Remote Sensing of the Ocean and Atmosphere: John Wilkin Orbits and Measurement Geometry IMCS Building Room 214C ext 251

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.T 2 : R 3 ratio is constant for all planets, where T is orbital period and R is semi- major axis of the orbit Johannes Kepler (1571 – 1630) German mathematician, astronomer and astrologer

Nov 5, 2007 view from Space Shuttle Epoch (UTC):10:07:53 AM, Monday, January 28, 2008 Eccentricity: Inclination: ° Perigee Height:334 km Apogee Height:341 km Right Ascension of Ascending Node: ° Orbit Number at Epoch:52631 Revolutions per Day:

Stewart, R. H., 1985, Methods of Satellite Oceanography, University of California Press, 360 pp.

x-axis

See graphics of orbital elements and data for ISS

Jason-1 launch from Vandenburg Air Force Base, California Orbit: Launch: Topex/Poseidon launched with Ariane rocket Pegasus vehicle aircraft launch Other launches: Delta-II (Themis): Ariane: Jason-2 OSTM

OSTM / Jason-2 Boost Profile Space craft separation:

Maneuver to different inclination Hohmann Transfer

On Jan 11, 2007, China tested an anti- satellite rocket. The initial collision added 800 to 1000 pieces of space junk to the current total of detectable objects. 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): 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. How many detectable objects (< 4 inches) are in orbit?

See graphics of orbital elements and data for ISS

Sidereal day = time it takes for Earth to rotate through 360 o This is slightly shorter than a solar day (24 hours) There are solar days in a year but sidereal days Sidereal day = /366.25*24 = hours sidereal solar

SeaWiFS daily coverage

Terra satellite, MODIS instrument, coverage of all instrument swaths during a single day ( 01/28/2006 )

Jason altimeter satellite Equatorial separation of Jason groundtracks is 315 km ENVISAT 35-day repeat

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

View satellite orbits and ground tracks at:

Internet resources on orbits and satellites Shows ground tracks and 3-D orbits for all satelliteshttp://science.nasa.gov/realtime/jtrack/Spacecraft.html –Notice the clusters of satellites in the major categories or orbits Geostationary Polar orbiting (NOAA, Topex, ERS, Envisat) Low Earth orbit (Iridium, HST, ISS) GPS –Unusual orbits (especially ground track) Chandra IMAGE CRRES (in a geosynchronous transfer orbit) Shows predicted orbits and visibility magnitudes and star charts of pass trajectories for all satelliteshttp://heavens-above.com –See Homework –See graphics of orbital elements and data for ISS Real-time satellite tracking at