Description
AISA Eagle VNIR remote hyperspectral sensor has a 1000 pixel swath width which is almost three times the size of AISA Classic. The benefits of a wider ground swath are 1) a reduction in the number of flightlines required to cover large targets, 2) increased operational flexibility. If an area where cloud cover is persistant the acquisitional window is narrow and a wider ground swath permits flight blocks to be finished more quickly as fewer lines are required.
AISA Eagle is designed with the field in mind making it compact and field friendly. The Eagle is relatively simple to install and remove from any aircraft. It takes approximately one hour to install or remove the system once the technique has been mastered.
The AISA Eagle is a complete, pushbroom system, consisting of a hyperspectral sensor head, miniature GPS/INS sensor, data acquisition unit in a rugged PC with display unit and power supply.
The acquisition system software also enables in-flight configuration changes. This ability facilitates on-site adjustments to mission parameters should they be needed to successfully complete a mission.
Specs
The following table identifys the general specifications for the AISA Eagle.
| Sensor Head | Typical specifications |
|---|---|
| Spectrograph | High efficiency transmissive imaging spectrograph. Throughput practically independent of polarization. Smile and keystone < 5 microns. |
| F/# | F/2.4 |
| Spectral Range | 400-970 nm |
| Spectral Pixels | 244 |
| Spectral Sampling/Pixel | 2.3 nm |
| Slit Width | 30 microns |
| Spectral Resolution | 2.9nm |
| Fore optics | Standard Optional |
| 17 mm 23 mm 10 mm | |
| FOV | 39.7 degrees 29.9 degrees 63 degrees |
| IFOV | 0.039 degrees 0.029 degrees 0,062 degrees; |
| Ground Resolution @ 1000m | 0.71 m 0.52 m 1.2 m |
| Camera | Progressive scan CCD camera |
| Output | 12 bits digital |
| Integration Time | Settable independent of image rate |
| Shutter | Electromechanical shutter for dark background registration, user controllable by software. |
| FODIS | Diffuse light collector and fiber optic cable (5 m standard) with SMA connector. |
| Calibration | Sensor head comes with wavelength and radiometric calibration file. |
| Image Rate | Up to 50 images/s @ 244 hyperspectral bands. Up to 80 images/s @ 60 hyperspectral bands. |
Processing
- radiometric correction
- rectification
- geo-referencing
After CaliGeo processing the data can be imported and analyzed using ENVI.
Radiometric correction
NIST traceable calibrations are used to radiometric correct the data. Once the corrections have been applied either an unrectified radiance or unrectified reflectance product is produced. Both products are corrected to altitude. No atmospheric corrections are applied to the data.
Rectification
Rectification compensates for incidental camera movement, which prevents attainment of true vertical image. Formerly this was achieved with ground control points (GCP) however AISA uses a C-Migits III GPS/INS unit manufactured by Systron Donner. The system records GPS and aircraft attitudinal positions (roll, pitch, yaw, speed and heading). The rectification process uses the GPS and INS inputs to generate a global lookup table which is applied to the unrectified image.
The highly accurate vector data coverage (white lines) over a georectified AISA image, illustrating the level of planimetric accuracy attainable without the use of ground control.
Products
Standard output files are in ENVI format. This format can be imported directly into Erdas Imagine. The ENVI data may also be imported by ArcGIS, provided the Arc extension for ENVI data has been added.
Additional value added processing can be provided on request.
