A Lunar Prospector mission was a third selected by NASA for full development & construction when section of the Discovery Program. At the prices of $62.8 million, the Nineteen-year mission was designed for a moo polar orbit investigation of the Moon, including mapping of surface composition and imaginable polar ice deposits, measurements of magnetic and gravity fields, and learn of lunar outgassing cases. A mission ended July 31, 1999 when the satellite was deliberately crashed into the crater near the lunar south pole in an unsuccessful attempt to detect a presence of a lake.

Information from either the mission allowed a construction of a elaborate map of the surface composition of the Moon, & helped to improve understanding of the origin, evolution, todays state, & resources of the Moon. The series of articles on the scientific outcomes were published in the journal Science ([http://www.sciencemag.org/cgi/content/full/281/5382/1476 Science Volume 281 Issue 5382]).

__TOC__

Spacecraft and Subsystems

the ballistic capsule was a graphite-epoxy drum, I.37 meters from side to side & Ace.Twenty-eight meters high using trey radial tire Two.Quintuplet m instrument booms. The Ace.One m extension boom at a prevent of one of a Deuce.Quintet m booms held a gaussmeter. Number initial mass (fully fueled) was 296 kilo. It was spin-stabilized (nominal spin rate Twelve rev) sustaining its spin axis rule to the ecliptic plane. A space vehicle was controlled by Six hydrazine monopropellant Xxii-newton thrusters, 2 abaft, ii forward, & deuce digressive. 3 fuel tanks mounted within a drum held 138 kilogram of hydrazine pressurised by atomic number 2. the power models consisted of immune system-mounted solar cells which produced an norm of 186 W & a Four.Eight The·h rechargeable NiCd battery. Communications were across ii S-b& transponders, the slotted, phased-array medium benefit antenna for downlink, & an omnidirectional sale-benefit antenna for downlink and uplink. There was there are no in-board computer; completely control was from either a ground, commanding one in-board comm& and information treating unit. Informatiin was downlinked directly & as well stored on the firm-state recorder & downlinked fallowing 53 proceedings, to assure tons information collected in the period of communications blackout periods would become received.

the probe besides carried a little a portion of the remains of Dr. Eugene Shoemaker (April 28, 1928 - July 18, 1997), astronomer & co-discoverer of Comet Shoemaker-Levy 9, to the moon for a space burial.

Mission Profile

A ballistic capsule was launched January 7, 1998 by a 3-stage Athena 2 rocket. A mission ended July 31, 1999 when a Lunar Prospector was deliberately targeted to impact around the for good shady crater touching the lunar south pole. It was hoped that a impact would liberate water vapour from either either a suspected ice deposits in a crater & that the plume would become detectable from Globe; but, there is no plume was found.

Below launch in 7 January 1998 UT (6 January Eastern time) aboard the 3-stage Athena Two rocket, the Lunar Prospector experienced a 105 hour sail to the Moon. When you took a sail, a leash instrument booms were deployed. A MAG & APS collected standardisation information, spell a GRS, NS, & ER outgassed for 1 day, when which it as well collected standardisation information around cis-sublunar space. A craft was inserted into an Xi.Six-hour time period capture orbit all about a Moon at a prevent of the sail phase. Fallowing Two dozen hours Lunar Prospector was inserted into the Tercet.Fin-hour time medium orbit, followed Twenty-four hours late (in 13 January 1998) by tranfer into the 92 ten 153 klick preliminary mapping orbit, then in 16 January by insertion into the touching-circular One c kilometer altitude nominal lunar polar mapping orbit using an inclination of Xc degrees & a period of 118 transactions. Lunar standardisation information was collected in a period of the Eleven.6- & Three.Cinque-hour orbits. Lunar mapping information collection began shortly fallowing a 118 microscopic orbit was achieved. the information collection wwhen sporadically interrupted in a period of a mission as plotted for even orbital maintenance burns, which took place to recircularize a orbit anytime a perilune or apolune was further than 20 to 25 klick from either the One c klick nominal orbit, astir it used to be that a year. In 19 December 1998, a maneuver lowered the orbit to Xl kilometre to perform higher guide studies. a orbit was altered once again in 28 January to a Fifteen ten 45 kilometre orbit, ending a Single month primary mission & beginning the extended mission.

A mission endwise 31 July 1999 at 9:52:02 UT (5:52:02 EDT) when Lunar Prospector was deliberately targeted to impact within the for good shady vicinity of the Shoemaker crater near the lunar south pole. It was hoped that a impact would liberate water vapour from either either a suspected ice deposits in a crater & that the plume would become detectable from Globe; notwithstanding, there are no such plume was found.

A Lunar Prospector mission wwhen a third mission selected by NASA for to the full development & construction as a portion of NASA's Discovery Program. Amount dollars and cents for the mission was $62.8 million including development ($34 million), launch vehicle (~$25 million) & operations (~$4 million).

Scientific experiments
the ballistic capsule carried Sestet experiments: a Gamma Ray Spectrometer, a Neutron Spectrometer, a Magnetometer, an Electron Reflectometer, an Alpha Particle Spectrometer, and the Doppler Gravity Experiment. A instruments were omnidirectional & involved there is no sequencing. A normal observation sequence was to record & downlink information day and night.

Gamma Ray Spectrometer (GRS)
A Lunar Prospector GRS produced a foremost spherical measure of gamma-ray spectra from either either a lunar surface, from which are then derived a foremost "direct" measure of the chemical composition for the entire lunar surface. This information profits maps a distribution of various significant elements through a Moon. E.g., a Lunar Prospector GRS has identified many regions by owning high cast-iron concentrations. For maps of lunar deposits of iron, potassium, and thorium, see [http://lunar.arc.nasa.gov/results/images/ironmap.jpg], [http://lunar.arc.nasa.gov/results/images/potassium.jpg], & [http://lunar.arc.nasa.gov/results/images/thorium.jpg] severally.

A fundamental purpose of the GRS experiment was to provide spherical maps of elementary abundances on the lunar surface. A GRS was designed to record a spectrum of gamma rays emitted by: Single) a radioactive decompose of elements contained in the Moon's crust; & Ii) elements in the crust bombarded by cosmic rays & solar wind particles. A first elements detectable per GRS were atomic number 92 (U), atomic number 90 (Th), & k (K), radioactive elements which generate gamma rays spontaneously, & cast-iron (Fe), ti (Ti), o (O), si (Si), aluminium (Al), mg (Mg), & atomic number 20 (Ca), elements which emit gamma rays while hit by cosmic rays or even solar wind particles. A u, th, & k particularly were utilized to map a location of KREEP (potassium, uncommon-globe element, & phosphorus containing lesson, which is believed to develop developed late in the formation of the crust & upper mantle, & is so crucial to understanding lunar evolution). A GRS was as well capable of detecting convenient (epithermal) neutrons, which complemented a neutron mass spectrometer in the seek for h2o on the Moon.

a Gamma Ray Spectrometer was a little cylinder which was mounted on the prevent of one of the 3 Two.Quintet m radial tire booms extending from either a Lunar Prospector. It consisted of the bi germanate crystal surrounded by the shield of borated polymer. Gammthe rays striking a atomic number 83 atoms produced a flash player of weak by having an intensity proportional to the energy of the gamma ray which was recorded by detectors. A energy of a gamma ray is associated by using the element responsible its emission. Due to the sale signal to noise ratio, multiple lives were needed to generate statistically important final result. At nine lives by the year, it was required to choose astir triad months to with confidence estimate abundances of atomic number 90, atomic number 19, & u, & Twelve months for the more elements. A preciseness varies based on data from element measured. For U, Th, & K, a preciseness is 7% to 15%, for Fe 45%, for Ti 20%, & for the overall distribution of KREEP 15% to 30%. A borated thin plastic shield was utilized in the detection of convenient neutrons. the GRS was designed to achieve spherical coverage from either an altitude of just about Hundred kilometre & sustaining a skin-deep guide of 150 kilometer.

Neutron Spectrometer (NS)
According to Lunar Prospector Neutron Spectrometer (NS) information, mission man of science keep close at hand determined that there exists indeed water ice in the polar craters of the Moon [http://lunar.arc.nasa.gov/results/neures.htm] -- an estimated Three billion metric tons (260 billion US gallons). For maps of concentrations (marked inside dark blue to magenta) at a northward & south poles look at [http://lunar.arc.nasa.gov/results/images/north.jpe] & [http://lunar.arc.nasa.gov/results/images/south.jpe] severally.

A NS was intentional to detect microscopic numbers of water system ice which were believed to survive on the Moon. It was capable ot detecting the water system ice at a level of less than Cipher.01%. a Moon has a total of for good shadowy craters touching the poles by owning continuous temperatures of -190 degrees C. These craters could work when cold-traps of h2o from either incoming comets & meteor. Any fluids from either these bodies which incurred its way into these craters can turn into for good frozen. A NS was as well wont to measure a abundance of atomic number 1 deep-rooted by solar wind.

a neutron mass spectrometer was a thinly cylinder colocated by owning a Alpha Particle Spectrometer at a prevent of one of the troika stellate Lunar Prospector science booms. the instrument got a superficial guide of 150 kilometre. For the polar ice studies, a NS was slated to examine the poles to Eighty degrees latitude by owning a sensitivity of at least Ten ppm by volume of h. For the ingrained atomic number 1 studies, a NS was designed to examine the entire earth using a sensitivity of Fifty ppmv. A neutron mass spectrometer consisted of deuce canisters to each one containing helium-Three & an energy counter. Any neutrons run into a he atoms give an energy signature which may be found & counted. a single of a canisters was wrapped around cd & one inside tin. A cd sieve thermal (moo energy or even slow-moving) neutrons spell a tin doesn't. Thermal neutrons come cosmic-ray generated neutrons which own misused very much of their energy within collisions sustaining hydrogen atoms. Differences in a numbers between them canisters show a total of thermal neutrons found, which successively indicates the total of atomic number 1 on the Moon's crust at the given location. Big quantities of h would belike become due to the presence of a stream.

The Alpha Particle Spectrometer (APS)
A Alpha Particle Spectrometer (APS) was damaged when you took launch, ruining one of a 5 detecting faces. In addition, due to sunspot activity peaking during a mission, a lunar information is obscured by solar interference. NASA has stated that a information potty finally become recovered by subtracting retired the results of the solar activity. Meanwhile, yet, a APS has non yielded any utile final result.

A APS was designed to detect rn outgassing cases on the surface of the Moon. A APS recorded alpha particle signatures of radioactive decompose of radon gas and its girl product, polonium. These reputed outgassing events, in which rn, n, & carbon dioxide come vented, come hypothesized to become a source of a tenuous lunar atmosphere, & can be the effect of the sale-subordinate volcanic/tectonic activity on the Moon. Tools on the being, timing, & sources one cases will serve around the determination of the style & rate of lunar tectonics.

a APS was a cube close to Eighteen cm in a side colocated using the neutron mass spectrometer on the prevent of one of the leash radial tire Deuce.Fivesome m Lunar Prospector science booms. It contained tenner si detectors sandwiched between gold & atomic number 13 disks intended in 5 of sise sides of the cube. Alpha particles, by a decompose of rn & atomic number 84, leave tracks of charge on a atomic number 14 wafers after it impact the si. a high voltage is applied to a atomic number 14, & the todays is amplified by existence funnelled along the tracks to the al disk & is recorded for identification. the APS was designed to produce the spherical examination of barking spiders release cases & po distribution by having the superficial guide of 150 kilometre & a preciseness of 10%.

Doppler Gravity Experiment (DGE)
A Doppler Gravity Experiment (DGE) was a number one polar, sale-low-level mapping of the lunar gravity field. A Clementine mission had previously produced a comparatively great-guide map, however a Prospector DGE found information or so 5 days when elaborated: the "first truly operational gravity map of the Moon" (NASA/ARC, [http://lunar.arc.nasa.gov/results/dopres.htm]). (View [http://lunar.arc.nasa.gov/results/images/newgrav.gif] for the comparison of Clementine & Prospector levels of detail.) A practical rewards of this come extra stable long-semipermanent orbits & better fuel efficiency. In addition, a DGE information is hoped to help investigator study other just about lunar origins & a nature and severity of the lunar core. A DGE has identified trinity fresh touching-side mascons (mass concentrations). Look at [http://lunar.arc.nasa.gov/results/images/doppler-globes.jpg] for a newly gravity map (when of Could 2005) according to Lunar Prospector information (values come expressed when deviation from either the mean; therefore, veto values do notShow antigravity).

A purpose of a Lunar Prospector DGE was to study just about the surface & internal mass distribution of the Moon. This is accomplished by with measurements of a Doppler shift in the S-band tracking signal as it reaches Globe, which may be converted to space vehicle accelerations. A accelerations may be filtered to provide estimates of a lunar gravity field, from either which a location & size of mass anomalies affecting the space vehicle orbit may be modelled. Estimates of the surface & internal mass distribution give info on the crust, geosphere, & internal structure of the Moon.

This experiment provided the number one lunar gravity information from either a moo polar orbit. Because line-of-sight tracking is compulsory for this experiment, just a touching-side gravity field can be calculated applying this Doppler method. A experiment occurs as byproduct of the ballistic capsule S-band tracking, so has there are no utilized weight or even power requirements. the experiment was designed to give a touching-side gravity field sustaining a surface guide of 200 kilometre & preciseness of Quint mGal (0.05 mm/s) in the form of spherical harmonic coefficients to degree and the correct sequence Sixty. In the extended mission, where the ballistic capsule descended to an orbit by owning an altitude of Fifty klick then to Tenner klick, this guide was potential to improve by a factor even of Century or thomas more.

the downlink telemetry signal was transmitted at 2273 MHz, above a ±Unity MHz bandwidth as a best-hand circularly polarized signal at a nominal power of Quintuplet W & peak power of Vii W. Command uplinks were sent at 2093.0542 MHz above the ±One MHz bandwidth. the transponder was a standard Loral/Conic S-Band transponder. An omnidirectional antennthe may be utilized for even uplink & downlink, or a medium benefit helix antenna may be utilized (downlink merely). Since the ballistic capsule was spwithin-stabilized, a spin resulted in a bias in the Doppler signal due to the ballistic capsule antenna pattern spinning sustaining respect to the Globe station of Cypher.417 Hz (Twenty-seven.Trine mm/s) for the omnidirectional antenna, & -0.0172 Hz (-Unity.Xii mm/s) for the medium benefit antenna. LOS information was sampled at V seconds to account for the some Five 2nd spin rate of the ballistic capsule, allowing a residual of less than Nought.One mm/s.

Electron Reflectometer and Magnetometer
the Gaussmeter & Electron Reflectometer (together, MAG/ER) found anomalous superficial magnetic fields on the Moon, which are then inside stark direct contrast to a spherical magnetosphere (which the Moon lacks). A Moon's overall magnetic field is as well feeble to deflect a solar wind, but MAG/ER found the little skin-deep anomaly that could wash sol. This anomaly, astir Century klick from side to side, has so been known as "the smallest known magnetosphere, magnetosheath and bow shock system in the Solar System" (NASA/ARC, [http://lunar.arc.nasa.gov/results/magelres.htm]). Due to this & more charismatic features of the Moon's surface, h deposited by solar wind is non-uniformly distributed, being denser at a fringe of the charismatic features. Since atomic number 1 density occurs as worthy characteristic for conjectural lunar bases, this page can be utile inside finding optimum web sites for conceivable long-semipermanent Moon missions.

A electron reflectometer (ER) & magnetometer (MAG) were designed to collect information on the lunar magnetic fields. A Moon has there is no spherical magnetic field, however it does use frail localized magnetic fields at its surface. These can be paleomagnetic remnants of the previous spherical magnetic field, or even can be due to meteor impacts or more local phenomena. This experiment was to help map these fields & provide facts in their origins, allow imaginable examination of distribution of minerals on the lunar surface, aid within the determination of the size & composition of the lunar core, & provide facts on the lunar caused magnetic dipole.

A ER determined a location & nature and severity of magnetic fields from either a energy spectrum and direction of electrons. A instrument measured a pitch angles of solar wind electrons reflected from a Moon by lunar magnetic fields. Stronger local magnetic fields might reflect negatron using big pitch angles. Field strengths when small as Zero.01 nT could be measured with the spacial accuracy of astir Triplet km at the lunar surface. the Magazine was a triaxial fluxgate gaussmeter similar within project to the instrument utilized in Mars Global Surveyor. It can measure a magnetic field amplitude and direction at ballistic capsule altitude using the spacial guide of astir Hundred klick whenever ambient plasma disturbances are minimum.

A ER & a electronics pack were placed at a prevent of one of a threesome stellate science booms in Lunar Prospector. the Magazine was successively extended farther in a Cypher.Eight m boom—a conjunctive Deuce.Sixer m from either either a Lunar Prospector sequentially to isolate it from space vehicle generated magnetic fields. the ER & Magazine instruments experienced a cooperative mass of 5 kg and used Quatern.Phoebe watts of power.