NASA Technical Reports Server (NTRS) 19910016144: NASA/Ames Research Center DC-8 data system

4 Pages·0.19 MB·English

by  NASA Technical Reports Server (NTRS)

N9 1-: 8
Title: NASA/Ames Research Center DC-8 Data System
Authors: S.C. Cherniss, Sterling Software ocq 3 fg
C.P. Scofieid, NASA/Ames Research Center
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Discipline: Aircraft Data Management
In-flight facility data acquisition, distribution, and recording on the
NASA Ames Research Center (ARC) DC-8 are performed by the Data
Acquisition and Distribution System (DADS). Navigational and
environmental data collected by the DADS are converted to engineering
units and distributed real-time to investigator stations once per second.
Selected engineering units data are printed and displayed on closed circuit
television monitors throughout flights. An in-flight graphical display of
the DC-8 flight track (with barbs indicating wind direction and magnitude)
has recently been added to the DADS capabilities. Logging of data run
starts]stops and commentary from the mission director are also provided.
All data are recorded to hard disk in-flight and archived to tape medium
post-flight. Post-flight, hard copies of the track map and mission director's
log are created by the DADS.
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The DADS is a distributed system consisting of a Data subsystem, an
Avionic Serial Data-to-VMEbus (ASD2VME) subsystem, and a Host
subsystem (see DC-8 DADS System Block Diagram). Each subsystem has a
dedicated central processing unit (CPU) and is capable of stand-alone
operation. All three subsystems are housed in a single 20-slot VME chassis
(6U form factor) and communicate with each other over the VMEbus (see
the DC-8 DADS Internal Configuration diagram).
The Data subsystem is dedicated to acquiring and processing data
from aircraft support systems, sensors and the ASD2VME subsystem;
transmitting processed data to an external Data Distribution subsystem;
and displaying processed data on video monitors. Information about data
formats and transmission rates are available through the Medium Altitude
Missions Branch at ARC. The Data subsystem is a real-time, turn key
subsystem in which custom software is combined with the pSOS-68K Real-
time, Multi-tasking Operating System Kernel.
The ASD2VME subsystem collects data from two inertial navigation
systems plus radar altitude data. The ASD2VME subsystem converts this
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data to engineering units, thus reducing processing on the Data subsystem.
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It is a real-time, turn key subsystem consisting of two custom-built
avionics receiver boards controlled by a CPU board running custom
software. H
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The Host subsystem performs functions that have no rigid real-time
requirements, such as printing engineering units data on a character ll
printer, recording data to disk files, logging mission director commentary,
and post-flight data archival. Unlike the Data and ASD2VME subsystems,
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the Host subsystem is not turn key. The Host subsystem consists of custom
software running under the UniFLEX Operating System.
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Displayed and printed DADS data are configurable based on mission
requirements. Calculated values, such as sun and moon azimuth and
elevation, specific humidity and potential temperature, are available from m
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the DADS. The majority of the avionics and environmental parameters that
are displayed remains fairly constant from mission to mission.
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