Remote Sensing of the Ocean and Atmosphere John L Wilkin jwilkin rutgers edu IMCS Building Room 214C 609 630 0559 g voice Orbits and Measurement Geometry 1 The flow of information from land or sea surface to satellite to user depends on features of the land ocean phenomena the observing system and the intervening atmosphere 4 resolution FOV aperture scan geometry can depend on satellite trajectory and altitude orbit pointing 5 Geolocation position time pointing Orbit affects repeat sample interval 6 Position of the satellite or range to target may be the actual data 3 Sensor the data is a measurement or image 2 Water leaving signal WLR can depend on relative position of sun and satellite time of day emissivity reflectance 1 Ocean phenomena color temperature roughness height Johannes Kepler 1571 1630 German mathematician astronomer and astrologer 1 Planets move in elliptical orbits with the sun as one focus 2 the radius vector from the sun to the planet sweeps out equals areas in equal times 3 T2 R3 ratio is constant for all planets where T is orbital period and R is semimajor axis of the orbit Isaac Newton 1643 1727 English physicist mathematician astronomer theologian 1 Newton discovered the laws of gravitation and explained planetary and satellite orbits in terms of the balance of forces 2 Centripetal acceleration dv F ma m dt 3 Gravity Fgravity GMm 2 r Galileo Galilei 1564 1642 Italian physicist mathematician astronomer and philosopher Galileo s pupil Vincenzo Viviani stated that Galileo had dropped balls of the same material but different masses from the Leaning Tower of Pisa to demonstrate that their time of descent was independent of their mass This was contrary to what Aristotle had taught that heavy objects fall faster than lighter ones in direct proportion to weight There is no account by Galileo himself of such an experiment and it is generally accepted that it was at most a thought experiment which did not actually take place v2 v2 change in velocity acceleration is perpendicular to the direction of travel v1 v1 v s r s r d r t t dt d v dt r v Epoch UTC 10 07 53 AM Monday January 28 2008 Eccentricity 0 0005362 Inclination 51 6418 Perigee Height 334 km Apogee Height 341 km Right Ascension of Ascending Node 22 2238 Orbit Number at Epoch 52631 Revolutions per Day 15 77540422 Nov 5 2007 view from Space Shuttle Remote Sensing of the Ocean and Atmosphere John L Wilkin jwilkin rutgers edu IMCS Building Room 214C 609 630 0559 g voice Orbits and Measurement Geometry 2 x axis Stewart R H 1985 Methods of Satellite Oceanography University of California Press 360 pp Right ascension declination coordinate system First Point of Aries One of the two points on the Celestial Sphere where the Ecliptic and the Celestial Equator cross one another Ecliptic An imaginary line in the sky that approximates the plane in which the planets orbit the Sun From the perspective of an observer on Earth the planets and the Sun will always remain close to this line When the Sun reaches the First Point of Aries as it does once each year the Northern hemisphere Vernal Equinox occurs The First Point of Aries which is actually in Pisces defines the zero point for Right Ascension Right ascension the celestial equivalent of longitude starting at the First Point of Aries Declination the celestial equivalent of latitude The celestial north pole is at declination 90 http spaceflight nasa gov realdata elements See graphics of orbital elements and data for ISS OSTM Jason 2 Boost Profile Space craft separation http www youtube com watch v 1aBpcCVljt4 Jason 1 launch from Vandenburg Air Force Base California Launch http www youtube com watch v Z4WHOSF2Ktg Other launches Delta II Themis http www youtube com watch v p pAhPecto0 Ariane launch failure http www youtube com watch v kYUrqdUyEpI Jason 2 OSTM http www youtube com watch v cf0loVEs lo Pegasus vehicle aircraft launch http www youtube com watch v QRHiTvRHHd8 Space craft separation http www youtube com watch v 1aBpcCVljt4 http www nytimes com 2007 02 06 science space 06orbi html emc eta1 On Jan 11 2007 China tested an antisatellite rocket The initial collision added 800 to 1000 pieces of space junk to the current total of detectable objects How many detectable objects 4 inches are in orbit Collisions between existing debris generate additional pieces of debris There is concern that eventually a chain reaction will ensue the Kessler syndrome littering the low earth orbit LEO with debris making it almost impenetrable to new satellite launches for fear of collision http www nytimes com 2007 02 06 science 20070206 ORBIT GRAPHIC html Kessler D J and Burton G Cour Palais Collision frequency of artificial satellites The creation of a debris belt Journal of Geophysical Research Vol 83 June 1978 2637 2646 ostm topex 5days orbit animation SeaWiFS daily coverage seawifs daily coverage animation Is this orbit prograde or retrograde Terra satellite MODIS instrument coverage of all instrument swaths during a single day 01 28 2006 Jason altimeter satellite ENVISAT 35 day repeat Equatorial separation of Jason groundtracks is 315 km Sidereal day time it takes for Earth to rotate through 360o This is slightly shorter than a solar day 24 hours There are 365 25 solar days in a year but 366 25 sidereal days Sidereal day 365 25 366 25 24 23 93 hours solar sidereal http en wikipedia org wiki Sidereal time Hohmann Transfer Maneuver to different inclination http en wikipedia org wiki Hohmann transfer Scan geometry zenith angle w r t satellite nadir look angle and solar zenith angle w r t local vertical Fixed solid angle Field of View FOV such as for an optical lens gives elliptical footprint off nadir and varying spatial resolution in the scan Panoramic distortion NOAA AVHRR Pixels 2 89 times bigger if earth flat Panoramic distortion NOAA AVHRR Pixels 2 89 times bigger if earth flat Pixels 4 94 times bigger if earth round Rotating mirror continuous scan e g AVHRR Whisk broom e g MODIS Push broom http maracoos org irene wpcontent uploads 2011 08 2011 08 29 1513 Terra RGB mab jp 2011 Aug 19 MODIS Aqua View satellite orbits and ground tracks at http science nasa gov realtime jtrack Spacecraft html Internet resources on orbits and satellites http science nasa gov realtime jtrack Spacecraft html Shows ground tracks and 3 D orbits for all satellites Notice the clusters of satellites in the major categories or orbits Geostationary Polar orbiting NOAA Topex ERS Envisat Low Earth orbit Iridium