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Falcon Brought Home an Asteroid Sample

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MUSES-C probe over the asteroid in ISAS artist conception
Artist concept of the Falcon/Hayabusa probe over Asteroid Itokawa.
Click to ISAS enlarge
Falcon, the interplanetary probe from the Japanese Aerospace Exploration Agency (JAXA), brought home it's sample of dust from an asteroid three years later than planned. Falcon is Hayabusa in Japanese.

The Japanese spacecraft in June 2010 successfully returned the first-ever samples gathered from the surface of an asteroid. Some 1,500 tiny dust grains were collected directly from the Asteroid Itokawa in 2005 by Japan's Falcon/Hayabusa spacecraft, which returned to Earth and landed in Australia in June after a 1.25 billion-mile, seven-year voyage.

The spacecraft was to have departed by December 10, 2005, from Asteroid Itokawa for a return to Earth in June 2007. Unfortunately, a problem with a control thruster threw the vehicle into an unexpected spin as it loitered near the asteroid. Its operators in Japan were unable to control the spacecraft.

The probe was hovering a few miles above the surface of the asteroid 186 million miles across the Solar System from Earth.

Unsure of how long it will take to stop the erratic spinning, JAXA delayed the start of the return flight to early 2007. That brought Falcon home to Earth in June 2010.

The successful collection. Falcon successfully collected a sample of dust from Asteroid Itokawa on November 26, 2005, in the first landing by a Japanese spacecraft on any Solar System body away from Earth, and the first spacecraft from anywhere on Earth to land on and take off from an asteroid.

The sample will be carried back to Earth in a capsule inside Falcon. If it returns successfully, Falcon will be the first probe to make a round trip from Earth to an asteroid and back to Earth.

When the spacecraft arrives back in Earth orbit, the sample capsule will be ejected to re-enter the atmosphere. It will parachute to land in the desert near the southern Australia town of Woomera in July 2010.

The landing. Despite rough terrain on the asteroid, which made it difficult for Falcon to pinpoint a precise landing spot, the probe touched down on November 26 for a few seconds and fired a metal pellet into the surface at a speed of about 671 mph.

The pellet kicked up dust from the surface into a horn-shaped collector protruding beneath Falcon. Then the spacecraft backed away from the surface carrying the dust.

Asteroid Itokawa is 2,300 feet long, 1,000 ft. wide, and oval shaped somewhat like a football. Its gravitational pull is only one one-hundred-thousandth of Earth gravity. It orbits the Sun between the orbits of Earth and Mars.

Falcom close-up image of the asteroid
Falcon close-up image of asteroid Itokawa's surface with lumps of hard matter.
Falcom close-up image of the asteroid
Photo from the other end.
Falcon photo of the asteroid's rough surface
The asteroid's rough surface.
JAXA photo of the shadow of Falcon on the asteroid's surface
Falcon's shadow on the surface

Artist concepts on this page of the Falcon spacecraft and photos by Falcon of the asteroid Itokawa are courtesy of the Japanese Aerospace Exploration Agency (JAXA).

Sequence of events. The Falcon interplanetary probe was a project of Japan's Institute of Space and Astronautical Science (ISAS). Today, ISAS is part of the Japanese Aerospace Exploration Agency (JAXA).

The spacecraft was launched May 9, 2003, on an ISAS MV5 three-stage solid-fuel rocket from the Uchinoura Launch Center at Kagoshima on Kyushu Island. Japan's main spaceport is on Tanegashima Island off the nation's southern main island of Kyushu, part of the Kagoshima Space Center.

Before launch, Falcon had been known as MUSES-C, short for Mu Space Engineering Spacecraft - C. After it was launched, the MUSES-C spacecraft was renamed Hayabusa, which in Japanese means Falcon.

The spacecraft flew 186 million miles across the Solar System for two years to get to asteroid 1998-SF36, one of the nearest to Earth. JAXA renamed the asteroid Itokawa after Hideo Itokawa, an early leader of the Japanese space program.

On the way to Itokawa, Falcon swung by Earth for a gravity assist that propelled the probe toward Itokawa.

On July 31, 2005, Falcon lost the use of one of its three reaction wheels, which help the deep space probe maintain its attitude, or orientation in space, without expending fuel.

Arrival. Falcon arrived at asteroid Itokawa on September 12, 2005. By October 1, Falcon was on station about four miles from the asteroid.

Falcon lost the use of the second of its three reaction wheels on October 3, 2005. Falcon then had to begin using bursts from its two chemical engines – hydrazine thrusters – along with the sole remaining reaction wheel to maintain a stable attitude.

The spacecraft also may have lost the use of two attitude sensors, or inertial measurement units.

Dust sample attempts. JAXA planned two quick landings on the asteroid for Falcon to grab samples of fine dust. One was to have been on a middle area of the asteroid that JAXA had named MUSES-Sea and the other from a broad, flat surface area at the tip of the asteroid that JAXA called Woomera Desert.

During each sampling fly-in, a fabric cone-shaped funnel protruding from Falcon was to touch the asteroid. Falcon than would fire a metal pellet weighing less than one-fifth of an ounce (5 grams) into the surface at a speed of about 1,000 ft/sec. (300m/s). It then would attempt to capture in the cone any dust, soil and rock fragments kicked-up by the pellet impact.

Spacecraft designers expected to retrieve a total of about one gram of material — less than a teaspoon of the ejected soil. Only a tiny sample will be needed for research back on Earth after the 4.5 year round trip.

First try. November 4, the planned touch down on the asteroid, and drop-off of a four-inch-tall science robot named Minerva, was called off at the last minute when an irregular radio signal from the probe was received by Japanese controllers on Earth.

JAXA reported Falcon had closed to within about 2,000 feet of the huge space rock when the landing operation was called off. The probe had been unable to identify its target on the surface of the asteroid, apparently because the asteroid's surface is strewn with large jagged rocks. However, Falcon functioned properly after the landing abort.

Landing command-and-control communications at the asteroid were routed through NASA's Deep Space Network (DSN) of ground-station antennas.

ISAS artist concept of Falcon touching down on the asteroid surface
ISAS artist concept of Falcon touching down on the asteroid surface.
Second try. November 12, as Falcon approached the surface, it dropped a shiny laser target on the surface, then illuminate the target with a laser range finder measuring the distance to the asteroid.

Falcon also spit out the four-inch-tall, can-shaped robot Minerva, which carried a thermometer and three cameras to take measurements from the surface. Unfortunately, Minerva was lost on the way down to the surface.

A rotating weight inside Minerva would have made it hop across the surface of the asteroid taking temperature readings and shooting high resolution pictures from its three cameras.

Minerva would have hopped 30 feet above the surface. It would have been the first such set of science instruments placed on an asteroid.

Third try. November 19, Falcon maneuvered to within 130 feet of the surface of the asteroid, the probe dropped another laser target. Then Falcon continued down to 56 feet from the asteroid.

Suddenly, controllers back in Japan lost contact with the spacecraft. It was a baffling three hours before it was heard from again. For some reason, Falcon had switched itself into a so-called "safe hold mode."

During the radio blackout, Falcon operated itself under automatic control and stored data about its condition, which it later transmitted to Japan for analysis.

Analysis of the data showed Falcon had bounced twice on the rough, rocky surface of Itokawa, landed, stayed there for 39 minutes, then took off in response to a command from Earth. The data showed the probe had landed within 99 feet of the landing target.

Falcon did not fire a pellet so sampling of asteroid dust by the collector horn was not carried out, although it's not known whether the unplanned spacecraft bounces might have raised some surface material into the collector.

Fourth try. November 26, the probe seems to have found the target marker covered with 877,490 names and then successfully collected a sample of dust from asteroid Itokawa. The horn apparently collected the powdery debris ejected after it shot a tiny metal ball into the surface.

After the touch-and-go landing, the probe backed three miles away from the asteroid where it's thrusters seemed to be making it shake vertically. The mission controllers in Japan switched the probe to safety mode so it would not be damaged while engineers tried to figure out the problem.

Whether or not Falcon actually picked up any surface samples won't be known for sure until the return capsule lands in the Australian Outback in June 2010.

Names etched in foil. Prior to the flight, the Japan Planetary Society used the Internet to collected names from the public to be etched on the laser target marker, which was the size and shape of a grapefruit.

A total of 877,490 names were etched on aluminum foil wrapped around the target marker. Some 40 percent of the names were Japanese and 50 percent were American, according to the society.

Map of Japan
Japan is a group of islands in the Pacific Ocean off the Asian mainland.
Itokawa portraits. As Falcon loitered near the asteroid, it observed the rocky surface with visible-light and infrared-light cameras.

Later, the spacecraft would swoop down on the asteroid to gather samples before returning to Earth.

While hovering near the asteroid, Falcon has sent to Earth remarkable photos of a bumpy surface.

Most asteroids seem to be blanketed by a powdery material – regolith – pulverized by small meteorites crashing into the rocky body. However, the photos of Itokawa show a surface with only small amounts of regolith. Instead, there are knots of hard matter looking like lumps.

Falcon data shows the asteroid's density is less than expected, which leads scientists to suggest Itokawa may be composed of small rocks held together by gravity – a pile of rubble flying though space.

ISAS described asteroids as the "fossils of the Solar System." The soil samples from asteroid Itokawa were intended to help scientists understand how the Solar System was formed.

Ion drive. Falcon has an ion drive that uses electricity to accelerate positive ions to a high velocity.

Such ion propulsion systems are lightweight, since they require only a few grams of gas per day. While the thrust exerted by an ion engine is gentle, moving a spacecraft along slowly, the engine's fuel efficiency actually can reduce trip times and lower the cost of the launch vehicle.

Deep Space 1 was the first use of an ion engine on a NASA spacecraft. It flew by an asteroid and a comet in 1998-2001. Europe's SMART-1 Moon probe also used an ion engine from 2003-2005 for a journey to orbit the Moon.

Earlier retrievals. No probe has brought back extraterrestrial samples since the American and Russian Moon programs of the late 1960s and early 1970s brought back lunar soil and rocks. Japan's future plans. Japan, which in 1972 became the fourth country to launch a satellite of Earth, announced in 2005 it plans to send its astronauts into space and set up a base on the moon by 2025.

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