 Jeff
Weinell
 Jason Mueller
 Brittany Dupre
 Mission
Goal
• Science Objectives
• Technical Objectives
 Science
Background
 Conclusion
 References
 Questions
 We
will build a payload to measure Earth’s
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.
 Analyze
and interpret data to find a correlation
between changes in Earth’s gravity as altitude
increases.
 Compare our data to theoretical models.
 Compare our data to results from previous
experiments.
 Meet
the design specifications provided by
LAACES.
 Isaac
Newton and his second law of motion
 Gravimeters (absolute and relative)
 Past and present gravimetry missions
 Atmospheric conditions
 Theorized
that an external force was pulling
objects towards Earth’s center
 His second law states
that the net force on
an object is equal to
the instantaneous
rate of change of
that object
 From
Newton’s second law, we can derive the
theoretical change in gravity with altitude
A
gravimeter is an instrument that measures
gravity
 Accurate for up to about 1.1 microgal

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
Expensive
Hard to transport
Takes a long time for
accurate measurements
 Invented
by Lucien LaCoste
• Zero-length spring
 Previous
experiments have
used a variety of relative
gravimeter types:
• GWR T020
• GRACE
• Geosat
• DUCKY Ia
 Twentieth
century
physicist and
metrologist
 Co-invented the
modern gravimeter
with Arnold Romberg
 Invented the
zero-length spring
in 1932
 Exert
zero force if at zero length
 Twisted and coiled springs create tension
 Can make pendulums with infinite period
 More
accurate than zero-length springs
 Involves levitating a super-conducting sphere
in a stable magnetic field
 Gravity
Recovery And Climate Experiment
 Maps Earth’s gravity field every 30 days
 Helps track sea levels, ocean
currents, polar ice sheets,
and Earth’s interior structure
 Used
radio
altimetry to detect
momentary
altitude deviations
from average orbit
 Altitude decreases
with local gravity
increase
 Altitude increases
with localized
gravity decrease
A
high altitude balloon
payload that measured
relative gravity changes
 Used a Vibrating String
Accelerometer (VSA)
• 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
• 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
 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 pseudoforce
 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
 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
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http://www.globalsecurity.org/space/systems/images/global_topo.jpg
http://www.cosmosmagazine.com/features/online/1678/gravity-ball
http://www2.mssu.edu/seg-vm/bio_lucien_lacoste.html
http://www.currentresults.com/Weather/Texas/humidity-annual.php
http://www.ualberta.ca/~dumberry/gravity.htm
http://www.britannica.com/EBchecked/topic/242391/gravimeter
http://www.gwrinstruments.com/pdf/Geothermal_Brochure_Prod_Rev1_
4PG.pdf
http://www.cage.curtin.edu.au/~will/grav_anoms.htm
http://www-scf.usc.edu/~kallos/gravity.htm
http://www.dtic.mil/cgibin/GetTRDoc?AD=ADA202985&Location=U2&doc=GetTRDoc.pdf
http://www.jclahr.com/science/psn/zero/winding/gravity_sensor.html
http://www.merriam-webster.com/dictionary/free%20oscillation
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http://www.microglacoste.com/fg5Principle.php
http://www.jpl.nasa.gov/news/press_kits/gracelaunch.pdf
http://ibis.grdl.noaa.gov/SAT/gdrs/geosat_handbook/docs/chap_1.htm
http://www.srh.noaa.gov/jetstream/atmos/layers.htm
http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/michel.html
http://www.splung.com/content/sid/2/page/newtons_laws
http://www.nasa.gov/audience/foreducators/k4/features/F_Measuring_Gravity_With_Grace.html
http://www.cleonis.nl/physics/phys256/eotvos.php
http://www.leakandflowtesters.com/pressure_decay.htm
http://observatory.ou.edu/Oct3-11.html
http://www.centennialofflight.gov/essay/Theories_of_Flight/atmosphere/
TH1G3.htm
http://ethesis.helsinki.fi/julkaisut/mat/fysik/vk/virtanen/studieso.pdf
http://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html
http://hep.physics.indiana.edu/~rickv/Standing_Waves_on_String.html
http://laspace.lsu.edu/aces/BalloonCourse/Introduction/Intro%201%20%20Overview%20of%20LA%20ACES.ppt