Magdalena Ridge Observatory Helps NASA Track Comet

SOCORRO, N.M. February 15, 2011 – When NASA's Stardust-NExT mission encountered Comet Tempel 1 on February 14, the exploration team could thank astronomers at New Mexico Tech for an assist in pinpointing the comet’s location and trajectory.
Dr. Eileen Ryan at the controls of the Magdalena Ridge Observatory.

Dr. Bill Ryan explains the workings of the 2.4-meter telescope to a group of visitors.

In early January, scientists at NASA and the Jet Propulsion Laboratory, which designed and built the spacecraft, needed to get an accurate fix on the fast-moving comet.

The Stardust-NExT, (New Exploration of Tempel 1) mission was en route for a Valentine’s Day rendezvous with the comet, which provided a unique opportunity to measure the dust properties of two separate comets (Wild 2 and Tempel 1) with the same instrument for accurate data comparison, according to a JPL press release. The encounter also provided a comparison between two observations of the same comet, Tempel 1, taken before and after a single orbital pass around the sun.

On February 14, Tempel 1 was 0.5 AU (or 46 million miles) from Earth. Meanwhile, NASA's Stardust-NExT spacecraft hoped to fly within 125 miles of the Comet. Preliminary data transmitted from the spacecraft indicated the time of closest approach was about 8:39 p.m. PST (11:39 p.m. EST), at a distance of 181 kilometers (112 miles) from Tempel 1.

Astronomers around the planet watched this mission because this was the second time a spacecraft has encountered Tempel 1. In July 2005, the Deep Impact mission sent a 370-kg impactor into Comet Tempel 1, but the resulting dust obscured its view of the newly formed crater. Now, Stardust-NExT obtain images of the surface, allowing scientists for the first time to see changes that occurred as a result of a comet's orbit around the sun.

According to a February 14 press release, mission controllers at NASA's Jet Propulsion Laboratory in, Pasadena, Calif., watched as data downlinked from the Stardust spacecraft indicated it completed its closest approach with comet Tempel 1. An hour after closest approach, the spacecraft turned to point its large, high-gain antenna at Earth. Mission scientists expected images of the comet's nucleus collected during the flyby will be received on Earth starting at about midnight California time (3 a.m. EST on Tuesday, Feb. 15)

Astronomers hoped that Comet Tempel 1 would conform to their orbital predictions . Images and trajectory data taken by astronomer Dr. Bill Ryan from the Magdalena Ridge Observatory provided valuable information to NASA and JPL scientists.

“The positional information that Bill [Ryan] gathered was important for the success of this mission,” said Dr. Eileen Ryan, Director of MRO’s 2.4-meter telescope.

The Stardust-NExT spacecraft is equipped with an imaging camera designed to gather detailed information, but that camera is not as sensitive to faint sources  as the instruments on the 2.4-meter telescope at the Magdalena Ridge Observatory. Mission navigators wanted to use all available resources to ensure that the spacecraft would transit close enough to the comet to retrieve the best imaging data.

“Our colleagues at JPL who work with us on asteroid research suggested that maybe our 2.4-meter telescope could get a new position on Tempel 1,” said Eileen Ryan.

 An image of Comet Tempel 1 as seen by the MRO's 2.4-meter telescope.

At its current location, Tempel 1 is best viewed from the southern hemisphere, which creates several challenges for telescopes in North America.

However, the 2-meter class telescope at New Mexico Tech is not just powerful; the telescope has special capabilities. In addition to tracking asteroids, comets and other near-Earth objects, the 2.4-meter telescope was built to track missiles. To accomplish that, the telescope was configured so that it can look below the horizon.

“Most telescopes can’t look below 20 degrees in elevation,” Ryan said. “Our mirror was specially built so it can look totally horizontally. Therefore, we are uniquely capable of observing objects as low in the sky as Tempel 1 from the northern hemisphere.”

Another complication associated with observing objects at very low elevations is that the telescope must look through lots of atmosphere, which distorts the images. An atypical advantage of the 10,600-foot location of the 2.4-meter telescope atop Magdalena Ridge is that the quality of the atmospheric seeing conditions, or the stability of the atmosphere, extends to even single-digit elevations. “Not only can we look very low in the sky, but we can also see very clearly when the seeing conditions cooperate, which is very beneficial to acquiring excellent data.

Just before dusk on January 5, Dr. Bill Ryan aimed the telescope at Tempel 1 and captured images at only 5 or 6 degrees above the horizon. Since then, Bill Ryan has been collaborating with NASA and JPL scientists to further refine the data and improve their tracking of the comet’s trajectory.

“Getting these observations and accurately interpreting them is a very challenging application of the telescope and highlights its unique abilities,” said Bill Ryan.” It’s also rewarding to contribute to the Stardust-NExT mission and to help ensure that it returns the best and most scientifically valuable images of the comet.”

The encounter with Tempel 1 was broadcast on NASA TV and at www.nasa.gov.

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By Thomas Guengerich/New Mexico Tech