America couldn’t have asked for more on its birthday. NASA
has yet again scripted a momentous success through insertion of Juno Spacecraft
into Jupiter’s orbit on a very special day. NASA has accomplished such astounding
feats earlier on the historically important July 4th, the
independence day of America. Previous successes include-landing of Sojourner of
Mars Pathfinder Mission on Martian surface in 1997 and the collision of Deep Impact with Comet Tempel 1 in 2005.
Juno mission assumes extraordinary significance since, it aims to unravel the
origins of our Solar System by understanding the origin and evolution of
Jupiter.
Around four and half million years ago, a giant cloud of gas
and dust, called nebula collapsed to form our solar system. Sun formed first,
and later on the swirling cloud condensed to form various planets, asteroids
and comets. The first planet formed from the Hydrogen and Helium left after the
birth of Sun was Jupiter. It is the largest, oldest planet of our Solar System.
Unlike earth, it retained the remnants of original nebula, making it an ideal
planet to trace the origins of Solar System. Juno Mission was commissioned to
understand the unique atmosphere composition of Jupiter, determine the amount
of water in its atmosphere, global structure and composition, map magnetic
rings, gravity fields, explore and study its magnetosphere, northern and
southern lights at its poles i. e., auroras. The mission is aptly named as
Juno, because as per the Roman Mythology, Jupiter, the King of Gods camouflaged
with clouds to hide his mischief. Jupiter’s wife Goddess Juno could penetrate
the clouds and decipher the mystery. Juno spacecraft is now assigned the task
of unfolding the mysteries of this largest terrestrial planet. While it is
known that Jupiter largely contains Hydrogen and Helium, the search is now on
to know the composition of other heavy elements present in the planet. Besides,
the enchanting characteristic features like swirling clouds, bands, storms, the
great red spot had enthused scientists to explore the planet.
The crushing weight of Jupiter resulted in generation of extreme
temperature and pressures deep inside. Consequently the gaseous hydrogen is
squeezed into electrically conducting liquid metallic hydrogen causing the
production of extremely strong magnetic field similar to solar magnetic field.
As a result any charged particle flying through the space gets pulled into
Jupiter’s magnetic field. The material so caught is channeled towards poles
creating an intense light showers or aurorae or the Northern and Southern light
(similar to polar auroras on earth). Evading the pull of powerful magnetosphere
of Jupiter became a formidable task for the Space scientists contemplating
Jupiter missions. Juno spacecraft was scientifically designed to carry powerful
instruments on board to observe and capture the aurora lights in ultraviolet
radiation that can enhance our understanding of Jupiter’s magnetic field.
Juno spacecraft,
designed under the New Frontiers Program was hoisted into space by the
expendable launch vehicle Atlas 551 rocket on August 5th 2011 from
Cape Canaveral, Florida. Equipped with nine instruments-microwave radiometer
for atmospheric sounding and composition (MWR), vector magnetometer (MAG),
plasma and energetic particle detector (JADE and JEDI), Ultra violet
imager/spectrometer (UVS), infrared imager/spectrometer (JIRAM), radio/plasma
wave experiment (waves), gravity/radio science system (Gravity science) and
Junocam the spacecraft will orbit around Jupiter 37 times and pass over the planet
within 3100miles range to make all crucial observations. Strength of gravity
will aid in calculating mass and a measure of magnetic radiation helps in
knowing composition. Powered by three extended solar panels of 20mts jutting
out from a hexagonal body Juno spins at 2 revolutions per minute to remain
stable. To protect the spacecraft from the high energy radiations emanated by
Jupiter (20,000 times as intense as earth’s magnetic field), it was armored
with 180kg of titanium shields.
After travelling for two years, in October 2013, Juno made
earth’s flyby (was within 350 miles of Earth’s reach). Earth’s gravity
propelled Juno towards Jupiter. Atlas rocket provided half of the energy needed
for Juno to reach Jupiter and the other half was provided by earth’s flyby. When
Juno arrived near Jupiter, it was moving faster than any human-made object ever
fired, moving at a speed of hundred and sixty-five thousand miles an hour. To
enter the Jupiter’s orbit it had to slow down. It was precisely at this moment
on July 4th, 9pm, Pacific Standard Time, engines were fired for 35
minutes. Juno’s rotation rate increased to 5rpm and altitude is changed to
enter the Jupiter’s orbit or capture orbit. Even the speed was reduced to 1212
miles per hour to facilitate insertion into Jupiter’s orbit. Accurate firing of
the engine made the $1.1 billion worth mission a tremendous success. Any discrepancy at this stage would have
doomed it. In 1995 NASA’s previous mission to Jupiter, Galileo arrived at the
planet in 1995 but its instruments including antenna were irreparably damaged
by radiation. Galileo indeed captured breathtaking images of the ammoniac
clouds swirling around the planet.
Juno is now almost five hundred forty million miles from
earth, electronic signals would take 48 min to travel. Juno’s orbital insertion was tracked by Jet
Propulsion Laboratory (JPL), Pasadena, California and Lockheed Martin Juno
Operations Centre, Colorado. Juno
entered the capture orbit where the probe will stay for 107 days. Scientist
preferred this long route rather than direct insertion, 14-day orbit, as this
requires more fuel. Capture orbit on the other hand, needs less fuel and
scientists would get a chance to recheck the functioning of all the instruments
on the board and can make some initial observations. On November 2nd,
Juno’s first science orbit would begin when engine is burned again to increase
its speed. In order to minimize the
effect of radiations, Juno will fly along a long elliptical orbit with a closet
range of 3100 miles at the south of the orbit and extends to 1.2 million miles
from Jupiter (flying beyond the orbit of Jupiter’s moon Castillo). Extended
elliptical orbits would keep the solar panels in sunlight.
Data collection from the instruments would begin from October
2016. Juno’s mission life is 2 years. Engines will be fired for the final time
in February 2018 when it will crash into Jupiter’s atmosphere as planned. While
the spacecraft would trigger its own annihilation, instruments on board will
capture data.
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