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This concept payload
study assumes the use of standard Hitchhiker/GAS hardware and specifications whenever
possible. The Hitchhiker canister, with its avionics and adapter ring, possibly mounted on
a JEM-EF (Japanese Experiment Module - Exposed Facility) or EXPRESS pallet with an
attachment interface for the ISS could conceivably mount at either the JEM, S3 or P3 PAS
(Payload Attach System) mounting sites. |
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| The camera system itself is built
around a Hitchhiker/GAS five cubic foot canister mated to a motorized door assembly, which
is fitted with a fused silica window. Construction is based on four circular plates
separated and supported by three equally spaced struts attached on the circumference. The
cameras will be mounted behind the first, a 16mm (5/8") 6061-T6 aluminum plate that
acts as a containment shield and structural stabilizer, fitted with a thin glass epoxy
light baffle to reduce reflected glare in the optical system. |
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| Six digital cameras operating in different
portions of the light spectrum from ultraviolet to infrared are aligned and mounted on the
second plate located near the containment shield. Below the camera mounting plate is the
third of four internal plates. This plate supports the camera electronics and any
ancillary electronics packages needed to interface with the ISS Hitchhiker avionics
package. Below this is the fourth or bottom structural plate, which provides support and
rigidity through the three base bumpers that provide a mechanical interface with the
flight hardware. |
Click
here to see plan |
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Click here
to see plan |
Each camera optical path is chosen to match
its Skylab equivalent in both spectral range and subject footprint size as closely as
practical. With improvements in exposure speed allowed by advances in digital technology,
the payload will be able to do away with the cumbersome mechanical rotating mechanism used
to stabilize the Skylab camera platform, which was necessary to compensate for orbital
motion and extended film exposure times. All six cameras will be fired simultaneously, and
the pictures transferred to each camera’s four picture buffer memory. The picture
data files will then be sequentially transferred to a mass storage unit which will
compress and warehouse the data until it can be downloaded through either the ISS MRDL
(Medium Rate Data Link) or the HRDL (High Rate Data Link) as may be available. Camera
control will be uplinked through the Hitchhiker control uplink, which is at present an
RS-422 serial format (1200 baud) channel. While in operation, the computer will
continually monitor all cameras, electronics, payload environment, and its own health, and
return the system status by way of the Hitchhiker downlink, which also runs at 1200 baud.
Operational power will be derived from the ISS through the Hitchhiker avionics package,
and further regulated for the payload requirements. |
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