1. Level 1.5 Geolocation Martin Bates, RAL GIST 24 15 th December, 2005

2. Questions How good is the level 1.5 GEO ? –is it an option for release ? –what known problems are there ? How would we handle operationally N/S & E/W drifts in a release ? What, if necessary, could be done on a short time scale to produce an improved GEO ? What are the longer term prospects for fixing the level 1.5 GEO ?

3. How good ? elevation off-centre azimuth (vs col)elevation (vs row)

4. Known Problems Derivation of a “good” optical model Axis misalignments –spin axis study –N/S drifts East-west systematic jump with change in rotation rate Noise in SOL_SOE_Delay

5. Derivation of a Good Optical Model

6. Observed rotation of banana in RGP L15G 90 min fits

7. N/S Shift N/S Shift commencing 15 Jan 2005

8. Manually Tracking N/S Changes Changes since 04 Nov 0.05 pixel: 12 changes 0.l pixel: 5 changes 0.2 pixel: 1 change

9. Tracking N/S Shifts StartTimeEndTimeN/S TuningParam2Param3 2005120700:00:002100010100:00:00-0.024500 2005120400:00:002005120700:00:00-0.02100 2005120200:00:002005120400:00:00-0.017500 2005112900:00:002005120100:00:00-0.01400 2005112700:00:002005112900:00:00-0.010500 2005112400:00:002005112700:00:00-0.00700 2005112100:00:002005112400:00:00-0.003500 2005111100:00:002005112100:00:00000 2005111000:00:002005111100:00:00-0.003500 2005110900:00:002005111000:00:00-0.00700 2005110700:00:002005110900:00:00-0.01400 2005110500:00:002005110700:00:00-0.010500 2005110400:00:002005110500:00:00-0.00700 1999010100:00:002005110400:00:00000 New data table – quickly tune N/S GEO

10. Automatic Tracking of N/S Changes Use difference between image and GEO –needs GEO to have run in order to run the GEO –2 pass process However, relatively slowly varying, so could use results from one image to process next –could use running average (as with gains but smaller τ) –enforce strict time order to processing (SDPL0 change) –handle systematics (espec. stray light) Would take significant development time to implement.

11. Spin Axis Correction IMPF makes a correction to spin axis as supplied by flight dynamics (SEV header) Have sample data (24 hrs) for 04 May, 16, 17 Aug, 28, 29 Oct: Δx, Δy, Δz over 24 hours What does it mean ? –a.) simple spin correction, no misalignment: r_spin = r_orig + r_corr –b) gives spin axis to structural axis misalignment need to know frame of reference to work out how to use it Further investigations at EUMETSAT. Processing tests for moment assume a.)

12. Spin Axis Test : Aug vs Oct 05 Aug 17 Oct 29 Normal Proc.Spin Axis Corr. Can spin axis correction account for 0.75 pixel jump in N/S geolocation ? No2 pixel jump

13. Regular spin axis correction ? As part of change to include TSOL jitter, and switch to transfer of L0 data by sftp: –asked for ~ 100 bytes of blank data in packet for spin axis correction et al. –too late for negotiations between EUMETSAT and contractor –means that any future change request will also involve UMARF (pkt size increase) –messy TSOL jitter style solution for spin axis corr ? could be more slowly varying Data only seem to have been recorded since 03 Feb 2005 –but suggests looking at horizon, landmark and star position info in SEVIRI trailer –may be able to regenerate error curves –would be regenerated by a SEVIRI reprocessing

14. Spin-Structure Misalignment z SAT spin axis z x spin axis correction

15. Axis Misalignments

16. Incomplete knowledge of E/W centring shifts with spin rate Spin rate change associated with 08 Feb manoeuvre No rotation rate change Retuning

17. Questions How good is the level 1.5 GEO ? –is it an option for release ? See later talks. –what known problems are there ? optical model, N/S drifts, lack of knowledge of misalignments... How would we handle operationally N/S & E/W drifts in a release ? –N/S: improved monitoring for spotting drifts quickly –N/S: new parameter and data table to implement tunings quickly –E/W: advance notice of spin rate changes; more stable (TSOL Jitter). What, if necessary, could be done on a short time scale to produce an improved GEO ? –improved optical model ? (see later talks) –automated system for N/S tunings ? What are the longer term prospects for fixing the level 1.5 GEO ? –improved optical model –better understanding of spin axis correction –access to MSG spin-structure misalignment –model for E/W centring with rotation rate –study use of FIFO data in conjunction with SOL_SOE.