Twelve radar images of the nucleus of comet Hartley 2 were obtained by the Arecibo Observatory's planetary radar from Oct 25 to 27, 2010. Image credit: NAIC-Arecibo/Harmon-Nolan
Provided by JPL/NASA (news : web)
Exactly one week before the world gets a new look at comet Hartley 2 via NASA's EPOXI mission, observations of the comet by the Arecibo Planetary Radar in Puerto Rico have offered scientists a tantalizing preview.
"It kind of looks like a cross between a bowling pin and a pickle," said EPOXI project manager Tim Larson of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Only it's about 14-thousand-times larger and hurtling through space at 23 miles per second." A new image is online at http://www.naic.ed … ~pradar/103P .
Scientists using Arecibo's massive radar dish began observations of Hartley 2 on Oct. 24, just four days after the comet made its closest approach to Earth since its discovery in 1986. (On Oct. 20, the comet came within 17.7 million kilometers, or 11 million miles, of Earth). The observations are scheduled to continue through Friday, Oct. 29.
During the Nov. 4 flyby, the cameras aboard the EPOXI mission spacecraft will get within 700 kilometers (about 435 miles) of the comet.\
"Observing comet Hartley 2 from the Earth with radar was like imaging a 6-inch spinning cucumber from 836 miles away," said Jon Giorgini, a scientist at JPL and a member of the Arecibo team that imaged the comet. "Even without all the data in, we can still make some basic assertions about Hartley 2. Its nucleus is highly elongated and about 2.2 kilometers [1.4 mile] long, and it rotates around itself about once every 18 hours. In addition we now know the size, speed and direction of particles being blown off the comet, and we immediately forwarded all this information to the EPOXI team."