Remote Sensing John Wilkin jwilkin rutgers edu IMCS Building Room 214C 732 932 6555 ext 251 Active microwave systems 3 more Altimeter Scatterometer Synthetic Aperture Radar SAR Future of Altimetry Cryosat ESA Altimeter dedicated to polar observation High inclination orbit 92o 710 km altitude 3 year mission to determine variations in the thickness of the continental ice sheets and marine ice cover Test the predictions of thinning arctic ice due to global warming Low resolution nadir altimeter operates in SAR mode over ice for increased spatial resolution Launch 8 October 2005 oops Cryosat 2 should launch in 2009 Rockot launch vehicle is a modified SS 19 ICBM 8 October 2005 1 1502 GMT Cryosat launches from Plesetsk northern Russia 2 1504 First stage separation 3 1508 Second stage separation due but scientists believe that a software error meant this did not happen The rocket plunged back to Earth when its fuel ran out Plesetsk Cosmodrome Russia IceSat US High inclination orbit 94o Geoscience Laser Altimeter System GLAS a space based LIDAR a combined precision surface LIDAR and dualwavelength cloud and aerosol LIDAR infrared and visible laser pulses at 1064 and 532 nm wavelengths GLAS produces a series of 70 m diameter laser spots separated by 170 m along ground track Future of Altimetry Ocean Surface Topography Mission OSTM will be a follow on to the Jason mission It is scheduled to launch June 15 2008 same orbit of Topex Jason extending the time series of precision sea level height data that began Sept 1992 Poseidon 3 altimeter research modes integrated with DORIS and onboard digital terrain model for more precise tracking over inland waters and coasts POD LRA NAS DORIS CNES new NASA Global Positioning System Payload GPSP Future of Altimetry WSOA the Wide Swath Ocean Altimeter An altimeter interferometer project Several altimeters mounted on masts will acquire measurements simultaneously providing continuous wide area coverage WSOA is based on a technique combining altimeter and interferometer measurements It is a wide field radar altimeter able to measure seasurface height across a swath centered on the satellite ground track The satellite payload will include dual frequency nadir looking radar altimeter in Ku and C bands to provide ionospheric corrections acquire measurements as accurate as Topex and the Jason A three channel radiometer GPS Doris and laser reflector precise orbit determination WSOA comprising two interferometers mounted on a mast with a baseline of 6 4 m each covering a swath of 15 to 100 km Where is Jason now Wide Swath Ocean Altimeter WSOA on a Jason type bus The interferometer principle measures the relative delay between reflected signals at 2 antennas separated by a baseline distance The range measurements from the 2 antennas and the baseline form a triangle used for determining the location of the target in the observation plane The triangle is made up of the baseline B and the ranges from the target to the two antennas r1 and r2 The baseline is known from the design of the instrument and the spacecraft attitude Range r1 is determined by system timing measurements The range difference between r1 and r2 is determined by measuring the relative phase shift between the two signals related to the range difference r by Wide Swath Ocean Altimeter Three factors underlying measurement uncertainty Measurement noise which depends on the antenna baseline longer baseline less noise With an antenna baseline of 6 4 m the raw noise is 5 2 cm Ionospheric tropospheric and sea state bias effects estimated at 1 to 2 cm Errors from satellite roll and pitch steering which impact measurement geometry Comparison of T P Jason 1 measurements and simulated WSOA data with Topex Poseidon shifted into an orbit parallel to Jason 1 This mosaic offers a huge advantage in terms of describing the dynamic topography at high resolution It allows a measure of sea surface gradient between pixels and therefore geostrophic velocity Simulations based on realistic model data yield an error of 4 7 cm s rms on the zonal velocity and 5 9 cm s on meridional velocity Future of Altimetry AltiKa Ka band altimeter 500 MHz can be flown on a microsatellite or as an auxiliary Signal frequencies in the Ka band will enable better observation of ice rain coastal zones land masses forests etc and wave heights Sensitivity to water vapor in troposphere is high so data are lost when rain rate is 1 5 mm hour 1 Part of plans to develop an operational satellite altimetry system Light weight and low power consumption Better signal to noise ratio than Poseidon 2 in Ku band reducing noise to 1 cm Antenna lobe is narrower and the ground footprint smaller With a higher pulse repetition frequency this allows more precise measurements near sea land boundaries 5 km from the shoreline and over inland water bodies Low ionospheric attenuation eliminating the need for a dual frequency altimeter Better description of sea surface roughness than in Ku The 8 mm wavelength is better suited to describing the slopes of small facets on the sea surface capillary waves etc Lower penetration of snow ice 1 cm compared to 5 m in Ku Improves snow data with respect to aging of ice in the surface layers Ice grain size would also be measurable Active microwave systems 3 Scatterometers and SAR Scatterometers satellite borne ocean surface vectors winds Incorporated into ECMWF meteorological analysis Synthetic Aperture Radar SAR satellite and aircraft high spatial resolution tens of meters image ocean surface wave field and by inference processes that modulate the surface waves All these systems exploit the resonant Bragg scattering of centimeter to decameter wavelength microwave radiation from ocean surface roughness due to short waves Bragg Scattering from Water Surfaces Wind creates small waves on the ocean surface capillary waves which in the absence of wind quickly die out If wind continues waves will grow in size and increase in wavelength and height to become ultra gravity waves and eventually gravity waves A water surface affected by wind will have a spectrum of surface waves e g multiple wavelengths and heights Microwave EM energy has been shown in wave tank experiments to constructively interfere or resonate with surface capillary and ultra gravity waves This phenomenon is known as Bragg Scattering Development of scatterometry is largely empirical relationship between backscattered microwave power and the energy density of the gravity