NASA - National Aeronautics and Space Administration

SECCHI Makes a Fantastic Recovery!

A: shows the location of the comet in a HI1-B image taken on Dec 13,2008 at 00:49UT. Also of note in the image is a beautiful coronal mass ejection.

B: shows the track of the comet through the data. This image is more useful to be viewed along-side one of the following movies.
View Larger Image December 17,2008: You would think that, after 13-years of historic comet discoveries with SOHO and two years of amazing STEREO/SECCHI observations and discoveries, we had put a check-mark in most of the boxes for comet-related achievements. But last week, Australian comet-hunter Alan Watson helped us with yet another historic achievement -- the recovery of a comet! Here's how it unfolded.

While diligently scouring the latest STEREO/SECCHI Heliospheric Imager ("HI") HI-1B data for comets and asteroids, Alan noticed the appearance of an object rising up from the lower-edge of the images. Immediately recognizing it as a "non-group comet" (not belonging to any known population), he reported it to the popular 'stereohunter' chat group page. It was soon established that this was not one of the known bright comets currenty gracing the skies and so we assumed it to be a new discovery for SECCHI. Meanwhile, veteran comet hunter Rainer Kracht (Germany) recorded a few positions of the comet in the data and produced a set of very approximate orbital elements for it. Maik Meyer, Rainer's fellow countryman and another of our most esteemed comet hunters, saw these orbital elements and noticed their similarity to those of a comet that was discovered back in 2003, but lost in the depths of space sometime thereafter. This theory was confirmed when Dr. Brian Marsden released the electronic circular designating it P/2008 X4 and linking the SECCHI observations to the comet P/2003 K2 (Christensen). And so it was official -- SECCHI had made a historic recovery of a comet!

STEREO (Solar TErrestrial RElations Observatory) is the third mission in NASA's Solar Terrestrial Probes program (STP). This two-year mission, launched October 2006, will provide a unique and revolutionary view of the Sun-Earth System. The two nearly identical observatories - one ahead of Earth in its orbit, the other trailing behind - will trace the flow of energy and matter from the Sun to Earth. They will reveal the 3D structure of coronal mass ejections; violent eruptions of matter from the sun that can disrupt satellites and power grids, and help us understand why they happen. STEREO will become a key addition to the fleet of space weather detection satellites by providing more accurate alerts for the arrival time of Earth-directed solar ejections with its unique side-viewing perspective.