Mission Atlas
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Mission record

Pioneer 4

NASA, Department of Defense · Launched

Explore trajectory

Completed · Partial success

The first United States spacecraft to escape Earth's gravity, passing the Moon and entering heliocentric orbit.

Destinations
Launch vehicle
Juno II (AM-14)
Launch site
Cape Canaveral Launch Complex 5
Countries
United States
Mission types
Flyby

Chronology

Mission timeline

  1. Launch

    Pioneer 4 launched

    NASA Science gives launch at 05:10:56 UT from Cape Canaveral Launch Complex 5 aboard Juno II vehicle AM-14.

    Earth

  2. Flyby

    Passed the Moon at a distant flyby

    NASA’s contemporary semiannual report gives closest approach as 5:24 p.m. on March 4, 41 h 13 min after liftoff. Converting 5:24 p.m. Eastern Standard Time to UTC gives approximately 22:24Z, consistent with the elapsed time and the 05:10:56Z launch. NASA Science currently prints 10:24 UT, which conflicts by 12 hours with both the report and its own “about 41 hours after launch” statement; the report-based epoch is retained with minute precision and the conflict remains explicit.

    Moon

  3. Loss of contact

    Radio contact lost

    NASA reports that transmissions ended on March 6 after about 82 hours, at roughly 655,000 km from Earth; no more precise contact-loss epoch is asserted here.

    Earth

Mission architecture

Vehicles

  • Pioneer 4 · Spacecraft

    Destinations: Moon

Trajectory record

Trajectory dataset not yet available

Known dates and encounters do not uniquely determine a flight path. This mission’s sourced timeline is available above; no verified trajectory is currently published here.

What is needed to reconstruct this path?
  • Post-injection Cartesian state in a named inertial frame and epoch, or the original flight-specific angle/Doppler/range records plus estimation covariance.
  • Reconciled final solar orbital elements, including orientation and solution epoch; the 1959 report labels flight estimates preliminary.
  • A definitive lunar B-plane/closest-approach state and uncertainty, with explicit range convention and lunar reference frame.
  • Scalar lunar geometry, injection speed and preliminary solar apsis estimates are not a unique continuous ephemeris; no frame-qualified state is present in the inspected report.

Provenance

Sources

Each source is listed once and labeled with the mission, event, trajectory, or destination/body context it supports.

Data verified through October 12, 2026