Landsat 1,2,3

1. Orbit
        - sun-synchronous
        - altitude 919km
        - inclination 80^o  80^oN - 80^oS
        - 103 minute per cycle, 14 times each day
        - because of the earth's rotation, each successive N/S pass
            is offset to the west by 2,875km
        - distance between the adjacent tracks (at the Equator) is 159km
        - passes over the same place every 18 days

2. Return Beam Vidicon (RBV)
        - generates high resolution television-like images
        - Landsat 1,2 consists 3 cameras sensitive to green, red, NIR, respectively
        - forms a 3-band multispectral image

        - Landsat 1 and 2 RBV were hardly used due to technical failures
        - Landsat 3 RBV was modified but did not perform as expected

3. Multispectral Scanner (MSS)
        - a scanning system of a oscillating mirror to scan W->E
        - the reflected energy is directed to 24 detectors
          that are sensitive to 4 bands with 6 detectors per band

       Spectral resolution:
        band4: 0.5-0.6mm (green)
        band5: 0.6-0.7mm (red)
        band6: 0.7-0.8mm (near infrared)
        band7: 0.8-1.1mm (near infrared)
        band8: 10.4-12.6mm (far infrared, Landsat 3 only)

        Radiometric resolution:
        6 bits, 64 levels and rescaled to 7 bits, 128 levels

        Spatial resolution: 79x79m, resampled into 79x56m

        Temporal resolution: 18 days Landsat 1-3, 16 days Landsat 4,5

4. Biophysical sensitivity of spectrums
        - the palisade cells absorb blue and red light
          and reflect green light at a peak of 0.54mm

        - the spongy mesophyll cells reflect near infrared light that is
            related to vegetation biomass because
            the intercellular air space of spongy mesophyll layer is
            where photosynthesis and respiration occur

        - vegetation moisture content absorbs mid infrared energy

        Reference: Jensen, J. R. "Biophysical Remote Sensing." Annals,
        73:(1),111-132.

5. MSS scene
        ground swath:
        - 185x185km
        - 5% overlap and 14-85% sidelap
        - 2340 scan lines, 3240 pixels per line
        - after skew correction, rectangle image becomes
            parallelogram due to spacecraft movement and the earth rotation

        Pictorial format vs. digital data

6. Worldwide Reference System (WRS)
        the nominal center of a Landsat scene is identified by combination of
        path: N-S along satellite orbital tracks (total 223 paths) &
        row: E-W along latitudinal center lines (total 119 rows)

7. Reading: chpt 6
 

Landsat 4, 5, 6, 7

1. Orbit
        - 705km, a lower altitude for finer spatial resolution and
          retrievable by space shuttle
        - inclination 98.20^o
        - 99 minutes per cycle, 14.5 times each day
        - image swath 185km
        - the gap between successive passes at the equator is 2752km
        - the gap is filled in 16 days
        - distance between the adjacent tracks (at the Equat.) is 172km
        - overlap at the equator 7.6%
        - adjacent swaths are acquired every 7 days
        - Landsat 4 and 5 are 8 days out of phase
        - new path system in WRS and less paths (233)

2. Second generation of Landsat
   MSS
        - band 1,2,3,4 are equivalent to band 4-7 on Landsat 1,2,3
        - spatial resolution 82m

   Thematic Mapper (TM)
        -Spectral resolution:
         seven bands and narrower bands

        band1: 0.45-0.52microm (blue-green, water, soil and vegetation)
        band2: 0.52-0.60microm (green, chlorophyll reflection)
        band3: 0.63-0.69microm (red, chlorophyll absorption)
        band4: 0.76-0.90microm (near infrared, vegetation biomass, )
        band5: 1.55-1.75microm (mid infrared, vegetation moisture, cloud,
                snow, ice)
        band6: 10.4-12.5microm (far infrared, temperature)
        band7: 2.08-2.35microm (mid infrared, geologic rock formation,
                plant heat stress)

        -Radiometric resolution: 8 bits, 256 levels of brightness

        -Spatial resolution: 30x30m, 120x120m for band6

        -Temporal resolution: 16 days

3. TM operation
   scanning
        - each scan of TM mirror acquires 16 lines of data (4 lines
            for band 6)
        - the mirror is active in both E->W and W->E directions
        - allows a slower mirror speed for better brightness response
        - sensors are located in focal plane

   Tracking and Data Relay Satellites (TDRS)
        - Landsats are teamed with two TDRS
        - TDRSs are geo-synchronous and
        - transmit sensor data to central ground receiving station
            near White Sand, New Mexico
        - TDRSs relay commands from mission control to the Landsats and
          telemetry from the Landsat to the ground

4. Landsat 6 and 7
   Landsat 6
        - lost on October 5, 1993
        - same orbit as Landsat 4 and 5
        - Enhanced Thematic Mapper (ETM)
        - an eighth panchromatic band 0.5-0.9microm with 15m resolution
        - improved radiometric sensitivity

   Landsat 7
        - launched on April 15, 1999
        - ETM+, Enhanced Thematic Mapper Plus
            design continuity with Landsat 4 and 5
            an eighth 15m-resolution panchromatic band
            60m spatial resolution for the thernmal band

5. Reading: Chpt 6
 

...Back to Ling Bian top page.