Now heading outward on its lengthy trek to tiny Pluto, NASA’s New Horizons spacecraft is on course to zip by gigantic Jupiter early next year.
Engineers and scientists are plotting out an agenda of at-Jupiter investigations. Thanks to high-tech instruments onboard the craft, new looks at the gas giant are slated, as are views of several moons circling the planet.
But while science at Jupiter is to be gained, the real game is to shakeout New Horizons long before it encounters the Pluto system in 2015. Earlier this year the spacecraft photographed both Jupiter, and its final destination, Pluto.
“The first objective at Jupiter is to hit the keyhole to get us to Pluto. If we don’t do that…nothing else matters,” said Alan Stern, principal investigator for New Horizons and executive director of the Space Science and Engineering Division here at Southwest Research Institute.
Hitting that little window in space is a priority, a predetermined but needed course correction for New Horizons. The adjustment will place the probe on a trajectory to attain a closest approach of Pluto some 8 years hence, on July 14, 2015.
Like a test drive of a new automobile, Stern said that New Horizons zooming by Jupiter is a full-up practice run. The flyby will show how the probe handles and help flesh out any unknown issues lurking within the spacecraft — from software and commands to the science instruments.
One nagging engineering issue has already been flagged.
New Horizons is using two of its 16 thrusters more than expected, Stern said. “So we’re going to have to limit our appetite and learn to fly the spacecraft a little bit differently…or we’ll use them all up before we get to Pluto.”
“Pluto is a one-shot,” Stern told SPACE.com. “I don’t fundamentally want things to go wrong…but I want them to go wrong at Jupiter and not at Pluto. At Pluto, my first and only objective is to learn about Pluto. If I learn anything at all about the spacecraft at Pluto…that would not be good.”
New Horizons will take on Jupiter operations for five months, from January to the end of June next year. But within that timeframe, there are 10 days of very intense science investigations now being scheduled.
“This is a stress test. Just like the doctor gets your heart racing on a treadmill…we are really putting that spacecraft through its paces,” Stern added.
New Horizons is the eighth spacecraft to arrive at the Jupiter system.
“We are going to do a lot of good science,” Stern explained. For one, the probe will fly down Jupiter’s magnetotail — never before done event.
Due to the Jupiter’s strong magnetic field, the planet’s magnetosphere fills a vast volume of space. As New Horizons departs the Jovian system, the path to Pluto happens to take the spacecraft down the “tail” of Jupiter’s magnetosphere that is pulled back behind the planet.
Goals at Europa
Jupiter science targets on the New Horizons to do list include looks at the planet’s little and great red spots, ring structure, as well as Io and Europa — two moons of Jupiter’s entourage of over 60 moons found so far.
“We have a few goals at Europa,” noted John Spencer, a staff scientist at SwRI’s Department of Space Studies and also the New Horizons deputy imaging node leader. “We’ll have a somewhat improved look at the infrared spectrum of the darker non-ice material on Europa’s surface,” he said.
That material seems to be some sort of water-bearing salt or perhaps sulfuric acid — and may hold clues to the composition of Europa’s subsurface ocean, Spencer pointed out.
Other goals at Europa are to understand its ultra-thin oxygen atmosphere better, Spencer added. That will be done by New Horizons obtaining spectra of the ultraviolet airglow emissions from that moon’s atmosphere. Also, the spacecraft will watch a star pass behind Europa and look for absorption of the starlight by Europa’s atmosphere. A similar tactic is being applied in observing Io’s more substantial atmosphere.
“We’ll also be mapping some very peculiar huge circular grooves on Europa which can only be seen when the Sun hits the surface at just the right angle,” Spencer said.
Staring at the rings
Spencer said that the New Horizons science team and associates are looking to do things that haven’t been done before at Jupiter…or inspecting things that are changing with time.
As example, infrared scans of ammonia clouds that appear and disappear in the wake of Jupiter’s great red spot are to be done. New Horizons totes a near-infrared instrument with much higher spectral resolution than equipment carried on the earlier Galileo mission at Jupiter, he said.
“So we’re focusing on something pretty cool that hasn’t been done before,” Spencer said.
In addition, New Horizons will spend a lot of time staring at the rings, looking for very small satellites that may be embedded in the rings that haven’t been discovered before, Spencer observed. “There’s some interesting structure in the rings that may be due to dust being shed off smaller bodies.”
Jupiter’s Io — a volcanically active moon studied intently by NASA’s Galileo spacecraft as a follow-up to earlier Voyager observations — is due for scrutiny by New Horizons, too.
“We’ll spend a lot of time staring at the night side of Io…looking in the visible and near-infrared,” Spencer said. New Horizons data, he added, should help bracket the high temperatures for volcanoes on Io.
“Some observations from Galileo found them embarrassingly hot,” Spencer explained. “Are there really super-heated eruptions on Io…some exotic lava being erupted…or is it plain old basalt?”
But to help clear up the mystery, Io will have to cooperate and cough up the goods on New Horizons time, Spencer said.
There’s much to do in readying both spacecraft and the entire New Horizon team for the close encounter of the Jovian kind. New Horizons will whisk by Jupiter at closest approach on February 28, 2007, speeding through space at some 47,000 miles per hour (about 21 kilometers per second).
“Right now, we wish we had more time. It’s a little too fast,” Spencer concluded.