The Kepler Mission Kepler will hunt for planets by measuring the variation in brightness of more than 100,000 stars, waiting for stars to “wink” when orbiting planets pass in front of them. These events, called “transits,” occur each time a planet crosses the line-of-sight between the planet’s parent star and the Kepler photometer, and the planet blocks some of the light from its star, resulting in a periodic dimming. This periodic signature is used to detect the planet and to determine its size and its orbit. The probability that a planetary orbit is aligned along our line-of-sight so that transits can be observed is about one-half of a percent for a solar-like star and planets at the distance the Earth is from the sun. Consequently, Kepler, will continuously and simultaneously monitor more than 100,000 stars . In this way, Kepler will permit astronomers to estimate the total number of Earth-size planets orbiting in and near the habitable zone around stars in our galaxy. http://www.nasa.gov/mission_pages/kepler/news/L-14-press-conference.html March 6, 2009 Spacecraft blasts off in search of 'Earths'Inteferometric Synthetic Aperture Radar (InSAR) and Electromagnetic Waves Phase Amplitude Most SAR Applications examine the magnitude of backscatter strength. InSAR examines the phase of the return signalPass 1: Before Motion Pass 2: After Motion Phase Difference Repeat Pass Inteferometric SARInSAR-Derived Displacement Phase Difference of ¼ wavelength Example: C-Band InSAR Wavelength = ~ 5.6 cm Phase shift of ¼ wavelength (π/2) = difference in travel time of ~1.25 cm/2 Corresponds to a displacement of 0.625 cm InSAR can measure relative displacements of a few mm from space This is the equivalent of the distance of a human hair from about 600 m awaySatellite Baselines Satellite Position 1 Satellite Position 1 Phase Shift between two signals caused by path difference Path Difference Ground In reality, satellites don’t repeat exactly the same orbit, there is some offset that changes the phase of the return signalInterferogram Showing Displacement from Landers Earthquake in 1992 One cycle of color corresponds to 2.8 cm of displacementRutford Ice StreamThis image is an interferogram of the Rutford Ice Stream in Antarctica. Both the rapid flow of the ice stream and the location of the grounding line are visible. The fringes show displacements over a 6 day period with each color cycle representing 28~mm of LOS displacement. (B) Location map for (A). Downstream from the grounding line, the ice stream is afloat. Courtesy D. Goldstein, JPL.Altimetry Provides precise elevation of a surface by measuring travel time of a pulse (lidar or radar) to a surface hsat = ct/2; Hsfc = Hsat - hsat Hsat = height of satellite above Earth c = speed of light t = pulse travel time Hsfc = height of surface above Earth’s center Hsat = height of satellite above Earth’s centerRange Resolution Δh = cτ/2 Δh = range resolution τ = pulse durationSatellite GEOS-3 1975-78 Seasat Jul-Aug 1978 Topex 1993-2003 Jason/OSTM Instrument Error 25 5 2 2 Media Error* 10-50 10-20 4 4 Orbit Error (cm) 200-1000 100 13 10 Footprint 3.6 1.6 0.7 0.7 Stand Error (m) 1.05 .13 0.03 0.025Footprint Size Beam-Limited footprint: Footprint size is determined by the height of the sensor (h) and the length of the antenna (L) X=λh/L Pulse-Limited footprint: Footprint size is determined by the interaction of the pulse with the surface X=2 sqrt(chτ)Pulse-Limited and Beam-Limited Footprint Pulse-Limited The width of the area illuminated by the leading edge of the pulse by the time the trailing edge first intersects the surface Beam-Limited The width of the area over which signal is collected by the antennaAltimetry Crossovers H1 + E/√2 H2 + E/√2 ΔH(t) = H1 - H2 + E S(T2) S(T1) O(T2) O(T1) Satellite Orbits Groundtracks Ranges Pulse-limited footprint HorizonObserving El Nino From Altimetry “normal” conditions El Niño conditions Purple = -18 cm anomaly; white = +14 cm anomalyMonitoring Sea Level Rise though not the same everywhere (Courtesy of Laury Miller, NESDIS) Sea level is rising… From NASA/CNES TOPEX/Poseidon & Jason missions, 1993 - 2008 (Mitchum and Nerem, 2007) Average Rate = 3.5 mm/year (1993-2006) SLR IPCC 2001: 1.8 mm/year Jason-class satellite altimetry is required to resolve the spatial variability of sea level rise in determining accurate global means. Tide gauges [ ] are poorly distributed, but they are critical for calibration.What is LIDAR? ! LIDAR (Light Detection and Ranging) is the technology of using pulses of laser (light) striking the surfaces of the earth and measuring the time of pulse return  Typically near-IR (1064 nm) or Green (532 nm) but others do exist) ! LIDAR acquisition system includes:  LIDAR sensor  GPSLIDAR Applications ! In 2003 NASA Launched the ICESat mission, to use lasers to measure ice elevation precisely ! Laser ranging from ground stations is used to determine orbits of satellites ! Advantages  Small FOV of about 1 mrad (0.2 m on ground from aircraft, 50 m on ground from satellites  Range Resolution (~10 cm)  No penetration in snowLIDAR Applications ! Ocean Surface topography ! Elevation and structure of the land surfaces ! Hydrological cycle ! Floodplain management ! Natural resource management (ex. forestry, soils, etc.) ! Hydrological modeling ! 3D visualization (security) ! Site selection analysis ! Coastal and shoreline mappingMARS® Visualization ! Color by:  Elevation  Classification  Flight lineElevation Measurements Along Ground Tracks Enable the Creation of Digital Elevation Models 21Calculation of Range: Simple Surface 23 Time (Distance) Energy Transmit Pulse (6 ns) Return Pulse Time from which range is calculatedCalculation of Range: Simple Surface 25 Time (Distance) Energy26Calculation of Range: Complex Surface 27 Time (Distance) Energy ? ? ? ?30 Max Canopy Height Crown Depth ~ 70 m diameter laser footprint spaced 175 m apart along ground track Amplitude (volts) Time (nsec) Outer Canopy Relief Ground Relief Transmit Pulse Threshold 1064 nm, 7 nsec laser pulse average detected elevation (alternate “land” elevation) Height Distribution of Reflected Laser power with 15 cm Vertical Sampling highest detected elevation lowest detected elevation Echo Pulse D. Harding/NASA- GSFC31 Vegetation Height