# Orbiting Astronomical Observatory

> series of four space observatories launched between 1966 and 1972

**Wikidata**: [Q1086325](https://www.wikidata.org/wiki/Q1086325)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Orbiting_Astronomical_Observatory)  
**Source**: https://4ort.xyz/entity/orbiting-astronomical-observatory

## Summary
The Orbiting Astronomical Observatory (OAO) was a series of four space telescopes launched by NASA between 1966 and 1972 to study the universe in ultraviolet and other wavelengths blocked by Earth's atmosphere. It marked one of the first major efforts to conduct astronomical observations from space, laying the groundwork for later missions like the Hubble Space Telescope. The program included both successful and failed missions, notably the OAO B, which was lost due to a rocket fairing failure.

## Key Facts
- **Launch Period**: 1966–1972 (four missions: OAO 1, OAO 2/Copernicus, OAO B, OAO 3).
- **Operator**: NASA.
- **Subclass Of**: Space telescope.
- **Notable Failure**: OAO B (1970) failed to deploy due to a rocket fairing malfunction.
- **Aliases**: OAO, Copernicus Observatory, ОАО (Russian), مرصد المدار الفلكي (Arabic).
- **Instrumentation**: Carried ultraviolet detectors and X-ray sensors.
- **Firsts**: Among the first space-based telescopes to conduct UV astronomy.
- **Legacy Missions**: OAO 2 (Copernicus) operated successfully from 1972 to 1981.

## FAQs
### Q: What was the purpose of the Orbiting Astronomical Observatory?
A: The OAO series was designed to observe the universe in ultraviolet and X-ray wavelengths, which are largely blocked by Earth's atmosphere, enabling groundbreaking studies of stars, galaxies, and cosmic phenomena.

### Q: Why did the OAO B mission fail?
A: OAO B failed in 1970 when its rocket fairing did not separate properly, preventing the telescope from deploying. The malfunction occurred during launch, resulting in the loss of the mission.

### Q: Which OAO mission was the most successful?
A: OAO 2, renamed the Copernicus Observatory, was the most successful. Launched in 1972, it operated for nine years, conducting thousands of observations and significantly advancing ultraviolet astronomy.

## Why It Matters
The Orbiting Astronomical Observatory program was a pioneering effort in space-based astronomy, demonstrating the viability of conducting observations beyond Earth's atmospheric interference. By capturing data in ultraviolet and X-ray spectra, the OAO missions provided unprecedented insights into stellar evolution, interstellar gas, and the structure of galaxies. Though not all launches were successful, the program's technological and scientific achievements paved the way for modern space telescopes like Hubble. The OAO series also highlighted the challenges of space instrumentation, informing future mission designs and risk mitigation strategies.

## Notable For
- **First Space-Based UV Telescopes**: Enabled systematic ultraviolet observations of celestial objects.
- **Longevity of OAO 2/Copernicus**: Operated for nine years, far exceeding initial expectations.
- **Technological Groundwork**: Tested instruments and systems later refined in missions like the Hubble Space Telescope.
- **International Collaboration**: Involved scientists from multiple countries, fostering global astronomical research.

## Body
### Program Overview
The OAO series consisted of four missions:  
- **OAO 1** (1966): Failed shortly after launch due to power system issues.  
- **OAO 2/Copernicus** (1972): Successfully operated until 1981, conducting over 45,000 observations.  
- **OAO B** (1970): Lost during launch due to a fairing deployment failure.  
- **OAO 3** (1972): Focused on X-ray astronomy but suffered instrument malfunctions.  

### Mission Details
- **OAO 1**: Launched on April 8, 1966, but failed after 77 days when its power supply failed.  
- **OAO B**: Launched on November 9, 1970, carrying a 45-cm UV telescope. The fairing failure prevented solar panel deployment, leading to mission termination.  
- **OAO 2/Copernicus**: Launched on August 21, 1972, with a 81-cm telescope. It studied over 10,000 stars and observed the Copernicus Crater on the Moon.  
- **OAO 3/Copernicus X-ray**: Launched on August 6, 1972, but its X-ray detectors degraded rapidly, limiting scientific output.  

### Instrumentation and Discoveries
- **UV Spectroscopy**: OAO 2 provided detailed spectra of hot stars and interstellar gas, measuring elements like deuterium in the interstellar medium.  
- **X-ray Observations**: OAO 3 detected X-ray emissions from binary systems and supernova remnants.  
- **Stellar Winds**: OAO 2 observed mass loss in massive stars, revolutionizing understanding of stellar evolution.  

### Legacy
The OAO program demonstrated the potential of space-based astronomy, despite its mixed success rate. Its lessons informed the development of the Einstein Observatory, International Ultraviolet Explorer, and Hubble Space Telescope. The Copernicus Observatory (OAO 2) alone generated over 1,000 scientific papers, cementing its role as a foundational mission in modern astrophysics.

## References

1. Freebase Data Dumps. 2013