Lecture 6 Flashcards
λ wavelength f/v frequency μm micrometer 10^-6 nm 10^-9 Ang 10^-10 
Microwave and thermal collected
collected all the time–radiation emitted
VIS, Near IR, Mid IR collected when?
day–need sun
perigee
nearest point to Earth in orbit
apogee
furthest point from Earth in orbit
orbital time
time for one complete revolution around Earth. Depends only on the height of satellite.
geostationary orbit
stationary with respect oto location on Earth
circular orbit about equator (no inclination, altitude 36,000 km)
travelling at same speed as Earth
Useful coverage up to 55* for quantititivework
geosynchronous orbit
nodal of one sidereal day
some inclination
traces a figure-8 on surface of Earth
sidereal day
Latin for “star day,” 86, 400 s
time needed for Earth turn around it’s axis in respect to star
civil day
time for Earth to revolve around sun
Sun synchronous orbit
crosses a given latitude at the same solar time every day
orbital plane rotates about the polar axis
orbital height ~1000 km
inclination > 96*
Good when need same time, radiation angle, etc.
Examples: Landsat, SPOT, NOAA, DMSP, RADARSAT
Altimetric orbit
Ascending and descending passes should cross close to 90 degrees
Because want same accuracy of swath? slope?
Molniya orbit
Highly eccentric orbit, Usually for communication
Kepler’s 2nd law. The line between a planets and the Sun sweeps out equal areas in equal times.
Thus, to cover hgiher lattitueds, need to change altitude.
Takes much longer to pass trhough the apogee than the perigee
The more eccentric an orbit, the longer the “dwell time” near apogee.
GPS examples
NAVSTAR GPS (US MILITARY) GLONASS GPS (RUssia) Galileo GPS (EU)
GPS what it is
System of satellites comprised of 24-32 GPS satellites (with 24, six orbits)
all-weather, day and night, anywhere on or near Earth (means active, using longer wave–microwave, radar, less affected, produce own energy, not dependent on Sun)
How GPS works
- receiver precisely times signals
- time converted to distance
- position accuracy increases with number of satellites (3 minimum, four for error correction)
- position determined within the terrestrial reference frame