Pluto mission: so far, so good
K.S. RAJGOPAL
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After the successful Jupiter encounter, the probe has slipped into the electronic slumber phase
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New Horizons has made the most detailed survey of Jupiter’s ring system
The probe made a first-ever trip down the long ‘tail’ of Jupiter’s magnetosphere
More than 700 observations of Jupiter and its four largest moons including scans of Jupiter’s turbulent, stormy atmosphere and dynamic magnetic cocoon (called a magnetosphere); the most detailed survey of its ring system; maps of the composition and topography of the large moons Io, Europa, Ganymede and Callisto; the first-ever trip down the long ‘tail’ of Jupiter’s magnetosphere, a wide stream of charged particles that extends tens of millions of m
iles beyond the planet, and the first close-up look at the ‘Little Red Spot,’ a nascent storm south of Jupiter’s famous Great Red Spot.
These were the achievements from January through June of New Horizons — a space probe due to arrive at Pluto (minimum distance 2.66 billion miles from Earth) and the Kuiper Belt in July 2015.
First close-up look
The spacecraft was built by scientists at the Johns Hopkins University’s Applied Physics Laboratory and launched by NASA in January 2006. “From the first close-up look at the Little Red Spot storm, to the best views ever of Jupiter’s rings, to sequences of a volcanic eruption on the Jovian moon Io, we’ve seen some amazing things,” says New Horizons Project Scientist Hal Weaver, of the Johns Hopkins University Applied Physics Laboratory (APL), Laurel, Maryland on www.spacedaily.com. Since passing Jupiter on February 28, New Horizons has sped nearly 100 million miles down the long dynamic tail of Jupiter’s magnetosphere, measuring charged particles in this previously uncharted environment.
“The particle spectrometer teams are very excited about what they’re seeing so far,” Stern says. “There is more complexity and organisation in the magnetotail than they expected. But that’s the way exploration works — once we visit a place for the first time, our knowledge is changed by the reality we find!”
The fastest spacecraft ever launched, New Horizons made its closest pass to Jupiter on February 28, 2007, threading its path through an ‘aim point’ 1.4 million miles from the centre of the giant planet.
Its speed was boosted by 9,000 miles per hour — half the speed of a space shuttle in orbit — pushing it past 52,000 mph and hurling it towards a pass through the Pluto system in July 2015. This boost in speed was made possible by the ‘gravity assist’ flyby technique by which a spacecraft gains speed while passing close by a planet moving in a direction opposite to that of the spacecraft.
New Horizons has provided the first close-up look at the Jovian system since Galileo, which orbited the planet from 1995-2003, and the last until Nasa’a Juno mission arrives in 2016.
Eight-year cruise
After an eight-year cruise from Jupiter across the expanse of the solar system, the probe will conduct a five-month long study of Pluto and its three moons in 2015, characterising their global geology and geomorphology, mapping their surface compositions and temperatures, and examining Pluto’s atmospheric composition and structure.
Then, as part of a potential extended mission, New Horizons would conduct similar studies of one or more smaller worlds in the Kuiper Belt, the region of ancient, rocky and icy bodies far beyond Neptune’s orbit.
The New Horizons science payload includes: Alice, an ultraviolet imaging spectrometer to probe the atmospheric composition and structure of a planet.
Ralph, a visible and infrared camera to obtain high-resolution colour maps and surface composition maps of the surfaces of planets and other heavenly bodies.
LORRI (Long Range Reconnaissance Imager), to image a planet’s surface at football-field sized resolution, resolving features as small as approximately 50 yards across.
PEPSSI (Pluto Energetic Particle Spectrometer Science Investigation) that will search for neutral atoms that escape the planet’s atmosphere and subsequently become charged by interaction with solar wind.
SDC (Student Dust Counter) — developed by students of Johns Hopkins University — that will count and measure the masses of dust particles along the spacecraft’s entire trajectory, covering regions of interplanetary space never before sampled.
REX or Radio Science Experiment — a circuit board containing sophisticated electronics that has been integrated with the spacecraft’s radio telecommunications system and will study Pluto’s atmospheric structure, surface thermal properties, make measurements of the mass of Pluto, Charon and Kuiper Belt objects.
Having achieved what it was scheduled to achieve by its Jupiter encounter, what lies between now and the probe’s arrival at its final destination (Pluto, Kuiper Belt)? Well, on June 27, it slipped into what is called ‘electronic slumber,’ also known as operational hibernation phase, during which the spacecraft’s redundant components and guidance control system are powered off.
This reduces wear and tear on electronics, lessens spacecraft operation costs and frees up tracking resources for other missions. New Horizons will ‘sleep’ in this state for most of the remaining 8-year cruise to Pluto; operators will wake New Horizons for about two months out of each year for system checkouts and instrument calibrations.
Onboard computer
During hibernation, New Horizons’ onboard flight computer monitors system health and broadcasts a beacon tone through a medium-gain antenna.
New Horizons will transmit a ‘green’ coded tone if all is well, or a ‘red’ tone if it detects a problem and requires help from the operations team. New Horizons is the first mission to make operational use of hibernation in flight and the associated beacon communications mode.
Good night Jupiter, good morning Pluto!
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