1. Monitoraggio Geodetico e Telerilevamento 3 Remote Sensing Images
Carla Braitenberg
Dip. Matematica e Geoscienze
Universita’ di Trieste
Tel Tel. Assistente Dr. Nagy:

2. View of Earth surface

3. Viewed area changes from circle to ellipse at off-nadir veiw angles

4. Immagine proiettata da una lente
ogetto
Punto focale
Punto focale
Immagine
Per un rivelatore di dimensioni finite, l’immagine maggiore che posso rappresentare
E’ definita dalla lunghezza focale f della lente.

5. Examples for Whiskbroom and Pushbroom scanners
Landsat Multispectral Scanner (MSS)
Landsat Thematic Mapper (TM)
Landsat 7 Enhancement Thematic Mapper (ETM+ )
Pushbroom
Landsat 8 Operational Land Imager (OLI) and Thermal Radiation Sensor (TIRS)

6. From Landsat7 Handbook
Optical path for Landsat 7 across track scanning image acquisition system.

7. From the handbook, description of previous figure
Scene energy passes through a number of major ETM+ subsystems, depicted in Figure 3.2, before the solid-state detectors at the focal plane collect it. The bidirectional scan mirror assembly (SMA) sweeps the detector's line of sight in west-to-east and east-to-west directions across track, while the spacecraft's orbital path provides the north-south motion. A Ritchey-Chretien telescope focuses the energy onto a pair of motion compensation mirrors (i.e. scan line corrector) where it is redirected to the focal planes. The scan linecorrector is required due to the compound effect of along-track orbital motion and crosstrack scanning which leads to significant overlap and underlap in ground coverage between successive scans. The aligned energy encounters the Primary Focal Plane (PFP), where the silicon detectors for bands 1-4 and 8 (panchromatic) are located. A portion of the scene energy is redirected from the PFP by the relay optics to the Cold Focal Plane where the detectors for bands 5, 7, and 6 are located. The temperature of the cold focal plane is maintained at a predetermined temperature of 91° K using a radiative cooler. The spectral filters for the bands are located directly in front of the detectors.

8. From Landsat8 Handbook
Landsat8 OLI and TIRS sensors arrangement.

9. Landsat 8 pushbroom sensor
OLI (Operational Land Imager) instrument
Sensor Chip Algnment (SCA) in focal plane. Each SCA contains rows of detectors.

10. Continues Landsat 8- redundant arrangament of sensitive devices to have sensor backup.

11. Thermal infrared sensor Landsat8
TIRS arrangament of sensors in the focal plane.

12. Dwell time comparison Whiskbroom Landsat TM Pushbroom
Time for one cross track sweep: T=w/v
w= down track pixel size (30m)
V=satellite velocity (7500 m/s)
Dwell time for one pixel: dT=T*dL/L
L: Cross track line width ( m)
dL: cross track pixel size (30m)
dT=6.5 10^-7 sec/pixel
Pushbroom
Dwell time dT=w/v
With the values of left side:
dT=20 sec/pixel
No reduction through cross track sweep.