|Modular Auxiliary Data System
instrumentation system measures and records selected pressure, temperature,
strain, vibration and event data to support payloads and experiments
and to determine orbiter environments during flight. It supplements
existing orbiter operational instrumentation by conditioning, digitizing
and storing data from selected sensors and experiments.
The MADS collects
detailed data during ascent, orbit and entry to define vehicle response
to flight environments. It permits correlation of data from one
flight to another and enables comparison of flight data from one
orbiter to another orbiter.
All MADS equipment
installed in the orbiter is structurally mounted and environmentally
compatible with the orbiter and mission requirements. Because of
its location, the MADS does not intrude into the payload envelope.
Equipment consists of a pulse code modulation multiplexer, a frequency
division multiplexer, a power distribution assembly and appropriate
signal conditioners mounted on shelf 8 beneath the payload bay liner
of the midfuselage.
In OV-102 Columbia),
MADS inputs its information to the system control module and records
it on the OEX recorder located below the crew compartment middeck
floor. In OV-103 Discovery) and OV-104 Atlantis), a MADS control
module and recorder are mounted below the crew compartment middeck
approximately 246 measurements from the orbiter airframe, skin and
orbital maneuvering system/reaction control system left-hand pod.
The MADS interfaces
with the orbiter through the orbiter's electrical distribution system
and operational instrumentation inputs for status monitoring. Coaxial
cables and wire harnesses from the sensors are routed through the
orbiter payload bay harness bundles to the signal conditioners,
PCM multiplexer and FDM, attached to the midfuselage shelf. After
the signal conditioners and the multiplexers have processed the
data, four outputs of the FDM and one output of the PCM multiplexer
are routed forward to the SCM in OV-102 for recording on the OEX
recorders. In OV-103 and OV-104, the four outputs of the FDM and
one output of the PCM multiplexer are routed forward to the MCM
for recording on five tracks of the MADS recorder. In addition,
the MADS recorder is used during ascent to record additional space
shuttle data consisting of solid rocket booster wide band and external
The MADS is
not considered mandatory for launch, and its loss during flight
does not cause a mission abort. It measures and records data for
predetermined events established by test and mission requirements.
For a typical
mission, approximately five hours before launch, the MADS is powered
on from the preset switch configuration to supply a prelaunch manual
calibration. (Power is supplied from the orbiter's main buses A
and B.) After calibration, all switches are returned to the preset
configuration, leaving the MADS in the standby position and only
the MCM receiving power. This mode continues until nine minutes
before launch, at which time the MADS attains the full-system mode
through uplink commands and all its components are powered on. In
this mode, the MADS recorder is operating at a continuous tape speed
of 15 inches per second, recording aerodynamic coefficient identification
package, flight acceleration safety cutoff, ET, SRB, wide-band and
PCM data. The MADS PCM bit rate is 64 kbps.
mode is used during the prelaunch automatic and manual calibrations.
This mode records the ac and dc calibration levels provided by the
FDM. Each manual calibration level is recorded for 10 seconds at
a tape speed of 15 inches per second in the continuous mode.
12 minutes after launch, the MADS is commanded into the PCM-snapshot-with-strain-gauge-signal-conditioner
mode. In this mode, the recorder is in the sample mode, conserving
power and recorder tape by recording data for 10 seconds every 10
minutes at a PCM bit rate of 32 kbps and a tape speed of 3.75 inches
per second. Two minutes before the second orbital maneuvering system
thrusting period, the MADS is commanded into the full-system mode
until the thrusting period is completed. Then it is commanded into
the PCM-only mode, which continues during the orbit until a quiescent
period is reached. In OV-102 only, one minute of ACIP calibration
is required during this period, after which the MADS continues in
the PCM-only mode. The system is switched to the full-system mode
for the OMS separation thrusting periods and can be returned to
the PCM-only mode for the majority of the on-orbit mission.
mode is similar to the PCM-only mode, but strain measurements are
also recorded during this period. The SGSC operation is cycled along
with the other MADS equipment and signal conditioners by uplink
commands to maintain the required operational temperatures. This
mode occurs between two full-system modes to minimize flight crew
participation and conserve power and recorder tape. It can be initiated
from the full-system mode or returned to the full-system mode by
one uplink command. To shift this mode to the PCM-only mode, the
SGSC must be commanded off manually by the flight crew. This mode
is used on orbit.
before the deorbit thrusting period, the MADS is put into the full-system
mode for one hour to record descent (entry) data. At the conclusion
of the one-hour period, it is placed in the PCM-only mode for approximately
four hours to measure postlanding thermal data and is then powered
down for the entire postlanding period.
With the use
of the MADS switches located in the crew compartment, control can
be initiated by the flight crew. To reduce the flight crew's participation,
all commands are uplinked from the Mission Control Center in Houston
and transmitted to the onboard payload forward 1 multiplexer/demultiplexer.
The MDM then routes the commands to the SCM for processing in OV-102
and to the MCM in OV-103 and OV-104. Power for the MADS will be
supplied by the orbiter's 28-volt dc main buses A and B.
acceleration safety cutoff system interfaces 12 orbiter main engine
vibration measurements with the MADS. The variety of MADS measurements
is collected by thermocouples, resistance thermometers, radiometers,
vibration sensors, strain gauges or pressure transducers.
The MADS shelf
8 components are protected from overheating by shelf temperature
monitoring and control of MADS operation by ground commands. The
MADS is thermally isolated from the orbiter structure by 0.049-inch
thin-wall titanium struts. It is also protected from the orbiter
environment by a 1.5-inch bulk-insulation enclosure.
The MADS recorders
in OV-103 and OV-104 are Data Tape/Kodak 28-track, wide-band, modular,
airborne recording systems similar to the OV-102 orbiter experiments
recorder. The recorders are capable of simultaneously recording,
and subsequently reproducing, 28 tracks of digital biphase L data
or any combination of wide-band analog and digital biphase L data
up to 28 tracks.
and OV-104 return from a mission, the recorder tape is played back
to record the data on a ground recording system. The tape is not
removed from the flight recorder. The total MADS weight is 641 pounds.