Encyclopedia of the Solar System 2nd ed

2001 Mars

Odyssey

U.S., NASA

MarsExplorationProgram

7-Apr-2001

Completed

primarymission;extendedmissionunderway

Mars

400 km altitude

circular polarmapping orbit

Over 2

Mars yearscompleted,Extendedmission inprogress

HPGe,

passivelycooled

Boron-loaded

plasticscintillators(NS);Stilbene and 3 He tubes(HEND

d)

Distribution of

water-equivalenthydrogen andhigh-latitude stratigraphy;seasonal variations inCO

2

ice and

noncondensable gasses;and global maps of majorand radioactive elements

MESSENGER

U.S., NASA

DiscoveryProgram

3-Aug-2004

Cruise phase

Mercury

Elliptical polar orbit

with periapsis at200 km altitude, 60

◦N latitude,

15,000 kmapoapsis

b

1 year starting

in 2011

b

HPGe, actively

cooled

6 Li-loaded glass

andboron-loadedplasticscintillators

Maps of elemental

composition in thenorthern hemisphere;search for polar hydrogendeposits

Dawn

U.S., NASA

DiscoveryProgram

Summer, 2007 Perparing for

launch

e

Vesta and

Ceres

Survey, high, and low

altitude circularpolar mappingorbits

b

6 months at

eachasteroid

b

CdZnTe and

BGO

6 Li-loaded glass

andboron-loadedplasticscintillators

Global maps of major and

radioactive elements andice constituents (H andC)

Selene

Japan

2007, TBD

Preparing for

launch

e

Moon

100 km circular polar

mapping orbit

1 year

HPGe, actively

cooled

None

Abundance of major and

radioactive elements.

aRefers to the time periods during which gamma ray and/or neutron data were acquired.bObjectives are listed for Mars Observer, MESSENGER, Dawn, and Selene.cNeutron and gamma ray spectrometers were flown on Phobos I, which was launched on 7-July-1988; however, Phobos I was lost during the cruise phase of the m

ission. The Mars 4 and 5 missions (U.S.S.R., 1973) flew identical

sodium iodide gamma ray spectrometers. A few gamma ray spectra were acquired by Mars 5 while in an elliptical orbit around Mars (apoapsis 32,560 km, per

iapsis 1760 km, inclination 35

◦to the equator).

dThe high energy neutron detector (HEND) was provided by the Russian Federation.eFuture missions that have advanced past the planning stage are listed.

777