Minimize AVNIR-2 & PRISM

The AVNIR-2 & PRISM menu to your right provide information concerning the SPPA activities for this mission. 

 

A brief description of the mission, its operations and main mission highlights is available in the sections below:

Sensor Description   |    Sensor Modes  
Minimize AVNIR-2 - Sensor Modes

The Advanced Visible and Near Infrared Radiometer type 2 (AVNIR-2) is a visible and near infrared radiometer for observing land and coastal zones. It provides better spatial land-coverage maps and land-use classification maps for monitoring regional environments. AVNIR-2 is a successor to AVNIR that was on board the Advanced Earth Observing Satellite (ADEOS), which was launched in August 1996.

 

The Advanced Visible and Near Infrared Radiometer type 2 (AVNIR-2) provides the following functionalities:

  • AVNIR-2 obtains high-resolution image data from observation in four bands of visible and near infrared. Instantaneous field of view angle is 14.28 µ rad (converted distance on the ground surface: approximately 10 meters), and field of view angle is approximately 5.8 degrees (converted distance on the ground surface: approximately 70 meters).
  • A cross track pointing function in the range ±44 degrees (positive for left of satellite flight direction).
  • Optical calibration function which calibrates all systems of AVNIR-2 including the optical system using internal lamp, and electrical calibration function for calibrating the electrical system installed after detector.
  • In order to enhance S/N, detector has a stagger alignment that increases the area ratio of pixel, and electronic scanning method which has linear array detector is being adopted. And AVNIR-2 obtains two-dimensional image of land and coastal area by scanning of two directions; in the cross track direction, the scanning of CCD itself, and in the along track direction, the scanning by using the motion of satellite body.
  • A gain switching function in the Analog Signal Processor which meets the difference between high and low latitudes and difference of the ground surface's luminance of each season, and an electronic shutter function which can control signal storage time are installed. Both functions can control their operations independently for each band.
  • AVNIR-2 exchanges (sends and receives) the following signals with ALOS, and carries out the operation control. 1) Telemetry signal for monitoring the AVNIR-2 condition. 2) Command signal for giving the instructions of each part's operation.
  • AVNIR-2 carries out thermal control independently aside from ALOS system. With respect to the instruments related to observation and calibration, the characteristic of these instruments is maintained by narrowing the thermal control range. For other instruments, they have a function for keeping the range of storage temperature or operation temperature.

The only mode of the instruments is the observation one which has the identification code OBS.



 
Illustration of AVNIR-2 observation capabilities (image credit: JAXA)
 

 

 
Mount Kenya, acquired with the AVNIR-2 instrument of ALOS on February 25, 2011 (image credit: JAXA, ESA)

 

Avnir-2 Characteristics

Number of Bands

4

Wavelength

Band 1 : 0.42 to 0.50 micrometers
Band 2 : 0.52 to 0.60 micrometers
Band 3 : 0.61 to 0.69 micrometers
Band 4 : 0.76 to 0.89 micrometers

Spatial Resolution

10m (at Nadir)

Swath Width

70km (at Nadir)

S/N

>200

MTF

Band 1 through 3 : >0.25
Band 4 : >0.20

Number of Detectors

7000/band

Pointing Angle

- 44 to + 44 degree

Bit Length

8 bits

 

Minimize PRISM - Sensor Modes

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).

The Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) provides the following functionalities:

  • PRISM has three telescopes for forward, nadir and backward views, where the observation range is panchromatic band in the visible near infrared region, and acquires each observation data.
  • Each telescope of PRISM has over 70Km of field of view: observation width will be 35Km in the normal observation mode for the three telescopes. The nadir telescope can output data with a 70Km swath width. When 70Km observation mode of the nadir is selected, only the observation data of the backward radiometer can be acquired simultaneously.
  • When 35Km observation mode is selected, the FOV can be pointed electrically ± 1.5 degrees. (Approximately 17.5 Km, cross-track direction)
  • In the nadir radiometer, resolution of horizontal direction is approximately 2.5meters. With respect to the forward and backward views, observation is carried out with the equivalent angle resolution to the nadir view.
  • PRISM has an Earth rotation correction function to correct the distortion of observation views due to the Earth's rotation, even if satellite does not carry out the yaw steering to correct it.
  • PRISM obtains images by selecting automatically the best image extraction position according to the satellite position information provided from the satellite system.
  • PRISM exchanges the following signals with ALOS, and carries out the operation control. 1) Telemetry signal for monitoring the PRISM condition 2) Command signal for giving the instructions of each part's operation
  • PRISM has an experimental function for obtaining the data for sensor development.
  • PRISM has an electrical calibration function in order to calibrate electrical system installed after a detector.
PRISM has the following sensor modes:
  • OB1: Nadir, Forward, Backward views at 35 KM width
  • OB2: Nadir view at 70 KM width and Backward view at 35 KM width

Illustration of the PRISM instrument and three-line imaging configuration (image credit: JAXA)

Illustration of the PRISM instrument and three-line imaging configuration (image credit: JAXA)

 

Artist's view of PRISM imaging concept (image credit: JAXA)

 

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.

 

PRISM 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)