1. Atmospheric, Oceanic & Planetary Physics, University of Oxford A Dudhia MIPAS QWG13 Firenze 12-14 June 2007 Page 1 Azimuth Dependence of LOS Pointing Anu Dudhia University of Oxford

2. Atmospheric, Oceanic & Planetary Physics, University of Oxford A Dudhia MIPAS QWG13 Firenze 12-14 June 2007 Page 2  Kiefer et al have noted a MIPAS absolute pointing bias which varies approximately linearly with latitude, with N.Pole about 1.5 km lower than S.Pole (orbit 2881, 18 Sep 2002)  They suggest this is linked to the MIPAS azimuth scan and coupled with a bias in the roll angle.  However, since MIPAS has always operated with azimuth scanning, could not separate latitude effects from azimuth scan angle  On 19 March 2007 the MIPAS azimuth scan was switched off for a day …

3. Atmospheric, Oceanic & Planetary Physics, University of Oxford A Dudhia MIPAS QWG13 Firenze 12-14 June 2007 Page 3

4. Atmospheric, Oceanic & Planetary Physics, University of Oxford A Dudhia MIPAS QWG13 Firenze 12-14 June 2007 Page 4

5. Atmospheric, Oceanic & Planetary Physics, University of Oxford A Dudhia MIPAS QWG13 Firenze 12-14 June 2007 Page 5

6. Atmospheric, Oceanic & Planetary Physics, University of Oxford A Dudhia MIPAS QWG13 Firenze 12-14 June 2007 Page 6

7. Atmospheric, Oceanic & Planetary Physics, University of Oxford A Dudhia MIPAS QWG13 Firenze 12-14 June 2007 Page 7

8. Atmospheric, Oceanic & Planetary Physics, University of Oxford A Dudhia MIPAS QWG13 Firenze 12-14 June 2007 Page 8

9. Atmospheric, Oceanic & Planetary Physics, University of Oxford A Dudhia MIPAS QWG13 Firenze 12-14 June 2007 Page 9  Adding the azimuth scan produces a shift of +1km at S Pole and between -0.5 and -1.0 km at N Pole  Using CIRA climatology as ‘truth’, pointing without azimuth scanning appears more accurate  Results are consistent with 1.5km net difference observed by Kiefer et al and confirm that variation is linked to azimuth scan angle rather than latitude Conclusions