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OFFICIAL PRESS RELEASE
about the findings of the commission established to analyze the
causes of the Soyuz TMA-1 descent vehicle returning to Earth in
ballistic mode 

May 26, 2003. Korolev, Moscow Region.
The findings of the technical commission established to analyze the
causes of the Soyuz TMA-1 descent vehicle returning to Earth in
ballistic mode were presented at a press conference held at S.P.
Korolev Rocket and Space Corporation Energia for journalists of
Russian and international TV companies and information agencies, as
well as representatives from NASA and European Space Agencies. The
chairman of the commission is the First Deputy General Designer of
RSC Energia N.I.Zelenschikov. Present at the press conference were
members of the commission - managers and specialists from RSC
Energia, Federal Office of Aviation and Space Rescue and Recovery,
Gagarin Cosmonaut Training Center and TsNIIMash.

The commission made a statement that basically all of the new systems
and structural elements of the vehicle have been tested in flight
during the mission. Fully tested were: the new control panel,
refrigerating and drying units of the thermal control system, linear
acceleration measuring unit, descent vehicle structure, the system
for recording and storing telemetry and voice information and all the
elements of landing system (baro unit, automatic equipment, upgraded
gamma-ray altimeter, soft-landing thrusters, new seats). The new
special computing unit KC020-M - the command unit of the controlled
descent loop - has not been tested to the full extent because the
descent vehicle switched from the automatic controlled descent mode
into ballistic descent mode. However, telemetry data have shown that
this computer unit, which was made to change from command mode into
indication mode during switching over to the ballistic descent,
generated all the necessary commands in accordance with its
pre-programmed logic, so there have been no anomalies in its
behavior.

Establishing Soyuz TMA-1 in-orbit orientation, starting propulsion
unit, generating a retro burn, and running module separation
operations have all been performed in accordance with the program and
technical documentation and no anomalies have been found.

In the course of 183 seconds after separation of the spacecraft
modules, the descent vehicle was moving along the controlled descent
trajectory. Switching to the ballistic descent mode occurred
automatically after the Motion Control System (MCS) generated the
command on the basis of the spacecraft reaching the maximum allowable
yaw angle. Operation of MCS and of the landing equipment, as far as
roll and pitch channels were concerned, stayed within design limits.

The ballistic descent has been performed nominally, in accordance
with the pre-programmed control logic. The maximum g-loads during
descent did not exceed 8.1g. The descent vehicle landing system
performed nominally and g-loads stayed within the design limits.

The descent vehicle of Soyuz TMA-1 landed in its target point for
ballistic descent. The search and rescue service found the descent
vehicle and the crew within prescribed timeframe. No anomalies have
been found in the operation of the communications and direction
finding systems during descent and landing.

During the descent the crew of Soyuz TMA-1 performed all the
necessary monitoring and control operations in accordance with
on-board instructions and recommendations from the Lead Operations
Control Team (LOCT) displaying good teamwork and mutual
understanding. The crew evinced high psychological stability,
endurance and self-control. High professionalism of N.M.Budarin as
the commander of the vehicle in this situation merits a special note
here. 

The commission findings: the cause of switching to the ballistic
descent mode was an inadequate reaction of the descent control unit
within the descent control system to the signals from gyroscope
KI00-18 and the angular rate meter. As a result, the descent vehicle
yawed to the limit angle, which caused the gyroscope end switch to
issue the command to switch to the ballistic descent mode.

In the course of its work the commission has run tests on the descent
control unit. During its electrical tests within the descent vehicle
brought from the landing site to RSC Energia there have been many
attempts to simulate the situation that occurred in flight, but they
failed to reproduce it. Only when one channel of the unit was
artificially disconnected, in one case (out of forty) a situation was
achieved which was close to the one in flight.

The analysis has not revealed any connection between the situation
and the descent vehicle modifications that have been introduced. The
MCS hardware as far as the applicable control functions are concerned
has not been modified since Soyuz T (since 1979). The descent control
unit has no electrical interfaces with the newly added special
computer unit and a unit for measuring linear accelerations.

Tests of the descent control unit after its return to Earth have
showed that its electrical properties are fully compliant with the
requirements of the technical documentation. However, an in-depth
analysis of the descent control unit done in course of the commission
activities revealed a peculiarity of its electrical design, which
could, under a very rare combination of input signals in any of the
three channels (pitch, yaw, roll), could lead to disabling the signal
and stopping output of commands to the effectors. The occurrence of
this problem is of very low likelihood, which is born out by the 48
successful controlled descents of the Soyuz-type vehicles, including
the ones involving the descent control unit, which, before it was
installed on Soyuz TMA-1, has passed flight tests in Soyuz TM-29 in
1999. The work to simulate and reproduce this situation in a
stand-alone electrical test setup for the descent control unit
continues. The analysis of the on-board documentation, mission
control documentation, LOCT actions, communication between search and
rescue teams, MCC-M and the crew has revealed some problems that have
not significantly affected the mission, but need to be resolved in
the future. 

The commission permits Soyuz TMA-2, currently operating in orbit
within ISS, to continue its mission without any reservations
regarding the on-board equipment of the spacecraft, however, it wants
to draw attention to the need to take into account its
recommendations about actions of the crew and LOCT, and
communications between search and rescue team and MCC-M. The final
version of the commission's findings was submitted for approval.  It
was recommended that, starting with Soyuz TMA-3, the descent control
unit be modified to introduce into it additional elements which will
rule out the unlikely but possible situation similar to the one that
occurred. After presenting the key findings of the commission, N.I.
Zelenschikov, managers and specialists on that commission, answered
journalists' questions, and then, together with them they visited the
Corporation's test and check-out facility, where they provided
additional explanations of the commission's findings and told about
the progress of work under the International Space Station project,
including the on-going work at RSC Energia to build Progress and
Soyuz TMA-3 spacecraft in support of ISS program for the year 2003.

The meeting continued for more than two hours.

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