Planetary Light-Travel Time

Translate Solar System distances into communication latency. Enter the Earth–target separation, optionally layer on a round-trip multiplier or safety margin, and read the resulting light-travel time in minutes.

Instantaneous geometric distance between Earth and the target in millions of kilometres.
Set to 2 for round-trip light time or adjust for relay hops and detours.
Optional percentage margin to buffer for ephemeris uncertainty or targeting bias.

Examples

  • Earth–Mars at 78 million km with a 2% safety margin applied ⇒ 4.42 minutes
  • Round-trip light time to Jupiter at 628 million km ⇒ 69.83 minutes

FAQ

How can I find the current distance to a planet?

Consult real-time ephemerides from NASA JPL, Horizons, or published astronomical almanacs, then enter the reported Earth–target distance in millions of kilometres.

Why use a path multiplier?

Deep-space missions budget for signal turnarounds, relay hops, or scanning delays. Set the multiplier to 2 for round-trip light time or higher for additional segments.

Does gravitational lensing change the light speed used here?

No. The tool assumes straight-line propagation at c. Relativistic corrections are negligible for most Solar System mission planning windows.

Additional Information

  • Uses the vacuum speed of light (299,792.458 km/s) with no plasma, relay, or atmospheric delays.
  • Distance margin scales the base separation before applying the path multiplier, mirroring conservative mission budgets.
  • Path multiplier lets you model two-way communications or multi-hop relays without changing the input distance.
  • Deep-space navigation teams often apply an extra 5–10% margin to account for orbital prediction uncertainty.

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