The SWIFT experiment on

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The SWIFT experiment on the Chinook Mission An
Overview
prepared by Ian McDade Department of Earth and
Space Science Engineering York
University Toronto
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SWIFT the Stratospheric Wind Interferometer
for Transport Studies is a Canadian satellite
instrument designed to make global stratospheric
wind measurements between 15 and 55 km and
provide simultaneous co-located ozone
profiles. Very few satellite measurements of
stratospheric winds exist, so this is something
really new and of great interest to the
international atmospheric science
community SWIFT completed its instrument Phase
B in July and is to start Mission Phase B/C for
implementation on a CSA SmallSat mission called
Chinook scheduled for launch in late 2010
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• OVERALL SCIENCE OBJECTIVES OF SWIFT
• To provide, for the first time ever, global maps
  of vector wind profiles in the stratosphere under
  both daytime and nighttime conditions in order to
  study
• Atmospheric dynamics and circulation in general
• Ozone transport from SWIFTs unique co-located
  wind
• and ozone density measurements
• The potential of stratospheric wind measurements
  for improving medium range weather forecasts

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SWIFT Science objectives in more detail

• Dynamics
• Detailed studies of the Quasi-Biennial
  Oscillation (QBO)
• and the Semi-Annual Oscillation (SAO)
• Equatorial waves and their roles in driving the
• QBO and SAO
• Understanding the influence of the QBO on
  extratropical circulation, e.g., the frequency of
  stratospheric warmings

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SWIFT Science Objectives in more detail
(continued)

• Ozone transport and monitoring
• Studies of the Brewer Dobson circulation
• The use of wind measurements in parcel
  trajectory studies to address the question of
  isolation of the tropical stratosphere
• The determination of the horizontal ozone flux
  and its global budget and interannual variability
  through simultaneous measurement of wind and
  ozone

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Observational goals and required performance
? Obtain vector winds to an accuracy of 3-5 m/s
or better between 15 km and 55 km ?
Simultaneously obtain ozone number densities to
an accuracy of 5 or better (15-30 km) ?
Vertical resolution 1.5 km ? Horizontal sampling
400 km along track ? Continuous near-global
coverage
 
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Brief history and current status

• After a very long gestation period going back
  to
• ? Initial SWIFT concept Gordon Shepherd, Phil
  Merilees, 14th Feb 1994
• ? Incubation with ESA 1998-2000
• ? More incubation with ESA/NASDA/JAXA 2000-2003
• ? The CSA decided in early 2004 to make SWIFT the
  primary instrument for their second SciSat
  mission subsequently named Chinook
• ? SWIFT and partner experiment ARGO are just
  about to start mission phase B/C contract/studies
  for projected launch in Nov 2010

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More detailed history (Chapter 1)

• Initial SWIFT concept Gordon Shepherd, Phil
  Merilees, Feb 1994
• SWIFT testbed built wsf CSA, MSC, EMS, NSERC,
  CRESTech 1996-1998
• SWIFT proposed to ESA as Earth Explorer
  Opportunity Mission, Dec, 1998
• SWIFT selected by ESA 5th out of 27
• (highest ranking atmospheric science proposal)
• ESA endorsed SWIFT submission to NASDA for
  GCOM-A1, Feb, 2000
• ESA funded SWIFT study for GCOM-A1 mission in
  March, 2000
• NASDA selected SWIFT for GCOM-A1 Phase A,
  December 28, 2000
• ESA and CSA contract EMS Technologies for Phase A
  Studies, 2001-2003
• ESA fund Assimilation Studies to assess SWIFT
  impact, 2002-2003
• NASDA (now JAXA) re-scope GCOM-A1 and rename
  GOSAT fall 2002
• ESA select Noveltis to develop SWIFT GDR system,
  Nov 2003
• The CSA releases RFP for SWIFT Phase B on
  GOSAT, October 2003

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More detailed history (Chapter 2)

• JAXA re-scope GOSAT and disembark SWIFT, Dec
  2003
• CSA and ESA investigate alternative flight
  opportunities for SWIFT
• 2004
• CSA assesses SWIFT on a CSA SmallSAT 2004/2005
• CSA selects EMS for 9 month SWIFT Phase B
  study on a SmallSAT
• Fall 2004
• CSA selects GPS instrument as secondary payload
  with SWIFT and
• creates the Chinook Mission March 2005
• EMS Phase B PDR for SWIFT on the Chinook
  Mission July 2005

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How does SWIFT work?
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SWIFT is based on the Doppler Imaging
Michelson concept already used by the WINDII
instrument on UARS. WINDII measured Doppler
shifts in the wavelengths of airglow emission
lines in the visible region of the spectrum to
determine winds in the upper mesosphere and
thermosphere and made remarkable discoveries
about atmospheric tides and mesosphere and
thermosphere dynamics SWIFT will do the same
thing but use a thermal emission line from ozone
in the mid IR region to push this successful
technique down into the stratosphere
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The Doppler Imaging Michelson concept as applied
on SWIFT
Using etalon filters, a single thermal emission
line (an ozone rotation-vibration line near 9
mm) is isolated as shown in the left panel
The wind produces a Doppler shift in the emission
line A Michelson interferometer produces the
Fourier transform (right) of the input line
spectrum (left) The phase shift of a single
fringe gives the Line of Sight (LOS) wind speed
as illustrated on the next slide

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Phase measurement and the LOS wind speed
The interferometer is phase-stepped to four
positions, yielding I1, I2, I3 and I4 From these
the phase is computed, and from this the apparent
LOS wind speed The radiance, Iav, is the average
of I1, I2, I3 I4 and is determined by the ozone
density and atmospheric temperature This
analysis is performed for each tangent height in
the image field
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SWIFT viewing geometry (side view)
Image field 1 degree square (50 km x 50 km) made
up of 81x81 pixels each 0.64 km high
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SWIFT viewing geometry (top view)
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For each tangent height in the limb image SWIFT
obtains a LOS wind speed (after correcting for
the satellite velocity and Earth rotation
components) By observing at two orthogonal (or
near orthogonal) directions as shown in the next
slide, SWIFT can resolve the wind speed and
direction i.e., measure the vector wind
profiles
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SWIFT viewing geometry SWIFT measures line of
sight wind speeds in two orthogonal directions
Image field 1 x 2 (50 km x 100 km) made up of
81x 162 pixels each 0.64 km high/wide. Stratosphe
ric coverage from 15 km to 65 km

• 650 km orbit has tangent distance of 2860 km.
• Orthogonal FOVs resolve full horizontal wind
  vector
• Spacecraft velocity means 8 minute delay
  between orthogonal components

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SWIFT Instrument Concept (Phase B)

• No pointing mirrors
• Satellite controls pointing with independent
  3-axis system
• Single etalon, tilted to tune for satellite
  Doppler shifts, isolates the ozone line for each
  viewing direction

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SWIFT Instrument Concept (Phase B) Solid model
SWIFT
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SWIFT Retrieval algorithm Uses iterative
Optimal Estimation with a forward model based on
a SWIFT Instrument Simulator (SIS) and an
atmospheric Radiative Transfer model, together
with the Maximum a Posteriori (MAP) solver of
Rodgers (2000), to find the FOV wind profile and
ozone density profiles most consistent with the
raw observations
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SWIFT Illustrative retrieval noise standard
deviations
MAPDR
MAP
Unconstrained
Wind and ozone random error standard deviations
(lines) and sample retrieval results from a
single realization/simulation (points) with
measurement noise
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SWIFT Science Team
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SWIFT Science Team Architecture
Principal Investigator Ian McDade (York U.)
Deputy P.I Craig
Haley (York U.) Co.I.
Co.I. Co.I. Co.I.
Co.I Lead IDC Lead GDRSOC
Lead GDV Lead GDAM Lead ECUIDA J
.Drummond B. Solheim K. Strong
T. Shepherd Y. Rochon (U. of T.)
(York U.) (U. of T.)
(U. of T.) (E.C.) Plus other
Co-Investigators now being identified IDC
Instrument Development, Characterization and
calibration GDRSOC Geophysical Data Retrieval
and Science Operations Centre GDV Geophysical
Data Validation GDAM Geophysical Data Analysis
and Modelling ECUIDA Environment Canada User
Interface Data Assimilation
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SWIFT and Chinook Schedule
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