 The Apollo 15 Solar Wind Spectrometer experiment on the Moon | |
| Acronym | SWS |
|---|---|
| Notable experiments | Apollo 12 and Apollo 15 |
The Solar Wind Spectrometer was a scientific package that flew on the Apollo 12 and Apollo 15 missions to the surface of the Moon. [1] [2] [3] The goal was to characterise the solar wind near the Moon's surface and to explore its interactions with the lunar environment. The experiments' principal investigator was Dr Conway W. Snyder of the Jet Propulsion Laboratory.
The Solar Wind Spectrometer (SWS) experiment aimed to provide the ability "to measure energies, densities, incidence angles and temporal variations of the solar wind plasma that strikes the surface of the moon". [4] The experiment instrument consist of seven Faraday cups, that measure the amount of charged particles. [5] One central cup points perpendicularly to the surface. The other six cups are angled at 30 degrees from the surface, located around the central cup in 60-degree intervals. Each cup can measure incoming negatively charged electron flow and positively charged proton-alpha particle flow. The angle of the incoming particle was measured by using readings from all Faraday cups. [6]
Below the instrument was an electronics package located in a container with active thermal control. The electronics packages consists of power control circuits, sensor voltage control, ammeter circuits, and finally signal/data conditioning circuits. [6] Thermal control was provided by three radiators, a sunshield and insulation. [4]
The Apollo 12 Solar Wind Spectrometer was deployed by astronaut Pete Conrad on the surface of the Moon on November 19, 1969. [6] It was located at 3S, 23W. The instrument's initial state had dust covers over the Faraday cup entrances. During the early phase of the experiment's activation with the dust covers in place, background baseline data was collected. [6] One hour after the departure of the Apollo 12 Lunar Module ascent stage at 15:25 on November 20, 1969, the dust covers were removed and the sensors exposed directly to the lunar environment. [6]
The Apollo 15 Solar Wind Spectrometer was deployed on the surface of the Moon on July 31, 1971, and was powered on at 19:37 UTC. [6] It was located at 26N, 4E. The instrument's initial state had dust covers over the Faraday cup entrances. During the early phase of the experiment's activation with the dust covers in place, background baseline data was collected. [6] One hour after the departure of the Apollo 15 Lunar Module ascent stage on August 2, 1971, the dust covers were removed and the sensors exposed directly to the lunar environment. [6]
Analysis of the two instruments' data found that the solar plasma found near to the lunar regolith surface was broadly similar to the solar plasma measured by probes some distance from the Moon. [2] It also found that no plasma is detectable in the shadow of the Moon during the lunar night. [2] The instrument was also able to distinguish plasma within interplanetary space and that found in the Earth's magnetosheath. [6] Magnetosheath plasma would exhibit large and frequent changes in plasma velocity, density and speed. [3] Highly variable spectra were observed at lunar sunrise, potentially due to interactions with the lunar surface. [2] [6]
Solar Wind Spectrometer data that was analysed after the landing of Apollo 14, confirmed the presence of a photoelectric layer and similar in nature to that found by the Charged Particle Lunar Environment Experiment. [5]
The instrument detected a neutral gas-ion shockwave produced by the impact of the Apollo 13 S-IVB stage on the lunar surface. It was suggested that the source of this gas shockwave may be a result of the vaporisation of 1100 kg of plastic materials contained with the rocket stage. The shockwave was estimated to have travelled 140 km at a speed of 2 km/s. [7]
Apollo 12 was the sixth crewed flight in the United States Apollo program and the second to land on the Moon. It was launched on November 14, 1969, by NASA from the Kennedy Space Center, Florida. Commander Charles "Pete" Conrad and Lunar Module Pilot Alan L. Bean performed just over one day and seven hours of lunar surface activity while Command Module Pilot Richard F. Gordon remained in lunar orbit.
Nozomi was a Japanese Mars orbiter that failed to reach Mars due to electrical failure. It was constructed by the Institute of Space and Astronautical Science, University of Tokyo and launched on July 4, 1998, at 03:12 JST with an on-orbit dry mass of 258 kg and 282 kg of propellant. The Nozomi mission was terminated on December 31, 2003.
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Explorer 35,, was a spin-stabilized spacecraft built by NASA as part of the Explorer program. It was designed for the study of the interplanetary plasma, magnetic field, energetic particles, and solar X-rays, from lunar orbit.
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Geotail was a satellite that observed the Earth's magnetosphere. It was developed by Japan's ISAS in association with the United States' NASA, and was launched by a Delta II rocket on 24 July 1992 from Cape Canaveral Air Force Station.
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The magnetic field of the Moon is very weak in comparison to that of the Earth; the major difference is the Moon does not have a dipolar magnetic field currently, so that the magnetization present is varied and its origin is almost entirely crustal in location; so it's difficult to compare as a percentage to Earth. But, one experiment discovered that lunar rocks formed 1 - 2.5 billion years ago were created in a field of about 5 microtesla (μT), compared to present day Earth's 50 μT. During the Apollo program several magnetic field strength readings were taken with readings ranging from a low of 6γ (6nT) at the Apollo 15 site to a maximum of 313γ (0.31μT) at the Apollo 16 site, note these readings were recorded in gammas(γ) a now outdated unit of magnetic flux density equivalent to 1nT.
The atmosphere of the Moon is a very scant presence of gases surrounding the Moon. For most practical purposes, the Moon is considered to be surrounded by vacuum. The elevated presence of atomic and molecular particles in its vicinity compared to interplanetary medium, referred to as "lunar atmosphere" for scientific objectives, is negligible in comparison with the gaseous envelopes surrounding Earth and most planets of the Solar System. The pressure of this small mass is around 3×10−15 atm (0.3 nPa), varying throughout the day, and in total mass less than 10 metric tonnes. Otherwise, the Moon is considered not to have an atmosphere because it cannot absorb measurable quantities of radiation, does not appear layered or self-circulating, and requires constant replenishment due to the high rate at which its gases are lost into space.
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 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.
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Tianwen-4, formerly known as Gan De, is a planned interplanetary mission by China to study the Jovian system and its environs, sharing a launch with a spacecraft which will make a flyby of Uranus.
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The Lunar Atmospheric Composition Experiment (LACE) was a miniature magnetic deflection mass spectrometer. The experiment's aim was to study the composition and variations of the lunar atmosphere. The only deployment of LACE was as part of the Apollo Lunar Surface Experiments Package (ALSEP) on Apollo 17 within the Taurus–Littrow valley.
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The Lunar Ejecta and Meteorites Experiment (LEAM) was a lunar science experiment that flew to the Moon on board Apollo 17 in 1972. It collected information on dust particles produced as a result of meteoroid impacts on the surface of the Moon.
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