Lunar Prospector (Discovery 3)

Launch data: Designation  25131 / 98001A Launch date  07 Jan 1998 - 02:28 UT Launch site  CC, SLC46 Launch vehicle  Athena-2 Mission  Lunar orbiter Heliocentric orbit Perihelion / Aphelion   Incl. to ecliptic   ° Period   min Lunar Prospector carried also a small capsule by Celestis called Celestis-02 with the ashes of the late Gene Shoemaker.

Lunar Prospector

Spacecraft data: Prime contractor  Lockheed Martin Platform  LM100 Operator  NASA Mass at launch  295 kg (fully fueled) Dry Mass  126 kg Basic shape  graphite-epoxy drum Dimension  1.4m dia, 1.22m high Solar array   Stabilization  spin-stabilized DC power

Lunar Prospector

Decay:

Description:

• Lunar Prospector was the third of NASA's Discovery missions. Lunar Prospector was designed to determine the origin, evolution, and current state of resources of the Moon via low-altitude mapping of its surface composition, magnetic fields, gravity fields, and gas release events. The mission provided a new map that shows in unprecedented detail the chemical composition and the magnetic and gravity fields of the Moon. After launch, the Lunar Prospector had a 105 hour cruise to the Moon, followed by insertion into a near-circular 100 km altitude lunar polar orbit with a period of 118 minutes. The nominal mission duration was one year. A two year extended mission following this was possible, during which the orbit was to be lowered to 50 km and then 10 km altitude to obtain higher resolution measurements.
• Spacecraft: The spacecraft was a graphite-epoxy drum, 1.4 meters in diameter and 1.22 meters high with three 2.5 meter radial instrument booms. It was spin-stabilized and used with Sun and limb sensors for attitude determination. It was controlled by 6 hydrazine monopropellant 22-Newton thrusters providing 1430 m/s of delta-V. Communications are through two S-band transponders and a slotted, phased-array medium gain antenna and omnidirectional low-gain antenna. There was no on-board computer; ground command was through a 3.6 kbps telemetry link. Body mounted solar cells provide 206 W complemented by 15 amp-hr NiH batteries.
• Payload
  • Gamma Ray Spectrometer (GRS) - Neutron Spectrometer (NS) - The GRS and NS returned global data on elemental abundances, to be used to help understand the evolution of the lunar highland crust and the duration and extent of basaltic volcanism, and to assess lunar resources. The NS also located significant quantities of water ice which existed in the permanently shadowed areas near the lunar poles.
  • Magnetometer (MAG) - Electron Reflectometer (ER) - The MAG/ER experiments will return data on the lunar crustal magnetic field and the lunar induced magnetic dipole. These data will help provide an understanding of the origin of lunar paleomagnetism and the degree to which impacts can produce paleomagnetism, and allow constraints on the size and composition of the (possible) lunar core.
  • Alpha Particle Spectrometer (APS) - The APS instrument will be used to find radon outgassing events on the lunar surface by detecting alpha particles from the radon gas itself and its decay product, polonium. Observations of the frequency and locations of the gas release events will help characterize one possible source of the tenuous lunar atmosphere. Determination of the relationship of outgassing sites with crater age and tectonic features may be possible. This may in turn be used to characterize the current level of lunar tectonic activity.
  • Doppler Gravity Experiment (DGE) - This investigation will use Doppler tracking of S-Band radio signals to characterize the spacecraft orbit and determine the lunar gravity field. This data will provide information on the lunar interior and, combined with lunar topographic data, will allow modelling of the global crustal asymmetry, crustal structure, and subsurface basin structure. It can also used for planning future lunar missions.

Mission details:

• Lunar Prospector was launched on Jan 7, 1998. The first Athena-2 launch vehicle took off from LC46 at Spaceport Florida, the commercial spaceport at the Cape Canaveral site. LP is a Lockheed Martin LM100 class satellite. The LM100 is a small spin stablized bus; in its LP configuration it has a triangular structure (half an Iridium bus) surrounded by a cylindrical solar panel shell.
• The first stage of Athena-2 is a Thiokol Castor 120 solid motor, derived from the Peacekeeper ICBM first stage. The second stage is another Castor 120, and the third stage is a UTC Orbus 21D solid motor. A fourth stage, although not formally counted as such, is the lower-thrust Primex OAM (Orbit Adjust Module) which performs final orbit insertion and trim burns. The OAM entered orbit with the payload, which then separated. The payload consisted of the LP probe and its TLI stage, which fired its Star 37 solid motor on the first orbit to place LP on a translunar trajectory. LP fired its own hydrazine propulsion system and entered a 71 x 8500 km x 89.7 deg lunar orbit on Jan 11.
• Lunar Prospector has now reached its final mapping orbit. After trim burns it was in a 99 x 100 km circular orbit, but the uneven lunar gravity field soon perturbed this to 80 x 120 km.
• Lunar Prospector continues in a 100 km lunar polar orbit. On Mar 5, 1998 NASA announced that LP has confirmed the presence of ice in the lunar soil in the polar regions, greatly increasing the possibilities for lunar colonization.
• Lunar Prospector lowered its polar lunar orbit on Dec 19, 1998 from 77 x 122 km to 25 x 55 km.
• Lunar Prospector lowered its orbit again on Jan 29, 1999 to only 25 x 35 km above the lunar surface.
• Lunar Prospector impacted the lunar surface at 09:52 UTC on Jul 31, 1999. Impact site was 42.1E, 87.7S near the lunar south pole. The orbit was raised to a 230 km apogee before the deorbit burn over the lunar farside at 09:19 UTC.