Three hours before encountering the upper fringes of Earth's atmosphere, the Hayabusa spacecraft spring-ejected a tiny 16-inch-wide capsule for landing in the Australian outback.

Credit: JAXA

The separation occurred at 1051 GMT (6:51 a.m. EDT) about 25,000 miles above Earth, according to an update posted on the mission's official Twitter account.

Landing at the Woomera Prohibited Area in South Australia should occur around 1411 GMT (10:11 a.m. EDT), or 11:41 p.m. local time.

Our comprehensive story has more details on Hayabusa's return to Earth.

Controllers stationed at the Japanese space agency's Sagamihara campus near Tokyo will no longer be in communications with the container, which may be shepherding the first samples from the surface of an asteroid.

Hayabusa was expected to use its lone reaction wheel to spin up the capsule in the hours before it separated. The rotation was designed to condition its battery, which has been in space three years longer than designed.

The battery powers crucial sensors governing the capsule's re-entry and parachute deployment sequence, plus a beacon transmitter that will give ground crews the craft's location after landing.

The Hayabusa mothership will follow seconds behind the capsule during re-entry, but the 950-pound spacecraft will burn up because it does not have a heat shield.

Japanese officials were planning to command Hayabusa to execute a few final observations of Earth, including pictures of Japan, during its final hours, Junichiro Kawaguchi, the mission's project manager, said in an interview Friday.

Hayabusa's ground track as it approaches Australia. Credit: JAXA

The capsule will plunge into the atmosphere around 1351 GMT (9:51 a.m. EDT) at more than 27,000 mph. Its carbon fiber heat shield must withstand temperatures of nearly 5,000 degrees Fahrenheit during the most severe period of heating.

A NASA DC-8 research plane will be positioned to study the re-entry. Instruments aboard the aircraft will determine the capsule's trajectory, measure the intensity of super-heated plasma from the capsule's bow shock, detect the loss of ablative carbon material and observe the break-up of the Hayabusa main spacecraft.

The Japan Aerospace Exploration Agency and NASA have also positioned a network of ground observers to record the re-entry.

Approaching Woomera from the northwest, the capsule will jettison part of its heat shield and backshell 6 miles above the ground, allowing its parachute to deploy.

Hayabusa's sample container will float to a gentle landing somewhere in a 100-kilometer, or 62-mile-long, target ellipse. Nearly 100 Japanese and Australian officials in helicopters and all-terrain vehicles will listen for the capsule's beacon transmissions signaling its location in the Australian outback.