The SWIFT experiment onThe SWIFT experiment onthe Chinook Mission:the Chinook Mission:

An OverviewAn Overview

prepared byprepared by

Ian McDadeIan McDade Department of Earth and Space Science Department of Earth and Space Science && Engineering Engineering

York UniversityYork UniversityTorontoToronto

SWIFTSWIFT the

SStratospheric WWind IInterferometer for TTransport SStudiesis 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 Chinook scheduled for launch in late 2010

OVERALL SCIENCE OBJECTIVES OF SWIFTOVERALL 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

SWIFTSWIFT Science objectives in more detail:

DynamicsDynamics

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

SWIFTSWIFT Science Objectives in more detail (continued)

Ozone transport and Ozone transport and monitoringmonitoring

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

 

Observational goals and required Observational goals and required performanceperformance

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 statusBrief 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

ChinookChinook

● SWIFTSWIFT and partner experiment ARGOARGO are just about to start mission phase B/C contract/studies for projected launch in Nov

2010

More detailed history More detailed history (Chapter 1)(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 More detailed history ((Chapter 2)Chapter 2)

• JAXA re-scope GOSAT and disembark SWIFT, Dec 2003

• CSA and ESA investigate alternative flight opportunities for SWIFT2004

• CSA assesses SWIFT on a CSA SmallSAT 2004/2005

• CSA selects EMS for 9 month SWIFT Phase ‘B’ study on a SmallSATFall 2004

• CSA selects GPS instrument as secondary payload with SWIFT andcreates the Chinook Mission Chinook Mission March 2005

• EMS Phase ‘B’ PDR for SWIFTSWIFT on the Chinook Mission Chinook Mission July 2005

How does SWIFTSWIFT work?

SWIFTSWIFT 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 visiblevisible 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

SWIFTSWIFT will do the same thing but use a thermal emission line from ozone in the mid IRmid IR region to push this successful technique down into the stratosphere

The Doppler Imaging Michelson concept as applied on SWIFTSWIFT

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

W avelength,

Inte

nsity

Path D ifference, D

Inte

nsity

~10 fringes5

Line Spectrum Interferogram

Using etalon filters, a single thermal emission line (an ozone rotation-vibration line near 9 m)

is isolated as shown in the left panel

Phase measurement and the LOS wind speedPhase 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

A'

Iav

I1I4

Path Difference

I23I

Idrk

Ibkg

Fring

e I n

tens

i ty

SWIFT viewing geometry 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

SWIFT viewing geometry SWIFT viewing geometry (top view)

For each tangent height in the limb image SWIFTSWIFT 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, SWIFTSWIFT can resolve the wind speed and direction – i.e., measure the vector

wind profiles

SWIFTSWIFT viewing geometrySWIFT 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

SWIF

T

on Chin

ook

FOV 1 and 2

• 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

• 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

SWIFTSWIFT Instrument Concept (Phase B)

SWIFT

SWIFTSWIFT Instrument Concept (Phase B)Solid model

SWIFTSWIFT 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

MAP+DR

MAP

Unconstrained

SWIFTSWIFT 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

SWIFTSWIFT Science Team

Principal Investigator |Ian McDade (York U.)

|Deputy P.I

Craig Haley (York U.)|

Co.I. Co.I. Co.I. Co.I. Co.ILead 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 calibrationGDR&SOC = Geophysical Data Retrieval and Science Operations Centre

GDV = Geophysical Data ValidationGDA&M = Geophysical Data Analysis and Modelling

ECUI&DA = Environment Canada User Interface & Data Assimilation

SWIFTSWIFT Science Team Architecture

SWIFT and ChinookSWIFT and Chinook Schedule