[meteorite-list] NASA's Jupiter-Bound Juno Spacecraft Buzzes Earth Today: Watch It Live

[Ron Baalke]

http://www.space.com/23127-juno-jupiter-probe-earth-flyby-webcast.html

NASA's Jupiter-Bound Juno Spacecraft Buzzes Earth Today: Watch It Live
by Tariq Malik
space.com
October 9, 2013

A NASA spacecraft will zoom by Earth today (Oct. 9) to use the planet's 
gravitational pull as a speed boost for its trip to Jupiter and you can 
see live views of the probe live online during the flyby.

NASA's Juno probe will be a mere 347 miles (558 kilometers) from Earth 
and over South Africa when it makes its closest approach at 3:21 p.m. 
EDT (1921 GMT). Later tonight, at 9:30 p.m. EDT (0130 GMT), the online 
Slooh Space Camera will track the Juno spacecraft's Earth flyby live in 
a free webcast.

You can watch the Juno flyby webcast live on SPACE.com, courtesy of Slooh. 
Viewers can also ask questions via Twitter using the hashtag #nasajuno. 

"Besides watching on Slooh, viewers near Cape Town, South Africa, will 
have the best opportunity to view the spacecraft traveling across the 
sky," Slooh officials said. "The spacecraft will most likely not be visible 
to the unaided eye, but binoculars or a small telescope with a wide field 
should provide an opportunity to view."

NASA launched the Juno in August 2011 on a mission to study Jupiter in 
unprecedented detail when it arrives at the gas giant planet on July 4, 
2016. The $1.1 billion Juno mission to Jupiter will use nine instruments 
to probe deep inside Jupiter to reveal glimpses into the planet's origin, 
structure, atmosphere and magnetic field. It is named after Juno, the 
mythological wife of the god Jupiter who used special powers to learn 
the secrets Jupiter had hidden beneath cloud cover.

But first, the Juno spacecraft has to get to Jupiter. NASA used an unmanned 
Atlas 5 rocket to launch Juno in 2011, but the rocket was not powerful 
enough to send the spacecraft all the way to Jupiter. Instead, it sent 
Juno on a looping trajectory that carried it beyond the orbit of Mars 
and back so it could around Earth today in what scientists call a "gravity 
assist."

Juno is currently streaking through the solar system at a speed of 78,000 
mph (126,000 km/h), with respect to the sun. During the gravity-assist 
speed boost, Earth's gravity will cause Juno to accelerate by as it approaches 
the planet. Once Juno completes the flyby, it will be travelling at about 
87,000 mph (140,000 km/h).

Juno mission principal investigator Scott Bolton, of the Southwest Research 
Institute in San Antonio, Texas, has likened the maneuver to a "second 
rocket launch."

While 97 percent of NASA is currently on furlough due to the ongoing government 
shutdown, the agency's Jet Propulsion Laboratory - which manages the Juno 
mission - remains on duty for now. During Juno's Earth flyby, the spacecraft 
is expected to test its science instruments and snap photos of Earth and 
the moon.

"One of Juno's activities during the Earth flyby will be to make a movie 
of the Earth-moon system that will be the first to show Earth spinning 
on its axis from a distance," Bolton said in a statement.

The probe will also flex its scientific muscle in other ways.

"We'll exercise the science instruments, since Juno's instruments will 
be operating in a magnetospheric environment for the first time," said 
spacecraft engineer Jeff Lewis, Juno operations lead for spacecraft builder 
Lockheed Martin Space Systems. "The Earth's magnetic field will allow 
a number of the instruments to be tested. We're also using the flyby of 
the moon as an opportunity to gauge how the spacecraft operates. Since 
Juno is a spinning spacecraft, we need to sense the right time to take 
data as the moon, or Jupiter, passes through the instruments' fields of 
view."

But the star of today's Earth flyby is the gravity assist maneuver itself, 
scientists said.

"Juno will be really smoking as it passes Earth at a speed of about 25 
miles per second relative to the sun. But it will need every bit of this 
speed to get to Jupiter for its July 4, 2016 capture into polar orbit 
about Jupiter," said research scientist Bill Kurth of the University of 
Iowa, who is the lead investigator for two of Juno's instruments. "The 
first half of its journey has been simply to set up this gravity assist 
with Earth."

Today's Slooh webcast of the Juno flyby of Earth can be tracked directly 
from the Slooh Space Camera website (http://www.slooh.com) and via the 
Slooh iPad app.