Galactic Positioning System

The GPS works so well for cars, ships and even planes, but have you ever wondered how the Sci-Fi space ships find their way in galaxy?? Yeah GPS, help them too, not the Global Positioning System but the Galactic Positioning System which is now under development. NASA’s new autonomous X-ray navigation system could provide deep-space missions with a cosmic version of GPS.  Instead of satellite signals, they use X rays from pulsars.  Pulsars are a type of dead star having enormous magnetic fields, whose rotation produces X-ray signals with an highly exact rhythm. Pulsars are called “cosmic lighthouses” because their rapid pulse of radio emission is so predictable, that it can be used as a simple straightforward method of Navigation. The system works by combining pulsar pulse data from a reference location such as Earth allowing spaceships to determine their location in space to an accuracy of 3 miles.

Pulsars As Galactic Positioning Systems.
NASA Setup a Galactic Positioning System for Astronauts to locate like GPS on Earth

NASA’ s multi-purpose mission, also known as NICER/SEXTANT (Neutron-star Interior Composition Explorer / Station Explorer for X-ray Timing and Navigation Technology), consists of 56 X-ray telescopes in a compact bundle, their associated silicon detectors, and a number of other advanced technologies. NICER is an International Space Station payload that will provide high-precision measurements of neutron stars. The SEXTANT have two projects namely: X-ray navigation (XNAV) and X-ray Communications (XCOM) which will focus on the development of the X-ray based technologies capable of providing accurate autonomous navigation and high bandwidth communications, respectively, beyond the inner solar system. The both experiments are installed on the exterior of the International Space Station. They monitor the clockwork-like pulses from a naturally occurring source- distant pulsars, rapidly rotating neutron stars that emit regular beams of light. Both NASA’s Science Mission Directorate’s Explorers Program and the Space Technology Mission Directorate’s Game Changing Program are contributing to the mission’s development.

The first successful demonstration of a system to use pulsars for navigation in space happened 11 November 2017, the research teams showed that millisecond pulsars, ones that rotate hundreds of times a second, could be used to accurately determine the location of an object moving at thousands of miles per hour through space.  Pulsars are two types : normal pulsars, and millisecond pulsars (MSPs). “Normal” pulsars have a pulse period P ~ 0.5 s, while MSPs have a period P between 1.4 ms and 30 ms.  

 X-ray telescope of  NICER would point at a minimum of 4 millisecond pulsars, timing their X-ray “ticks” like that of the ticks of satellites. 3 of those pulsars would inform the spacecraft its position in space, while the 4th would adjust its biological rhythm to make sure it was determining the others effectively. With these predictable pulsations, pulsars can provide high-precision timing information similar to the atomic-clock signals supplied through the GPS system.

Till now, deep-space navigation mostly depends on using radio signals sent from Earth to the distant space probe i.e.signals must be sent with giant antennas. The probe responds by sending a signal back. So it’s not hard to figure out range overall distance with good precision from how long a signal traveling at the speed of light takes to get to the probe and back. But angles are tougher to nail down. As a result, such position fixes degrade as you move away from Earth.. As light can only travel at a finite speed, it takes time to send a signal to Earth and back again to determine the spacecraft’s position and also farther from Earth, the larger the errors in the measured location will be.

The biggest advantage of using X rays for communication is the ability to transcend obstacles that usually hinder radio communication. Whenever a spacecraft is entering the atmosphere, it generates an intensely hot plasma cover that blocks radio waves leading to ‘radio blackout’ during re-entry. But, high-energy X-rays can pass through this hot plasma, thereby keeping transmission intact during every phase of shuttle deployment, including atmosphere re-entry.

  • Since the navigation system is based on pulsars and not based upon signals from Earth, robotic probes could continue navigational tracking even when objects such as planets or moons are directly in between the spacecraft and Earth.
  • This  technology would eliminate the need to do imprecise fly-bys that probes currently have to do by planets to get close to them
  • Because X-rays have shorter wavelengths i.e. they can transmit more data with less power. Hence, XCOM will also use less energy in communicating over vast distances.
  • Passive Navigation: No transmission between the user and satellite/pulsar segment is needed
  • its navigational accuracy does not decline with time, as constant
    correction is available from different X-ray sources;
  • This could allow scientists to be able to navigate space if they lose communication from Earth. The navigation systems on the ships or orbiters would be autonomous and not controlled from Earth.
  • This would also eliminate the need of expensive transmitting stations.

Even though not an entirely new idea, it’s NASA’s brave new step towards discovering an unexplored world and we might soon see such a futuristic device in action in the very near future. This could revolutionize the way that astronauts travel in space  and will enable autonomous navigation throughout the solar system and beyond.

PS: Since the term “GPS” is already taken, I would suggest PPS(Pulsar Positioning System) or Sky Finder or Milky Way Finder…:)

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