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
GPS satellite network
altitude ~ 12,000 mi (192000 km) two complete orbits in less than day approx 11200 km/hr solar powered with backup batteries small rocket boosters to correct orbit
Civillian applications of GPS
surveying, mapmaking, navigation, cellular technology, tectonics, disaster relief, Geotracking,etc
Receivers capable of functioning above 18 km altitude and 515 m/s are classified as munitions. Licenses are required.
Military applications of GPS
navigation, target tracking, miissile and projectile guidance, search and rescue, reconnaissance.
GPS satellites also carry a set of nuclear detonation detectors (major part o USNDDS)
Types of cameras
more than 100 diff models of aerial film cameras
- single-lens frame
- Multi-lens (multi-band) frame
- Panoramic
- Digital
Single-lens frame
- one lens
- most common
- used for mapping (x,y) features and to derive topo maps
- Extremely high geometric and radiometric image quality
- Film size commonly 24 cm wide and 100-500ft long
- large-format camera (LFC), metric camera (space)
- Wild RC-10 airplane (for example)
Multi-lens frame camera
- multi spectra–image taken in several EM regions
- photos taken using diff filter and film combinations
- multi-band photography provides spectral info for classification (can get spectral signatures for things)
Panoramic camera
- narrow strip of ground areas covered by either a rotating camera lens, or a rotating prism in front of lens
- 180* scan angle
- Common use in military reconnaissance
Digital camera
- no film, using charge-coupled device (CCD) is used–photon hits detector and is converted to digital number of brightness value
- lens focus light onto detectors
- signal converted into a digital brightness value (diff number for different colors)
Panchromatic film
sensitive to whole visible light spectrum
Camera optics
TBA
vertical aerial photograph
camera’s optical axis is within +- 3* of perpendicular to Earth
Oblique aerial photograph
deviates more than 3*
low and high (can see horizon)
can cover larger area than vertical
Focal plane
the area in a camera where light is focused during exposure (in digital, CCDs. In analog cameras, the film)
focal length
distance from the surface of a lens or mirrow to its focal point
smaller the focal length, the greater the field of view, the larger the projected image is likely to be
