| definition |
- OSA was designed and custom-built by Kodak Co. of Rochester, NY (Space Imaging owns the design of OSA). The instrument features a Cassegrain-type telescope with a 70 cm diameter primary mirror, a 10 m focal length (folded optics design). The OTA (Optical Telescope Assembly) captures imagery across a swath of 11-13 km, it uses five mirrors to reflect the imagery to the imaging sensor arrays at the back end of the telescope. Three of the mirrors are powered (curved), and are of TMA (Three Mirror Anastigmatic) design. Note: TMA refers to lenses that are able to form approximately point images of target (object) points. The other two mirrors are flat, and serve to `fold' or bounce the imagery across the width of the telescope.
Pushbroom detector technology (a large focal plane detector array, generation of 6500 lines/s of panchromatic image data) is employed. Simultaneous imaging in panchromatic and multispectral modes is provided. The pixel size on the detector array is 12 µm for the panchromatic (PAN), and 48 µm for the multispectral (MS) detectors.
The MS bands correspond to those of TM on Landsat in the visible range of the spectrum. The instrument light level is governed by a 70 cm aperture and a choice of 10, 13, 18, 24, or 32 TDI (Time Delay Integration) stages for panchromatic (gray-scale) imaging. The detector array offers a cumulative exposure concept for panchromatic imaging.(1)
On-board electronics provide low-loss data compression of the original 11-bit data using ADPCM (Adaptive Differential Pulse Code Modulation). - The OSA instrument design features lightweight materials and advanced manufacturing techniques. The mass of the primary mirror was reduced by cutting a honeycomb pattern into its core using abrasive waterjet technology, and fusing thin mirror plates to each face.
|
