Tuesday, December 8, 2015

Second Time's a Charm: Japanese Akatsuki Spacecraft Enters Venus Orbit

Artist's rendering of the Akatsuki spacecraft entering Venus orbit. Image Credit: Go Miyazaki

Japan’s first Venus probe, Akatsuki, successfully entered the planet’s orbit on Monday, Dec. 7, the Japan Aerospace Exploration Agency (JAXA) said. It was the second attempt to insert the spacecraft into Venusian orbit as the first try ended in failure five years ago. At 8:51 a.m. JST (6:51 p.m. EDT on Dec. 6), the mission controllers performed the attitude control engine thrust to inject the probe into orbit.

“The Japan Aerospace Exploration Agency performed the attitude control engine thrust operation of the Venus Climate Orbiter Akatsuki for its Venus orbit insertion from 8:51 a.m. on Dec. 7,” JAXA said in a statement.

The thrust lasted for 20 minutes, as scheduled and the spacecraft is now in good health, according to the agency. The probe’s exact orbit is now being measured and calculated. It could take the mission controllers few days to determine it precisely.

“In fact now that the spacecraft is in orbit, the attitude of the spacecraft has to be continuously updated. The commands will be generated manually and uploaded until the orbit is known better,” reports Sanjay Limaye, Senior Scientist at the Space Science and Engineering Center of the University of Wisconsin-Madison. He witnessed the orbit injection operations at the Institute of Space and Astronautical Science (ISAS) in Sagamihara, Japan.

“Akatsuki is now moving with respect to Venus at only slightly more than 1 km/sec and is about 250,000 km away from Venus,” he added.

Akatsuki (meaning “dawn” in Japanese), also known as Venus Climate Orbiter (VCO) or Planet-C, was designed to study the atmosphere of Venus. It was launched on a H-IIA 202 rocket from the Tanegashima Space Center on May, 20, 2010. After the first unsuccessful attempt on Dec. 6, 2010 to insert it into Venusian orbit due to an engine malfunction, the spacecraft was sent on a five-year trip around the sun. The trajectory correction maneuvers in August 2015 put it back on track for a rendezvous with Venus.

“At last, we’ve achieved what should have been done five years ago,” Masato Nakamura of JAXA, the manager of the Akatsuki project, told a news conference after the successful orbit injection.

“I didn’t expect it to be so hard,” said Chikako Hirose of JAXA. Hirose is a specialist in orbital determination for space debris. He was assigned to a team charged with calculating and adjusting the trajectory for inserting the Akatsuki orbiter.

“It’s been a long time since the first attempt five years ago, but those years have passed quickly. It was a once-in-a-lifetime experience,” he added.

Akatsuki is a 4.8 by 3.4 by 4.7 feet (1.45 by 1.04 by 1.44 meters) box-shaped spacecraft with a mass of 1,141 lbs. (517.6 kg). It features two solar arrays, providing over 700 W of power. It is equipped with six scientific instruments: the Lightning and Airglow Camera (LAC), an ultraviolet imager (UVI), a longwave infrared camera (LIR), a 1 μm camera (IR1), a 2 μm camera (IR2), and the radio science (RS) experiment.

The spacecraft’s main goal is to unveil the mechanism of "super-rotation" of Venus atmosphere by continuous high-resolution mapping, similarly to meteorological satellites orbiting the Earth.

The probe will obtain meteorological information about Venus by globally mapping clouds and minor constituents successively with four cameras at ultraviolet and infrared wavelengths, detecting lightning with a high-speed imager, and observing the vertical structure of the atmosphere with radio science technique.

Additional targets of the mission are the exploration of the ground surface and the observation of zodiacal light.

Akatsuki is Japan's first planetary exploration mission since the Nozomi probe, launched in 1998, that failed to go into Martian orbit in 2003.

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