Earth Spacecraft Reaches Icy Comet

Artist illustration of NASA's Stardust-NExT spacecraft  approaching comet Tempel1
Two NASA Missions have now flown close to Tempel 1. An illustration of what the approach of NASA's Stardust-NExT spacecraft looked like when it arrived at the comet Tempel 1 on Valentine's Day (Feb. 14) in 2011.

Twelve years after launch and seven years after it collected dust from comet Wild 2, NASA's Stardust probe streaked past comet Tempel 1 late Monday in a Valentine's Day encounter to find out how the icy body has changed since it was visited by another NASA spacecraft in 2005.

The renamed Stardust-New Exploration of Tempel mission -- Stardust-NExT -- passed within about 124 miles of the nucleus of Tempel 1 at 11:38 p.m. EST, snapping 72 high-resolution images and collecting data about the dust environment in the immediate vicinity as it raced past at a relative velocity of 24,300 mph.

Telemetry from the spacecraft confirmed its systems were operating normally and that its navigation camera was operating as expected during the close approach phase of the flyby.

"We have a great spacecraft and a great spacecraft team," said Joe Veverka, the Stardust-NExT principal investigator. "And apparently, everything has just worked perfectly. The only hard thing now is we have to wait a couple of hours before we see all the goodies stored on board."

Because radio signals to and from the spacecraft took about 45 minutes to cover the 418-million-mile round-trip distance between Earth and the spacecraft, Stardust NExT carried out the flyby autonomously under control of its on-board computer. The first images of Tempel 1 were expected to reach NASA's Jet Propulsion Laboratory in Pasadena, Calif., around 3 a.m. EST Tuesday.

"In the few minutes around closest approach, we'll be taking the bulk of our images, we'll be taking 72 high-resolution images," JPL Project Manager Tim Larson said during a pre-encounter news conference. "We cannot transmit those to the ground real time because of the flyby geometry. So we have to store all of those on board in the spacecraft memory.

"An hour after the flyby, we turn the spacecraft to point the high gain antenna back to Earth and at that point, we'll start relaying all the information back to Earth. It will take approximately 12 hours to get all the data back own on the ground. The first images should be hitting the ground around midnight Pacific time on the 14th."

The $300 million Stardust mission was launched in 1999. On Jan. 2, 2004, the spacecraft flew past comet Wild 2, using an innovative collector to capture particles from the coma, the cloud of debris surrounding the nucleus. Passing back by Earth two years later, a small re-entry capsule carrying the collected material was ejected and fell to a landing in Utah where it was recovered for detailed analysis.

In the meantime, NASA carried out the Deep Impact mission, sending another spacecraft to comet Tempel 1, a roughly potato-shaped body with a nucleus measuring 4.7 by 3 miles. During a dramatic encounter in 2005, Deep Impact released an instrumented probe that crashed into the comet, throwing up a cloud of debris from the surface. The Deep Impact spacecraft monitored the crash from a safe distance and carried out remote observations with cameras and other instruments.

NASA Photos of Tempel 1

But the cloud of debris, or ejecta, thrown up by the Deep Impact probe prevented scientists from seeing the crater the crash excavated.

With the Stardust probe still healthy after its successful mission to Wild 2, NASA approved a $29 million mission extension and agreed to send the spacecraft to Tempel 1 to study how the comet had changed during a full trip around the sun.

The first image taken during the Stardust-NExT's approach to comet Tempel 1 on Feb. 14, 2011.
Thar she blows. NASA's Stardust-NExT mission transmitted the first image it took during its approach to comet Tempel 1 on Feb. 14, 2011.

In the pre-encounter briefing, Veverka said Tempel 1 turned out to be "unusually interesting."

"In places on Tempel 1, we see layered terrains, which probably contain information about how comet nuclei are put together, and we would like to see more of these terrains," he said, explaining why Tempel 1 was targeted for a second visit. "Deep Impact saw only about a third of the surface. We would like to see more."

Deep Impact also showed areas that appear to be smooth flow-like deposits, along with crater-like features that could be ancient vents.

  • William Harwood

    Bill Harwood has been covering the U.S. space program full-time since 1984, first as Cape Canaveral bureau chief for United Press International and now as a consultant for CBS News. He covered 129 space shuttle missions, every interplanetary flight since Voyager 2's flyby of Neptune and scores of commercial and military launches. Based at the Kennedy Space Center in Florida, Harwood is a devoted amateur astronomer and co-author of "Comm Check: The Final Flight of Shuttle Columbia."