A sequence of images (screen grabs from the live coverage of the mission) showing the Hayabusa fireball as the spacecraft re-entered the atmosphere over Australia (JAXA/Ian O’Neill).

UPDATE (10:00 a.m. EST): As expected, the Hayabusa mission has come to an end in the Australian skies. Just after 9:51 a.m. EST (11:21 p.m. local time), a bright fireball lit up the Australian Outback as the main body of the Hayabusa spacecraft re-entered the Earth’s atmosphere, burning up. The search is now on for the sample return capsule that should have opened its parachute, floating back to Earth. More to follow…

ORIGINAL POST: At 9:51 am EST on Sunday, the Japanese space agency’s (JAXA) Hayabusa mission will return to Earth. A 40 cm-wide capsule possibly containing some precious cargo will re-enter the atmosphere over Australia after visiting a potato-shaped asteroid in 2005.

SLIDE SHOW: Hayabusa: A 7-Year Asteroid Odyssey

Should the capsule deploy its parachute and be recovered from the Australian Outback’s Woomera Prohibited Range in one piece, this will mark a highly successful end to a highly problematic mission.

GALLERY: See why Hayabusa was selected as one of Discovery News’ “Best Space Probe Photographers of the Decade.”

WATCH VIDEO: With thousands of asteroids, comets and other near-Earth object buzzing by our planet, Jorge Ribas finds out how we can avoid the same fate as the dinosaurs.

In 2003, Hayabusa was launched from Uchinoura Launch Center, Kagoshima, Kyushu, Japan. Hayabusa means “peregrine falcon” in Japanese.

Using its ion engines, the space probe gave chase to Itokawa, an asteroid measuring 500 meters in length.

Unfortunately, it wasn’t long before the first problem struck the probe; it was hit by one of those annoying solar flares. But this wasn’t an average solar flare, it was the biggest solar flare in recorded history! If you ever wanted a space mission to get off to a bad start, this would be it.

The probe sustained damage to its solar panels, which reduced the spacecraft’s power-producing efficiency. As Hayabusa’s means of getting around space was by using ion engines, the reduction in power delivered by the solar array meant the thrust of the engines suffered, causing a delay in Hayabusa reaching Itokawa.

Despite this early set-back, the probe reached Itokawa in 2005 and took some stunning imagery of the space rock. It was obvious from the photographs that the asteroid was formed of smaller chunks of rock held together by a mutual gravity (known as a “rubble pile”). These observations revealed that Itokawa has a surprisingly low density.

ANALYSIS: How are Asteroids Like Geckos? In a recent study of the science to come from Hayabusa, it would appear Itokawa has a strange force (that geckos use) holding it together.

This is when things started to go even worse for the solar flare-battered probe. There was an attempt to get a closer look at the asteroid, but in doing so, the spacecraft overheated and switched into “safe mode” when accidentally making contact with the sun-baked side of Itokawa.

After regaining control, JAXA scientists made an attempt to grab samples of the asteroid to bring back to Earth. Unfortunately, that didn’t go smoothly either. The sampling device intended to kick pieces of asteroid from the surface into a collector didn’t work as it was supposed to. However, there is hope that some disturbed particles of asteroid dust made it on board during these maneuvers.

After a delayed limp back to Earth (the mission was supposed to return in 2007), Hayabusa is finally on its final straight, aimed right at the Australian outback.

Shortly before Sunday’s re-entry, the return capsule — hopefully containing the invaluable particles of asteroid dust — will separate from the main spacecraft, leaving the majority of the probe to burn up high in the atmosphere.

The capsule is designed to withstand temperatures of up to 3,000 degrees Celsius. After falling through the atmosphere, the return capsule should deploy its parachute at an altitude of 10 km (6.2 miles).

All going well, by Sunday night, the JAXA scientists commanding Hayabusa will be able to (finally) breathe easy when they know their precious cargo made it back to Earth in one piece.

Despite the unfortunate circumstances of this pioneering mission to land on an asteroid, perhaps we’ll get a fairytale ending when it is announced that Hayabusa did capture a small piece of Itokawa.

NOTE: For a comprehensive and fascinating run-down of mission events, read Emily Lakdawalla’s article: “Six days left for Hayabusa: A recap of the mission.”

Image (top): Artist impression of Hayabusa floating above the asteroid (JAXA). Image (bottom): Photograph by Hayabusa of Itokawa (JAXA).