Mission Atlas
← Mission directory

Mission record

Mars 4

Also known as M-73 No.52S, Mars4

U.S.S.R · Launched

Explore trajectory

Partial success · Partial success

The first of the associated group of four Soviet spacecraft, Mars 4, 5, 6 and 7, launched towards Mars in July and August of 1973. The Mars 4 automatic station was intended to be a Mars orbiter mission, very similar in design and intended mission to the Mars 5 orbiter launched 4 days later. Due to a flaw in a transistor which resulted in degradation of the computer chip during the voyage to Mars, the retro-rockets never fired to slow the craft into Mars orbit, and Mars 4 flew by the planet instead. It returned one swath of pictures and some radio occultation data which NSSDCA records as the first detection of the nightside ionosphere on Mars, and continued to return interplanetary data from solar orbit after the flyby.

Destinations
Launch vehicle
Proton Booster Plus Upper Stage and Escape Stages
Launch site
Tyuratam (Baikonur Cosmodrome), U.S.S.R
Countries
Soviet Union
Mission types
Orbiter, Flyby

Chronology

Mission timeline

  1. Launch

    Launched from an Earth orbital platform

    NSSDCA's launch/orbital information page gives the launch date and time as 1973-07-21T19:30:59Z and an Earth orbit with a periapsis of 147.00 km, an apoapsis of 179.00 km, a period of 87.50 minutes and an inclination of 51.500°. The orbiter had a fully fueled launch mass of 3440 kg. It was put into Earth orbit by a Proton SL-12/D-1-e booster and launched from its orbital platform roughly an hour and a half later on a Mars trajectory.

    Earth

  2. Milestone

    Mid-course correction burn

    A mid-course correction burn was made on 30 July 1973.

  3. Flyby

    Flew by the planet after the retro-rockets never fired

    It reached Mars on 10 February 1974. Due to the flaw in the transistor which resulted in degradation of the computer chip during the voyage to Mars, the retro-rockets never fired to slow the craft into Mars orbit, and Mars 4 flew by the planet at a range of 1844 km at 15:34 UT. Two disagreements between NSSDCA's own pages are recorded rather than resolved: the launch/orbital information page gives the same encounter a closest approach time of 1974-02-10 00:00:00, which is midnight rather than the 15:34 UT the master catalog prints, and a periapsis of 2200.00 km against that page's 1844 km. This record follows the master catalog and keeps day precision, because the two times cannot both be right. The later NASA chronology reports 15:34 UT and 1844 km, whereas the orbit summary and designer account give 2200 km. The retro system did not place the spacecraft into Mars orbit; no precise flyby vector is inferred.

    Mars

Mission architecture

Vehicles

  • Mars 4 · Orbiter

    Destinations: Mars

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?
  • A frame-qualified position and vector velocity at an epoch, or equivalent complete orbital elements.
  • Approach/departure directions and burn vectors between the reported encounters; body names and encounter distances alone are insufficient.
  • Finer event-time constraints where required by an orbital reconstruction; the stored day/month/year precision is retained.

Provenance

Sources

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

Data verified through September 14, 2026