by bystander » Fri Oct 29, 2010 5:47 pm
Arecibo Radar Observations of 103P/Hartley 2
We observed comet 103P/Hartley 2 on 2010 October 24-27. Observations are scheduled through Oct 29.
This mosiac shows sixteen radar delay-Doppler images of the nucleus on (from top to bottom) Oct 25-27 and 29. Within a row, each of the four frames is a sum of about 15 minutes of data with a 30 minute gap between the second and third frame. Range from the the observer increases downward. The Doppler (horizontal) axis has been scaled by eye to make the pixels square. The pixel spacing is 75m (0.5 microseconds), with 150m resolution. Absolute range information has been forwarded to the EPOXI nav team.
Credit: NAIC-Arecibo/Harmon, Nolan, Howell; JPL/Giorgini
Space Radar Provides a Taste of Comet Hartley 2
NASA JPL | 2010-358 | 28 Oct 2010
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."
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."
Just what a celestial pickle means for the EPOXI mission remains to be seen. Mission engineers and scientists are discussing the new findings and what - if anything - they signify for the upcoming comet encounter.
Along with Giorgini, observations of comet Hartley 2 were led by Arecibo Obervatory's John Harmon, with contributions by Mike Nolan and E. S. Howell.
[float=left][img2]http://www.naic.edu/~pradar/103P/103Px2.gif[/img2][/float]
[url=http://www.naic.edu/~pradar/103P/][b][size=120]Arecibo Radar Observations of 103P/Hartley 2[/size][/b][/url]
We observed comet 103P/Hartley 2 on 2010 October 24-27. Observations are scheduled through Oct 29.
This mosiac shows sixteen radar delay-Doppler images of the nucleus on (from top to bottom) Oct 25-27 and 29. Within a row, each of the four frames is a sum of about 15 minutes of data with a 30 minute gap between the second and third frame. Range from the the observer increases downward. The Doppler (horizontal) axis has been scaled by eye to make the pixels square. The pixel spacing is 75m (0.5 microseconds), with 150m resolution. Absolute range information has been forwarded to the EPOXI nav team.
Credit: NAIC-Arecibo/Harmon, Nolan, Howell; JPL/Giorgini
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[url=http://www.jpl.nasa.gov/news/news.cfm?release=2010-358][size=120][b][i]Space Radar Provides a Taste of Comet Hartley 2[/i][/b][/size][/url]
NASA JPL | 2010-358 | 28 Oct 2010
[quote]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."
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."
Just what a celestial pickle means for the EPOXI mission remains to be seen. Mission engineers and scientists are discussing the new findings and what - if anything - they signify for the upcoming comet encounter.
Along with Giorgini, observations of comet Hartley 2 were led by Arecibo Obervatory's John Harmon, with contributions by Mike Nolan and E. S. Howell. [/quote]