China will launch world's first X-ray pulsar navigation satellite in November 2016
Oct. 9, 2016, Beijing, China --- China Academy of Space Technology today said it is planning to launch world's first X-ray pulsar navigation satellite (XPNAV-1) in November 2016.
X-ray pulsar navigation is an innovative navigation technique whereby the periodic X-ray signals emitted from pulsars are used to determine the location of a spacecraft in deep space. Once the technology comes true, the ground intervention for satellite orbit control could be minimized.
However, since X-ray from the pulsars would be absorbed by the atmosphere, scientists have to launch satellite to continue the research of the new technology.
According to Shuai Ping, the Chief Scientist of the XPNAV-1 satellite, the key object of his satellite is to detect the details of 26 nearby pulsar (in the range of thousands to tens of thousands light years to earth), and create "a pulsar navigation database ". Shuai says the target could be achieved in 5 to 10 years.
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Pulsar navigation: Chinese scientists to reconstruct temporal reference
Time: October 9, 2016 Source: Xinhua News Agency Hits: 12 Font: medium and small
The picture shows the pulsar "lighthouse" models. Photos provided by the Chinese Academy of Space Technology.
Xinhua News Agency, Beijing, October 9 (Reporters Quan Xiao and Shu Yufei) - In the mobile Internet era, people increasingly rely on satellite navigation and travel GPS navigation household name, Beidou navigation has become more perfect, but you heard pulsar navigation it. ?
Yes, that is light years away from we must pulsars! Although distant and unfamiliar, as long as the use of science to be, they can give artificial earth satellites and spacecraft to provide navigation, and even human interplanetary journey to open oh. Now, chinese scientists are trying to put this "fantasy" into reality.
October 8 coincides with the 60th anniversary of China's space industry. Reporters learned from the China Academy of Space Technology, China will be held in November to choose the launch of the first pulsar navigation satellite test (XPNAV-1), X-ray signal emitted by pulsars found, try to verify the feasibility of the pulsar navigation system.
According to the China Academy of Space Technology pulsar navigation satellite system science mission chief designer handsome flat researcher, the star's life like people, from conception through birth, to grow mature, aging and eventually death of the whole process. Generally speaking, remains after the death of a star can be divided into three categories: white dwarfs, neutron stars and black holes.
"Pulsar is a rapidly rotating neutron stars with extremely stable periodicity, its stability is even higher than the most stable atomic hydrogen than 10,000 times, known as nature's most stable astronomical clock, making human universe navigation beacon." Shuai Ping said.
The picture shows the pulsar magnetic signal radiation. Photos provided by the Chinese Academy of Space Technology.
Nature's most precise astronomical clock
A typical pulsar radius of only 10 km, and its quality is between 1.44 times and 3.2 times the mass of the Sun, is in addition to the black hole outside the densest objects. Pulsar mass per cubic centimeter to reach 100 million tons, use the 1000-megaton wheel to drag.
Between the pulsar's axis of rotation and a magnetic pole axis angle, two magnetic poles each have a radiation beam. When the star's rotation and magnetic beam sweeps the floor or mounted on a spacecraft detection equipment, detection equipment will be able to receive a pulse signal . Pulsar has a good cycle stability, the stability of the negative 19 power of 10 is reached.
"Negative 19 power of 10 What is the concept? It is the difference between the two pulse signals cycle between points, only 19 behind the decimal point will appear change." Shuai Ping explained that the current international atomic time reference is when system, stability of the best atomic hydrogen can only reach the level of negative 15 power of 10, lower than the degree of stability of the pulsar clock four orders of magnitude.
"It's like the original time scale ruler encryption to 1/10000, finer scale, and we have energy more precisely, to see more detail." Shuai Ping said.
However, precise navigation and timing accuracy is not what does it matter?
In fact, whether it is to navigate the text first appeared, or the Age of Discovery celestial navigation, radio navigation or modern, will take time.
For example, the longitude of the measurement positions have to depend on the time measurement. As we all know, the Earth rotates once every 24 hours, which is 360 per hour, the equivalent of 15 degrees longitude. So long as we know the time difference between the two, we can know the longitude difference between the two. If a place is exactly 12:00 noon London 10:00, then it shows here in London, where 30 degrees east. Therefore, the core navigation is to solve the problem of time measurement.
Shuai Ping, said in a radio navigation, time measurement is the basic concept of measurement based on the signal propagation time to calculate the distance between the two. Satellite navigation system is a radio navigation system for space-based, one-way to reach time to measure the distance. Pulsar navigation and satellite navigation and positioning principle is very similar to its observation distance is to use the same X-ray pulsar emission pulse signal to determine the difference between the centroid of the solar system and the time to reach the spacecraft . Currently, satellite navigation and positioning accuracy of 10 meters, the final pulsar navigation accuracy can reach 10 m level.
The picture shows the use of pulsar spacecraft navigation. Photos provided by the Chinese Academy of Space Technology.
X-ray pulsar unique advantages
Pulsar at radio, infrared, visible light, ultraviolet, X-rays or gamma (γ) rays, electromagnetic spectrum transmission signal. Why choose X-ray pulsar to explore the formation of the navigation system?
In fact, as early as 1974, the US National Aeronautics and Space Administration (NASA) Jet Propulsion Laboratory scientists first proposed determination is based on pulsar radio signals of the spacecraft orbital method. However, this method of obvious defects, the biggest problem is that the pulsar at radio frequency signal is extremely weak, at least 25 m diameter antenna can detect it. "Such a large-diameter antennas weigh a few tons, placed on satellites, have been crushed." Shuai Ping said.
For the infrared, visible and ultraviolet pulsars, because the number of rare, low luminosity, require larger diameter telescope and high pointing accuracy and signal processing techniques, should not be used in spacecraft autonomous navigation.
"X-ray part of high-energy photons, concentrated most of pulsar radiation energy, easy to miniaturization of the device to detect and signal processing, making it possible to apply to the spacecraft." Shuai Ping said, "is the use of navigation pulsar pulsar emission X-ray signal as a natural beacon to guide the spacecraft in space freedom of navigation. "
However, X-rays is difficult to penetrate the Earth's dense atmosphere, so only in the Earth's atmosphere into outer space can be observed. So, pulsar navigation system can not navigate directly on the ground, but the near-Earth orbit satellites, deep space exploration and interplanetary spacecraft navigation.
Shuai Ping pointed out that to achieve long-precision navigation satellite constellation autonomous navigation, will be an important pulsar navigation applications. Currently, navigation constellation ground control system itself needs to continue to inject information to support, not off the ground information long run independently.
"If the navigation constellations can achieve autonomous navigation, it will effectively reduce the workload of the ground control system, reducing the number and layout of the station to the satellite ground station monitoring and control of information injection times, reduce the construction and long-term operation and maintenance costs of a satellite navigation system. "Shuai Ping said," reducing reliance on navigation constellation ground control system, but also to enhance the viability of autonomous systems, has very important engineering value and strategic significance. "
He noted that the X-ray pulsar signals as a natural beacon navigation satellite navigation message can independently generate and control instructions to maintain the constellation basic configuration, there is no constellation rotation error accumulation problem, in order to achieve autonomous navigation constellation long run.
Meanwhile, the autonomous navigation satellite navigation but also to achieve high-precision low-orbit spacecraft autonomous navigation of the basis and premise, can reduce low-orbit spacecraft management and maintenance costs, Shuai Ping said.
At present, it has been found and cataloged pulsars reach more than 2000, of which about 160 pulsars have good X-ray radiation signal cycle stability characteristics, can be used as navigation candidate stars.
Future time may be time pulsar
Although the prospects exciting, pulsar navigation in the end okay? Nobody knows.
"X-ray pulsar navigation technical problems despite the 1970s, the concept of navigation on the pulsar, but based on modern satellite navigation system, the arrival time of the ranging thought proposed, it is only a matter of the past 10 years. At present , X ray pulsar navigation technology research in key technology research and ground validation phase, the upcoming space flight test, found to verify its feasibility. "Shuai Ping said.
This time, China no longer follow the footsteps of the US and Europe, but to become "the first person to eat crabs." "The world's first pulsar navigation experimental satellite in November will choose the launch of the probe will be equipped with two types of loads: a collimated type microchannel plate detector to detect an area of 2400 cm2; the other is the focus type probe, a focusing lens diameter of 17 cm "Shuai Ping said..
According to him, there are three satellite test objectives:
First, God found two kinds of different types of detector performance, while taking advantage of background noise detector research universe. Background noise is like the sand, and the pulsar signal they're looking for gold. Amoy gold from sand to understand the background noise is a basic work.
Second, the detection of the Crab Nebula pulsar (Crab), developed to solve China probe "visible" pulsar problem. As early as 1054, the Song of the first astronomers to observe and record the Crab Nebula pulsar supernova explosions, explore ancestors discovered pulsar , China will become the X-ray pulsar detection historic leap. Plans are also probing additional seven pulsars, including four pulsar binary system and three low-flow pulsars and carry out related expand test.
Third, low-flow detection of three pulsars. Crab Nebula pulsar traffic per second per square centimeter 1.54 photons, but low-flow per square centimeter per second pulsar only 0.001 photon detection more difficult, but more promising for navigation. This is because there are a lot of low flow pulsar, but not like the Crab Nebula pulsar that because the transition period leading to decreased stability. If you can detect three low flow pulsars, it can be found pulsar navigation technology feasibility validation.
"Next, we intend by 5-10 years of efforts, the probe 26 pulsars put their measured data very accurate, establish pulsar navigation database." Shuai Ping said that 26 pulsars were distributed throughout the celestial sphere, are very distant from Earth, ranging from a few thousand to tens of thousands of light years.
Because the work is almost no precedent to follow, Shuai Ping led the research team took 10-year research study, breaking detectors, database, time synchronization, and key technologies such as large-scale navigation.
Although not yet know what will happen, handsome flat in the future is full of confidence. "In time pulsar as a reference system, if built, it would be subversive. Maybe in the near future, we do not need a long spacecraft can take care of people, our time table will be pulsars time. "
