NASA Sends Aircraft to Watch Asteroid Probe's Fiery Re-entry
Project scientist Peter Jenniskens of the SETI Institute and NASA's Ames Research Center and Christina Giannopapa of the Netherlands' Eindhoven University prepare lenses for one of the specialized cameras for installation on NASA's DC-8 flying laboratory.
Credit: NASA /Dryden/Tom Tschida

NASA has dispatched a jet filled with scientists to Australia ahead of the long-awaited return of a Japanese asteroid probe, which began its final approach to Earth Wednesday.

A Douglas DC-8 aircraft outfitted to serve as a flying laboratory carried 30 NASA scientists to Australia to track the incoming Japanese spacecraft Hayabusa during its fiery re-entry through Earth's atmosphere on Sunday, June 13 at the end of its seven-year trek to an asteroid.

Hayabusa, built by the Japan Aerospace Exploration Agency (JAXA) is expected to drop a sample capsule through the atmosphere that, if all goes well, will parachute down to a landing zone in Australia's Woomera Prohibited Area (WPA).

Hayabusa also fired its ion engine for one last course correction Wednesday to fine-tune its approach to a remote landing zone in Australia's WPA.

"By this operation, Hayabusa spacecraft was precisely guided to WPA in Australia," JAXA officials said in an update.

All eyes on Hayabusa

The DC-8 aircraft will give NASA scientists a front row seat to the asteroid probe's landing.

"Hayabusa is hurtling toward Earth at an immense speed, comparable to that of an asteroid impact," said Peter Jenniskens, the observation campaign's principal investigator and a scientist at NASA's Ames Research Center in Moffett Field, Calif., and the SET Institute in Mountain View, Calif. "The capsule that protects the asteroid sample will be only 6,500 feet ahead of the rest of the spacecraft, which will break into numerous pieces, essentially making it a man-made meteor."

Jenniskens and an pack of eager astronomers ?onboard the DC-8 will have their instruments secured near the plane's specialized windows. At an altitude of 39,000 feet, above light pollution and clouds, the scientists will be able to study what happens when the spacecraft and sample return capsule heat up high in the atmosphere.

When Hayabusa reaches an altitude of 190,000 feet, its heat shield will experience sweltering temperatures of over 5,000 degrees Fahrenheit (2,700 degrees Celsius), while the gas surrounding the capsul will reach 13,000 degrees Fahrenheit (7,200 degrees Celsius) ? which is hotter than the surface of the sun.

Probe's fiery plunge home

The team is primarily interested in studying the Hayabusa capsule's re-entry, in order to gain technological insight into the heat shield that designers and engineers can use in developing future exploration vehicles.

Hayabusa's unique heat shield material, shape and the tremendous interplanetary re-entry speed of 7.58 miles per second mean that the probe's descent will provide new and valuable information about how heat shields that can be used for computer models of re-entry conditions.

In fact, Hayabusa is expected to be the second fastest man-made object to return to Earth. NASA's Stardust sample return capsule set the record re-entry speed of 7.95 miles per second in January 2006.

"The return of Hayabusa provides NASA and JAXA with a rare opportunity to monitor the performance of an atmospheric entry vehicle at speeds much higher than that of the space shuttle returning from low-Earth orbit," said Jay Grinstead, the observation campaign project manager and a research scientist at NASA Ames.

"The spectrum of light emitted by the gas and surface at these extreme temperatures tells us about the physics and chemistry of atmospheric entry," he said. "Our vantage point onboard the DC-8 and the variety of instruments enable us to track the evolution of the spectrum and compare it to simulations used for design and analysis of entry systems."

The observation team will also provide JAXA with data and images that will be obtained during the flight to correlate with the Japanese space agency's ground optical and radio observations to assist in locating the capsule once it reaches Earth.

Additionally, since the breakup of the main spacecraft will also be visible, scientists will use images of the debris to validate computer models that astronomers use to predict how an object will fragment and disperse upon entering Earth's atmosphere at extremely high speeds.

NASA astronomers made similar airborne studies from the DC-8 flying observatory for the September 2008 re-entry of the European Space Agency's Automated Transfer Vehicle "Jules Vern," as well as the Stardust sample return re-entry campaigns. For these missions, scientists studied the light emitted by the descending spacecraft in order to better understand the mechanisms of atmospheric entry heats of? natural and man-made objects.