2011 IEEE International Geoscience And Remote Sensing Symposium

2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA A synergy between SMOS & AQUARIUS: resampling SMOS maps at the resolution and incidence of AQUARIUS Eric ANTERRIEU, Yann KERR, François CABOT, Gary LAGERLOEF and David LE VINE

A synergy between SMOS & AQUARIUS… 1 SMOS ESA mission for global monitoring of surface Soil Moisture and Ocean Salinity from space. Ø 1 synthetic aperture imaging radiometer v L-band 1. 413 GHz v 69 antennas/receivers v diluted apertures (6. 75 m) Ø launched November 2 nd 2009 Ø http: //www. esa. int/smos 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA

A synergy between SMOS & AQUARIUS… 2 AQUARIUS Partnership between NASA and CONAE for monitoring Sea Surface Salinity from space. Ø 3 radiometers (+ 1 scatterometer) v L-band 1. 413 GHz v parabolic reflector, 3 feed horns v filled aperture (2. 5 m) Ø launched June 10 th 2011 Ø http: //www. nasa. gov/aquarius 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA

2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA

A synergy between SMOS & AQUARIUS… AQUARIUS in SMOS 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA

A synergy between SMOS & AQUARIUS… 3 Why resampling? Ø The spatial resolution achieved by SMOS is always smaller than the footprint of any of the 3 beams of AQUARIUS radiometers. Ø SMOS and AQUARIUS do not share the sampling grids. Ø There is a need for resampling the temperature maps provided by SMOS down to the ground resolution of AQUARIUS beams so that a synergy between both missions can be properly set. 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA

A synergy between SMOS & AQUARIUS… How to interpolate? Ø Resampling: discrete inverse Fourier transform T( , ) = u, v H +2 j (u + v ) T(u, v) e v only 1396 terms in the sum (band-limited reconstruction…) v does not introduce any interpolation artifact Ø Resampling + Windowing: filter Gibbs effects Tw( , ) = u, v H +2 j (u + v ) W(u, v) T(u, v) e 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA 4

A synergy between SMOS & AQUARIUS… 5 Kaiser window: 1 parameters Ø Kaiser windows are widely used for filtering out Gibbs effects. Ø Parameter 0 and constant over all the frequency coverage H ( is the radial distance normalized to the circumscribed circle). Ø For = 0, the Kaiser window reduces to the rectangle window (no tapering). I 0( 1 - ² ) W(u, v) = I 0( ) v 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA u =1

A synergy between SMOS & AQUARIUS… 5 Kaiser window: 1 parameters Ø The shape of the synthesized PSF W( , ) is controlled by the value of : I 0( 1 - ² ) W(u, v) = I 0( ) v Fourier domain W(u, v) =3 = 10 spatial domain W( , ) 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA u =1

A synergy between SMOS & AQUARIUS… How to interpolate? Ø Resampling + Windowing: with a single window Tw( , ) = u, v H +2 j (u + v ) W(u, v) T(u, v) e v the same window is attached to each pixel ( , ) Ø Resampling + Windowing: with multiple windows Tw( , ) = u, v H +2 j (u + v ) W (u, v) T(u, v) e v a unique window is attached to each pixel ( , ) 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA 6

A synergy between SMOS & AQUARIUS… 7 Kaiser window: 3 parameters Ø Value of continuously depends on with the aid of 3 parameters 1 , 2 and 1 according to the linear relation: 1 = 1 + ( 2 1) 2 1 I 0( 1 - ² ) W(u, v) = I 0( ) 2 v Ø It is possible to control the shape of W( , ). 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA 2 1 1 u =1

A synergy between SMOS & AQUARIUS… 7 Kaiser window: 3 parameters Ø It is possible to control the shape of W( , ): 1 = 0° 1 = 3 2 = 10 Fourier domain W(u, v) I 0( 1 - ² ) W(u, v) = I 0( ) 2 v 1 = 30° 1 = 10 2 = 3 spatial domain W( , ) 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA 2 1 1 u =1

A synergy between SMOS & AQUARIUS… 8 Optimization of the multiple windows Ø Characteristics of the footprint of AQUARIUS beams: incidence resolution orientation angle a b 28. 7° 194 76 Km -19. 8° 37. 8° 120 84 Km -15. 3° 45. 6° 156 96 Km -16. 5° b a Ø Resolution of SMOS is better than that of AQUARIUS for the same incidence angles (50 -100 Km). 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA

A synergy between SMOS & AQUARIUS… Optimization of the multiple windows Ø Characteristics of the field of view of SMOS: @ Earth surface along track distance (Km) @ instrument level cross track distance (Km) 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA 9

A synergy between SMOS & AQUARIUS… 10 Optimization of the multiple windows Ø Parameters 1, 2 and 1 can be optimized for degrading SMOS pixels down to the resolution of AQUARIUS at the Earth surface (non-linear optimization). I 0( 1 - ² ) 1 W(u, v) = with = 1 + ( 2 1) I 0( ) 2 1 1 2 local azimuth angle (deg) 1 local azimuth angle (deg) 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA

A synergy between SMOS & AQUARIUS… 10 Optimization of the multiple windows Ø Non-linear optimization is an heavy task, precluding any real time application. Ø These curves are tabulated in such a way that a linear interpolation does not introduced an error larger than 0. 01 Km (a and b) and 0. 01° ( ) on the final ground resolution. 1 2 local azimuth angle (deg) 1 local azimuth angle (deg) 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA

A synergy between SMOS & AQUARIUS… Concrete illustration Ø Orbit 2010 June 6 th 10: 56: 31 to 11: 50: 33 Ø Step 1: v Tx and Ty read from SMOS L 1 b file v and resampled at AQUARIUS resolution/incidence Tx @ 28, 7° Tx @ 37, 8° Tx @ 45, 6° 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA 11

A synergy between SMOS & AQUARIUS… Concrete illustration Ø Orbit 2010 June 6 th 10: 56: 31 to 11: 50: 33 Ø Step 1: v Tx and Ty read from SMOS L 1 b file v and resampled at AQUARIUS resolution/incidence Ty @ 28, 7° Ty @ 37, 8° Ty @ 45, 6° 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA 11

A synergy between SMOS & AQUARIUS… Concrete illustration Ø Orbit 2010 June 6 th 10: 56: 31 to 11: 50: 33 Ø Step 2: v geometric rotation angle read from SMOS L 1 c file (DGG) v and interpolated (LSQ) at AQUARIUS incidence geometric @ 28, 7° geometric @ 37, 8° geometric @ 45, 6° 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA 12

A synergy between SMOS & AQUARIUS… Concrete illustration Ø Orbit 2010 June 6 th 10: 56: 31 to 11: 50: 33 Ø Step 2: v faraday rotation angle read from SMOS L 1 c file (DGG) v and interpolated (LSQ) at AQUARIUS incidence faraday @ 28, 7° faraday @ 37, 8° faraday @ 45, 6° 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA 12

A synergy between SMOS & AQUARIUS… Concrete illustration Ø Orbit 2010 June 6 th 10: 56: 31 to 11: 50: 33 Ø Step 3: v Th and Tv computed from Tx and Ty and rotation angles v and written in SMOS L 1 c file (DGG) Th @ 28, 7° Th @ 37, 8° Th @ 45, 6° 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA 13

A synergy between SMOS & AQUARIUS… Concrete illustration Ø Orbit 2010 June 6 th 10: 56: 31 to 11: 50: 33 Ø Step 3: v Th and Tv computed from Tx and Ty and rotation angles v and written in SMOS L 1 c file (DGG) Tv @ 28, 7° Tv @ 37, 8° Tv @ 45, 6° 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA 13

A synergy between SMOS & AQUARIUS… 14 Conclusion q How to resample the temperature maps retrieved from SMOS interferometric measurements down to the ground resolution and at the incidence angles of AQUARIUS. q Resampling procedure is fast, accurate and operational. q A synergy between SMOS and AQUARIUS can be set for the benefit of both missions. 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’ 11 July 24 -29, 2011 Vancouver, CANADA