LADEE

LADEE was a robotic mission launched by NASA to orbit the Moon and investigate the composition and dynamics of its tenuous atmosphere, or exosphere. The spacecraft was designed, built, and operated by the NASA Ames Research Center and aimed to address long-standing questions about the lunar environment. Its findings were intended to inform future human exploration and provide a deeper understanding of similar exospheres around other Solar System bodies.

Overview

The mission represented a significant step in NASA's Lunar Quest Program, focusing on fundamental science from lunar orbit. It was notable for being the first deep-space mission launched from the Mid-Atlantic Regional Spaceport and the inaugural flight of the Minotaur V rocket. The project emphasized a cost-capped development approach, utilizing a modular common spacecraft bus to reduce expenses and accelerate construction. Data from its instruments contributed to studies of the lunar surface interaction with the solar wind and the potential transport of lunar dust.

Mission objectives

The primary science goal was to determine the composition of the lunar atmosphere and investigate processes controlling its distribution and variability. A key objective involved measuring the density, composition, and temporal changes of the exosphere, particularly to understand the sources of gases like sodium and potassium. The mission also sought to characterize the lunar dust environment, testing hypotheses about levitated dust particles observed during the Apollo program. These measurements were critical for modeling exospheric conditions on other airless bodies, such as Mercury or large asteroids.

Spacecraft design

The spacecraft bus was based on the Modular Common Spacecraft Bus architecture, a novel design promoting flexibility and low cost. Power was provided by gallium arsenide solar cells generating up to 295 watts, stored in a lithium-ion battery. Propulsion for major maneuvers was handled by a hypergolic propellant bi-propellant system, while attitude control used cold gas thrusters. The science payload included the Ultraviolet and Visible Spectrometer (UVS) for atmospheric composition, the Neutral Mass Spectrometer (NMS) for detecting exospheric gases, and the Lunar Dust Experiment (LDEX) to measure dust grain impacts. Communications were facilitated via an experimental Lunar Laser Communication Demonstration terminal.

Launch and mission profile

Liftoff occurred on September 7, 2013, aboard a Minotaur V from Pad 0B at the Mid-Atlantic Regional Spaceport on Wallops Island. After a series of phasing loops around Earth, the spacecraft executed a trans-lunar injection burn. It entered an initial elliptical lunar orbit on October 6, 2013, later lowering to its science orbit. The primary science phase lasted approximately 100 days in a quasi-equatorial orbit with a perilune as low as 20 kilometers. Following mission extension, controllers performed a controlled descent, with the spacecraft impacting the lunar surface near the eastern rim of Sundman V crater on April 18, 2014.

Scientific results

Data from the Neutral Mass Spectrometer confirmed the presence of several noble gases, including argon-40 and helium, and detected temporary, localized signatures of neon and ammonia. The Ultraviolet and Visible Spectrometer made detailed observations of the lunar horizon glow and mapped exospheric sodium and potassium. The Lunar Dust Experiment recorded thousands of dust impact events, confirming a permanent, asymmetric dust cloud around the Moon, primarily fed by micrometeoroid impacts from streams like the Geminids. Findings significantly advanced models of exospheric generation and dust transport, with implications for the operation of future assets like the Lunar Gateway.