# Ranger 7

> space probe

**Wikidata**: [Q862558](https://www.wikidata.org/wiki/Q862558)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Ranger_7)  
**Source**: https://4ort.xyz/entity/ranger-7

## Summary
Ranger 7 was an American space probe launched on 28 July 1964 that became the first U.S. mission to successfully transmit close-up images of the Moon’s surface before intentionally crash-landing in Mare Cognitum. Part of NASA’s Ranger program, it returned 4,316 photographs during its final 17 minutes of flight, paving the way for Apollo crewed landings.

## Key Facts
- Launch date: 28 July 1964 at Cape Canaveral Launch Complex 12 on an Atlas-Agena B rocket
- COSPAR/NSSDCA ID: 1964-041A
- Manufacturer: Jet Propulsion Laboratory
- Mission sequence: follows Ranger 6, followed by Ranger 8
- Total lunar images returned: 4,316
- Impact site: Mare Cognitum (Latin for “Known Sea”)
- Part of: NASA Ranger program
- Spacecraft class: unmanned lunar impactor / space probe
- Wikidata sitelinks: 32 language editions

## FAQs
### Q: What did Ranger 7 accomplish?
A: Ranger 7 transmitted the first high-resolution photographs of the lunar surface, showing craters as small as 1.5 m across. The 4,316 images proved the Moon was solid enough for crewed landers and helped select Apollo landing sites.

### Q: When and where did Ranger 7 hit the Moon?
A: It impacted the Moon on 31 July 1964 at 13:25:49 UTC in Mare Cognitum, a region that became “known” because of this mission.

### Q: How was Ranger 7 different from Ranger 6?
A: Ranger 6 carried identical cameras but all failed; Ranger 7’s cameras worked perfectly, making it the first fully successful Ranger mission.

### Q: Why did Ranger 7 crash instead of orbiting?
A: The Ranger series used a cost-effective “impact” strategy—cameras transmitted real-time video until the spacecraft hit the surface at ~2.6 km/s.

## Why It Matters
Ranger 7 ended a string of U.S. lunar failures and gave scientists their first close look at an alien world. The images dispelled fears that Apollo landers might sink into deep dust and revealed a rugged but navigable surface. By proving JPL could build reliable deep-space cameras and mid-course navigation systems, Ranger 7 directly enabled the Surveyor soft-landers and the Apollo crewed missions that followed. Politically, the success restored American confidence during the Cold-War space race after multiple Soviet firsts. Technically, the mission validated real-time television transmission across 380,000 km of space, a capability still used by planetary spacecraft today.

## Notable For
- First fully successful American lunar probe after six consecutive failures
- Returned more lunar images in 17 minutes than all previous missions combined
- Cameras worked within 17 minutes of impact, the shortest operational window of any planetary mission to date
- Impact region renamed Mare Cognitum (“Known Sea”) because Ranger 7 made it known
- Demonstrated live TV transmission from deep space, a first for 1964 technology

## Body
### Mission Overview
NASA’s Ranger program (1961-1965) sought to obtain close-up images of the Moon before Apollo landings. Ranger 7, the seventh spacecraft in the series, lifted off on 28 July 1964 at 12:50 UTC aboard an Atlas-Agena B booster from Cape Canaveral Launch Complex 12. After a 68-hour cruise, the 306-kg probe oriented its cameras and began transmitting at 13:08 UTC on 31 July. Impact occurred 17 minutes later at 10.63° S, 20.68° W.

### Payload & Cameras
JPL equipped Ranger 7 with six vidicon television cameras—two wide-angle (25-mm f/1.0) and four narrow-angle (76-mm f/2.0) —mounted in a sealed temperature-controlled compartment. The system could send 1,132 scan lines per frame at 200 kHz, relaying data through Goldstone’s 64-m dish antenna.

### Data Return
During descent the cameras took one image every 2.5 seconds. Resolution improved from 1.4 km at high altitude to 1.5 m just before impact. The final complete frame was transmitted 0.2 s before the spacecraft struck the surface at ~2.6 km/s.

### Legacy
Ranger 7’s success led to two more Ranger missions (8 and 9) that refined landing-site imagery. The engineering model’s camera system became the ancestor of Mariner, Surveyor, and Apollo television systems.

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## References

1. Jonathan's Space Report
2. Freebase Data Dumps. 2013