Pale Blue Crescent: Earth Photographed from Deep Space
By Tariq Malik
SPACE.com Managing Editor
posted: 28 May 2010
12:06 pm ET
Two Japanese spacecraft, one headed to Venus and another limping home from an asteroid, have beamed home snapshots of Earth that reveal our planet in different hues amid a sea of stars.
The latest photos of Earth come from Japan's brand new Venus Climate Orbiter Akatsuki and the Hayabusa asteroid probe.
Akatsuki launched May 20 alongside a novel solar sail vehicle and other smaller payloads to begin a six-month trek toward the second planet from the sun. Hayabusa is returning to Earth from the asteroid Itokawa, which it visited in late 2005 and is due to land in Australia in June.
The photos of Earth from space by Akatsuki reveal a stunning crescent as the planet appeared to the probe's ultraviolet and infrared cameras.
In ultraviolet, the Earth appears as a dazzling blue sliver, while the same crescent has a vibrant orange hue in infrared. Akatsuki (which means "Dawn" in Japanese) was flying about 155,342 miles (250,000 km) from Earth when it photographed the planet.
Akatsuki also used its long-wave infrared camera to take a snapshot of the entire Earth, though the planet may be unrecognizable to the uninitiated. Earth's trademark blue oceans and white clouds are rendered only in black and white.
Japan's Akatsuki mission is expected to observe Venus in unprecedented detail to study its ever-present clouds and hidden surface. The spacecraft is expected to reach Venus in December and spent two years studying the planet.
The IKAROS solar sail vehicle also launched with the Akatsuki probe and will make a pit stop at Venus before heading off to the far side of the sun. Both spacecraft are doing well, JAXA officials said.
Asteroid probe spies Earth
The other view of Earth is an ultra-long shot that came earlier this month from Japan's beleaguered asteroid probe Hayabusa, which means "Falcon" in Japanese.
Hayabusa photographed Earth and the moon, from a distance of nearly 8.4 million miles (13.5 million km) on May 12.
"The Earth was seen so brightly that the image contained [a] strong smear in it, but the image clearly separates the Moon from the Earth," officials with the Japan Aerospace Exploration Agency (JAXA) said in a statement.
Hayabusa used the CCD sensor on its star tracker device to take the portrait of Earth and the moon as they hovered between the constellations Sagittarius and Capricornus.
In the photo, the moon is clearly seen as a separate bright object to the left of Earth, which is so bright it overwhelmed Hayabusa's sensor. Many stars, which Hayabusa's star tracker also picked up, are visible and can be identified in the image.
Hayabusa launched in 2003 to visit the asteroid Itokawa and snatch samples of the space rock so they could be returned to Earth.
But the 950-pound (430-kg) spacecraft has suffered a series of setbacks.
Telemetry has shown it did not fire the projectile device intended to kick up material from Itokawa's surface after it landed. Mission scientists hope that some material managed to enter Hayabusa's sample container despite the glitch.
A fuel leak, power outage and communications drop out beset the probe during its seven-year voyage. Its ion engines have also suffered multiple failures, though JAXA engineers managed to revive some systems and send the probe on a long detour through space in order to return it to Earth.
Hayabusa is currently on track to land in the Australian outback sometime in June, about three years later than its original scheduled return.