Oct 072008

Image sequence showing changing brightness of asteroid 2008 TC3.

October 7, 2008 — Something happened yesterday that got professional and amateur astronomers whipped into a rare frenzy. A telescope in Arizona discovered a small asteroid that, for the first time ever, was certain to hit Earth — and it gave us only 19 hours’ advance warning. Fortunately, the object (designated 2008 TC3) was far too small to reach the ground intact. Instead, it exploded this morning at a height of about 23 miles (37 km) over Sudan in northeast Africa, lighting up the predawn darkness and frightening thousands of Sudanese making their way home after morning prayers.

In the hours before the asteroid’s demise, the world’s astronomers amassed nearly 600 observations. Yet few were more important than a long sequence of images taken by Ron Dantowitz and Clay Center astronomers. In a perfect example of being in the right place at the right time, the Clay Center Observatory was in a position to track the asteroid in the hours just preceding its fateful collision, and the skies were clear over Boston that evening.

With everything ready, the two astronomers started snapping away with an electronic camera attached to the observatory’s 25-inch telescope. Every 4.1 seconds, another image streamed into computer memory. By the time the asteroid slipped into Earth’s shadow some 2 hours later, they’d amassed 1,770 perfectly exposed images. Other observatories captured the asteroid’s spectrum and its position, but no one else photographed it so extensively.

Even without the aid of computer analysis, Dantowitz could see that the asteroid was changing brightness dramatically, an indication that it was irregularly shaped and spinning or tumbling. Three Czech researchers led by Peter Scheirich have deduced both the shape of 2008 TC3 (like a loaf of bread with a flat side) and how it was tumbling just before striking Earth.

Although seemingly chaotic, the asteroid’s motion resulted from twirling around two different spin axes every 99 and 97 seconds. This conclusion relied heavily on the long sequence of images taken by the Clay Center Observatory. According to Czech asteroid specialist Petr Pravec and Dantowitz’s observations of the asteroid were unique. “Without them,” he noted, “we wouldn’t know much about its rotation.”

Oct 022008

October 2, 2008 — When NASA researchers want to study meteor showers or spacecraft streaking through Earth’s atmosphere, one of the first places they call is the Clay Center Observatory in Brookline, Massachusetts. This state-of-the-art facility is part of Dexter and Southfield Schools, which provides K-12 education for more than 700 students.

The “NASA hotline” rang again earlier this year, and in the predawn hours of September 29th a Clay Center team found itself crammed with dozens of other scientists aboard two aircraft high over the South Pacific Ocean. Their mission was to record the dramatic nighttime reentry of a large European spacecraft called Jules Verne as it slammed into Earth’s atmosphere at more than 5 miles per second.

Aboard one chase plane, a commercially owned Gulfstream V, were Dexter Southfield faculty member Ronald Dantowitz and astronomers from the Clay Center Observatory. They operated a bank of eight sensitive cameras and spectrographs, built at the school, to record the temperature and composition of superheated fragments created during the spacecraft’s blazing atmospheric plunge. Meanwhile, undergraduate student David Sliski operated an additional camera and spectrograph on the second aircraft, a DC-8 that NASA has converted into an airborne laboratory.

Dantowitz, director of the Clay Center Observatory, reports that the team’s make-or-break observations were a complete success. As the instruments continuously tracked Jules Verne’s final moments, the spacecraft first broke into three large chunks before exploding violently into hundreds more. Dantowitz and Sliski had ringside seats as the dramatic disintegration unfolded some 50 miles up.

“The reentry was spectacular,” Dantowitz admits, but his team wasn’t there to sightsee. “The images we took will help NASA and the European Space Agency to understand the dynamics of spacecraft reentry more fully,” he explains, “and will result in safer and more reliable designs for future spacecraft.”

Jules Verne, a passengerless craft also known as an Automated Transfer Vehicle, had been docked to the International Space Station from March 9th to September 5th. Roughly the size of a large bus, it already weighed 20 tons before astronauts stuffed it with another 2.5 tons of garbage and waste that had accumulated on the Space Station.

To prepare for this airborne expedition, NASA scientist Peter Jenniskens first assembled a contingent of 30 researchers at the space agency’s Ames Research Center in Mountain View, California. After days of checks, calibrations, and test runs, the team climbed aboard the two aircraft and flew to Tahiti, which served as the staging base for September 29th’s predawn encounter.

Once back in Massachusetts, Dantowitz will need many months to analyze the data. “The work of the Clay Center is often exciting, but the impact of this mission makes it truly extraordinary and very rewarding,” Dantowitz notes, adding that Dexter-Southfield students will be able to use the instruments and the accumulated data for research projects to enhance their science education.

© 2014 Clay Center Observatory at Dexter Southfield