NASA’s EPOXI mission is closing in on its target – comet Hartley2.
The spacecraft is to fly within 700 kilometers (435 miles) of the comet’s nucleus on Thursday, November 4.
Closest approach of comet Hartley 2 is expected to occur at roughly 9:50 am EDT, 6:50 am PDT). The craft will image the comet as the two slip past each other at a relative velocity of more than 12 kilometers per second, or some 27,000 miles per hour.
This flyby will mark the fifth time in history that a spacecraft has been close enough to image the heart of the comet, more commonly known as the nucleus.
There’s increasing excitement about what will be seen, specifically the ability to analyze activity in the comet’s coma and study its jets of cyanide (CN). Onboard the NASA spacecraft, the High Resolution and Medium Resolution Imagers (HRI and MRI) have captured great views of multiple jets turning on and off.
Explains EPOXI Principal Investigator Mike A’Hearn of the University of Maryland: “These jets can act as thrusters and actually make small changes to the comet’s orbit around the Sun.”
Ground and space-based observations
According to researchers at the Planetary Science Institute (PSI) in Tucson, Arizona, both the flyby and ground observations are to offer researchers a clearer view of the comet’s nucleus.
Numerous nights of observation from Earth can offer data to bolster encounter information to be gleaned by the passing spacecraft, said Beatrice Mueller, senior scientist at PSI.
For example, utilizing images taken from September to October using a 2.1-meter telescope at Kitt Peak National Observatory near Tucson, Mueller and Nalin Samarasinha, senior scientist at PSI, were able to analyze activity in the comet’s coma and study the cyanide jet that was revealed after images were enhanced to carefully remove background contribution and focus on the CN jet activity.
Samarasinha likened the CN jet to a garden hose gushing water, which places a torque on the comet’s nucleus and causes it to change its spin.
Check out some fascinating video of comet Hartley 2 and its jet of CN gas as it emerges from the nucleus of comet Hartley.
Go to:
http://epoxi.umd.edu/3gallery/20101027_jets.shtml
EPOXI is an extended mission that uses the already “in-flight” Deep Impact spacecraft to explore distinct celestial targets of opportunity.
The name EPOXI itself is a combination of the names for the two extended mission components: the extrasolar planet observations, called Extrasolar Planet Observations and Characterization (EPOCh), and the flyby of comet Hartley 2, called the Deep Impact Extended Investigation (DIXI).
The spacecraft – built by Ball Aerospace & Technologies Corporation of Boulder, Colorado — will continue to be referred to as “Deep Impact.” JPL, a division of the California Institute of Technology in Pasadena, manages the EPOXI mission for NASA’s Science Mission Directorate in Washington, D.C.
By Leonard David