MARSCHALS: a new airborne millimetre-wave

limb-sounder for the UTLS

COST UTLS WorkshopESTEC, 11-13 March 2004

Victoria Jay, Brian Kerridge, Jolyon Reburn, Richard Siddans, Brian Moyna, Matthew Oldfield, Dave Matheson

Earth Observation and Atmospheric Science Division, SSTD Rutherford Appleton Laboratory

Introduction

• MARSCHALS

– Millimetre-wave Airborne Receiver for Spectroscopic CHaracterisation of Atmospheric Limb-Sounding

– a new airborne mm-wave limb sounder for the UTLS

– built under ESA contract by a consortium led by Rutherford Appleton Laboratory in the UK

• Contents

– Background, scientific rationale

– Instrument description

– Current status

– Future Plans

Marschals Objectives

• Demonstrate the capability of the mm-wave limb-sounding technique, to be employed by MASTER, to sound H2O, O3 and CO in the UT/LS region

– MASTER: proposed spaceborne limb sounder to measure thermal emission spectra at mm and sub-mm wavelengths

– mm-wave region: where extinction by aerosol and polar stratospheric clouds is negligible and extinction by cirrus clouds is low

• Participate in field campaigns in its own right (strat-trop exchange, radiative forcing, UT&LS chemistry)

MARSCHALSon Geophysica

The Marschals Instrument

• To simulate UTLS capabilities of MASTER as closely as possible, deployment on:– Geophysica near 20 km (primary carrier)

• Potential to retrieve horizontal and vertical structure in UTLS H2O, O3 and CO fields

– High-altitude balloon (secondary carrier) near 35 km• Capability for profile retrieval up to the mid-

stratosphere

Instrument Details

• MARSCHALS:– High efficiency antenna (22 cm) to make precise

elevation scans though the atmosphere– Heterodyne receiver concept– SSB receivers – 200 MHz spectral resolution (cf 50 MHz for MASTER)– Sideways viewing (cf rearwards for MASTER)

Instrument Details

• Bands:

– B: 294 - 305 GHz O3, pointing

– C: 316.5 – 325.5 GHz H2O

– D: 342.8 – 348.8 GHz CO– Modular design: more bands

can be added• Baseline scan sequence:

– -2 to 21 km in 1 km steps

MASTER Bands

OCM

• Optical Cloud Monitor:

– CCD array coupled to standard lens and broad-band filter (835-875nm)

– Records near-IR sunlight scattered in limb direction

• to identify cloud-free measurements for initial data analysis

• to indicate cloud conditions of each mm-wave measurement for analysis and interpretation, e.g.

– confirm mm-wave insensitivity to cloud

– relate mm-wave retrieved trace gas abundances to cloud

SAGE-II Cloud Climatology

Cirrus Extinction vs Wavelength

Retrieval simulations - PrecisionBand B O3

MARSCHALS (aircraft)

MASTER

MARSCHALS (balloon)

% Error % Error

Alt

/ km

Alt

/ km

Band C H2O

% Error

Alt

/ km

Band D CO

Structural Test Model, May 2002

Structural Test Model, May 2002

Jan 2004

Current Status

• Instrument ~ 95% complete• Two RAL receivers, bands C and D, each with 12 GHz of

instantaneous bandwidth (@ 200MHz resolution)• Need to pass EMC test before flight• Characterisation of the full instrument is underway• L1 software ready

Deployment plans

• Funding for initial test flight and campaigns from EU APE-INFRA and ESA MALSAC

• Geophysica test flight March cancelled– Alternatives being investigated

• Rescheduled Geophysica flight (May/June earliest)• Jungfraujoch ?

• Scientific flights in future Geophysica campaigns– Alongside MIPAS-STR and SAFIRE-A

Summary

• MARSCHALS– New mm-wave airborne limb sounder

– O3, H2O, CO and other trace gases in the UTLS

– First flight soon

• See poster: Tomographic limb-sounding of the Upper Troposphere and Lower Stratosphere– 2-D retrieval simulations for MASTER

MARSCHALS L1 ATB ReviewBaseline Scan Sequence

– Scan -2km to 21km tangent height, integrating for 0.25s at each observation state.

– At each tangent height– 7 observations, 2 RF

switches: 50ms each– Total time per tangent

height: 2.2s– Total time for sequence:

52.8s (antenna motion during a cal.load view).

– In addition, limb scan– Starts hot/cold observation – Ends with cycle through all

bands at max. elevation (above horizontal).