About ALOS - PRISM

PRISM Panchromatic Remote-sensing Instrument for Stereo Mapping

Image of PRISM The Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) is a panchromatic radiometer with 2.5m spatial resolution at nadir. Its extracted data will provide a highly accurate digital surface model (DSM).
PRISM has three independent optical systems for viewing nadir, forward and backward producing a stereoscopic image along the satellite's track. Each telescope consists of three mirrors and several CCD detectors for push-broom scanning. The nadir-viewing telescope covers a width of 70km; forward and backward telescopes cover 35km each.
The telescopes are installed on the sides of the optical bench with precise temperature control. Forward and backward telescopes are inclined +24 and -24 degrees from nadir to realize a base-to-height ratio of 1.0. PRISM's wide field of view (FOV) provides three fully overlapped stereo (triplet) images of a 35km width without mechanical scanning or yaw steering of the satellite. Without this wide FOV, forward, nadir, and backward images would not overlap each other due to the Earth's rotation.


PRISM Characteristics
Number of Bands 1 (Panchromatic)
Wavelength 0.52 to 0.77 micrometers
Number of Optics 3 (Nadir; Forward; Backward)
Base-to-Height ratio 1.0 (between Forward and Backward view)
Spatial Resolution 2.5m (at Nadir)
Swath Width 70km (Nadir only) / 35km (Triplet mode)
S/N >70
MTF >0.2
Number of Detectors 28000 / band (Swath Width 70km)
14000 / band (Swath Width 35km)
Pointing Angle -1.5 to +1.5 degrees
(Triplet Mode, Cross-track direction)
Bit Length 8 bits
Note: PRISM cannot observe areas beyond 82 degrees south and north latitude.


Observation Modes
Mode 1 Triplet observation mode using Forward, Nadir, and Backward views (Swath width is 35km)
Mode 2 Nadir (70km) + Backward (35km)
Mode 3 Nadir (70km)
Mode 4 Nadir (35km) + Forward (35km)
Mode 5 Nadir (35km) + Backward (35km)
Mode 6 Forward (35km) + Backward (35km)
Mode 7 Nadir (35km)
Mode 8 Forward (35km)
Mode 9 Backward (35km)
Swath Width(35km) of PRISM Swath Width(70km) of PRISM