Mars 4
Mars 4 — a Soviet Mars orbiter (launched 21 July 1973). Faulty transistors crippled its computer on the way, so its engine never fired to put it into orbit. It flew past Mars 1,844 km away on 10 February 1974, returning one swath of pictures and the first detection of the ionosphere on the night side of Mars.
Key facts
Mission & specifications
Mission
- Operator
- Lavochkin (USSR)
- Launched
- July 21, 1973
- Status
- Lost
Trajectory
- Distance from the Sun
- 1.58 AU
- Computed from the cached position
- Distance from Earth
- 1.5 AU
- Computed from cached positions
- Distance from Mars
- 7,359,295 km
- Computed from cached positions
Mission
Mars 4 was one of four Soviet spacecraft launched toward Mars in July and August 1973. That year the planets were poorly placed, so each rocket carried a smaller payload, and the usual orbiter-and-lander pairs were split: two orbiters, Mars 4 and 5, and two flyby craft carrying landers, Mars 6 and 7. Less than four months before launch, ground tests found that a type of transistor used in all four craft was faulty: to save money the factory had used aluminium contacts instead of gold-plated ones, and they degraded over time. The analysis gave the missions roughly even odds, and they were launched anyway. On Mars 4, two of the three channels of the onboard computer failed on the way, and its engine never fired to slow it into orbit. It flew past Mars at 1,844 km on 10 February 1974. Controllers switched on its camera two minutes before closest approach; it took 12 images from 1,900 to 2,100 km and two panoramas, and its radio signals passing through the thin air made the first detection of the ionosphere on the night side of Mars. It went on into orbit around the Sun, still returning data from interplanetary space.
- 1973Mars 4 launches toward Mars on a Proton rocketLaunch
The first of four Soviet craft sent to Mars that summer.
Its engine never fires; it takes 12 pictures and detects the night-side ionosphere.
Images
Images from open archives · credit shown per image