probe parachuted into Jupiter and descended nearly 160 km to pressures exceeding 23 Earth atmospheres. They expected to find water clouds and did not. This was a surprise to our scientists. They think that maybe the probe passed through a dry area, where other areas may have water clouds. Juno is fitted with a microwave instrument that is meant to detect water clouds. Knowing the amount of water in Jupiter’s clouds can help scientists better understand the make-up of Jupiter. This is important, because of the abundant number of Jupiter sized exo-planets...understanding Jupiter's makeup allows us to better understand planet formation in general.
  • Juno will be the 10th spacecraft to study Jupiter at close range. Even during the brief flybys, they have been able to glimpse interesting information about Jupiter and its moons. For example, New Horizons caught a large outburst on the volcanic moon Io. 
  • This will be the first spacecraft sent to the outer solar system that generates its power from solar panels. All other spacecraft have used the radioactive decay of plutonium.
  • To date, however, only one mission stayed for the long term: Galileo. After being launched from space shuttle Atlantis in October 1989, Galileo arrived at Jupiter in 1995 and spent eight years studying the planet and its moons. 
  • Galileo's discoveries include finding potential salt-water oceans under the crusts of Europa, Callisto and Ganymede. It also sent a descent probe into Jupiter's atmosphere. Much of the mission's value also came from spending nearly a decade in Jupiter's system, allowing scientists the rare chance to do up-close, lengthy observations of the largest planet in the solar system.
  • Images from Galileo Mission:







Juno aims to go further. It will focus solely on Jupiter and try to answer at least some of the following questions, according to NASA:
The Juno Spacecraft will orbit around the poles in order to study is massive magnetosphere which stretches 7 million kms towards the Sun and out past Saturn's orbit on the farside!
  • The polar orbit will also give mankind its first look straight down at the poles of Jupiter!
  • Juno's scientists and engineers loaded the spacecraft with instruments that can measure charged particles, magnetic fields and electric waves as it flies for the first time through the magnetic field lines where we think the auroral particles are generated.'
  • How much water does Jupiter have in its atmosphere? This is important to figure out if our formation theories of the solar system are correct, or if they need some work.
  • What is Jupiter's atmosphere like? Specifically, what are the properties at every layer such as gas composition, temperature and cloud motions? Figuring out the weather on Jupiter will help us learn more about gas giant weather generally. (It's important for planets in our solar system, as well as exoplanets.)
  • What are the magnetic and gravity fields of Jupiter? This will give scientists some hints of what the interior structure of Jupiter looks like.
  • How does the magnetic environment of Jupiter affect its atmosphere? Part of that study will come through looking at auroras.
  • Planetary researcher Fran Bagenal worries that the magnetic field lines, which generate millions of amps of electrical current around the poles of Jupiter will pose a danger to Juno.
  • Juno is the fastest man made object ever, having reached 160,000mph or 44 miles/second as it approached Jupiter.

The Juno spacecraft will, for the first time, see below Jupiter's dense cover of clouds. This is why the mission was named after the Roman goddess, who was Jupiter's wife, and who could also see through clouds.


Major questions that remain today about Jupiter:
How did Jupiter form?
  • How much water or oxygen is in Jupiter?
  • What is the structure inside Jupiter?
  • Does Jupiter rotate as a solid body, or is the rotating interior made up of concentric cylinders?
  • Is there a solid core, and if so, how large is it?
  • How is its vast magnetic field generated?
  • How are atmospheric features related to the movement of the deep interior?
  • What are the physical processes that power the auroras?
  • What do the poles look like?
Spacecraft
Juno uses a spinning, solar-powered spacecraft in a highly elliptical polar orbit that avoids most of Jupiter's high-radiation regions. The designs of the individual instruments are straightforward and the mission did not require the development of any new technologies.
The Juno spacecraft will, for the first time, see below Jupiter's dense cover of clouds. This is why the mission was named after the Roman goddess, who was Jupiter's wife, and who could also see through clouds.
Why A Rotating Spacecraft?
For Juno, like NASA's earlier Pioneer spacecraft, spinning makes the spacecraft's pointing extremely stable and easy to control. Just after launch, and before its solar arrays are deployed, Juno will be spun-up by rocket motors on its still-attached second-stage rocket booster. Juno's planned spin rate varies during the mission: 1 RPM for cruise, 2 RPM for science operations and 5 RPM for main engine maneuvers.
Structure
The spacecraft's main body measures 11.5 feet (3.5 meters) tall and 11.5 feet (3.5 meters) in diameter.

Propulsion System
For weight savings and redundancy, Juno uses a dual mode propulsion subsystem, with a bi-propellant main engine and mono-propellant reaction control system thrusters.
The Leros-1b main engine is a 645-Newton bi-propellant thruster using hydrazine-nitrogen tetroxide. Its engine bell is enclosed in a micrometeoroid shield that opens for engine burns. The engine is fixed to the spacecraft body firing aft and is used for major maneuvers and flushing burns.
The 12 reaction control system thrusters are mounted on four rocket engine modules. They allow translation and rotation about three axes. They are also used for most trajectory correction maneuvers.

Power
Power generation is provided by three solar arrays consisting of 11 solar panels and one MAG boom. Two 55 amp-hour lithium-ion batteries provide power when Juno is off-sun or in eclipse, and are tolerant of the Jupiter radiation environment. The power modes during science orbits are sized for either data collection during an orbit emphasizing microwave radiometry or gravity science.
Science Instruments
The Juno spacecraft carries a payload of 29 sensors, which feed data to nine onboard instruments. Eight of these instruments (MAG, MWR, Gravity Science, Waves, JEDI, JADE, UVS, JIRAM) are considered the science payload. One instrument, JunoCam, is aboard to generate images for education and public outreach.
JunoCam
At the JunoCAM website, anyone can vote on which images the spacecraft will take. Www.missionjuno.swri.edu/junocam
JunoCam will capture color pictures of Jupiter's cloud tops in visible light.
JunoCam will provide a wide-angle view of Jupiter's atmosphere and poles. JunoCam is designed as an outreach full-color camera to engage the public. The public will be involved in developing the images from raw data and even helping to design which areas of Jupiter should be imaged.
The JunoCam camera head has a lens with a 58-degree cross-scan field of view. It acquires images by sweeping out that field while the spacecraft spins to cover an along-scan field of view of 360 degrees. Lines containing dark sky are subsequently compressed to an insignificant data volume. It takes images mainly when Juno is very close to Jupiter, with a maximum resolution of up to 1 to 2 miles (2 to 3 kilometers) per pixel. The wide-angle camera will provide new views of Jupiter's atmosphere.
JunoCam's hardware is based on a descent camera that was developed for NASA's Mars Science Laboratory rover. Some of its software was originally developed for NASA's Mars Odyssey and Mars Reconnaissance Orbiter spacecraft. JunoCam is provided by Malin Space Science Systems, San Diego, Calif.
Science Overview
With its suite of science instruments, Juno will investigate the existence of a possible solid planetary core, map Jupiter's intense magnetic field, measure the amount of water and ammonia in the deep atmosphere, and observe the planet's auroras.
Atmosphere
How deep Jupiter's colorful zones, belts and other features penetrate is one of the most outstanding fundamental questions about the giant planet. Juno will determine the global structure and motions of the planet's atmosphere below the cloud tops for the first time, mapping variations in the atmosphere's composition, temperature, clouds and patterns of movement down to unprecedented depths.

Magnetosphere 
Deep in Jupiter's atmosphere, under great pressure, hydrogen gas is squeezed into a fluid known as metallic hydrogen. At these enormous pressures, the hydrogen acts like an electrically conducting metal, which is believed to be the source of the planet's intense magnetic field. This powerful magnetic environment creates the brightest auroras in our solar system, as charged particles precipitate down into the planet's atmosphere.
Juno will directly sample the charged particles and magnetic fields near Jupiter's poles for the first time, while simultaneously observing the auroras in ultraviolet light produced by the extraordinary amounts of energy crashing into the polar regions. These investigations will greatly improve our understanding of this remarkable phenomenon, and also of similar magnetic objects, like young stars with their own planetary systems.
Juno provides the first survey and exploration of the three-dimensional structure of Jupiter's polar magnetosphere.


SOURCES








Galileo Images from this site


From July 2016 issue of Sky & Telescope article by Fran Bagenal, 'Revealing Jupiter's Inner Secrets'







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