Experiments Support Systems for OV-102 (Columbia)
system for the orbiter experiments was developed to record data
obtained and to provide time correlation for the recorded data.
The information obtained through the sensors of the OEX instruments
must be recorded during the orbiter mission because there is no
real-time or delayed downlink of OEX data. In addition, the analog
data produced by certain instruments must be digitized for recording.
system for OEX comprises three subsystems: the OEX recorder, the
system control module and the pulse code modulation system. The
SCM is the primary interface between the OEX recorder and the experiment
instruments and between the recorder and the orbiter systems. It
transmits operating commands to the experiments. After such commands
are transmitted, it controls the operation of the recorder to correspond
to the experiment operation. The SCM is a microprocessor-based,
solid-state control unit that provides a flexible means of commanding
the OEX tape recorder and the OEX and modular auxiliary data system.
The PCM system
accepts both digital and analog data from the experiments. It digitizes
the analog data and molds it and the digital data received directly
from the experiments into a single digital data stream that is recorded
on the OEX recorder. The PCM also receives time information from
the orbiter timing buffer and injects it into the digital data stream
to provide the required time correlation for the OEX data.
The SCM selects
any of 32 inputs and routes them to any of 28 recorder tracks or
four-line driver outputs to the T-0 umbilical; executes real-time
commands; controls experiments and data system components; and provides
manual, semiautomatic and automatic control.
carries 9,400 feet of magnetic tape that permits up to two hours
of recording time at a tape speed of 15 inches per second. After
the return of the orbiter, the data tape is played back for recording
on a ground system. The tape is not usually removed from the recorder.