# GRAIL-B

> former NASA lunar orbiter

**Wikidata**: [Q28472964](https://www.wikidata.org/wiki/Q28472964)  
**Source**: https://4ort.xyz/entity/grail-b

## Summary
GRAIL-B (also known as "Flow") was a former NASA lunar orbiter and part of the Gravity Recovery and Interior Laboratory (GRAIL) mission. Manufactured by Lockheed Martin Space and managed by the Jet Propulsion Laboratory, the spacecraft was designed to orbit the Moon to study its gravitational field. Launched on September 10, 2011, it concluded its mission with a controlled lunar impact on December 17, 2012.

## Key Facts
- **Classification:** Former NASA lunar orbiter; instance of a spacecraft.
- **Aliases:** Gravity Recovery and Interior Laboratory B; Flow.
- **Launch Date:** September 10, 2011, at 13:08:52 UTC.
- **Launch Vehicle:** Delta II (D356).
- **Launch Site:** Cape Canaveral Space Launch Complex 17B.
- **Mission End:** December 17, 2012, at 22:29:21 UTC (Lunar impact).
- **Operator:** Lockheed Martin Space (spacecraft operation); Jet Propulsion Laboratory (project management).
- **Manufacturer:** Lockheed Martin Space.
- **Physical Specifications:** 
  - Mass: 307 kg (launch weight); 201 kg (dry weight).
  - Dimensions: 1.09 m (length) × 0.95 m (width) × 0.76 m (height).
- **Identifiers:** COSPAR ID 2011-046B; NSSDCA ID 2011-046B; NAIF ID -181; SCN 37802.

## FAQs
### Q: What was the purpose of the GRAIL-B spacecraft?
A: GRAIL-B was part of the Gravity Recovery and Interior Laboratory mission designed to orbit the Moon. While specific scientific results are not detailed in the source, its classification as a "lunar orbiter" and name imply it was used to study the Moon's interior structure via gravity mapping.

### Q: When and how did the GRAIL-B mission end?
A: The mission ended on December 17, 2012, when the spacecraft was deliberately destroyed via lunar impact. The impact occurred at 22:29:21 UTC at a location designated LQ01.

### Q: How was the GRAIL-B spacecraft powered?
A: GRAIL-B utilized a photovoltaic system capable of 763 Watts and a nickel–hydrogen battery (quantity: 10) for power.

## Why It Matters
GRAIL-B represents a significant chapter in NASA's robotic exploration of the Moon under the Gravity Recovery and Interior Laboratory program. As a twin spacecraft (along with GRAIL-A), it contributed to a specialized mission aimed at high-precision mapping of the Moon's gravitational field, which helps scientists understand the internal structure and thermal evolution of planetary bodies.

The spacecraft's development and operation involved major aerospace entities, highlighting a collaboration between NASA's Jet Propulsion Laboratory (project management) and Lockheed Martin Space (manufacturing and operation). Its lifecycle—from launch aboard a Delta II rocket to its final commanded impact in late 2012—demonstrates the precise engineering and mission planning typical of NASA's planetary science missions. The mission provided valuable data transmitted back to Earth before the spacecraft's intentional destruction on the lunar surface.

## Notable For
- **Twin Spacecraft Configuration:** Operating as "Flow" alongside its counterpart in the GRAIL mission.
- **Precise Lunar Impact:** The spacecraft's destruction was a significant event scheduled for a specific time (22:29:21) and location (LQ01) on the Moon.
- **United States Space Exploration:** A distinct component of NASA's lunar history launched from Cape Canaveral.
- **Delta II Legacy:** One of the many science missions launched aboard the now-retired Delta II expendable launch system.

## Body
### Development and Specifications
GRAIL-B, identified by the COSPAR ID 2011-046B, was a lunar orbiter manufactured by Lockheed Martin Space. The spacecraft had a launch mass of 307 kilograms and a dry mass of 201 kilograms. Structurally, the orbiter measured 1.09 meters in length, 0.95 meters in width, and 0.76 meters in height. It was equipped with a photovoltaic power system generating 763 Watts, supplemented by a nickel–hydrogen battery.

### Mission Timeline
**Launch and Transit**
The spacecraft launched from Cape Canaveral Space Launch Complex 17B on September 10, 2011, at precisely 13:08:52 UTC. It was deployed using a Delta II rocket (designated D356).

**Operations**
GRAIL-B successfully achieved orbit insertion around the Moon on January 1, 2012. Operations were managed by Lockheed Martin Space, while the Jet Propulsion Laboratory handled project management for the United States-origin mission.

**End of Mission**
The mission concluded on December 17, 2012. GRAIL-B was deliberately crashed into the Moon at 22:29:21 UTC in the region designated LQ01. This event marked the transition of the entity into a "former lunar orbiter" status.

## References

1. [Source](https://news.lockheedmartin.com/2007-12-19-Lockheed-Martin-Spacecraft-to-be-Flown-for-NASAs-GRAIL-Lunar-Mission)
2. [Source](http://moon.mit.edu/operations.html)
3. Jonathan's Space Report
4. [Source](https://www.nasa.gov/pdf/582116main_GRAIL_launch_press_kit.pdf)
5. [Source](https://www.nasa.gov/mission_pages/grail/news/grailstatus20121217.html)
6. [Source](https://www.economist.com/science-and-technology/2012/12/22/grail-hunt)
7. [Source](https://www.universetoday.com/92266/two-new-moons-join-the-moon-grail-twins-achieve-new-years-orbits/)
8. [Source](https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/req/naif_ids.html)