2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA A synergy between SMOS & AQUARIUS: resampling SMOS maps at the resolution and incidence of AQUARIUS Eric A NTERRIEU, Yann K ERR, François C ABOT, Gary L AGERLOEF and David L E V INE
A synergy between SMOS & AQUARIUS… 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA ESA mission for global monitoring of surface Soil Moisture and Ocean Salinity from space. SMOS 1 synthetic aperture imaging radiometer L-band GHz 69 antennas/receivers diluted apertures (6.75 m) launched November 2 nd 2009 1
A synergy between SMOS & AQUARIUS… 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA Partnership between NASA and CONAE for monitoring Sea Surface Salinity from space. AQUARIUS 3 radiometers (+ 1 scatterometer) L-band GHz parabolic reflector, 3 feed horns filled aperture (2.5 m) launched June 10 th 2011 2
2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA
A synergy between SMOS & AQUARIUS… 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA AQUARIUS in SMOS
A synergy between SMOS & AQUARIUS… 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA Why resampling? The spatial resolution achieved by SMOS is always smaller than the footprint of any of the 3 beams of AQUARIUS radiometers. SMOS and AQUARIUS do not share the same sampling grids. 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. 3
A synergy between SMOS & AQUARIUS… 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA How to interpolate? Resampling: discrete inverse Fourier transform only 1396 terms in the sum (band-limited reconstruction…) does not introduce any interpolation artifact Resampling + Windowing: filter Gibbs effects 4 T( , ) = T(u,v) e +2j (u + v ) u,v Hu,v H T ( , ) = W(u,v) T(u,v) e u,v Hu,v H +2j (u + v ) w
A synergy between SMOS & AQUARIUS… 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA Kaiser window: 1 parameters Kaiser windows are widely used for filtering out Gibbs effects. Parameter 0 and constant over all the frequency coverage H ( is the radial distance normalized to the circumscribed circle). For = 0, the Kaiser window reduces to the rectangle window (no tapering). 5 u v = 1 = 1 W(u,v) = I0()I0() I0( 1² )I0( 1² )
A synergy between SMOS & AQUARIUS… 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA Kaiser window: 1 parameters The shape of the synthesized PSF W( , ) is controlled by the value of : 5 u v = 1 = 1 W(u,v) = I0()I0() I0( 1² )I0( 1² ) = 3 = 10 spatial domain W( , ) Fourier domain W(u,v)
A synergy between SMOS & AQUARIUS… 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA How to interpolate? Resampling + Windowing: with a single window the same window is attached to each pixel ( , ) Resampling + Windowing: with multiple windows a unique window is attached to each pixel ( , ) 6 T ( , ) = W(u,v) T(u,v) e u,v Hu,v H +2j (u + v ) w T ( , ) = W (u,v) T(u,v) e u,v Hu,v H +2j (u + v ) w
A synergy between SMOS & AQUARIUS… 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA Kaiser window: 3 parameters Value of continuously depends on with the aid of 3 parameters 1, 2 and 1 according to the linear relation: It is possible to control the shape of W( , ). 7 u v 11 22 11 22 = 1 = 1 = 1 + ( 2 1 ) 1 1 2 12 1 W(u,v) = I0()I0() I0( 1² )I0( 1² )
A synergy between SMOS & AQUARIUS… 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA Kaiser window: 3 parameters It is possible to control the shape of W( , ): 7 W(u,v) = I0()I0() I0( 1² )I0( 1² ) 1 = 0° 1 = 3 2 = 10 1 = 30° 1 = 10 2 = 3 u v 11 22 11 22 = 1 = 1 spatial domain W( , ) Fourier domain W(u,v)
A synergy between SMOS & AQUARIUS… 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA Optimization of the multiple windows Characteristics of the footprint of AQUARIUS beams: Resolution of SMOS is better than that of AQUARIUS for the same incidence angles ( Km). 8 incidence angle resolution a b orientation 28.7° 37.8° 45.6° 194 76 Km 120 84 Km 156 96 Km 19.8° 15.3° 16.5° a b
A synergy between SMOS & AQUARIUS… 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA Optimization of the multiple windows Characteristics of the field of view of SMOS: 9 instrument level cross track distance (Km) along track distance Earth surface
A synergy between SMOS & AQUARIUS… 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA Optimization of the multiple windows 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). 10 11 11 22 local azimuth angle (deg) = 1 + ( 2 1 ) 1 1 2 12 1 W(u,v) = with I0()I0() I0( 1² )I0( 1² )
A synergy between SMOS & AQUARIUS… 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA Optimization of the multiple windows Non-linear optimization is an heavy task, precluding any real time application. 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. 10 11 11 22 local azimuth angle (deg)
A synergy between SMOS & AQUARIUS… 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA Concrete illustration 11 Orbit 2010 June 6 th 10:56:31 to 11:50:33 Step 1: T x and T y read from SMOS L1b file and resampled at AQUARIUS resolution/incidence T 28,7°T 37,8°T 45,6°
A synergy between SMOS & AQUARIUS… 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA Concrete illustration 11 Orbit 2010 June 6 th 10:56:31 to 11:50:33 Step 1: T x and T y read from SMOS L1b file and resampled at AQUARIUS resolution/incidence T 28,7°T 37,8°T 45,6°
A synergy between SMOS & AQUARIUS… 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA Concrete illustration 12 Orbit 2010 June 6 th 10:56:31 to 11:50:33 Step 2: geometric rotation angle read from SMOS L1c file (DGG) and interpolated (LSQ) at AQUARIUS incidence 45,6°
A synergy between SMOS & AQUARIUS… 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA Concrete illustration 12 Orbit 2010 June 6 th 10:56:31 to 11:50:33 Step 2: faraday rotation angle read from SMOS L1c file (DGG) and interpolated (LSQ) at AQUARIUS incidence 45,6°
A synergy between SMOS & AQUARIUS… 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA Concrete illustration 13 Orbit 2010 June 6 th 10:56:31 to 11:50:33 Step 3: T h and T v computed from T x and T y and rotation angles and written in SMOS L1c file (DGG) T 28,7°T 37,8°T 45,6°
A synergy between SMOS & AQUARIUS… 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA Concrete illustration 13 Orbit 2010 June 6 th 10:56:31 to 11:50:33 Step 3: T h and T v computed from T x and T y and rotation angles and written in SMOS L1c file (DGG) T 28,7°T 37,8°T 45,6°
A synergy between SMOS & AQUARIUS… 2011 IEEE International Geoscience And Remote Sensing Symposium IGARSS’11 July 24-29, 2011 Vancouver, C ANADA Conclusion 14 How to resample the temperature maps retrieved from SMOS interferometric measurements down to the ground resolution and at the incidence angles of AQUARIUS. Resampling procedure is fast, accurate and operational. A synergy between SMOS and AQUARIUS can be set for the benefit of both missions.