GeodesiaGeodesia SpazialeSpaziale

GeodesiaGeodesia

forma,forma, dimensionidimensioni e campo di e campo di gravitàgravità delladella TerraTerra

e e loroloro variazionivariazioni temporalitemporali

Sputnik 1Sputnik 1

Sputnik 1Sputnik 1

More than twice the size More than twice the size

of a basketballof a basketball

October 4, 1957 October 4, 1957

Sputnik 2Sputnik 2

Larger and heavierLarger and heavier

November 3, 1957November 3, 1957

In the late 1950’s, only 3 or 4 coefficients of the gravity In the late 1950’s, only 3 or 4 coefficients of the gravity

field had been estimated and global geocentric field had been estimated and global geocentric

coordinates were known to perhaps 500 m.coordinates were known to perhaps 500 m.

Modified from Cazenave and Feigl, 1994

Line of nodes

Perturbed Keplerian orbit

3 SLR systems at Grasse3 SLR systems at Grasse

The targetsThe targets

Courtesy of ILRS Courtesy of ILRS

MLROMLRO

A broad range of applications in A broad range of applications in

support of Earth System Sciencesupport of Earth System Science

•• monitoring crustal deformationmonitoring crustal deformation

•• seasea--level variations/changeslevel variations/changes

•• space weatherspace weather

••………………....

After NASA data base, Heflin et al. 2001.8After NASA data base, Heflin et al. 2001.8

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

99.58

99.60

99.62

99.64

99.66

99.68

99.70

-9.41± 0.05 mm/yr

Height (m)

Time

Bologna

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

44.22

44.24

44.26

44.28

44.30

44.32

-6.24± 0.02 mm/yr

Height (m)

Time

Marina di Ravenna

IGS network of over 350 stationsIGS network of over 350 stations

221 stations221 stations

Orbits accuracy <5 cm Orbits accuracy <5 cm

PositionsPositions

VelocitiesVelocities

Horizontal 3 mmHorizontal 3 mm 2 mm/yr2 mm/yr

Vertical 6 mmVertical 6 mm 3 mm/yr3 mm/yr

Latency ~13 daysLatency ~13 days

Polar motion, PM rate, LOD, Polar motion, PM rate, LOD,

zenith tropospheric path delay, zenith tropospheric path delay,

ionospheric TECionospheric TEC

ProductsProducts

Weekly coordinate estimates (~Weekly coordinate estimates (~

cm)cm)

Time series analysisTime series analysis

Zenith path delay Zenith path delay

After After ReilingerReilinger et al., J. Geophys. Res., et al., J. Geophys. Res.,

BO5411, 2006BO5411, 2006

GPS clearly provides now GPS clearly provides now

the motion pattern.the motion pattern.

Relative to Eurasia. GPSRelative to Eurasia. GPS--derived, secular velocity field for the period 1988derived, secular velocity field for the period 1988––2005. 2005.

TopexTopex//PoseidonPoseidon(1992(1992--2006)2006)

JasonJason--1 (20011 (2001-- ) ) JasonJason--2 (20082 (2008-- ))

Courtesy of A. Courtesy of A. CazenaveCazenave

uncertainty ~0.4 mm/yr

Rate: 2.5 +/- 0.4 mm/yrover 2003-2008

Courtesy of A. Courtesy of A. CazenaveCazenave

Sea level is still rising but causes are different:

1993-2003 : Ocean thermal expansion 50%Land ice 40%

2003-2008 : Land ice 80%!

Ocean thermal expansion: <20%

Courtesy of A. Courtesy of A. CazenaveCazenave

Monitoring of mass transport has Monitoring of mass transport has

startedstarted

Monthly mapping of the gravity field over Monthly mapping of the gravity field over

spatial scale from 400 km to 40,000 kmspatial scale from 400 km to 40,000 km

Courtesy of ESACourtesy of ESA

March 17, 2009March 17, 2009

LongLong--time waited for and needed! time waited for and needed!

Mapping the Earth gravity field with Unprecedented accuracy Mapping the Earth gravity field with Unprecedented accuracy

Spatial resolution 100 kmSpatial resolution 100 km

11--2 cm 2 cm geoidgeoid

From ESA SPFrom ESA SP--13041304

Planet Earth is a Planet Earth is a

complex, interconnected complex, interconnected

system. To build an system. To build an

understanding of the understanding of the

whole system requires whole system requires

an increase in our an increase in our

knowledge of its knowledge of its

components and the components and the

ways these interact.ways these interact.

Operational numerical Operational numerical

weather prediction 5weather prediction 5--day day

forecasts of 500forecasts of 500--hPa hPa

geopotential heights over geopotential heights over

the Northern and Southern the Northern and Southern

Hemisphere.Hemisphere.

Operational oceanography 7Operational oceanography 7--

day forecast of seaday forecast of sea--level level

anomaly over the tropical and anomaly over the tropical and

North Atlantic North Atlantic

(courtesy of N. Ferry)(courtesy of N. Ferry)