Airglow studies using observations made with the GLO Instrument on the Space Shuttle

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Airglow studies using observations made with the
GLO Instrument on the Space Shuttle

• REC 2002
• Ana Luisa Alfaro

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Outline

• Introduction
• GLO instrument
• Airglow
• Gravity waves
• Tomographic inversion Least-squares method
• Tests with synthetic data
• Future work

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The GLO instrument

• Set of five imaging spectrographs
• (1150Å to 9000Å)
• Imagers
• TV camera
• Shuttle missions 53, 63, 69, 74 and 85

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Segment of a GLO spectral image
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Introduction
Dayglow Nightglow

• Near UV to mid-IR
• 80 - 100km

Airglow

• Processes
• Excitation of atoms and molecules
• Recombination of atoms to form molecules
• Recombination of ions and electrons to form
  neutral atoms or molecules.

• Composition of the atmosphere
• Excitation and deactivation mechanisms

Gravity wave activity
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Gravity waves

• Localized disturbances
• thunderstorms, deep convection regions, front
  systems in the lower atmosphere, and orographic
  forcing due to wind flow over mountains.
• Carry energy and momentum
• In the mesosphere and lower thermosphere, impact
  on the thermal structure and circulation
• Airglow intensity variations are optical
  signatures of gravity wave dynamics

Gravity waves have been studied as a key element
in the spatial and temporal variations above the
troposphere.
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Tomography

• Tomography is used to determine the internal
  structure of an object
• Tomographic inversion can be used to estimate 2-D
  distribution of VER from from a series of
  consecutive 1-D limb scans

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Tomographic inversion cont...
Jtot is the total number of elements for which
the volume emission rates are to be
recovered i1,.., Nobs Nobs is the total of
independent line of sight measurements

• Reconstruction grid
• The measured airglow limb brightness, Oi, can be
  expressed in terms of the volume emission rates
  within the grid elements weighted by the
  geometric path length, Lij, through each element.

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The least-squares method
The least-squares method is an iterative
algorithm
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Tests

• First stage
• 85km - 105km
• 1km intervals
• 40 degrees segment
• Grid elements size 1km high x 0.4deg wide
• 2000 grid elements
• 300 km altitude

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TESTS
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TESTS
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TESTS
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TESTS
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TESTS
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Tests _at_ GLO resolution

• Second stage
• 53km - 117km
• 4km intervals
• 97.5 degrees segment
• Grid elements size 4km high x 1.3 deg wide
• 1500 grid elements
• 400 km altitude

• First stage
• 85km - 105km
• 1km intervals
• 40 degrees segment
• Grid elements size 1km high x 0.4deg wide
• 2000 grid elements
• 300 km altitude

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TESTS _at_GLO resolution
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TESTS _at_GLO resolution
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TESTS _at_GLO resolution
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TESTS _at_GLO resolution
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TESTS _at_GLO resolution
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TESTS _at_GLO resolution
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Future work

• The inversion routines will be applied to actual
  GLO observations
• The emission of the O2(0-0) atmospheric band will
  be studied first since it is the brightest
  emission in the nightglow spectrum observed from
  orbit
• Absorption has to be taken into account, this
  will be done by using existing O2(0-0) line by
  line absorption code