 The Apollo 12 Lunar Surface Magnetometer experiment on the Moon | |
| Acronym | LSM |
|---|---|
| Notable experiments | Apollo 12, 14, and 16 |
The Lunar Surface Magnetometer (LSM) was a lunar science experiment with the aim of providing insights into the interior of the Moon and how its latent magnetic field interacts with the solar wind. It was deployed on the Moon as part of Apollo 12, Apollo 14 and Apollo 16 missions.
Two lunar orbital satellites, Luna 10 and Explorer 35, laid much of the groundwork for a working understanding of the Moon's magnetic field. They established that the Moon has at best little more than a remnant field, and at worst no intrinsic magnetic field at all. Those spacecraft's instruments were not sensitive enough, and too far from the Moon's surface to distinguish between these two possibilities. [1] [2] In addition to these two missions, analysis had been conducted on regolith samples brought back from the Moon by Apollo 11. [1] This analysis established some of the surface materials' magnetic properties. [1]
A lunar magnetometer experiment had a number of requirements that shaped its capabilities. The instrument needed to be able to operate during the lunar night since it was believed the collection of data from a full lunar rotation would be required. The instrument also needed to be able to perform its own self-calibrations on a regular cadence to account for wide temperature ranges experienced over a long period of time. [1]
The instrument's main magnetic measurements were calculated from three Ames fluxgate magnetometer sensor heads, located at the end of three 100 cm (39 in) booms, positioned perpendicular to each other. [1] Each sensor consists of a flattened toroidal core made of permalloy tape placed inside a wound sensing element. [3] [4] The sensors could be gimballed by motors, controlled either from commands sent from Earth or from commands generated by the Apollo Lunar Surface Experiments Package (ALSEP). [1] These sensors were thermally controlled by thermistors driving the operation of resistance heaters. Alignment and positional measurement of the instrument were provided by two features: the onboard gravimeters that measured the tilt-angle of the magnetometer, and a sundial or "shadowgraph" that enabled astronauts to take an azimuthal reading. [1] The sensor booms were folded to facilitate easier stowage and reduced strain during transportation during flight. When deployed, the three sensors were situated 75 cm (30 in) above the ground at a 35-degree angle from the surface. [1] [3]
To be able to measure the magnetic properties of the Moon as a whole, instrument placement would need to avoid any localised nickel-iron/stoney-iron material. If this material was magnetized or capable of producing localised induction fields, this would result in incorrect readings of the Moon-wide magnetic field. [1]
The magnetometer received its power from a 70 watt radioisotope thermoelectric generator that provided power to a number of ALSEP instruments which enabled the LSM to operate both day and night. The instrument would on average use 3 watts of power. Power and a connection to the ALSEP radio transmitter were made available via a 15-meter (49 ft) ribbon cable. [4]
The first LSM was fully deployed and activated on the Moon at 14:40 UTC November 19, 1969, by astronauts Charles Conrad and Alan Bean, within the Oceanus Procellarum. [1] [2] In the selenographic coordinate system, the instrument was located at 23.35W and 2.97S. The instrument returned the first measurements of a magnetic field intrinsic to the Moon, rather than induced by the solar wind. The instruments detected a field strength of 32-36 nanotesla that was likely produced mainly by a nearby localised magnetised body, between 200 m (660 ft) and 200 km (120 mi) from the magnetometer. [2] [3] This was due to constraints on the lunar magnetic dipole strength due to measurements made simultaneously by Explorer 35, [3] and the ruling out of other artificial sources due to their size. [1] The instrument likely detected a field effect caused by the hydromagnetic flow of the solar wind as it passed the Moon. [3] [2]
While the instrument carried on Apollo 16 was similar to that on Apollo 12, its sensors were upgraded with high stability cores developed by the Naval Ordnance Laboratory. [4]
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.
Mariner 2, an American space probe to Venus, was the first robotic space probe to report successfully from a planetary encounter. The first successful spacecraft in the NASA Mariner program, it was a simplified version of the Block I spacecraft of the Ranger program and an exact copy of Mariner 1. The missions of the Mariner 1 and 2 spacecraft are sometimes known as the Mariner R missions. Original plans called for the probes to be launched on the Atlas-Centaur, but serious developmental problems with that vehicle forced a switch to the much smaller Agena B second stage. As such, the design of the Mariner R vehicles was greatly simplified. Far less instrumentation was carried than on the Soviet Venera probes of this period—for example, forgoing a TV camera—as the Atlas-Agena B had only half as much lift capacity as the Soviet 8K78 booster. The Mariner 2 spacecraft was launched from Cape Canaveral on August 27, 1962, and passed as close as 34,773 kilometers (21,607 mi) to Venus on December 14, 1962.
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.
Lunar Prospector was the third mission selected by NASA for full development and construction as part of the Discovery Program. At a cost of $62.8 million, the 19-month mission was designed for a low polar orbit investigation of the Moon, including mapping of surface composition including lunar hydrogen deposits, measurements of magnetic and gravity fields, and study of lunar outgassing events. The mission ended July 31, 1999, when the orbiter was deliberately crashed into a crater near the lunar south pole, after the presence of hydrogen was successfully detected.
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.
Explorer 33, also known as IMP-D and AIMP-1, is a spacecraft in the Explorer program launched by NASA on 1 July 1966 on a mission of scientific exploration. It was the fourth satellite launched as part of the Interplanetary Monitoring Platform series, and the first of two "Anchored IMP" spacecraft to study the environment around Earth at lunar distances, aiding the Apollo program. It marked a departure in design from its predecessors, IMP-A through IMP-C. Explorer 35 was the companion spacecraft to Explorer 33 in the Anchored IMP program, but Explorer 34 (IMP-F) was the next spacecraft to fly, launching about two months before AIMP-E, both in 1967.
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.
Spacecraft magnetometers are magnetometers used aboard spacecraft and satellites, mostly for scientific investigations, plus attitude sensing. Magnetometers are among the most widely used scientific instruments in exploratory and observation satellites. These instruments were instrumental in mapping the Van Allen radiation belts around Earth after its discovery by Explorer 1, and have detailed the magnetic fields of the Earth, Moon, Sun, Mars, Venus and other planets and moons. There are ongoing missions using magnetometers, including attempts to define the shape and activity of Saturn's core.
Explorer 14, also called EPE-B or Energetic Particles Explorer-B, was a NASA spacecraft instrumented to measure cosmic-ray particles, trapped particles, solar wind protons, and magnetospheric and interplanetary magnetic fields. It was the second of the S-3 series of spacecraft, which also included Explorer 12, 14, 15, and 26. It was launched on 2 October 1962, aboard a Thor-Delta launch vehicle.
The Apollo Lunar Surface Experiments Package (ALSEP) comprised a set of scientific instruments placed by the astronauts at the landing site of each of the five Apollo missions to land on the Moon following Apollo 11. Apollo 11 left a smaller package called the Early Apollo Scientific Experiments Package, or EASEP.
The Apollo 12 Passive Seismic Experiment (PSE) was placed on the lunar surface by the Apollo 12 mission as part of the Apollo Lunar Surface Experiments Package (ALSEP). The PSE was designed to detect vibrations and tilting of the lunar surface and measure changes in gravity at the instrument location. The vibrations are due to internal seismic sources (moonquakes) and external. The primary objective of the experiment was to use these data to determine the internal structure, physical state, and tectonic activity of the Moon. The secondary objectives were to determine the number and mass of meteoroids that strike the Moon and record tidal deformations of the lunar surface.
The Apollo 14 Passive Seismic Experiment (PSE) was placed on the lunar surface on February 5, 1971, as part of the Apollo 14 ALSEP package. The PSE was designed to detect vibrations and tilting of the lunar surface and measure changes in gravity at the instrument location. The vibrations are due to internal seismic sources (moonquakes) and external. The primary objective of the experiment was to use these data to determine the internal structure, physical state, and tectonic activity of the Moon. The secondary objectives were to determine the number and mass of meteoroids that strike the Moon and record tidal deformations of the lunar surface.
The Charged Particle Lunar Environment Experiment (CPLEE), placed on the lunar surface by the Apollo 14 mission as part of the Apollo Lunar Surface Experiments Package (ALSEP), was designed to measure the energy spectra of low-energy charged particles striking the lunar surface. It measured the fluxes of electrons and ions with energies from 40 eV to 20 keV. The primary purpose of the experiment was to examine plasma particles originating from the Sun and the low-energy particle flux in the Earth's magnetic tail.
FIELDS is a science instrument on the Parker Solar Probe (PSP), designed to measure magnetic fields in the solar corona during its mission to study the Sun. It is one of four major investigations on board PSP, along with WISPR, ISOIS, and SWEAP. It features three magnetometers. FIELDS is planned to help answer an enduring questions about the Sun, such as why the solar corona is so hot compared to the surface of the Sun and why the solar wind is so fast.
The Cold Cathode Gauge Experiment, also known as the Lunar Atmosphere Detector, was a scientific package that flew on board Apollo 12, Apollo 13, Apollo 14, and Apollo 15. The goal of the experiment was to measure the density of the Moon's tenuous atmosphere, but not its composition.
The Suprathermal Ion Detector Experiment (SIDE) was a lunar science experiment, first deployed by astronauts on the lunar surface in 1969 as part of Apollo 12, and later flying on Apollo 14 and Apollo 15. The goal of SIDE was to study any potential lunar ionosphere and the solar wind.
The Solar Wind Spectrometer was a scientific package that flew on the Apollo 12 and Apollo 15 missions to the surface of the Moon. 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 Heat Flow Experiment was a United States NASA lunar science experiment that aimed to measure the rate of heat loss from the surface of the Moon. Four experiments were carried out on board Apollo missions. Two experiments were successfully deployed as part of Apollo 15 and Apollo 17. The instrument on Apollo 16 was deployed but the cable from it to the ALSEP central station was broken and the experiment was rendered inoperable. A heat flow experiment was carried onboard Apollo 13 but the mission was aborted in-flight and the instrument never reached the surface.
The Lunar Surface Gravimeter (LSG) was a lunar science experiment that was deployed on the surface of the Moon by the astronauts of Apollo 17 on December 12, 1972. The LSG was conceived by its principal investigator Joseph Weber. Weber proposed a number of experimental methods for the detection of gravitational waves, and would go on to be described as the "founding father" of gravitational wave detection. The experiment aimed to measure changes in the local gravitational strength on the Moon's surface through the use of a gravimeter. These measurements were intended to provide insight into the internal structures of the Moon as it tidally deformed due interaction with the gravitational fields of the Earth and Sun. In addition the experiment hoped to contribute experimental evidence of the existence of gravitational waves.
The Lunar Traverse Gravimeter was a lunar science experiment, deployed by astronauts on the lunar surface in 1972 as part of Apollo 17. The goal of the experiment was to use relative gravity measurements to infer potential attributes about the geological substrata near the Apollo 17 landing site.
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