Sensor
PRISM Panchromatic Remote-sensing Instrument for Stereo Mapping
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.
| 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 |
| 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) |
