page_title: LADEE
section_title: Lunar transit
hierarchical_section_title: LADEE / Spaceflight operations / Lunar transit
caption_attribution_description: English: An artist's concept of NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft firing its maneuvering thrusters in order to maintain a safe altitude as it orbits the moon.
context_page_description: The Lunar Atmosphere and Dust Environment Explorer was a NASA lunar exploration and technology demonstration mission. It was launched on a Minotaur V rocket from the Mid-Atlantic Regional Spaceport on September 7, 2013. During its seven-month mission, LADEE orbited around the Moon's equator, using its instruments to study the lunar exosphere and dust in the Moon's vicinity. Instruments included a dust detector, neutral mass spectrometer, and ultraviolet-visible spectrometer, as well as a technology demonstration consisting of a laser communications terminal. The mission ended on April 18, 2014, when the spacecraft's controllers intentionally crashed LADEE into the far side of the Moon, which, later, was determined to be near the eastern rim of Sundman V crater.
context_section_description: LADEE took an unusual approach in its transit of the Moon. Launched into a highly elliptical Earth orbit, the spacecraft made three increasingly larger laps around Earth before getting close enough to enter into Lunar orbit. The transit required approximately one month.
  After separating from the Minotaur, high electrical currents were detected in the satellite's reaction wheels causing them to be shut down. There was no indication of a fault, and after the protection limits were adjusted, orientation with reaction wheels was resumed the following day.
  The LADEE spacecraft made three "phasing orbits" of Earth before it accomplished a Lunar orbit insertion (LOI), which occurred at perigee of the third orbit using a three-minute engine burn. The target orbit for the third Earth orbit had a perigee of 200 kilometers (120 mi), an apogee of 278,000 km (173,000 mi) and an inclination of 37.65 degrees. The planned argument of perigee is 155 degrees, while its characteristic energy, C3 is -2.75 km²/s². The novel trajectory using orbital phasing loops was done for four main reasons:
  the Minotaur V launch vehicle had insufficient delta-v to put the 383 kg (844 lb) LADEE directly into a trans-lunar injection.
  to handle potential off-nominal launch dispersions from the Minotaur V—which is a stack of five solid rocket stages, and is not considered to be a particularly precise rocket—in a propellant-efficient manner while leaving the orbit profile flexible to large dispersions in the initial injection orbit.
  to widen the launch window to five days. In the event, LADEE did not need this as the launch occurred at the beginning of the window on the first day.
  to increase mission robustness in the face of any anomalous or missed orbital maneuvers with the spacecraft.
caption: Artist concept of LADEE firing thrusters
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