Level 1.5 Processing Issues

Martin Bates

RAL

Level 1.5 Processing Issues

• Geolocation– Current Status– TSOL Jitter (CSOL-TSOL) correction– Longterm TSOL Jitter Solution– Comparisons with RGP Processing

• Upcoming Updates to Processing

• Processing Validation

Current Status

• Level 1.5: Adhoc E-W geolocation correction– sinusoid (amplitude, phase, offset

tunable)– ESU dependent– accurate to ~1 pixel, a bit worse N-

S.

• Level 2: fit to SEVIRI data (formerly MS7A)– decoupled from Level 1.5– accurate to ~ 0.2 pixels (< 0.5

pixels)

09 Nov 2003

TSOL Jitter

• Predicted TSOL – actual TSOL– as used by IMPF

– predicted TSOL (CSOL) from rotational model

• Temporary scheme– data available on ftp server at EUMETSAT since

16 February• coverage > 99.6 % (dropouts at sun-satellite colinearity)

– copy across and use as correction to E-W geolocation

– ggsps correction for early April.

TSOL Jitter

14 Nov 2003

data spikey – needs filtering

Smoothed TSOL Jitter

Result of median filter ( 1 minute)

One spike in close-up

Corrected Data (15 Nov 2003)

no filtering

am/pm Systematic

15 Nov 2003

TSOL Jitter Correction

23 March 2004

TSOL Jitter Correction

23 March 2004

23 March 2004

am/pm systematic still present

offset slightly different

Long term solution

• Robustness of ftp server solution in question.• Longer term solution:

– append (TSOL Jitter) value to GERB packet– correction algorithmically no different– improved reliability and timeliness of information

• Timescale: 6-12 months.– requires Engineering Change Proposal (for IMPF

and UMARF)– still to be approved by EUMETSAT

• SEVIRI reprocessing ?– can then get values for before 16 Feb.

RGP Comparisons

• Process data from 14-16 Nov 2003 using TSOL jitter correction.

• Compare to RGP geolocation (high CPU fit) comparing to SEVIRI.

North-South Compression

15 Nov 2004 11:56:58 (SW)

Still there !

N/S offset not perfect for these data

Quasi-Rotation

15 Nov 2004 11:56:58 (SW)

Also still there ...

Retune Optical Model ?

1. Could be due to local deformations in one of the mirrors – but no estimate of possible sizes of effects

2. Image ratio plots more structure in GGSPS plot

GGSPS RGP

Geolocation Plans

• Interim TSOL Jitter Correction (April)• Long term TSOL Jitter Correction

– for improved robustness– still to be approved, end of year ?

• Optical Model – tune using RMIB info• Axis misalignments

– MSG spin to MSG structure• large (~0.3 ?)• changes at each manoeuvre

– action on EUMETSAT to investigate• Mirror Side Effects (non-parallel N/S ?)

Upcoming Processing Updates

• New BAT, BBRAD tables– but may be coordinated with data release

• Offline gains (stray light & moon avoidance)– depends on gain stability:

• if update < once per month– use offline gains (data table)

• if update more frequently– avoid problem regions or– use gains calculated at good times of day

» startup problems & time dependent processing

• Stray Light Correction TBD• Numerous minor updates

– NCR fixes– additions (diagnostics) to NANRG product– confidence flag definitions

Processing Validation

• Geolocation Validation– Comparisons with SEVIRI / RGP geolocation (RMIB)

• Overall Validation– series of unit and integration tests done (test data,

limited set of circumstances)

– step by step validation using real data and checkpoint files suggested (validation plan) – TBD

– monitoring of calibration parameters using engineering report (Imperial).