Encyclopedia of the Solar System 2nd ed

TABLE

1

Summary of orbital planetary science and exploration missions with gamma ray and/or neutron spectrometers. Missions prior to Apollo,including Luna and Ranger, are not listed.

Country/

Launch

Planet or

Mapping

Gamma ray

Neutron

Mission

Program

date(s)

Status

minor body Orbit

duration

a

spectrometer

spectrometer

Results or Objectives

b

Apollo 15 and 16 U.S.

26-Jul-1971

16-Apr-1972

Completed

Moon

Equatorial orbit

covering 20% ofthe lunar surface

10.5 days

(Apollo 15and 16combined)

NaI(Tl) with

plastic anti-coincidenceshield

None

Maps of major and

radioactive elements,including Fe, Th, and Ti.

Phobos II

c

U.S.S.R.

12-July-1988

Lost during

Phobosencounter

Mars and

Phobos

Elliptical, equatorial

orbit, 900 kmperiapsis, 80,000km apoapsis

2 orbits

analyzed

CsI(Tl)

None

Abundances for O, Si, Fe, K

and Th in two equatorialregions in the westernhemisphere

Mars Observer

U.S., NASA

MarsExplorationProgram

25-Sep-1992

Lost prior to

orbitalinsertion

Mars

400 km altitude

circular polarmapping orbit

b

1 Mars year

b

HPGe,

passivelycooled

Boron-loaded

plasticscintillators

Global maps major

elements andwater-equivelenthydrogen (Objectives notachieved)

Near Earth

AsteroidRendezvous(NEAR)

U.S., NASA

DiscoveryProgram

17-Feb-1996

Completed

mission

Eros

Useful data acquired

followingsuccessful landingon Eros

7 days on the

surface

NaI(Tl) with

BGO antico-incidenceshield

None

Abundances for O, Mg, Si,

Fe, and K

Lunar

Prospector

U.S., NASA

DiscoveryProgram

6-Jan-1998

Completed

mission byplannedimpact in asouth polarcrater

Moon

High and low altitude

circular polarmapping orbits(100 km and 30km, respectively)

300 days at

highaltitude;220 days atlow altitude

BGO with

boron-loadedplastic anti-coincidenceshield

3 He gas

proportionalcounters andboron-loadedplasticscintillator

Discovery of enhanced

water-equivalenthydrogen associated withpolar cold traps; globalmaps of major andradioactive elements

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