Rejuvenated Hubble spies giant impact scar on Jupiter
BY STEPHEN CLARK
Posted: July 24, 2009
The freshly-upgraded Hubble Space Telescope snapped a dramatic image of a dark blemish on Jupiter Thursday, using the observatory's brand new camera installed by astronauts in May.
Taking a break from extensive testing following May's shuttle repair mission, Hubble pointed toward Jupiter for several hours Thursday afternoon to take the sharpest picture yet of the scar.
Astronomers believe the spot was most likely caused by a comet that slammed into the giant planet out of view of Earth telescopes. The violent impact propelled reflective aerosol-like particles from Jupiter's lower atmosphere into a region that can be observed from Earth some 360 million miles away.
Infared imagery shows a bright spot against a darker background. Visible light pictures show a darker feature similar to a bruise in the planet's southern hemisphere.
"Because we believe this magnitude of impact is rare, we are very fortunate to see it with Hubble," said Amy Simon-Miller of NASA's Goddard Space Flight Center. "Details seen in the Hubble view show a lumpiness to the debris plume caused by turbulence in Jupiter's atmosphere."
Hubble's Wide Field Camera 3, a $132 million imager conceived as the telescope's next workhorse instrument, was tasked with the unexpected assignment, even though the new component has not been thoroughly tested.
WFC 3's ultraviolet and visible channel took the picture, an early sneak preview of Hubble's new imaging capabilities.
"This impact is regarded as a target of opportunity. You drop everything and go look at it," said Ray Villard, spokesperson for the Space Telescope Science Institute in Baltimore.
"Even though the camera isn't completely finished with its calibrations, we've got to collect the data because the spot is going to fade away relatively rapidly," said Dave Leckrone, Hubble project scientist.
The object responsible for the this week's scar hit Jupiter on the 15th anniversary of the Shoemaker-Levy 9 impact events in 1994.
More than 20 fragments struck Jupiter over a six-day period in July 1994 after the gas giant's gravity tore the comet apart two years earlier.
This week's event is only the second time astronomers have studied an impact elsewhere in the solar system.
"Observing it both in infrared and visible light indicates to us that it is very similar to the phenomenon that was produced in the atmosphere of Jupiter by the fragments of Shoemaker-Levy 9 back in 1994," Leckrone said.
Hubble was in the midst of a nearly four-month Servicing Mission Observatory Verification, or SMOV, period, a series of tests and calibrations designed to check new equipment astronauts installed during May's upgrades.
"This is a situation where the science is so important that we felt compelled to interrupt our normal standard SMOV process and go off and take some images, just so that we have the data," Leckrone said.
Hubble operators at the Space Telescope Science Institute gave observation time to a team of astronomers led by Heidi Hammel of the Space Science Institute in Boulder, Colo.
"Hubble's truly exquisite imaging capability has revealed an astonishing wealth of detail in the impact site," Hammel said. "By combining these images with our ground-based data at other wavelengths, our Hubble data will allow a comprehensive understanding of exactly what is happening to the impact debris."
Scientists hope to determine more details about the object that struck Jupiter, which is currently estimated to be the size of several football fields, according to NASA.
More WFC 3 imaging of Jupiter is planned next week.
Scientists plan procedures for such quickie observations, but Hubble has never been ordered to look at a target of opportunity so soon after a servicing mission, Villard said.
Hubble is about 73 percent through the post-mission testing, according to Ed Ruitberg, deputy associate director for Goddard's astrophysics projects division.
The storied observatory was rejuvenated in May with repaired equipment, two new state-of-the-art instruments, gyroscopes, batteries and a guidance unit. Atlantis' servicing mission left Hubble more powerful than ever before, officials said.
"The main thing we're doing is preparing for science," Leckrone said. "That means making sure our spacecraft operates nominally to, for example, point to the right place and to be stable so we can take clear images."
The gyroscopes, batteries and fine guidance sensor have all passed their tests.
"The scientific instruments are more complicated than that because you test them on the ground, but you can't test them on the ground as accurately as you can test them in orbit looking at real stars," Leckrone said.
Like a photographer changing camera settings, ground controllers can adjust the focus and alignment of sensors inside the instruments to get the best possible pictures.
"It's not just a point and shoot situation," Leckrone said. "We want the very best quality data we can get, and we don't want to break our instruments. We want to protect to make sure they function for a long lifetime."
Regular science operations are just now getting started again on some instruments, but officials were not planning to release the first new pictures until September.
That was the plan until Jupiter threw the science team a curveball this week.
"This is just one example of what Hubble's new, state-of-the-art camera can do, thanks to the STS-125 astronauts and the entire Hubble team," said Ed Weiler, associate administrator for NASA's science mission directorate.
Astronauts also added a new sensor called the Cosmic Origins Spectrograph, a cutting edge tool astrophysicists will use to answer fundamental questions about the universe.
ACS has already been turned over to guest observers, external astronomers that are selected to use Hubble through peer reviews.
A visible light channel of STIS is also being used for science work, less than a month after the 12-year-old imager froze due to an apparent software timing error, according to Leckrone.
Ruitberg said WFC 3 and COS will be opened up for normal science activities by the middle of August.
Hubble's new Science Instrument Command and Data Handling Unit, an electronics package that synchronizes the spacecraft's science instruments, also "latched up" last month.
"This is almost certainly the result of a cosmic ray particle impinging on the electronics of the SIC&DH and causing bits to flip," Leckrone said.
The SIC&DH replacement was a late addition to the shuttle flight after it failed weeks before Atlantis was originally scheduled to launch last year. The mission was delayed until this spring to give engineers time to prepare a spare unit.
The SIC&DH is a critical part of the telescope because it acts as a nerve center for Hubble science operations.
"I have electronics components at home in my stereo system and sometimes they just freeze up. If I just power cycle it, it seems to be just fine, and that's exactly what happened with the SIC&DH. So it's dandy and working very well right now," Leckrone said.
Officials believe problems with STIS and the SIC&DH are well understood and will not happen again, at least not frequently.
Scientists plan the first formal post-servicing mission data release in September. The announcement is tentatively scheduled for Sept. 9.
"I know it's frustrating to people because they want a picture the first day," Leckrone said. "I don't want to show you a blurry image because the camera was out of focus. I want to show you a sharply-focused image."
The 19-year-old spacecraft should be fully operational again by early fall.
"Hubble is just so far better than it's ever been before. I just can't wait for the science to start happening because we have just never had a set of tools to observe the universe that is this powerful, ever. I can't wait to see what we're going to find," Leckrone said.