SWIFTOverview

Slide1: 

The SWIFT experiment on the Chinook Mission: An Overview prepared by Ian McDade Department of Earth and Space Science & Engineering York University Toronto

Slide2: 

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

Slide3: 

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 SWIFT’s unique co-located wind and ozone density measurements The potential of stratospheric wind measurements for improving medium range weather forecasts

SWIFT Science objectives in more detail:: 

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

SWIFT Science Objectives in more detail (continued): 

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

Slide6: 

  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

Brief history and current status: 

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

More detailed history (Chapter 1): 

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

More detailed history (Chapter 2): 

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

Slide10: 

How does SWIFT work?

Slide11: 

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

Slide12: 

The Doppler Imaging Michelson concept as applied on SWIFT 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 Using etalon filters, a single thermal emission line (an ozone rotation-vibration line near 9 mm) is isolated as shown in the left panel

Slide13: 

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

Slide14: 

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

Slide17: 

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. Stratospheric 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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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 SWIFT Instrument Concept (Phase B)

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SWIFT SWIFT Instrument Concept (Phase B) Solid model

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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

Slide21: 

MAP+DR MAP Unconstrained SWIFT Illustrative retrieval noise standard deviations 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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Principal Investigator |Ian McDade (York U.) | Deputy P.I Craig Haley (York U.) | Co.I. Co.I. Co.I. Co.I. Co.I Lead ID&C Lead GDR&SOC Lead GDV Lead GDA&M Lead ECUI&DA 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 ID&C = Instrument Development, Characterization and calibration GDR&SOC = Geophysical Data Retrieval and Science Operations Centre GDV = Geophysical Data Validation GDA&M = Geophysical Data Analysis and Modelling ECUI&DA = Environment Canada User Interface & Data Assimilation SWIFT Science Team Architecture

Slide24: 

SWIFT and Chinook Schedule