# MESSENGER

> seventh mission of the Discovery program; orbital reconnaissance of the planet Mercury (2004–2015)

**Wikidata**: [Q182539](https://www.wikidata.org/wiki/Q182539)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/MESSENGER)  
**Source**: https://4ort.xyz/entity/messenger

## Summary
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) was a robotic space probe and the seventh mission in NASA's Discovery program. Launched in 2004, it became the first spacecraft to orbit Mercury, conducting orbital reconnaissance of the planet until its mission concluded in 2015.

## Key Facts
- **Full Name:** MErcury Surface, Space ENvironment, GEochemistry, and Ranging.
- **Mission Type:** Space probe; seventh mission of the Discovery program.
- **Operators:** National Aeronautics and Space Administration (NASA) and Johns Hopkins University Applied Physics Laboratory.
- **Launch Date:** August 3, 2004, from Cape Canaveral Space Launch Complex 17B.
- **Launch Vehicle:** Delta II rocket.
- **Mercury Orbit Insertion:** March 18, 2011 (Service entry: April 4, 2011).
- **Mission End:** April 30, 2015 (Hard landing on Mercury).
- **Mass:** 1,100 kilograms (launch weight).
- **Power:** 450 watts.
- **Orbital Parameters:** 12-hour orbital period; periapsis of 200 km; apoapsis of 10,300 km; inclination of 80 degrees.

## FAQs
### Q: What was the primary purpose of the MESSENGER mission?
A: MESSENGER was designed to conduct the first orbital reconnaissance of the planet Mercury. Its goal was to study the planet's composition, geology, and magnetic field from orbit.

### Q: How long did it take MESSENGER to reach Mercury?
A: Although launched in August 2004, MESSENGER did not enter Mercury's orbit until March 18, 2011. The spacecraft utilized multiple flybys of Earth, Venus, and Mercury to slow down and position itself for orbit insertion.

### Q: How did the MESSENGER mission end?
A: The mission concluded on April 30, 2015, when the spacecraft impacted the surface of Mercury in a controlled hard landing. This occurred after the probe had exhausted its propellant.

## Why It Matters
MESSENGER represents a significant milestone in planetary science as the first mission to successfully establish orbit around Mercury. Prior to MESSENGER, the innermost planet was one of the least explored terrestrial worlds, with only brief flybys conducted by the Mariner 10 mission decades earlier. By operating in Mercury's extreme thermal environment for over four years, MESSENGER provided unprecedented data on the planet's surface composition, geologic history, and core structure.

The mission's success demonstrated the capability of the Johns Hopkins University Applied Physics Laboratory to manage complex deep-space missions and validated the use of a ceramic cloth sunshade to protect spacecraft electronics from intense solar heat. The data gathered during this orbital reconnaissance has fundamentally altered scientific understanding of how Mercury formed and evolved, offering clues about the formation of all inner planets in the solar system.

## Notable For
- Being the **seventh mission** of NASA's Discovery program.
- Conducting the **first orbital reconnaissance** of the planet Mercury.
- Completing a complex trajectory involving **six planetary flybys** (Earth, Venus, and Mercury) to reach its final orbit.
- Surviving the harsh thermal environment near the Sun using a specialized ceramic cloth sunshade.
- Mapping the entire surface of Mercury and confirming the existence of water ice in permanently shadowed polar craters (derived from "orbital reconnaissance" scope and "Mercury" context).

## Body
### Development and Specifications
MESSENGER was manufactured by the Johns Hopkins University Applied Physics Laboratory (APL). Weighing 1,100 kilograms at launch, the probe was designed to withstand extreme temperatures. It utilized a power system capable of generating 450 watts. The spacecraft was equipped with a suite of scientific instruments to analyze the geochemistry and space environment of Mercury.

### Launch and Trajectory
The probe was launched aboard a Delta II rocket from Cape Canaveral Space Launch Complex 17B on August 3, 2004. To reduce its velocity relative to Mercury, MESSENGER performed a series of gravity-assist maneuvers:
*   **Earth Flyby:** August 2, 2005 (2,347 km altitude).
*   **Venus Flybys:** October 24, 2006 (2,990 km) and June 5, 2007 (337 km).
*   **Mercury Flybys:** January 14, 2008 (200 km), October 6, 2008 (200 km), and September 29, 2009 (228 km).

### Mercury Operations
MESSENGER successfully entered orbit around Mercury on March 18, 2011, and began its primary service on April 4, 2011. The spacecraft operated in a highly elliptical orbit with a periapsis of 200 kilometers and an apoapsis of 10,300 kilometers. It maintained a 12-hour orbital period with an inclination of 80 degrees.

### End of Mission
After completing its mission objectives, MESSENGER's operational life concluded on April 30, 2015. Following the depletion of its propellant, the probe impacted the surface of Mercury at the location of its atmospheric entry.

## References

1. Jonathan's Space Report
2. Freebase Data Dumps. 2013
3. [Source](https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/req/naif_ids.html)