# Viking 1 Orbiter

> NASA spacecraft which orbited Mars

**Wikidata**: [Q4011610](https://www.wikidata.org/wiki/Q4011610)  
**Source**: https://4ort.xyz/entity/viking-1-orbiter

## Summary
The Viking 1 Orbiter was a NASA spacecraft manufactured by the Jet Propulsion Laboratory that orbited Mars as part of the wider Viking 1 mission. Launched on August 20, 1975, aboard a Titan IIIE/Centaur rocket, it entered orbit around Mars on June 19, 1976, and operated until its decommissioning on August 7, 1980. Weighing 2,339 kilograms at launch, its primary role was to orbit the Red Planet and support the mission's scientific objectives.

## Key Facts
- **Classification:** Orbiter (spacecraft designed to orbit a celestial body).
- **Operator:** National Aeronautics and Space Administration (NASA).
- **Manufacturer:** Jet Propulsion Laboratory.
- **Launch Date:** August 20, 1975, at 21:22:00 UTC.
- **Launch Site:** Cape Canaveral Space Launch Complex 41.
- **Launch Vehicle:** Titan IIIE (model 23E-4) with a Centaur (TC-4) upper stage.
- **Mass (Launch):** 2,339 kilograms.
- **Mass (Dry):** 883 kilograms.
- **Mars Orbit Insertion:** June 19, 1976.
- **Decommissioning Date:** August 7, 1980.
- **Identifiers:** COSPAR ID 1975-075A; NSSDCA ID 1975-075A; NAIF ID -27.

## FAQs
### Q: When did the Viking 1 Orbiter launch and cease operations?
A: The Viking 1 Orbiter launched on August 20, 1975, and was decommissioned nearly five years later on August 7, 1980.

### Q: What rocket was used to launch the Viking 1 Orbiter?
A: It was launched using a Titan IIIE rocket equipped with a Centaur upper stage (specifically Titan IIIE 23E-4 and Centaur TC-4).

### Q: How much did the spacecraft weigh?
A: The orbiter had a launch weight of 2,339 kilograms and a dry weight of 883 kilograms.

## Why It Matters
The Viking 1 Orbiter represents a critical chapter in the exploration of Mars. As part of the Viking 1 mission, which included both an orbiter and a lander, it provided the first detailed, high-resolution global views of the planet and served as a vital communications relay for surface operations. Its four-year operational lifespan allowed for extensive observation of Martian atmospheric and surface conditions, setting a precedent for long-duration Mars missions. The data gathered regarding orbital dynamics, mass specifications, and power systems (620 watts nominal output) contributed significantly to the engineering knowledge base used in subsequent Mars orbiters.

## Notable For
- Being a primary component of the **Viking 1** mission, the first U.S. mission to land a spacecraft safely on the surface of Mars.
- Utilizing the **Titan IIIE** launch vehicle configuration in conjunction with the **Centaur** upper stage to achieve trans-Mars injection.
- Undergoing significant **orbital maneuvers** throughout its mission, altering its apoapsis, periapsis, and orbital period to optimize scientific data collection and lander support.
- Operating with a nominal power output of **620 watts**.

## Body

### Mission Profile and Timeline
The Viking 1 Orbiter was launched from the United States at Cape Canaveral Space Launch Complex 41. Following its launch on August 20, 1975, the spacecraft traveled to Mars, successfully entering orbit on June 19, 1976. The orbiter conducted operations for over four years before the mission was terminated on August 7, 1980.

### Technical Specifications
The spacecraft was constructed by the Jet Propulsion Laboratory. At launch, it had a total mass of 2,339 kilograms, which included propellant; the dry mass of the craft was 883 kilograms. The orbiter was designed to operate on a nominal power output of 620 watts.

### Orbital Dynamics
The Viking 1 Orbiter's orbit around Mars changed significantly over its operational life to meet different mission objectives.
*   **Initial Orbit (June 21, 1976):** The spacecraft initially established an orbit with a periapsis (closest approach) of 1,510 kilometers and an apoapsis (furthest distance) of 32,600 kilometers. The orbital period was approximately 24.66 hours.
*   **Operational Changes:** Throughout 1976 and 1977, the orbiter adjusted its periapsis, descending to as low as 296 kilometers by March 1977 to observe the moon Phobos, before stabilizing around 300–350 kilometers.
*   **Final Orbit (Aug 7, 1980):** By the time of its decommissioning, the orbiter had moved to a high-elliptical orbit with an apoapsis of 56,000 kilometers and a periapsis of 320 kilometers. This final orbit had a period of 47.26 hours and an eccentricity of 0.88221.

## References

1. Jonathan's Space Report
2. [Source](https://www.nasa.gov/wp-content/uploads/2018/09/beyond-earth-tagged.pdf)
3. [Source](https://science.nasa.gov/mission/viking-1/)
4. [Source](https://nssdc.gsfc.nasa.gov/nmc/spacecraft/displayTrajectory.action?id=1975-075A)
5. [Source](https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1975-075A)
6. [Source](http://www.tsgc.utexas.edu/spacecraft/viking/profile_vik1orb.html)