PROGRAM TITLE:	Solid Earth Science
ACTIVITY STREAMS:	Process Studies, Observation and Data 
SCIENCE ELEMENT:	Solid Earth Processes
				Climate and Hydrologic Systems


SCIENTIFIC MERIT:  The goal of the Solid Earth Branch is to improve 
our understanding of the evolution, structure, and dynamics of the 
Solid Earth's interior and surface by testing hypotheses through a 
vigorous program of measurement and analysis of space-based 
geodetic, remote sensing, space-based geopotential, field, laboratory, 
and related data.   The branch focuses on programs which a) are 
responsive both to the solid earth science research community and to 
the requirements of the USGCRP, and b) can be fruitfully addressed 
using technologies and approaches appropriate or unique to NASA. 
The following paragraphs describe their development, evolution, and 
progress to date of four programs developed under these criteria.

FLINN/DOSE :  Fiducial Laboratories for an International Natural 
Science Network  (FLINN) Goal:  To provide a globally distributed, 
high resolution space geodetic reference network for geophysical 
research.The study of the precise reference frame of the Earth and its time 
variations are among the most central unifying themes in the history 
of science.  Working with some 45 countries NASA provides the 
technology development leadership, experimental observation 
coordination, and data archiving and distribution for an international 
Satellite Laser Ranging (SLR), Very Long Baseline Interferometry 
(VLBI), and Global Positioning System (GPS) observation program 
which monitors global plate motion, regional horizontal and vertical 
crustal deformation, earth rotation and oceanic/atmospheric angular 
momentum changes, day length variation, sea-level change, post-
glacial rebound.  SLR also provides an important service through high 
resolution tracking of a cadre of satellites including TOPEX, LAGEOS I 
& II, ETALON I & II, ERS-1, AJISAI, and Starlette. 

Dynamics of the Solid Earth (DOSE) Goal:  To characterize crustal 
deformation in regions of active tectonic activity and the processes 
driving solid earth's dynamics
This area includes atmosphere angular momentum variations, ocean 
tides and currents, and core flow dynamics and angular momentum 
transfer between the various interfaces of this complex system. 
These studies are aimed at better understanding the physical 
mechanisms of this transfer, how it evolves and what the 
consequences are of these momentum transfers within the Earth 
System as a whole.  NASA currently supports campaigns to measure 
crustal deformation in Arctic, Asian, North American, and South 
American regions of active tectonics. NASA is developing of real time 
GPS-based monitoring of the San Andreas Fault system with the 
Permanent GPS Geophysical Array (PGGA) and GPS monitoring of the 
volcanologically active Long Valley Caldera as pilot efforts in natural 
hazards reduction.  As measurements of earth rotation and temporal 
gravity field variations become more accurate they will place 
stronger constraints on  Global Climate Modeling models, and snow 
and ice distribution models for both past and present.  

Volcano-Climate Interaction Goal:  To understand volcano-
atmospheric interaction and the influence of volcanic activity on past, 
present and future climate changeMajor volcanic eruptions can effect a short 
term influence on climate over a regional to global scale which can 
modify/obscure the signature of other causes of climate change including 
anthropogenic contributions.  NASA selected eleven investigations in 1991 to 
study topics including volcanic gas and aerosol sources (including 
petrochemistry of magmas), their concentrations in plumes, and 
spectral characterization; remote detection and tracking of plumes, 
modeling the geometry and dynamics of plumes; and modeling the 
effect of volcanic gasses and aerosols on atmospheric chemistry and 
climate.  We plan a follow-on solicitation for FY94.  

Geopotential Fields Goals: To characterize the mechanisms of main  
magnetic field  generation and reversal;  To produce an improved 
gravity geoid for purposes of improving models of ocean circulation 
and earth's interior structure, composition, and dynamics
A fundamental problem remaining in the field of solid earth science 
is understanding how  dynamics at the earth's center generates the 
earth's magnetic field.  Long-term (decade) monitoring of the earth's 
magnetic field from space is the most promising approach  to this 
problem.  To address this NASA developed the Gravity and Magnetics 
Earth Surveyor together with the French government.  NASA has also 
developed a collaboration with the Danish Government to launch the 
proposed ¯rsted Satellite. The continuous monitoring of the main 
magnetic field into the year 2002 by ¯rsted and then GAMES will 
provide the unprecedented level of data to characterize field-
generating core dynamics and the processes of magnetic field 
polarity reversal.  The availability of simultaneously measured 
gravity & magnetic fields will greatly advance our knowledge of 
source distributions.  

Global Topography Goals:  1)  To obtain a global, high-resolution, 
high-accuracy digital elevation data set of the Earth's continents and 
ice caps, as well as information on vegetation heights.; and,  2)  To 
understand the processes related to evolution of the landscape 
through study of the Earth's surface topography using digital 
elevation data.  Topography constitutes a critical data set for a broad range of 
earth science disciplines: hydrology, ecology, cryospheric studies as well as 
solid earth science.  It is a fundamental geophysical parameter 
reflecting the interaction of aggredational and degredational 
processes, largely determined by internal tectonics modified by 
denudation driven by climate/weather and  gravitational forces, and 
human activity.  NASA is developing a spaceborne system to acquire 
and analyze global digital topographic data.  

STAKEHOLDERS:  This program plays a lead role in the Global 
Geodetic Network (~45 countries, ~80 agencies including NOAA) 
which monitors global plate motion, crustal deformation (including 
earthquake research), and sea level change; participates as major 
partner with NOAA and USNO in the U.S. National VLBI Program 
which provides an absolute reference frame for detecting such 
motions; participates with NOAA,the Smithsonian, DOE, NSF and the 
U.S. Geological Survey in tracking  volcanological events and their 
consequences, participates with DMA in producing update to the 
World Geodetic Standard (WGS) 84 (used by US agencies, NATO 
members, & other non-US agencies), participates with USGS, NSF, 
FEMA, DOE, NOAA in Subcomiittee on Natural Disaster Reduction.

POLICY RELEVANCE:  Differentiate effects of global warming (vs 
regional tectonics, subsidence, etc) on sea level; monitor and model 
short term effects on climate of natural volcanological phenomena; 
provide means of improving ocean circulation models (thus earth's 
surface heat budget) through improved gravity field characterization; 
improve understanding of earthquake and volcanologic processes 
with goal of reducing hazard to human life from these sources.

				NASA Headquarters Code YSG
				Washington, D.C.  20546
				telephone: 202/358-0273
				fax: 202/358-3098
				e-mail: M.Baltuck/omnet