Moon Miners' Manifesto

#89 October 1995

Lunar Prospector

Sunnyvale California, July 20, 1995

The Lunar Prospector program, headed by Principal Investigator Dr. Alan Binder of Lockheed Martin Missiles & Space, will build on the science of the Apollo program and return America to the Moon in June 1997.

It is the first peer reviewed, competitively selected mission in NASA's new Discovery series of "Faster, Better, Cheaper" solar system exploration missions, and the Missiles & Space and Ames team was selected on February 28, 1995. G. Scott Hubbard of NASA Ames Research Center at Moffett Field, is the NASA mission manager for Lunar Prospector.

The overall management of the Lunar Prospector program is the responsibility of Dr. Binder. The spacecraft and launch vehicle, a Lockheed Launch Vehicle 2, are being built at the Sunnyvale facility and are being readied for launch in June 1997. Dr. Dominick Tenerelli of Lockheed Martin in Sunnyvale is the project manager.

During a one-year polar orbiting mission, Lunar Prospector will map the Moon's surface composition, gravity and magnetic fields, and volatile release activity. These data are needed for expanding the lunar science legacy of Apollo, and for planning future exploration missions. Lunar Prospector will demonstrate that high quality science missions can be accomplished economically and within short time scales.

SCIENCE PAYLOAD

The Lunar Prospector science payload was chosen from a list of experiments proposed by NASA scientists for lunar mapping missions. The spacecraft carries six of the highest priority experiments, chosen for their scientific value, their ability to be flown on a simple, spin-stabilized spacecraft, and for their low mass, power and data rate requirements.

The experiments are:

• Gamma-Ray Spectrometer -- a more advanced system than was flown on the Apollo missions which will provide global maps of the elemental composition of the surface layer of the Moon. The main elements to be mapped are uranium, thorium, potassium, iron, titanium, oxygen, silicon, alum-inum, magnesium, and calcium. Knowledge of the concentra-tions of these elements over the entire lunar surface will aid in understanding the composition and evolution of the lunar crust

  [Ed.: and the planning of lunar industrial development.]

  Though uranium, thorium and potassium are only trace elements, they are found concentrated in a material called KREEP (potassium [K], rare earth elements [REE] and phos-phorus [P]). KREEP is not only the main source of these elements, but many other important trace elements such as zirconium, fluorine, and chlorine. Mapping the locations and concentrations of KREEP deposits is important to lunar science as it is believed that the material developed late in the formation of the lunar crust and upper mantle, and thus can help define how the crust and mantle formed and evolved.

• Neutron Spectrometer -- While the Moon does not have any water of its own, theoretical calculations suggest that water brought to the Moon by comets and water-rich meteoroids may be frozen in the bottom of small craters in the polar regions. The floors of some small craters located within 30 degrees of the north and south poles never see sunlight and have continuous temperatures below -190 degrees centigrade. At such temperatures, water ice would be stable over the lifetime of the solar system. The neutron spectrometer on Lunar Prospector has a water ice detectability limit of better than 0.01%, which means it can locate 200 grams of water (a cup of water) in a cubic meter (about a cubic yard) of regolith (lunar soil). The discovery of lunar polar ice would have a profound effect on the economics and logistics of the explora-tion and colonization of the Moon and the inner solar system. It would mean that water, necessary for life support and as a source of both oxygen and hydrogen needed to produce rocket propellant, would be available in situ to future lunar explorers.

• Alpha Particle Spectrometer -- The alpha particle experiment is an advanced version of an experiment flown on Apollo 15 and 16. It will determine the locations and frequency of radon gas release events by detecting alpha particles from both radioactive radon gas and its decay product, polonium. This is the only orbital instrument which provides information on the current level of tectonic and volcanic out-gassing activity of the Moon. Thus, it provides unique information about the Moon which, until Apollo, was thought to be tectonically and volcanically dead. As a result of the Apollo surface seismometers and mass spectrometer and the orbiting alpha particle experiment, scientists now know that the Moon is active, though much less so than Earth or Mars.

• Magnetometer and Electron Reflectometer -- These two experiments map the lunar magnetic fields. While the Moon does not have a global magnetic field like the Earth, it does have weak fields of local extent. Mapping the strengths and distributions of these local fields over the Moon will determine if they were caused by an earlier global magnetic field like the Earth's, if they were caused by meteoroid impacts, or if they have some other origin. The data should also provide information on the size and composition of the lunar core and, coupled with Neutron Spectrometer data, could reveal correlations between magnetic fields and solar wind implanted hydrogen and helium concentrations.

  On Earth, magnetic mapping is an important tool for locating economically important ore bodies. Similarly, the magnetic experiments will provide information to help under-stand the economic potential of the Moon.

• Doppler Gravity Experiment -- The experiment provides the first complete gravity map of the Moon. Because no earlier mission was in a low polar orbit, NASA does not have an adequate lunar gravity model for planning follow-on unmanned and manned lunar missions. Lunar Prospector will define the lunar gravity field that affects the altitude, and thus the fuel quantity required for orbit maintenance, of all orbiting spacecraft. It will also provide data on density differences in the crust, the internal density of the Moon, and the nature of the core.

THE SPACECRAFT

The Lunar Prospector spacecraft is a small, simple, reliable, spin stabilized spacecraft with a fully fueled mass of 233 kg (513 lb.). It is 1.42 m (4.6 ft) in diameter, 1.22 m (4.1 ft) in axial length drum with solar cells mounted on its outer surface which provide 202 watts of power. The scientific instruments are mounted on three booms to isolate them from the bus and simplify the spacecraft-instrument interfaces.

THE MISSION

The mission begins with launch in June of 1997. The flight to the Moon will take five days, during which two midcourse maneuvers occur, booms are deployed, and science instruments begin to collect calibration data.

Once the spacecraft reaches the Moon, it will perform three separate Lunar Orbit Insertion burns. The first burn will put the spacecraft into a 24-hour, elliptical orbit. One day later, the second burn will put the spacecraft into a four-hour elliptical orbit. Finally, 24-hours later, the third burn will insert the spacecraft into a circular, 118-minute, 100 km altitude, polar mapping orbit. At that point, the spacecraft will begin its nominal one-year mapping mission. During this phase, periodic orbital maintenance maneuvers will be made to keep the spacecraft in its proper orbit.

If, as expected, fuel is available at the end of the one-year nominal mission, the mapping may be extended, first during a six-week phase in a circular, 50 km altitude orbit to obtain much more sensitive magnetic and gravity data and then from elliptical orbits as low as 10 km above the surface over a few areas of special interest.

The mission will end when the fuel needed for orbital maintenance is depleted and the spacecraft impacts on the lunar surface.

Contents of this issue of Moon Miners' Manifesto