April 28, 2017

China lofts pulsar navigation demo satellite

A Long March 11 rocket blasts off from the Jiuquan space center at 2342 GMT (6:42 p.m. EST) Wednesday. Credit: CCTV
A Long March 11 rocket blasts off from the Jiuquan space center at 2342 GMT (6:42 p.m. EST) Wednesday. Credit: CCTV

China launched an innovative satellite Wednesday that will look for X-ray signals from pulsars, the fast-spinning super-dense remnants of collapsed stars, to determine its exact location in space.

The experimental pulsar navigation mission carries two sensors tuned to pick up incoming X-rays from objects scattered across the galaxy, and use the detections to plot the craft’s position without relying on GPS satellites or pre-loaded navigation fixes.

Chinese officials say the XPNAV 1 satellite weighed more than 440 pounds (200 kilograms) at launch, and was developed by the China Aerospace Science and Technology Corp., a contractor in the country’s state-run space industry.

“X-ray pulsar navigation techniques will help reduce the reliance of spacecraft on ground-based navigation methods and are expected to achieve autonomous spacecraft navigation in the future,” China’s official Xinhua news agency reported before the launch.

“In its mission, the satellite will test the detectors’ functions in responding to the background noise of the universe, outline pulsar contours, and create a database for pulsar navigation,” Xinhua said.

The trailblazing navigation platform and several small secondary payloads took off at 2342 GMT (6:42 p.m. EST) Wednesday from the Jiuquan space center in northwest China, according to Xinhua.

Liftoff occurred at 7:42 a.m. Thursday Beijing time.

XPNAV 1 and its co-passengers rode a four-stage Long March 11 rocket into an orbit with an average altitude of 310 miles (500 kilometers). The satellite circles Earth on a path over the planet’s poles, flying along a track inclined 97.4 degrees to the equator, according to tracking data released by the U.S. military.

“The successful launch is only the first step,” said Xue Lijun, chief designer of testing of the fifth academy at the China Aerospace Science and Technology Corp. “Now, we are running experiments to test X-ray signals that have been emitted from pulsars for two months.”

The navigation pathfinder probe was joined on the Long March 11 by several CubeSat-class spacecraft.

Wednesday’s launch was the second flight of China’s Long March 11 rocket, a solid-fueled booster designed as a quick-response launcher for rapid call-up.

Developed by the China Academy of Launch Vehicle Technology, or CALT, the Long March 11 is about 68 feet (21 meters) tall and nearly 7 feet (2 meters) in diameter. It is one of two light-class solid-fueled launchers recently added to China’s rocket fleet, alongside the Kuaizhou designed by the China Aerospace Science & Industry Corp., a different unit in China’s state-run defense and aerospace apparatus from CALT.

Both of the new rocket types blast off from a wheeled mobile transporter, and are sized to send small payloads into orbit.

One of the secondary payloads was Xiaoxiang 1, a 17-pound (8-kilogram) satellite from Changsha Gaoxinqu Tianyi Research Institute in China’s Hunan province. The People’s Daily, a government-owned newspaper, reported the small satellite will test new computer systems and high-precision optical image stabilization technology.

An amateur radio payload was also aboard the Long March 11 flight, but it was expected to remain attached to the rocket’s upper stage.

Additional CubeSats were also on the launch, according to China Great Wall Industry Corp., but official details on their identities and purpose were unavailable.

The XPNAV 1 spacecraft is one of a handful of space missions that have experimented with X-ray pulsar navigation.

A detector on the U.S. military’s ARGOS satellite launched in 1999 demonstrated a rudimentary form of navigation using stellar X-ray sources as they slipped behind Earth’s horizon from the spacecraft’s perspective in orbit.

A NASA X-ray astronomy payload named NICER — the Neutron star Interior Composition Explorer — set for delivery to the International Space Station next year on a science mission to study the leftovers of supernova explosions. One objective of the NICER instrument is to test navigation using pulsars.

The powerful stellar explosions leave behind black holes or neutron stars, depending on their mass. Neutron stars are typically about the size of a small city, but contain several times the mass of the sun.

Pulsars are a class of neutron stars that spin quickly like a top — often many times per second — and send off beams of energy. If that energy beam happens to point toward Earth, an X-ray detector in space can predictably see the light during each rotation.

Scientists have timed the pulses with extraordinary precision, and a satellite in space could register its location based on when the pulsar beam reaches its X-ray detector. For example, an X-ray pulse traveling at the speed of light from an object thousands of light-years away could reach a spacecraft on one side of the Earth a fraction of a second before the beam arrives at a sensor on the other side of the planet.

If mastered, X-ray pulsar navigation could have military and commercial applications for spacecraft if the U.S. Air Force’s GPS navigation network, or complementary systems in Russia, Europe and China, suddenly went down. The technique could also be applied to deep space missions out of range of GPS satellite navigation, which is only effective near Earth, scientists said.

Pulsar navigation is not an option on Earth because X-rays do not penetrate Earth’s atmosphere.

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