Bryan HUNEYCUTT (NASA/JPL) WMO, Geneva, Switzerland 20-21 March 2006 Earth Exploration-Satellite Service (Active) Active Spaceborne Remote Sensing Bryan HUNEYCUTT (NASA/JPL) WMO, Geneva, Switzerland 20-21 March 2006

Active Sensor Types SYNTHETIC APERTURE RADARS - Sensors looking to one side of nadir track, collecting phase and time history of coherent radar echo from which typically can be produced a radar image or topographical map of the Earth surface ALTIMETERS - Sensors looking at nadir, measuring the precise time between a transmit event and receive event to extract the precise altitude of ocean surface SCATTEROMETERS - Sensors looking at various aspects to the sides of the nadir track, using the measurement of the return echo power variation with aspect angle to determine wind direction and speed on Earth ocean surface PRECIPITATION RADARS - Sensors scanning perpendicular to nadir track, measuring the radar echo from rainfall to determine the rainfall rate over Earth surface, usually concentrating on the tropics CLOUD PROFILE RADARS - Sensors looking at nadir, measuring the radar echo return from clouds, to determine cloud reflectivity profile over Earth surface 20-21 March 2006

ACTIVE SENSOR AND SERVICE DEFINITIONS Active Sensor: a measuring instrument in the Earth exploration-satellite service or in the space research service by means of which information is obtained by transmission and reception of radio waves (RR)   Earth Exploration-Satellite Service: a radiocommunication service between earth stations and one or more space stations, which may include links between space stations, in which: -      information relating to the characteristics of the Earth and its natural phenomena including data relating to the state of the environment is obtained from active sensors or passive sensors on earth satellite; -      similar information is collected from airborne or earth-based platforms; -      such information may be distributed to earth stations within the system concerned Space Research Service: a radiocommunications service in which spacecraft or other objects in space are used for scientific or technological research purposes 20-21 March 2006

Active Sensors Applications by Sensor Type 20-21 March 2006

Active Sensor Characteristics 20-21 March 2006

Active Sensor Examples SAR-Radar Image Bora Bora, French Polynesia Altimeter-Sea Level Scatterometer-Wind Speeds Precipitation Radar-Rain Rates Cloud Radar-Cloud Reflectivity Profile 20-21 March 2006

Synthetic Aperture Radars (SARs) Provide radar images and topographical maps of the Earth’s surface RF center frequency depends on the Earth’s surface interaction with the EM field RF bandwidth affects the resolution of the image pixels Allowable image pixel quality degradation determines allowable interference level SAR Illumination Swath Chirp Spectrum 20-21 March 2006

Synthetic Aperture Radars (SARs) (contd) Shuttle RadarTopography Mission (SRTM) Synthetic Aperture Radar (SAR) SIR-C L,C band interferograms Ft. Irwin, CA SRTM perspective with Landsat overlay, Antelope Valley, CA SRTM France, shaded relief and colored height 20-21 March 2006

Illustration of Altimeter Return Altimeters Provide altitude of the Earth’s ocean surface RF center frequency depends on the ocean surface interaction with the EM field Dual frequency operation allows ionospheric delay compensation JASON-1 uses frequencies around 13.6 GHz and 5.3 GHz Allowable height accuracy degradation determines the allowable interference level Illustration of Altimeter Return 20-21 March 2006

Altimeters (contd) Jason Sea Level Residuals TOPEX/POSEIDON maps of sea surface height relative to normal Sea Topography 20-21 March 2006

Jason 1-TOPEX/Poseiden Tandem Mission Altimeters (contd) Jason 1-TOPEX/Poseiden Tandem Mission Ocean Surface Topography Mission (OSTM) follow-on to Jason to launch in 2008 20-21 March 2006

Variation of Backscatter with Aspect Angle Scatterometers Provide the wind direction and speed over the Earth’s ocean surface RF center frequency depends on the ocean surface interaction with the EM field and its variation over aspect angle Narrow RF signal bandwidth provides the needed measurement cell resolution Allowable wind speed accuracy degradation determines the allowable interference level Variation of Backscatter with Aspect Angle 20-21 March 2006

Scatterometers (contd) SEAWINDS scanning pencil beam illuminates scans at two different look angles from nadir, and scans 360 degrees about nadir in azimuth NSCAT illuminated the Earth’s surface at several different fixed aspect angles 20-21 March 2006

Scatterometers (contd) NSCAT illustration Synoptic View of Ocean Surface Wind by NASA Scatterometer On-orbit satellite overview of NSCAT 20-21 March 2006

Scatterometers (contd) QuickSat SeaWinds Ocean Surface Winds by QuickSat ADEO II SeaWinds 20-21 March 2006

Precipitation Radars Provide precipitation rate over the Earth’s surface, typically concentrating on rainfall in the tropics RF center frequency depends on the precipitation interaction with the EM field Narrow RF signal bandwidth provides the needed measurement cell resolution Tropical Rainfall Measurement Mission (TRMM) uses only 0.6 MHz RF bandwidth Allowable minimum precipitation reflectivity degradation determines the allowable interference level 20-21 March 2006

Precipitation Radars (contd) TRMM Precipitation Radar Latest Tropical Cyclone data TRMM Average Precipitation ’98-’04 (combined with gauge information) TRMM Latest Week of Global Rainfall Accumulation data Mosaic of TRMM overpasses of Hurricane Isabel crossing the Atlantic (Sept ’04) 20-21 March 2006

Cloud Profile Radars Provide three dimension profile of cloud reflectivity over the Earth’s surface RF center frequency depends on the ocean surface interaction with the EM field and its variation over aspect angle Antennas with very low sidelobes so as to isolate the cloud return from the higher surface return illuminated by the sidelobes Narrow RF signal bandwidth provides the needed measurement cell resolution Allowable reflectivity accuracy degradation determines the allowable interference level 20-21 March 2006

Cloud Profile Radars (contd) Cloudsat Formation flying of Cloudsat with Calipso to overlap lidar footprint with CPR footprint Time-height cross section of radar reflectivity from 94 GHz radar 20-21 March 2006

Active Sensor Interference And Performance Criteria 20-21 March 2006

Typical Interference Levels at Earth’s Surface 20-21 March 2006

Compatibility Studies 20-21 March 2006

Compatibility Studies 20-21 March 2006

WRC’06 Issues/Concerns 20-21 March 2006

9.3-9.5 GHZ BAND CURRENT STUDIES The WRC-2006 resolution 747 resolves to consider the possible extension of up to 200 MHz in the band of 9.3-9.5 GHz to the EESS (active) and SRS (active).   Agreement from the spaceborne active sensor community to use extension band for wideband applications only such as for wideband SARs; ongoing studies analyze the interference from spaceborne SARs in the band 9.3-9.8 GHz into radiodetermination systems; studies analyzing the interference into SARs showed about a 4 dB margin from the interference threshold from a worldwide deployment of radiodetermination transmitters. Another study by the the spaceborne active sensor community analyzes the compatibility between spaceborne SARs and fixed systems in the band 9.8-10 GHz; simulation results showed that the worst case interference levels from SARs was -29.8 dB exceeded 1% of the time for an FS station at 45 deg latitude; studies analyzing the interference into SARs showed about a 5.3 dB margin from the interference threshold from a worldwide deployment of FS stations. 20-21 March 2006

OTHER CURRENT STUDIES JRG 1A-1C-8B: major issue of the “design objective” in ITU-R Rec SM. 1541 Annex 8 for primary radars (includes EESS (active)) with the possibility of making more stringent the “roll-off” of out-of-band emissions from the current 20 dB/decade to 40 dB/decade 94.0-94.1 GHz band: PDNR on the “Mutual planning between the EESS (active) and the RAS in the 94 GHz and 130 GHz bands” to ensure that the RAS receivers are not damaged by the EESS (active) CPRs, but no undue burden is put on the EESS (active) CPR operations   Approved Revised recommendations in SG7: ITU-R Rec SA.577 “Preferred frequencies and necessary bandwidths for spaceborne active remote sensors” ITU-R Rec SA.1166 “Performance and interference criteria for active spaceborne sensors” Approved New recommendation in SG7: ITU-R SA.[MITIGATE] “Mitigation technique to facilitate the use of the 1 215-1 300 MHz band by the Earth exploration-satellite service (active) and the space research service (active)” 20-21 March 2006