We will build a payload to measure Earths gravity field as a
function of altitude for heights of up to 100,000 feet, and compare
our findings to theoretical and experimental high altitude gravity
models.
Slide 4
Analyze and interpret data to find a correlation between
changes in Earths gravity as altitude increases. Compare our data
to theoretical models. Compare our data to results from previous
experiments.
Slide 5
Meet the design specifications provided by LAACES.
Slide 6
Isaac Newton and his second law of motion Gravimeters (absolute
and relative) Past and present gravimetry missions Atmospheric
conditions
Slide 7
Theorized that an external force was pulling objects towards
Earths center His second law states that the net force on an object
is equal to the instantaneous rate of change of that object
Slide 8
From Newtons second law, we can derive the theoretical change
in gravity with altitude
Slide 9
A gravimeter is an instrument that measures gravity Accurate
for up to about 1.1 microgal Expensive Hard to transport Takes a
long time for accurate measurements
Slide 10
Invented by Lucien LaCoste Zero-length spring Previous
experiments have used a variety of relative gravimeter types: GWR
T020 GRACE Geosat DUCKY Ia
Slide 11
Twentieth century physicist and metrologist Co-invented the
modern gravimeter with Arnold Romberg Invented the zero-length
spring in 1932
Slide 12
Exert zero force if at zero length Twisted and coiled springs
create tension Can make pendulums with infinite period
Slide 13
More accurate than zero-length springs Involves levitating a
super-conducting sphere in a stable magnetic field
Slide 14
Gravity Recovery And Climate Experiment Maps Earths gravity
field every 30 days Helps track sea levels, ocean currents, polar
ice sheets, and Earths interior structure
Slide 15
Used radio altimetry to detect momentary altitude deviations
from average orbit Altitude decreases with local gravity increase
Altitude increases with localized gravity decrease
Slide 16
A high altitude balloon payload that measured relative gravity
changes Used a Vibrating String Accelerometer (VSA)
Slide 17
The VSA on the DUCKY Ia payload detected changes in
acceleration along a single axis The difference between the
oscillation frequencies of the two strings is proportional to the
acceleration along the sensitive axis
Slide 18
Gravimeters cannot distinguish between gravitational
acceleration and acceleration due to external forces It is
necessary to obtain additional acceleration measurements from an
inertial reference frame independent of the gravimeter to isolate
gravitational acceleration
Slide 19
Objects travelling east appear to experience a decrease in
gravitational acceleration Objects travelling west appear to
experience an increase in gravitational acceleration Vertical
component of centrifugal pseudo- force
Slide 20
Temperature Decreases with altitude in the troposphere
Increases with altitude in the stratosphere Pressure Decreases as
altitude increases Humidity Approximately 65% in Palestine, Texas
Weather dependent Turbulence Greatest in the troposphere
Slide 21
Temperature, pressure, humidity, and turbulence will vary
during balloon flight We anticipate that gravity measurements will
be most accurate in the stratosphere Gravity should decrease
slightly with increasing altitude
