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THE MTG-IRS MISSION

Stephen Tjemkes, Stefano Gigli,

Gary Fowler, Rolf Stuhlmann

EUMETSAT

2 NWC-SAF 215 Users‘ Workshop: ref: EUM/MTG/VWG/15/793016

Overview

• The MTG-IRS Mission• The MTG-IRS Instrument, design and main

performance• The MTG-IRS Level 1B data • L2 Processing• Data volume and dissemination


The MTG-IRS Mission

The Post-MSG user consultation process identified the following user needs:• Information on vertical structure of moisture,

temperature and wind at high spatial and temporal resolution,

• support to emerging operational air-chemistry and air-quality applications.


The MTG-IRS Instrument: high level requirements

Analysis of these needs by remote sensing experts resulted observational requirements:• Sampling at moderate high spectral,

• Sampling of a full disc within 60 minutes,

• Sampling at high spatial resolution.


The MTG-IRS Instrument: Characteristics

These requirements resulted in the design of MTG-IRS instrument:

• Mounted on MTG-S platform• Observations in two broad bands

• MWIR: 1600 – 2175 cm-1

• LWIR: 700 – 1210 cm-1 • at moderate spectral resolution (0.625 cm-1)

• Two large detector arrays • 160x160 detectors• Spatial sampling 4 km at SSP• covering region of approximately 600 x 600 km2

• Observations in step and stare.• Sampling of one stare: 10 sec.• Approximately 300 stares to cover GEO Disc


Front Telescope

Scan MirrorBaffle

Interferometer

BackTelescope

CooledFocusing

OpticsCooled Matrix

Detectors

Blackbody

OPTICS

The MTG-IRS Instrument: Sketch

IRS design: OHB – Munich

Source: MTG-KT-IR-DD-0004

Volume: 1.4 x 1.6 x 2.2 m3

Mass: 400 kg

Power: 750 W


The MTG-IRS Instrument: Working Principle

• The instrument works in step-&-stare mode, with the Earth disc covered through a sequence of contiguous square sub-images (dwells).

• With the current design, each dwell is taken in 10s and covers about 640 x 640 km2 (at nadir) with 160 x 160 spatial samples.

• Within a single dwell, a set of interferograms, one per spatial sample, is produced.

• A spectral sounding is the result of the Fourier transformation of an interferogram from a single spatial sample

L1 processing

L0

Spectral sounding

Interferogram

Earth

Dwell

Spatial sample

time

L1

wavenumber


The MTG-IRS Instrument: Spatial Coverage & Repeat Cycle

• The Earth disc is split in 4 Local Area Coverage (LAC) Zones

• Each LAC has about 80 dwells

• Numbered from South to North

• Sampling:

• It takes 15 min to sample a LAC.

• LAC4 is revisited every 30 min

• In 6 hours (BRC): 12xLAC4, 5xLAC3, 4xLAC2, 3xLAC1

LAC 1

LAC 2

LAC 3

LAC 4


The MTG-IRS Instrument: Radiometric Calibration

• To generate radiometric and spectral accurate level 1b data for the users a number of corrections to the raw observations have to be applied.

• The temperature variations inside the instrument generate the need for a continuative radiometric calibration; this is achieved by regularly looking at Deep Space (DS) views and at an internal calibrated blackbody (BB view)

• The Sun (when near the FOV) and the Earth itself (at any time) produce straylight, that spoils the radiometric accuracy. Straylight correction algorithms will be introduced in the L1 processing


The MTG-IRS Instrument: Timeliness

• Objective is to make the observations available as soon as it makes physical sense (calibrated and navigated).

• According to current status of development this implies that release of observations is limited by availability of auxiliary information needed to perform radiometric calibration.

• Currently an interpolation between the two DS views at beginning and end of scan line is needed to give the best performance possible.

• Level 1 Processing of a raw observation can only start after completion of full scan line: 3 min at equator (worse case).

• However, a trade with an extrapolation method to remove the dependency of the second DS view is needed.

• Release of the level 1 data depends further on performance of level 1 processor which is currently TBD.

DS2

DS2


The MTG-IRS Instrument: Spectral Calibration

• Need for spectral calibration:• Large detector arrays introduce effects which result in a spectral

shift of the observations collected by detector at centre or at the edge of array

• Thermo-mechanical instabilities produce misalignments of the interferometric axis, which induces additional spectral shifts

• Instabilities of the metrology laser introduces inaccuracies in spectral axis

• Scope of the spectral calibration is determining a spectral scaling shift factor, to be used for correctly rescaling the spectra of the observed Earth views to a common reference spectral axis for all detectors


The MTG-IRS Instrument: Spectral Calibration

• No spectral calibration device is present inside the instrument; the calibration is achieved looking at suitably selected Earth scenes with known and stable spectral behaviour

• To this aim a number of dwells in an area over the North Atlantic Ocean has been selected for two main reasons:• They belong to LAC4, hence they are revisited more often (every 30

min)• They ensure stable and well known conditions, thanks to the fact that

the entire observed surface is sea


The MTG-IRS Instrument: L1B Products

1. Level 1b data are the radiometric and spectral calibrated observations with geolocation information appended. The level 1b data will not be rectified to a reference grid.

2. Plan to store radiances in the 1B product as 16-bit Integer value with fixed scaling factors (8-bit ) per channel. Estimates show the dynamic radiance range in a channel can be accommodated without information loss.

3. Level 1B will be generated in netCDF format complying to the MTG Generic Format Specification (GFS).

4. Estimated Volume Level 1B data full spectrum:1. 9.01 Gbyte per LAC2. 865 Gbyte per 24 h (48xLAC4, 20xLAC3, 16xLAC2, 12xLAC1).

5. Level 1B data is disseminated as a Principal Components compressed dataset to reduce datavolume:1. 1.35 Gbyte per LAC2. 139 Gbyte per 24 h (48xLAC4, 20xLAC3, 16xLAC2, 12xLAC1).

6. No cloud information is provided with the Level 1B data.


The MTG-IRS Level 2 Processor: Overview

• To generate Moisture, temperature profiles from MTG-IRS a level 2 processor is foreseen.

• Processor is a basic 1DVAR using ECMWF short term forecast as background (both state and error covariance matrix)


The MTG-IRS Level 2 Processor: Planned Products

Product Type Parameter Description

Temperature Profile Prior and Posterior temperature profiles with standard deviation

Specific Humidity Profile

Prior and Posterior humidity profiles with standard deviation

Ozone Profile Archive. Prior and Posterior ozone profiles with standard deviation

Surface State Product Surface parameters: Temperature, pressure and emissivity

Scale Projected State For data assimilation of L2 products by regional scale NWP based on only the temperature and specific humidity profiles.Archive flavour additionally contains Eigen values and vectors.

Meta data Navigation information, ancillary parameters, processing and quality flags and exit statuses.


The MTG-IRS Level 2 Products dissemination

• Products will be generated in netCDF format complying to the MTG Generic Format Specification (GFS).

• Level 2 products only disseminated for clear sky regions within LAC-4


The MTG-IRS MAG and User Readiness

• To support the MTG-IRS development a MTG-IRS Mission Advisory Group (MAG) has been formed. • Key element is to give guidance to

Secretariat on issues of L1 and L2 products and processing and support the CAL/VAL.

• MAG link to NWCSAF: M. Martinez (AEMET)


The MTG-IRS MAG and User Readiness

• Some user readiness activities have been started also to support definition of L2 products.

• This is done with IASI as MTG-proxy and the Level 2 Validation and Demonstration Processor (L2VDP).


MTG-IRS L2VDP

• Supports the detailed definition of the operational processor,

• End-to-end Processor• Pre Processing: Scene classification: based on

information contained is spectrum.• Product generation:1DVAR

• T(p), q(p), O3(p), Emissivity, surface temperature • Based on UWPHYSRET/Mirto used for CrIS/IASI at

Univ. of Hawaii with direct readout

• Post Processing: Scaled Projected State

20 NWC-SAF 215 Users‘ Workshop: ref: EUM/MTG/VWG/15/79301619.01.10

Results 29 July 2012, 18UTC

LAPS org LAPS L2VDP

TT-index values: > 50 moderate-severe thunderstorms > 60 severe thunderstorms

Time UTC

18 UTC

E. Gregow: FMI

Analysis of TT index with and without L2 products by LAPS

20


Location of the single level 2 profile: Altenstadt, Germany


Initial results projected state assimilation


Summary

• Introduced MTG-IRS mission, instrument, level 1b and level 2 products.

• Further information, questions:• Contact: [email protected]

Documents

Go to ‚View‘ menu and click on ‚Slide Master‘ to update this footer. Include DM reference, version number and date1 THE MTG-IRS MISSION Stephen Tjemkes,