# Solar and Heliospheric Observatory

> space observatory

**Wikidata**: [Q320638](https://www.wikidata.org/wiki/Q320638)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Solar_and_Heliospheric_Observatory)  
**Source**: https://4ort.xyz/entity/solar-and-heliospheric-observatory

## Summary
The Solar and Heliospheric Observatory (SOHO) is a joint European Space Agency and NASA mission launched in 1995 to study the Sun from the L1 Earth-Sun Lagrangian point. This space observatory provides continuous monitoring of the Sun's interior, atmosphere, and solar wind, making it a critical tool for understanding solar activity and space weather.

## Key Facts
- Official name: Solar and Heliospheric Observatory (SOHO)
- Type: Space observatory, solar probe, and space telescope
- Launch date: December 2, 1995 at 08:08:01 UTC
- Launch vehicle: Atlas II (AC-121) from Cape Canaveral Launch Complex 36
- Operators: European Space Agency and National Aeronautics and Space Administration
- Mass: 1,850 kilograms (launch weight)
- Dimensions: 2.7m width (spacecraft bus), 9.5m width (spacecraft solar array), 3.65m height, 4.3m length
- Power sources: Solar array (1,500W) and nickel-cadmium battery (950W)
- Orbital location: L1 Earth-Sun Lagrangian point in a Lissajous orbit (since February 14, 1996)
- Scientific instruments: Extreme-ultraviolet Imaging Telescope and Large Angle and Spectrometric Coronagraph
- Official websites: http://sohowww.nascom.nasa.gov/, https://www.nasa.gov/soho, https://sci.esa.int/web/soho/

## FAQs
### Q: What is the Solar and Heliospheric Observatory?
A: The Solar and Heliospheric Observatory (SOHO) is a space observatory jointly operated by the European Space Agency and NASA that studies the Sun from the L1 Lagrangian point between the Earth and Sun. It provides continuous observations of the Sun's interior, corona, and solar wind, making it one of the most important tools for understanding solar physics and space weather.

### Q: When was SOHO launched and what was its mission?
A: SOHO was launched on December 2, 1995 aboard an Atlas II rocket from Cape Canaveral Launch Complex 36. Its primary mission is to study the Sun's structure, composition, and activity to better understand solar processes and predict space weather events that can affect Earth's technology and communications systems.

### Q: Where is SOHO located in space?
A: SOHO orbits at the L1 Lagrangian point between the Earth and Sun, approximately 1.5 million kilometers from Earth toward the Sun. This location allows the spacecraft to maintain a continuous, uninterrupted view of the Sun without Earth blocking the line of sight.

### Q: How long has SOHO been operational?
A: SOHO became operational on April 16, 1996, and has been continuously observing the Sun since then, far exceeding its initial two-year mission lifespan. As of now, it has been operational for over 25 years, making it one of the longest-running space observatories in history.

### Q: What makes SOHO unique among solar observation missions?
A: SOHO's unique position at the L1 Lagrangian point provides an uninterrupted view of the Sun 24/7, allowing for continuous monitoring of solar phenomena. It also carries multiple complementary instruments that study different aspects of the Sun simultaneously, from its core to its extended atmosphere, providing comprehensive data on solar activity and space weather.

## Why It Matters
The Solar and Heliospheric Observatory has fundamentally transformed our understanding of the Sun and its influence on Earth. By providing continuous, high-resolution observations of solar activity for over 25 years, SOHO has enabled scientists to study the Sun's internal structure, solar flares, coronal mass ejections, and the solar wind in unprecedented detail. This data has improved space weather forecasting, which is crucial for protecting satellites, power grids, and astronauts from harmful solar radiation and geomagnetic storms. SOHO's observations have also led to numerous discoveries about solar oscillations, the solar corona's heating mechanisms, and the connection between solar activity and Earth's magnetosphere. The mission's longevity and scientific productivity make it an invaluable asset for both solar physics research and practical space weather prediction.

## Notable For
- Being the longest-running solar observatory in history, operating continuously for over 25 years since becoming operational in 1996
- Providing the first comprehensive 3D view of the Sun's interior through helioseismology
- Discovering over 4,000 previously unknown comets during its operational lifetime, primarily through its Large Angle and Spectrometric Coronagraph
- Maintaining uninterrupted observations of the Sun from the L1 Lagrangian point, providing critical data for space weather forecasting
- Being a joint ESA-NASA mission that has successfully operated well beyond its original two-year design lifetime

## Body

### Mission Overview
The Solar and Heliospheric Observatory (SOHO) is a space observatory designed to study the Sun. It was launched on December 2, 1995, aboard an Atlas II rocket (AC-121) from Cape Canaveral Launch Complex 36. The observatory entered service on April 16, 1996, and has been operating continuously since then. SOHO is jointly operated by the European Space Agency and NASA, representing a significant collaboration between European and American space agencies.

### Physical Characteristics
SOHO has a mass of 1,850 kilograms at launch. The spacecraft bus has a width of 2.7 meters, while including its solar arrays, the spacecraft reaches a width of 9.5 meters. The observatory stands 3.65 meters tall and has a length of 4.3 meters. It is powered by both a spacecraft solar array generating 1,500 watts and two nickel-cadmium batteries providing 950 watts of power.

### Orbital Characteristics
SOHO is positioned at the L1 Earth-Sun Lagrangian point, approximately 1.5 million kilometers from Earth toward the Sun, in a Lissajous orbit. This position was established on February 14, 1996. The L1 location provides several advantages for solar observation: it allows for continuous observation of the Sun without Earth blocking the view, and it provides relatively stable orbital dynamics with minimal fuel requirements.

### Scientific Instruments
The observatory carries multiple scientific instruments for studying the Sun, including:
- Extreme-ultraviolet Imaging Telescope (EIT)
- Large Angle and Spectrometric Coronagraph (LASCO)

These instruments are designed to observe different aspects of the Sun, from its internal structure to its outer corona and solar wind. The combination of instruments allows for a comprehensive study of solar phenomena.

### Mission Duration and Accomplishments
Originally designed for a two-year mission, SOHO has been operational for over 25 years, far exceeding its planned lifetime. The observatory has made numerous scientific contributions, including discoveries about solar oscillations, coronal heating, and solar wind dynamics. During its operational lifetime, SOHO has discovered over 4,000 previously unknown comets, primarily through the LASCO instrument.

### Program Affiliations
SOHO is part of several scientific and space exploration programs:
- Horizon 2020 (EU framework program for research and innovation)
- International Solar-Terrestrial Physics Science Initiative

These affiliations reflect the mission's importance in understanding the relationship between the Sun and Earth's environment.

### Communication and Public Outreach
SOHO has official websites maintained by both NASA and ESA:
- http://sohowww.nascom.nasa.gov/ (NASA)
- https://www.nasa.gov/soho (NASA)
- https://sci.esa.int/web/soho/ (ESA)

These websites provide real-time solar images, data, and educational resources to the public and scientific community.

## References

1. [Source](https://solarsystem.nasa.gov/missions/soho/in-depth/)
2. [Source](https://directory.eoportal.org/web/eoportal/satellite-missions/s/soho)
3. [Source](https://www.agenciasinc.es/Entrevistas/Un-viaje-por-las-misiones-espaciales-de-la-ESA)
4. Jonathan's Space Report
5. Freebase Data Dumps. 2013
6. [Source](https://www.minorplanetcenter.net/iau/lists/ObsCodes.html)
7. [Source](https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/req/naif_ids.html)
8. National Library of Israel Names and Subjects Authority File