1 / 15

SATELLITE ORBITS

SATELLITE ORBITS. The monitoring capabilities of the sensor are, to a large extent, governed by the parameters of the satellite orbit. Different types of orbits are needed to achieve different data: Continuous monitoring – meteorological Global mapping- Land cover mapping

cormac
Download Presentation

SATELLITE ORBITS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. SATELLITE ORBITS The monitoring capabilities of the sensor are, to a large extent, governed by the parameters of the satellite orbit. Different types of orbits are needed to achieve different data: Continuous monitoring – meteorological Global mapping- Land cover mapping Selective imaging- Urban area

  2. What is orbit? The course of the motion of an object around a primary body in space or the path traced by it is called an orbit. Elliptic orbit is an orbit with the eccentricity greater than 0 and less than 1. Our Moon and the planets travel in orbits that are very close to being circular. A circle is a special kind of ellipse. Orbits of artificial satellites can be elliptical or circular. In general an orbit is a circular path described by the satellite in its revolution about the earth

  3. For Remote Sensing purpose the following orbit characteristics are relevant: • Altitude • Inclination angle • Period • Repeat Cycle • Orbit Altitude- Distance between the satellite and the earth surface. The altitude influences the area that can be viewed (Coverage) and the details that can be observed (resolution) • LEO the Low earth orbit- 150 to 1000km • GEO the Geostationary orbit – 36,000km

  4. Orbit Inclination Angle • Angle in degrees between the orbital plane and equatorial plane. • It decides together with the field of view the latitude up to which the earth can be observed • If inclination is 600, the satellite flies over the earth between latitudes 600 north and 600 south. • If it is LEO, it can not observe parts of earth at latitude above 600 north and 600 south. It means it can not observe polar region.

  5. Orbital period • Time, in minutes, required to complete one full orbit. • Orbit period and the mean distance to the centre of the earth are interrelated (Kepler’s third law) • Example: If a polar satellite orbits at 860km mean altitude, • its orbital period is 101 minutes • Its ground speed is 23,700km/h = 6.5km/sec • Speed of an aircraft is 400km/h i.e. 60 times slower than satellite

  6. Repeat Cycle • The time, in days, between two successive identical orbits. • The revisit time, the time between two successive images of the same area, is determined by the repeat cycle together with the pointing capability of the sensor. • Pointing capability means possibility of the sensor-platform to look to the side or fore and aft. • The sensors mounted on SPOT, IRS and Ikonos have this capability

  7. Orbit TypesCommon for RS missions • Polar orbit • Sun- synchronous orbit • Geostationary orbit • Other orbits

  8. POLAR ORBIT • Inclination angle between 800 and 1000 • An orbit having more than 90 degree angle means that the satellite motion is in westward direction • Launching a satellite in eastward direction requires less energy due to eastward rotation of earth • Such orbit enables observation of the whole globe, also near the poles • Typically placed in orbit at 600km to 1000km

  9. Sun-Synchronous Orbit • Near polar orbit chosen in such a way that the satellite always passes overhead at the same time • The inclination angle is between 980 and 990 to achieve this. • Most sun synchronous orbits cross the equator at mid-morning at around 10:30 hours local solar time • At this time the sun angle is low and the resultant shadows reveal terrain relief • In addition to day-time images, this orbit also allows the satellite to record night-time images (thermal or radar) during the ascending phase of the orbit at the dark side of the earth. • Examples of Polar and SS orbits: Landsat, SPOT and IRS

  10. Polar/Sun Synchronous Orbits Pass roughly over the north and south poles Fly over the same place on earth at the same time of day (sun always in same position) Examples: Landsat, AVHRR Good for land remote sensing Return time depends on Swath Width

  11. Swath Width Swath Width

  12. Geostationary orbit( GEOS, weather,Geosynchronous orbiting earth satellite) • The orbit in which the satellite is placed above the equator i.e. inclination angle is 00 • The altitude of placement is 36,000km • At this distance the orbit period of the satellite is equal to the rotational period of the earth, exactly one sidereal day • Used for meteorological and telecommunication satellites • Combination of geostationary orbit and polar orbit are used in meteorology

  13. Other Orbits • Lagrangian or Liberation Points: For a satellite circling two massive bodies it appears that there are five points where pull of gravity of two bodies is at equilibrium (L1 to L5). • In these points the satellite can be positioned at zero velocity with respect to both bodies. • L1 point of sun-earth system (1,5 mkm from the earth) is in use by number of solar observation satellites.

  14. DATA TRANSFER • The data of space borne sensors need to be sent to ground for further analysis. • Some old systems utilized film cartridge that fell back to a designated area on earth. • Now practically all earth observation satellites apply satellite communication technology as a downlink of data. • The data are directly sent down to a receiving station, or to a geostationary communication satellite that transmits the data to receiving stations on the ground.

  15. Orbital Characteristics • Geosynchronous • Polar • Sun synchronous

More Related