1/177th SMOS Workshop, Frascati, 29-31 October 2007

AMIRAS campaign

Fernando Martin-Porqueras

2/177th SMOS Workshop, Frascati, 29-31 October 2007

Contents

• AMIRAS instrument and campaign

• L1 Processor

• Description of L1A, L1B and L1C processors

• Performances

• Examples

• Data format and availability

3/177th SMOS Workshop, Frascati, 29-31 October 2007

AMIRAS instrument

• Small MIRAS instrument

• Y-shape

• 13 antennas:

4 LICEF per arm 1 NIR in the centre

• Angular resolution: 11.8 degrees• Spatial resolution: 84 metres

(altitude = 400 m)

• PMS of receiver B1 has to be repaired

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AMIRAS installation

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• Location: Lahti, Finland• Dates: June 20th, 2006 (Flight1) – night• Acquired data: Measurements over land, sea

and fresh water (Lake Lohja)

Duration: 1 hour 39 minOperation mode: Dual polarization

AMIRAS Campaign – Flight 1

6/177th SMOS Workshop, Frascati, 29-31 October 2007

• Location: Lahti, Finland• Dates: July 19th, 2006 (Flight2) - night• Acquired data: Measurements over land, sea

and fresh water (Lake Lohja)

AMIRAS Campaign – Flight 2

Duration: 2 hours 24 minOperation mode: Dual polarization Full polarization

Full polarization

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AMIRAS L1 Processor

Snapshot LayerInst

rum

ent

Cha

ract

eriz

atio

nda

taba

se

Libr

arie

s

L1B processor

L1C processor

L1C product

Visibility Layer

L1A processor

Correlation layer

Database reader

Raw data

8/177th SMOS Workshop, Frascati, 29-31 October 2007

L1A processor

Scope: The computation of the denormalized visibilities

Processing: Calibration algorithms are based on the SMOS In-Orbit Calibration documentation

Input: Correlations, physical temperatures, PMS voltages, NIR output, instrument characterization database

Output: Denormalized visibilities

Differences with SMOS: • Variable integration time (0.3 – 1.2 s)• Centralized calibration• Calibration based on internal load, cold sky and lake

9/177th SMOS Workshop, Frascati, 29-31 October 2007

L1B processor

Scope: The computation of the brightness temperature at the antenna polarization frame

Processing:

Input: Denormalized visibilities, instrument characterization database

Output: Brightness temperature snapshots

Inversion algorithm: Inverse FFT (Blackman windowing)

Flat Target TransformationAntenna pattern correction

10/177th SMOS Workshop, Frascati, 29-31 October 2007

L1B processor

The processor implements the Flat Target Transformation (FTT)

The FTT minimizes the impact of the antenna errors in the brightness temperature snapshots

Location: Lahti

Date: 19:43 UTC 20/07/2006

Orientation: Azimuth 180 deg Elevation 76.5 deg

11/177th SMOS Workshop, Frascati, 29-31 October 2007

L1C processor

Scope: The geolocation of the brightness temperatures over a fixed grid (UTM) on the surface and the computation of the polarization rotation angles

Input: Brightness temperature snapshots, flight database

Output: Brightness temperature geolocated, incidence and polarization rotation angles

Differences with SMOS: • No pixel-flagging• Only AF-FOV

Processing: Polarization rotation angle computation Geolocation using navigation information Incidence angle computation

Vel

ocity

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Radiometric Performances

Radiometric performances estimated from L1B data

Data used: 51 snapshots over the sea

Assumptions: Constant flight dynamics along the dataset Unpolarized sea surface at 3 deg incidence angle Homogeneous sea surface

Radiometric variability at boresight

Radiometric accuracy

= 1.5 K (1-sigma, 300 ms)

= 2 K

Equivalent radiometric variability in 1.2 sec = 0.75 K (1-sigma)

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Examples

X polarizationY polarization

Vel

ocity

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ExamplesV

- p

olar

izat

ion

H -

pol

ariz

atio

n

Vel

ocity

Vel

ocity

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L1C product content

Planned data content:

• Time

• Position in UTM coordinates

• Incidence angle

• Brightness temperatures in the antenna polarization frame (X-Y)

• Polarization rotation angle between the antenna polarization and ground polarization frame

Each UTM coordinate has different incidence angle availability

xutm

yutm

Amount of data

Velocit

y

16/177th SMOS Workshop, Frascati, 29-31 October 2007

Data availability

• Release date: Christmas 2007

• Distribution method: FTP

• Released data: L1C product from AMIRAS Flight1

• Format: ASCII (data structure still on definition)

17/177th SMOS Workshop, Frascati, 29-31 October 2007

On-going and future tasks

• L1C development

• Format definition for L1C

• Delivery Flight1 – dual polarization data (Christmas 2007)

• Delivery Flight2 – dual/full polarization data (March 2008)

On-going tasks:

Future tasks: