S 1The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE

Gravity Field and Steady-State Ocean Circulation

Explorer(GOCE)

Graphics files in directories:

d:\nico\proj\GOCE\graphics\*

d:\nico\proj\GOCE\GranadaIIreport\graphics

d:\images\geo

Graphics files in directories:

d:\nico\proj\GOCE\graphics\*

d:\nico\proj\GOCE\GranadaIIreport\graphics

d:\images\geo

S 2The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE Issues of Concern

Earthquakes &volcanic activities

Thermohalineocean circulation & heat transport

Ice Sheet Melting

Global unificationof height system

Sea level change

S 3The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE International Programme

• International Lithosphere Programme (ILP)

• Int. Decade of Natural Disaster Reduction (IDNDR)

• International Association of Geodesy (IAG)

• World Climate Research Programme (WCRP)- GEWEX- WOCE/CLIVAR- GCOS/GOOS- ACSYS/CLIC

• International Geosphere/Biosphere Program (IGBP)- LOICZ

• Intergovernmental Oceanographic Commission (IOC)- GLOSS

Earthquakes andVolcanic Activities

Global Unification ofHeight System

Thermohaline Ocean Circulation and Transportof Heat.

Ice Sheet Melting

Sea Level Change

S 4The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE Research Goals

• Solid Earth Physicsanomalous density structure of lithosphere and upper mantle

• Oceanographydetermination of dynamic ocean topography

• Ice Sheetsimproved knowledge of ice sheet balance

• Geodesyunified height systems, “levelling by GPS”

and from the above improved Sea Level Change Studies

S 5The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE

• determine the Earth’s gravity field with an accuracy of

1 mgal (1 mgal = 10-5 m/s2 )

• determine the geoid (= equipotential surface for a hypothetical ocean at rest) with an accuracy of 1 cm

• achieve this at length scales down to L = 100 km

(degree and order 200)

Mission Objectives

S 6The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE Presentation Outline

• Mission Rationale

• Science & Application

• Mission Design

• Performance

• Conclusions

S 7The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE

• terrestrial gravity anomalieslarge unsurveyed areas, heterogeneous data, offsets and biases

• geoid mapping via satellite altimetry not acceptable for oceanography

• satellite orbit analysis- only large spatial scales are satisfactory - heterogeneous data - error correlation

Mission Rationale

Limitations of Existing Gravity Field Data

S 8The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE Mission Rationale

Incomplete Data Coverage

gravdensBGI.gifgravdensBGI.gif

S 9The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE

GEOID

terrainALTIMETRY

Mission Rationale

Limitation with Satellite Altimetry

geoid_altim2.pptgeoid_altim2.ppt

S 10The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE egm.bw.epsegm.bw.eps

Mission Rationale

Signal Accuracy versus Spatial Scales

S 11The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE

• Satellite-to-Satellite Tracking in High-Low Mode

SST-hl

• Satellite-to-Satellite Tracking in Low-Low Mode

SST-ll

• Satellite Gravity Gradiometry

SGG

Mission Rationale

Spaceborne Gravity Field Methods

S 12The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE

GPS - satellites

Earthmassanomaly

3-D accelerometer

Mission Rationale

SST - hl

sst_hl.epssst_hl.eps

SST - hl

S 13The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE

SST - hl

GPS - satellites

Earthmassanomaly

Mission Rationale

Combined SST - ll and SST - hl

sst_ll.epssst_ll.eps

SST - ll

S 14The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE

SGG

Earthmassanomaly

GPS - satellites

Mission Rationale

Combined SGG and SST - hl

gradiometry.epsgradiometry.eps

SST - hl

S 15The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE

• Orbit as low as possible and near polar

• Uninterrupted tracking in 3-D

• Isolation of gravitational signal

• Amplification of gravitational signal by principle of differentiation

Mission Rationale

Gravity Field Satellite Design Criteria

S 16The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE

• Orbit altitude 250 km and sun-synchronous (inc.= 96.5˚)

• Uninterrupted and 3-D high-low tracking with GPS satellites relative to ground network

• Drag-free system and elimination of residual drag common mode rejection

• Gravity signal amplification by gradiometry (differential accelerometry)

in addition: all component gradiometer

Mission Rationale

GOCE versus Design Criteria

S 17The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE Mission Rationale

Full Tensor Gradiometer Measurements

goce_eqn.jpggoce_eqn.jpg

gravity gradient

angular acceleration

angular velocities

acceleration differentiation

S 18The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE

translationalforces

angularforces

starsensors

drag control angular control

*

*GPS/GLONASS

SST -hl

GRAVITY GRADIOMETER

measures:

GRAVITY GRADIENTS

angular accelerations

common mode accelerations

A B

Mission Rationale

Instrument Concept

satellit.pptsatellit.ppt

S 19The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE Mission Rationale

Uniqueness

CGG_fill_bw.eps

CGG_plainx.eps

CGG_overlayx.eps

CGG_fill_bw.eps

CGG_plainx.eps

CGG_overlayx.eps

SGG achieves highest attainable resolution SGG and SST-ll are complementary

S 20The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE Mission Rationale

The 3-D structure of the Gravity Field

vik.bw.epsvik.bw.eps

S 21The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE Mission Rationale

The 3 -D structure of the Error Coefficient

S 22The Four Candidate Earth Explorer Core Missions Consultative Workshop 12-14 October 1999, Granada, Spain, Revised 2006-01-05 by CCT

GOCE Mission Rationale

The Interdisciplinary Research

GIGGOS.doc (.eps)GIGGOS.doc (.eps)

Earth System Model

- ocean- ice sheet

- lithosphere- mantle

- core

Solid Earth Physics

Geodesy

Cryosphere Oceanography

Sea Level Change