Why in the News?

A recent study has showcased that spacecrafts can locate themselves using a simple stellar parallax method with just two nearby stars, without relying on Earth.

What is Stellar Parallax?

• Overview: Stellar parallax is the apparent shift in a star’s position against background stars when observed from two different vantage points.
• Example: On Earth, this is measured every 6 months as the planet moves to opposite sides of its orbit.
• Parallax Angle: The degree of this shift gives the star’s distance. Larger parallax means the star is closer.
• Application in Space: By observing stars from both Earth and a spacecraft (billions of km apart), the relative positions can be compared to calculate the spacecraft’s distance.

About the New Horizons Demonstration:

• Spacecraft: Launched in 2006, New Horizons explored Pluto (2015) and is now beyond 60 AU (astronomical units).
• Observation: On April 23, 2020, astronomers measured parallaxes of Proxima Centauri (4.2 light years) and Wolf 359 (7.9 light years) using Earth-based telescopes and New Horizons’ onboard instruments.
• Results:
  • Proxima’s parallax: 32.4 arcseconds
  • Wolf 359’s parallax: 15.7 arcseconds
  • Derived spacecraft position: 46.89 AU, matching DSN’s 47.11 AU reading.
• Requirements: Only a camera, onboard computer, and stellar catalogue — no special equipment needed.

Significance:

• Self-sufficient Navigation: Enables spacecraft to calculate their position without depending solely on Earth-based radio signals.
• For Future Missions: Particularly useful for interstellar missions, where Earth’s beacons won’t be practical.
• Simplicity: Unlike more complex astrometric navigation or pulsar navigation, this method is accessible with minimal hardware.
• Educational Value: Though not precise enough yet for real-time navigation, it is a proof of concept for deep-space autonomy.

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