Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT_ZIP/spacedig/V15_1/V15NO166.ZIP/V15NO166

Internet Message Format | 1993-07-13 | 47KB

Date: Fri,  4 Sep 92 05:02:58
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #166
To: Space Digest Readers
Precedence: bulk


Space Digest                Fri,  4 Sep 92       Volume 15 : Issue 166

Today's Topics:
               Mars Observer Press Kit (long) [Part 1]

    Welcome to the Space Digest!!  Please send your messages to
    "[e-mail]", and (un)subscription requests of the form
    "Subscribe Space <your name>" to one of these addresses: listserv@uga
    (BITNET), rice::boyle (SPAN/NSInet), utadnx::utspan::rice::boyle
    (THENET), or [e-mail] (Internet).
----------------------------------------------------------------------

Date: 4 Sep 92 06:02:03 GMT
From: Ron Baalke <[e-mail]>
Subject: Mars Observer Press Kit (long) [Part 1]
Newsgroups: sci.space,sci.astro

               NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
                              MARS OBSERVER
                                PRESS KIT
                             SEPTEMBER 1992

PUBLIC AFFAIRS CONTACTS


NASA HEADQUARTERS, WASHINGTON, D.C.

Office of Space Science and Applications
Paula Cleggett-Haleim
(Phone:  [phone])
Donald L. Savage
(Phone:  [phone])

Office of Communications
Dwayne C. Brown
(Phone:  [phone])


JET PROPULSION LABORATORY, PASADENA, CALIF.
Robert J. MacMillan
Diane Ainsworth
(Phone:  [phone])


KENNEDY SPACE CENTER, FLA.
Dick Young
Karl Kristofferson
George H. Diller
(Phone:  [phone])


MARSHALL SPACE FLIGHT CENTER, HUNTSVILLE, ALA.
Dom Amatore
Jerry Berg
(Phone:  [phone])


LEWIS RESEARCH CENTER, CLEVELAND
Marilyn S. Edwards
Mary Ann Peto
(Phone:  [phone])


CONTENTS


General Release                                             1
Mars Observer Science Objectives                            6
Mission Design                                              7
Spacecraft Science Instruments                              9
Mission Timeline                                           16
Mapping Cycle                                              17
The Spacecraft System                                      18
Spacecraft Description                                     19
Titan III Launch Vehicle                                   20
Titan III Facts                                            21
Transfer Orbit Stage                                       23
Launch Vehicle and Payload Processing                      27
Launch Countdown and Flight Control                        28
Countdown Milestone Events                                 29
Mars Observer/Titan III/TOS Tracking Support               30
Salient Facts on Speed and Distance                        31
Science Operations                                         32
Mars Observer Investigators                                33
Interdisciplinary Scientists                               36
Mars Observer Management                                   37
Previous Mars Missions                                     39


RELEASE:  92-142

MARS OBSERVER READY TO TAKE THE NEXT STEP IN MARS EXPLORATION

     NASA will continue the exploration of Mars -- started by
the Mariner IV spacecraft 28 years ago -- when Mars Observer
is launched in September.  The last U.S. spacecraft to visit
Mars was Viking 2 in 1976.

     "Mars Observer will examine Mars much like Earth
satellites now map our weather and resources," said Dr.
Wesley Huntress, Director of NASA's Solar System Exploration
Division, Washington, D.C.  "It will give us a vast amount of
geological and atmospheric information covering a full
Martian year.  At last we will know what Mars is actually
like in all seasons, from the ground up, pole to pole.

     "In the mid 1960s, the Mariner flybys resulted in the
historic first pictures of the cratered surface of Mars,"
Huntress continued.  "Then, the Viking landers looked for
signs of life at two landing sites.  The Viking orbiters also
made global maps which gave us a good picture primarily of
surface features.  Now, the Mars Observer mission marks the
next phase in planetary exploration."

     "Mars Observer will tell us far more about Mars than
we've learned from all previous missions to date," said David
Evans, Project Manager, NASA's Jet Propulsion Laboratory
(JPL), Pasadena, Calif.  "We want to put together a global
portrait of Mars as it exists today and, with that
information, we can begin to understand the history of Mars.

     "By studying the evolution of Mars, as well as Venus',
we hope to develop a better understanding as to what is now
happening to planet Earth," Evans said.  "As we look even
further into the future, this survey will be used to guide
future expeditions to Mars.  The first humans to set foot on
that planet will certainly use Mars Observer maps and rely on
its geologic and climatic data," Evans said.

Launch and Cruise to Mars

     Mars Observer is scheduled for launch aboard a Titan III
rocket in late September from Cape Canaveral Air Force
Station, Fla.  The beginning of the launch opportunity is
Sept. 16, 1992.  The launch window opens at 1:02 p.m. EDT and
closes at 3:05 p.m. EDT.  The daily launch window will vary
slightly on subsequent days.  The 28-day launch opportunity
extends through Oct. 13, 1992.

     Mars Observer will be lofted into Earth orbit aboard a
Titan III launch vehicle.  After separation from the Titan,
an upper stage vehicle -- the Transfer Orbit Stage (TOS) --
will fire to free the spacecraft from Earth's gravity and
send it on to Mars.

     "During its 11-month transit from Earth to Mars, known
as the cruise phase, Mars Observer will deploy four of its
six solar panels to begin drawing solar power," said George
Pace, Spacecraft Manager at JPL.

       "The dish-shaped, high-gain antenna will be deployed
and the Magnetometer and Electron Reflectometer (MAG/ER) and
the Gamma Ray Spectrometer (GRS) will be partially deployed,"
Pace said.  "Four trajectory correction maneuvers are planned
during the cruise phase to guide the spacecraft to its
destination."

       On Aug. 19, 1993, Mars Observer will arrive in the
vicinity of Mars.  As it approaches the planet, the
spacecraft will fire onboard rocket engines to slow its speed
and allow the gravity of Mars to capture it in orbit around
the planet.

       Mars Observer will first enter a highly elliptical
orbit.  Then, over a period of 4 months, onboard rocket
thrusters will gradually move the spacecraft into a nearly
circular orbit inclined 93 degrees to the planet's equator at
204 nautical miles (378 kilometers) above the Martian
surface.  In this orbit, the spacecraft will fly near the
Martian poles.

Global Mapping Mission and Science Operations

      Mars Observer will provide scientists with an orbital
platform from which the entire Martian surface and atmosphere
will be examined and mapped.  The measurements will be
collected daily from the low-altitude polar orbit, over the
course of 1 complete Martian year -- the equivalent of 687
Earth days.

     "The scientific payload consists of seven science
instruments to examine Mars from the ionosphere -- an
envelope of charged particles that surrounds Mars -- through
the atmosphere and to the surface," said Dr. Arden Albee,
Project Scientist at the California Institute of Technology.

      "The science instruments will provide teams of
experimenters with daily global maps of the planet," Albee
said.  "Mars Observer's camera (MC) will resolve objects far
smaller than was previously possible -- down to about 33 feet
(10 meters) in diameter."

     Scientists will control their spaceborne experiments
from their home institutions through a computer network
linking them to the Mars Observer operations center at JPL.
They can access data from their experiments daily using
special workstations and electronic communications links and
distribute results to other mission science teams.

International Participation

     Near the end of its prime mission in the fall of 1995,
Mars Observer may be joined by the Russian "Mars '94"
spacecraft.  Current plans call for the Russian spacecraft to
deploy penetrators as well as small surface stations.  Mars
Observer's Mars Balloon Relay (MBR) radio-receiver equipment,
supplied by the Centre National d'Etudes Spatiales (CNES) in
France, is designed to relay data from the penetrators and
surface stations to Earth.

     The Mars Observer mission also includes scientists from
three countries besides the United States on its seven
investigation teams, both as team members and as co-
investigators.  In addition, four foreign participating
scientists will join the teams in October 1992.

     Also in October, 11 participating scientists from Russia
will be added to the teams as part of the continuing formal
U.S. - Russian cooperation in planetary exploration.

Program and Mission Management

     The Mars Observer spacecraft was built under contract to
NASA and JPL by the Astro-Space Division of General Electric,
Princeton, N.J.

     NASA's Lewis Research Center in Cleveland, Ohio, managed
the commercial launch services contract with Martin Marietta
Commercial Titan, Inc., Denver, which supplied the Titan III
launch vehicle.

     The Transfer Orbit Stage (TOS) was built by Martin
Marietta under contract to Orbital Sciences Corp., Vienna,
Va.  The TOS project was managed by NASA's Marshall Space
Flight Center, Huntsville, Ala.

     Launch Complex 40 at the Cape Canaveral Air Force
Station was completely refurbished for the launch by Martin
Marietta and the Bechtel Corporation under contract to the
U.S. Air Force.

     NASA's Deep Space Network (DSN) will support the launch,
mission operations and tracking of the spacecraft throughout
its primary mission.  Tracking and data retrieval through the
DSN are managed by JPL for NASA's Office of Space
Communications, Washington, D.C.

     The Mars Observer Project Manager is David D. Evans of
JPL.  Dr. Arden Albee of the California Institute of
Technology is the Project Scientist.  Dr. William L.
Piotrowski of NASA Headquarters is the Mars Observer Program
Manager and Dr. Bevan French is the Program Scientist.

     JPL manages the mission for the Solar System Exploration
Division of NASA's Office of Space Science and Applications
at NASA Headquarters, Washington, D.C.

- end of general release -



Mission Outline graphic




Mapping Phase timeline graphic



MARS OBSERVER SCIENCE OBJECTIVES

     The Mars Observer mission will study the geology,
geophysics and climate of Mars.  The primary objectives are
to:

        % identify and map surface elements and minerals;
        % measure the surface topography and features;
        % define globally the gravitational field;
        % determine the nature of the magnetic field;
        % determine the distribution, abundance, sources and
          destinations of volatile material (carbon dioxide, water) and
          dust over a seasonal cycle; and
        % explore the structure and aspects of the circulation
          of the atmosphere.

     The mission will provide scientists with a global
portrait of Mars as it exists today using instruments similar
to those now used to study the Earth.  The seven instruments
have been selected so that observations from one provide a
complimentary approach to the mission objectives.  For
example, the composition of surface minerals will be
addressed by both the Gamma Ray Spectrometer (chemical
composition) and the Thermal Emission Spectrometer (mineral
composition).

     The interdisciplinary investigations of the Mars
Observer mission also will combine data from more than one
instrument to explore questions that cross boundaries between
scientific disciplines and individual investigations.  The
six interdisciplinary investigations are:

        % atmospheres/climatology;
        % data management/archiving and surface weathering processes;
        % geosciences;
        % polar atmospheric sciences;
        % surface-atmosphere interactions; and
        % surface properties and morphology.

     The mission will provide a major increase in available
scientific data about Mars.  During its 687-day mapping
mission, Mars Observer will return about 120 megabytes of
data per day, for a total of about 80 - 90 gigabytes (about
600 billion bits of information).  This amounts to more
scientific information than has been returned by all previous
planetary missions, whether to Mars or elsewhere, not
including the current Magellan mission.


Mission Design

     Following launch and insertion into a trans-Martian
trajectory by TOS, the spacecraft will perform four
trajectory correction maneuvers (TCM) to correct and adjust
the trajectory.  TCM-1, scheduled for L+15 days (Oct. 1,
1992), will correct any errors from injection.  Following
TCM-2, both the GRS and the MAG/ER will be activated to
collect data on the space environment.  On Jan. 20, 1993, the
MOC will be powered on to take two narrow angle images as a
check-out.

     The Mars orbit insertion phase is the transition from
the interplanetary cruise phase to the mapping orbit.  Since
direct transition into the mapping orbit would require
undesirable out-of-plane maneuvers, a series of seven orbit
insertion maneuvers will be performed to bring the spacecraft
into the proper orbit for mapping.  During these maneuvers
there will be limited scientific activity.

     The polar orbit chosen for the Mars Observer mission is
low enough to allow close-range study of Mars, but high
enough so that the atmosphere does not drag excessively on
the spacecraft.  The orbit also is sun-synchronous, meaning
that the spacecraft will pass over Mars' equator at the same
local time during each orbit -- about 2 p.m. on the day side
and about 2 a.m. on the night side.  This orbit is essential
for a number of measurements, as it helps distinguish daily
atmospheric variations from seasonal variations.

     During the mission's mapping cycle, which begins in
earnest on Jan. 13, 1994, data reception from the spacecraft
and command updates to the spacecraft and individual science
instruments will be conducted on a daily basis.

     Once the primary task is completed, the Mars Observer
mission may be extended -- if the spacecraft and instruments
are still in good condition and if there is enough fuel to
control the spacecraft's altitude and orientation.


Spacecraft Instrument graphic



SPACECRAFT SCIENCE INSTRUMENTS

     Collectively, Mars Observer's seven scientific
instruments will cover much of the electromagnetic spectrum
and form a complementary array.  Each instrument produces
sets of data that contribute to a wide variety of scientific
investigations.

Gamma Ray Spectrometer (GRS)

     The Gamma Ray Spectrometer will characterize the
chemical elements present on and near the surface of Mars
with a surface resolution of a few hundred kilometers.  The
data will be obtained by measuring the intensities of gamma
rays that emerge from the Martian surface.  These high-energy
rays are created from the natural decay of radioactive
elements or can be produced by the interaction of cosmic rays
with the atmosphere and surface.

     By observing the number and energy of these gamma rays,
it is possible to determine the chemical composition of the
surface, element by element.  The GRS also can measure the
presence of any volatiles, such as water and carbon dioxide,
as "permafrost" in the surface materials and the varying
thickness of the polar caps.

Mars Observer Camera (MOC)

     The Mars Observer Camera system will photograph the
Martian surface with the highest resolution ever accomplished
by an orbiting civilian spacecraft.  Resolution is a measure
of the smallest object that can be seen in an image.

     Low-resolution global images of Mars  -- a daily
'weather map' -- also will be acquired each day using two
wide-angle cameras operated at 4.7-mile (7.5-kilometer)
resolution per picture element (pixel).  These same cameras
will acquire moderate-resolution photographs at 787 feet (240
meters) per pixel.

     A separate camera will acquire very-high-resolution
images at 4.6 feet (1.4 meters) per pixel for features of
special interest.  Each of these camera systems uses a line
array of several thousand detectors and the motion of the
spacecraft to create the images.

     The low-resolution camera system will capture global
views of the Martian atmosphere and surface so that
scientists may study the Martian weather and related surface
changes on a daily basis.  Moderate-resolution images will
monitor changes in the surface and atmosphere over hours,
days, weeks, months and years.  The high-resolution camera
system will be used selectively because of the high data
volume required for each image.


GRS graphic




Mars Observer Camera graphic



Thermal Emission Spectrometer (TES)

     The Thermal Emission Spectrometer will measure infrared
thermal radiation emitted from the Martian atmosphere and
surface.  The thermal properties of Martian surface materials
and their mineral content may be determined from these
measurements.  When viewing the surface beneath the
spacecraft, the spectrometer has six fields of view, each
covering an area of 1.9 by 1.9 miles (3 by 3 kilometers).

     The spectrometer, a Michelson interferometer, will
determine the composition of surface rocks and ice and map
their distribution on the Martian surface.  Other
capabilities of the instrument will investigate the advance
and retreat of the polar ice caps, as well as the amount of
radiation absorbed, reflected and emitted by these caps.  The
distribution of atmospheric dust and clouds also will be
examined over the 4 seasons of the Martian year.

Pressure Modulator Infrared Radiometer (PMIRR)

     This radiometer will measure the vertical profile of the
tenuous Martian atmosphere by detecting infrared radiation
from the atmosphere itself.  For the most part, the
instrument will measure infrared radiation from the limb, or
above the horizon, to provide high-resolution (3-mi./5-km.)
vertical profiles through the atmosphere.

     The measurements will be used to derive atmospheric
pressure and determine temperature, water vapor and dust
profiles from near the surface to as high as 50 miles above
the surface.  Using these measurements, global models of the
Martian atmosphere, including seasonal changes that affect
the polar caps, can be constructed and verified.

Mars Observer Laser Altimeter (MOLA)

     The Mars Observer Laser Altimeter uses a very short
pulse of laser light to measure the distance from the
spacecraft to the surface with a precision of several meters.
These measurements of the topography of Mars will provide a
better understanding of the relationship among the Martian
gravity field, the surface topography and the forces
responsible for shaping the large-scale features of the
planet's crust.

Radio Science

     The Radio Science investigation will use the
spacecraft's telecommunication system and the giant parabolic
(dish-shaped) antennas of NASA's Deep Space Network to probe
the Martian gravity field and atmosphere.  These measurements
will help scientists determine the structure, pressure and
temperature of the Martian atmosphere.

     Each time the spacecraft passes behind the planet or
reappears on the opposite side, its radio beam will pass
through the Martian atmosphere briefly on its way to Earth.
The way in which the radio waves are bent and slowed will
provide data


TES graphic



MOLA & PMIRR graphic


 about the atmospheric structure at a much higher vertical
resolution than any other Mars Observer experiment.

     During that part of the orbit when the spacecraft is in
view of Earth, precise measurements of the frequency of the
signal received at the ground tracking stations will be made
to determine the velocity change (using the Doppler effect)
of the spacecraft in its orbit around Mars.  These Doppler
measurements, along with measurements of the distance from
the Earth to the spacecraft, will be used to navigate the
spacecraft and to study the planet's gravitational field.

     Gravitational field models of Mars will be used along
with topographic measurements to study the Martian crust and
upper mantle.  By the end of the mission, as a result of the
low altitude of the orbit and the uniform coverage of Mars
Observer, scientists will have obtained unprecedented global
knowledge of the Martian gravitational field.

Magnetometer and Electron Reflectometer (MAG/ER)

     Mars is now the only planet in the solar system, aside
from Pluto, for which a planetary magnetic field has not yet
been detected.  In addition to searching for a Martian
planetary magnetic field, this instrument also will scan the
surface material for remnants of a magnetic field that may
have existed in the distant past.  The magnetic field
generated by the interaction of the solar wind with the upper
atmosphere of Mars also will be studied.

Mars Balloon Relay (MBR)

     The spacecraft carries a radio system supplied by the
French Centre National d'Etudes Spatiales (CNES) to support
the Russian Mars 94 mission.  The Mars 94 spacecraft consists
of an orbiter, to be launched in October 1994, which will
deploy penetrators and small stations designed to land and
operate on the Martian surface.

     The landers and penetrators will carry instruments to
directly sample both the atmosphere and the surface.  The
landers and penetrators will send data to the Mars 94
orbiter, or to Mars Observer as a back up, for subsequent
relay to Earth.  Both the landers and penetrators are
designed to operate for several years.

     The MBR equipment consists of a transmitter/receiver
that will periodically receive and relay scientific and
engineering data to Earth.

     If it is still operating on an extended mission, Mars
Observer also may support the Russian Mars '96 mission, which
is planning to release a balloon into the Martian atmosphere
and possibly deploy landed stations or rover vehicles which
can move about on the surface under their own power, operated
either by remote control from Earth or autonomously under
computer control.  Following a launch during the 1996 window,
the Mars '96 spacecraft would reach Mars in 1997.




Mars Observer activity timeline chart



MAPPING CYCLE

     In its near-circular mapping orbit, the Mars Observer
spacecraft will rotate once per orbit to keep the instruments
pointed at the planet.  This will allow all instruments to
view the planet continuously and uniformly during the entire
Martian year.

     The spacecraft, instruments and mission were designed so
that sufficient resources, especially power and data rate,
are available to power all instruments as they collect data
simultaneously and continuously on both the day and night
sides of the planet.  The camera system takes photos only on
the day side and will acquire additional images every 3 days
during real-time radio transmissions to the Deep Space
Network.

     The rotation and orientation of the spacecraft are
controlled by horizon sensors, a star sensor, gyroscopes and
reaction wheels, as is common on Earth-orbiting satellites.
The horizon sensors, adapted from a terrestrial design,
continuously locate the horizon, providing control signals to
the spacecraft.  The star sensor will be used for attitude
control during the 11-month cruise and as a backup to the
horizon sensors during the mapping orbit.

     Once during each 118-minute orbit, the spacecraft will
enter the shadow of Mars and rely on battery power for about
40 minutes.  The battery is charged by the spacecraft's large
solar panel, which generates more than a kilowatt of power
when it is in the sunlight.

     Control of the spacecraft and instruments is
accomplished through the use of onboard microprocessors and
solid-state memories.  Scientific and engineering data are
stored on tape recorders for daily playback to Earth.
Additional data operations will allow information to be
returned in real-time from selected instruments whenever
Earth is in view.

     The lifetime of the spacecraft will most likely be
determined by the supply of attitude-control fuel and the
condition of the batteries.


THE SPACECRAFT SYSTEM

     The Mars Observer spacecraft uses, where possible,
existing Earth-orbiting satellite component designs.  The
craft's main body is shaped like a box and is about 3.25 feet
(1.1 meters) high, 7.0 feet (2.2 meters) wide, and 5.0 feet
(1.6 meters) deep.  Mars Observer was built by General
Electric's Astro-Space Division in Princeton, N.J.

     With its fuel, the spacecraft and its science
instruments weigh about 5,672 pounds (2,573 kilograms).  The
spacecraft has a 3-year design lifetime and is equipped with
one large solar array, consisting of six 6 x 7.2 x 0.3-foot
(183 x 219 x 9.1-centimeter) solar panels.

     At launch, the spacecraft's main communication antenna,
instrument booms and solar array will be folded close to the
spacecraft.  During the cruise phase these structures will be
partially extended.  The two 20-foot (6-meter) instrument
booms carry two of Mars Observer's seven scientific
instruments, the Magnetometer and Electron Reflectometer and
the Gamma Ray Spectrometer.

     After the Mars Observer spacecraft reaches its mapping
orbit at Mars, the solar array and instrument booms will be
fully unfolded.  The main communication antenna -- a 4.75-
foot (1.45-meter) diameter parabolic antenna -- will be
raised on a 20-foot (6-meter) boom and rotated to have a
clear view of Earth.  The spacecraft then will power its
instruments to begin conducting the mission experiments.

Spacecraft Statistics

GENERAL
Design Life                      3 years
Mapping Orbit                    Mars polar, nearly circular
Altitude Above Mars              400 km (242 miles), nominal
Key Features                     Seven science instruments
                                 (two mounted on 6-m booms)
                                 Bi- and monopropulsion systems
                                 Three-axis control system
                                 (highly stabilized)
                                 Semiautonomous operation
                                 (stores up to 2000 commands)
Reliability                      Redundancy used to avoid
                                 single-point failures
Payload Weight                   156 kg (343 lb)
Total Weight                     2573 kg (5672 lb)
Size (launch configuration):
   Length                         1.6 m (5.0 ft)
   Width                          2.2 m (7.0 ft)
   Height                         1.1 m (3.25 ft)

COMMUNICATIONS
Command Rate                      12.5 commands/s (max)
Uplink Data Rate                  500 bits/s (max)
Downlink Data Rate                85.3 kbits/s (max)
Antennas                          1.45-m-diam. high-gain
                                  parabolic articulating (on 6-m boom)
                                  Three low-gain
Downlink RF Power                 44 watts
Tape Recorders                    1.38 x 109-bit capacity

PROPULSION
Bipropellant System               Monomethyl hydrazine and
                                  nitrogen tetroxide
Monopropellant System             Hydrazine
Thrusters (24 total)              (4) 490 N
                                  (4) 22 N
                                  (8) 4.5 N (orbit trim)
                                  (8) 0.9 N (momentum unloading and steering)
Total Propellant Weight           1346 kg (2961 lb)

ATTITUDE AND ARTICULATION CONTROL
Pointing Accuracy                 Control:  10 mrad
                                  Knowledge:  3 mrad
Pointing Stability                1 mrad (for 0.5 s)
                                  3 mrad (for 12 s)

ELECTRICAL POWER
Solar Array                       6 panels, each 183 ~ 219 cm
Array Output Power                1130 watts
Batteries                         42-amp-hr NiCd (2)
Electronics                       Bus voltage regulation

Definitions:
      mrad = milliradian (E 0.057!)
      N = newton (E 0.225 lb force)


TITAN III LAUNCH VEHICLE

Launch Services Contract

     The NASA Lewis Research Center, Cleveland, is
responsible for the management of the Titan III launch
services contract with Martin Marietta Corp., Denver, for the
launch of the Mars Observer.

     Lewis is responsible for the management, technical
oversight and integration of the payload with the Titan
launch system which includes the analytical, physical,
environmental and operational integration activities.

     Lewis, along with the Jet Propulsion Laboratory and the
Marshall Space Flight Center, is responsible for integrated
trajectory design, including development of an integrated
sequence of events from lift-off through planetary spacecraft
separation from the upper stage.

Launch Vehicle

     The Titan III can place payloads in excess of 31,000
pounds into low-Earth orbit and up to 11,000 pounds into a
geosynchronous transfer orbit.  The Titan III is a member of
the Titan launch vehicle series that has been in use by the
U.S. Air Force and NASA for more than 20 years, including use
in the Gemini program.  The Titan III also was used for
NASA's Voyager missions as well as the two Viking missions,
the last U.S. spacecraft to Mars.

     The core vehicle consists of two liquid-propellant
booster stages that are the central propulsion element.  Twin
10.2-foot diameter solid-propellant rocket motors (SRMs) are
attached to the core vehicle and provide thrust during
initial lift-off and boost phase.


TITAN III FACTS

SOLID ROCKET MOTORS (2)  Length:  90.4 feet (27.6 meters)
                         Diameter: 10.2 feet (3.1 meters)
                         Motor Thrust:  1.4 million pounds
                         (6,200 kiloNewtons) per motor
                         Weight:    552,000 pounds (250,387
                         kilograms) per motor
                         Propellants:   UTP-30001B solid
                         Contractor:   United Technologies

FIRST STAGE             Length:   78.6 feet (24 meters)
                        Diameter:     10 feet (3 meters)
                        Engine Thrust:    548,000 pounds
                        (2,43 kiloNewtons)
                        Propellants:    Aerozine 50, nitrogen
                         tetroxide
                        Contractor:    Martin Marietta

SECOND STAGE            Length:     32.7 feet (10 meters)
                        Diameter:     10 feet (3 meters)
                        Engine Thrust:    105,000 pounds (467
                           kiloNewtons)
                        Propellants:     Aerozine 50,
                        nitrogen tetroxide
                        Contractor:   Martin Marietta

PAYLOAD FAIRING         Diameter:    13.1 feet (4 meters)
                        Overall Length: 34.2 feet (10.4
                         meters)
                        Contractor:  Contraves AG

EXTENSION MODULE        Single Payload Mission
                        Length:     4.4 feet (1.34 meters)
                        Diameter:  13.1 feet (4 meters)
                        Contractor:   Dornier GmbH

LAUNCH SITE             Launch Complex 40 and associated
processing
                        facilities at Cape Canaveral Air
                         Force Station, Fla.

COMMERCIAL TITAN        United Technologies, Chemical Systems
CONTRACTOR TEAM         Division  (solid rocket motors)
                        Aerojet TechSystems Co. (liquid-
                        propellant engines)
                        General Motors' Delco Systems
                        Contraves AG (payload fairing)
                        Dornier GmbH (extension module)


Titan III CONFIGURATION

Transfer Orbit Stage

     A new upper stage vehicle, known as the Transfer Orbit
Stage (TOS), will make its maiden flight during the Mars
Observer mission.  Following launch aboard the Titan III
rocket, the TOS will propel the spacecraft on its 11-month
interplanetary journey to Mars.

     TOS is a single-stage, solid-propellant upper stage
vehicle used to propel a spacecraft from low-Earth orbit
toward its ultimate destination.  It is a versatile addition
to NASA's inventory of upper stage vehicles, designed to
retain reliability and reduce cost.

     Under the terms of a 1983 agreement with Orbital
Sciences Corp., Fairfax, Va., NASA provided technical

assistance during the development of TOS.  NASA's TOS Project
Office at the Marshall Space Flight Center, Huntsville, Ala.,
ensured vehicle performance, reliability and compliance with
launch vehicle and spacecraft integration and flight-safety
requirements.

TOS Vehicle Description

     The Mars Observer TOS weighs 24,000 pounds, with a
diameter of approximately 11.5 feet and length of just under
11 feet.  The TOS system consists of flight vehicle hardware
and software, as well as associated ground support equipment.
This vehicle uses a United Technologies Chemical Systems
Division ORBUS-21 solid rocket motor main propulsion system,
a Honeywell, Inc., laser inertial navigation system, a
hydrazine reaction control system, and sequencing and power
subsystems.  It has an inertial guidance and three-axis
control system, allowing the spacecraft to roll, pitch and
yaw.

     The propulsion systems for TOS are a main propulsion
system and an attitude control system.  The ORBUS-21 solid
rocket motor, the main propulsion for TOS, has a gimbaled, or
pivoting, nozzle to provide pitch and yaw control during
motor firing.

     For the Mars Observer mission, TOS will be loaded with
approximately 22,000 pounds of the solid propellant HTPB
(hydroxyl terminated poly-butadiene).  The motor can be
loaded with a reduced propellant quantity -- as low as 50
percent of the full load -- to handle a wide range of mission
payload and energy requirements.

     Motor ignition is provided by a pyrotechnically
initiated solid propellant ignitor system.  The vehicle's
hydrazine-powered reaction control system provides for
attitude control of the TOS and TOS/spacecraft combination
during solid rocket motor firing and during periods when the
large solid rocket motor is not firing.  The system uses 12
attitude control system thrusters, or small maneuvering
rockets.

     TOS avionics hardware and software perform guidance
functions, manage the in-flight data, initiate the sequence
of events, determine the distance traveled and send back
engineering data on rocket systems operation during the
boosting phase of the mission.

     The laser inertial navigation system is the heart of the
package which provides the required guidance, navigation and
control functions.

The First TOS Mission

     Fifteen minutes after liftoff, the Titan III will
separate from the TOS and the Mars Observer spacecraft.  For
about the next 20 minutes, TOS  will provide attitude control
of the movements of the spacecraft.  It will perform the
necessary calculations and generate the proper commands,
including rotating the spacecraft for thermal control, to
ensure the spacecraft is placed into the proper position for
rocket motor ignition which will propel Mars Observer on its
interplanetary course.

     Approximately 20 minutes after separation from the Titan
III, the TOS solid rocket motor will fire for its 150-second
burn.  The powered-flight period of TOS operation will last
approximately 2.5 minutes, during which the spacecraft/TOS
combination will reach a speed of 25,575 miles per hour.
Then, having done its job, it will separate from the Mars
Observer.



TRANSFER ORBIT STAGE CONFIGURATION


Launch Sequence graphic



Launch Vehicle and Payload Processing

     On June 19, the Mars Observer spacecraft arrived at the
Kennedy Space Center (KSC) in an over-the-road
environmentally controlled payload transporter known as PETS,
the Payload Environmental Transportation System.  It was
taken to Hangar AO located on Cape Canaveral Air Force
Station to begin checkout. Spacecraft subsystem testing was
performed, the integrity of the onboard propulsion system was
checked and compatibility with the world-wide Deep Space
Network tracking stations was verified.

     On July 9, Mars Observer was again moved by the PETS
from Hangar AO to the Payload Hazardous Servicing Facility
(PHSF) on KSC.  There, final electrical testing was
completed, the spacecraft was fueled with its flight load of
hydrazine propellant and a weight and balance measurement was
taken.

     On Aug. 3, it was mated to the upper stage vehicle, the
Transfer Orbit Stage (TOS).  The TOS arrived at the PHSF on
Jan. 10 to begin processing and electrical testing which was
completed in late June.

     The Titan III rocket arrived from Martin Marietta in
Denver by C-5 aircraft on Feb. 28 and was taken to the
Vertical Integration Building (VIB) to begin build up.  The
first and second stage engine installation activity began in
mid-March, and on March 26 the vehicle was erected on the
launch platform.

     Meanwhile, in the near-by Solid Rocket Motor Assembly
Building (SMAB) the build-up of the solid rocket boosters
also began in mid-March and was completed on May 18.  On June
24, the Titan core vehicle was moved from the VIB to the SMAB
for mating to the twin solid rocket booster stack.  The
rollout of the complete Titan III vehicle to Launch Complex
40 occurred on June 2.

     The integrated Mars Observer/Transfer Orbit Stage
payload was encapsulated in the Titan III nose fairing at the
PHSF on Aug. 19.  It was transported to Launch Complex 40 on
Cape Canaveral Air Force Station on Aug. 21 and hoisted into
the clean room of the gantry-like mobile service tower and
mated to the rocket.

     On Aug. 25 a routine inspection of the payload revealed
particulate contamination on the surface of the spacecraft.
The payload was demated and returned to the PHSF for cleaning
on Aug. 29.  On Sept. 4 the payload was scheduled to be mated
to the launch vehicle.  A countdown dress rehearsal is
scheduled for Sept. 17, with launch scheduled for Sept. 25.


LAUNCH COUNTDOWN AND FLIGHT CONTROL

     The countdown for the launch of the Titan III with the
Mars Observer spacecraft will be conducted from a combination
of NASA and U.S. Air Force Facilities on Cape Canaveral Air
Force Station.  The primary facility from which management
decisions will be made is the Mission Director's Center (MDC)
located in Hangar AE.  This is the nerve center of expendable
vehicle launch operations.  From here and the adjacent Launch
Vehicle Data Center (LVDC), the health of the launch vehicle
and the Mars Observer spacecraft will be monitored before
launch.

     Actual control of the Titan III rocket before launch,
and from where the terminal launch countdown events are
initiated, will be from the Vertical Integration Building
(VIB) in the Titan complex.  Control of the upper stage
before launch, the Transfer Orbit Stage, will be from the TOS
Payload Operations Control Center (POCC) on Kennedy Space
Center.

     Also in Hangar AE is where NASA's central telemetry
facility, or telemetry lab, is located.  During powered
flight performance data from the Titan III, the TOS and Mars
Observer will arrive here.  The data will be recorded and
displayed, then forwarded to flight control areas.  Among
those areas are the MDC and LVDC in Hangar AE, the Mars
Observer Mission Operations Center in nearby Hangar AO and
the TOS POCC.

     All events which occur during powered flight will be
monitored and displayed in the Mission Director's Center.
Vehicle flight data will also be displayed in the LVDC and
the VIB.  After payload separation, primary monitoring will
be from the Mars Observer Mission Operations Center in Hangar
AO, the TOS POCC at KSC and from Jet Propulsion Laboratory in
Pasadena.


Countdown Milestone Events:


     T-Time
(minutes:seconds)
                Call to stations
T-420           Power-up TOS
T-410           Titan Inertial Guidance System alignment complete
T-400           Range Safety holdfire checks
T-345           Load Mars Observer star catalog
T-255           Begin Titan III final checks
T-230           Titan III checks complete
T-150           Poll launch team for mobile service tower rollback
T-100           Mobile service tower in launch position
T-30            Enter planned 50-minute built-in hold
T-30            Resume countdown
T-25            Mars Observer to flight mode
T-10            Enter 10-minute built in hold/poll launch team
T-10            Resume countdown
T-07            Poll launch team for final status checks
T-05            Resume countdown
T-04            Mars Observer to internal power
T-2:30          Range Safety clear to launch
T-2:00          Start data recorders
T-1:55          Arm firing chain relay
T-1:05          Start launch sequence
T-1:03          Enter terminal count
T-0:50          TOS to inertial guidance
T-0:37          TOS to internal power
T-0:32          Titan III to internal power
T-0:16          Arm Range Safety Command Destruct system
T-0:02          Titan to inertial guidance/arm booster igniters
0.0             Sold rocket booster ignition
0.2             Liftoff
00:54           Maximum dynamic pressure
01:48           Titan core vehicle ignition
01:56           Solid rocket booster jettision
03:51           Jettision payload fairing
04:28           Stage 2 ignition
04:29           Stage 1 separation
08:06           Stage 2 cutoff
15:00           Vehicle/payload separation
31:20           TOS ignition
33:56           TOS burnout
53:31           TOS/Mars Observer separation
68:30           Deploy solar array for cruise
71:40           Deploy high gain antenna
75:26           Deploy Gamma Ray Spectrometer boom for cruise
76:00           Deploy Magnatometer boom for cruise
76:10           Turn on attitude control system
80:42           Turn on low gain transmitter

MARS OBSERVER/TITAN III/TOS TRACKING SUPPORT

     Tracking data and telemetry for the Mars Observer/Titan
III/TOS launch will be provided by a combination of NASA and
U.S. Air Force ground stations down range and around the
world.

     Spacecraft X-band tracking data and telemetry will be
received by the Deep Space Network (DSN) managed by the Jet
Propulsion Laboratory, Pasadena, Calif.

     Titan III and TOS S-band tracking data and telemetry
information and also coverage by C-band radars for ballistic
trajectory information will be handled by U.S Air Force
tracking stations and the NASA Spacecraft Tracking and Data
Network (STDN).

     Data coverage also will be supplemented by U.S. Air
Force Advanced Range Instrumentation Aircraft (ARIA).  Two
ARIA will provide support over the Atlantic Ocean and three
other ARIA will provide support in the Indian Ocean region.

     Following is a partial list of primary tracking station
locations and the role they play, either S-band for telemetry
and tracking data or C-band for radar coverage and the span
of time during the flight when data can be supplied if the
launch occurs at the opening of the launch window:

% Merritt Island/Cape Canaveral (NASA S-band/USAF S-band C-Band)  0:00-8:00
% Jupiter Inlet (USAF S-band/C-band)  0:30 - 8:05
% Bermuda (NASA S-band/C-band)  4:12 - 10:48
% Antigua Island (USAF S-band/C-band)  6:10 - 11:48
% ARIA-Atlantic Region (USAF S-band)  13:00 - 17:00
% Canberra, Australia (NASA S-band/X-band)  49:00 - end of support

Communication After Launch

     NASA's DSN has the responsibility to communicate with
the Mars Observer following injection into its trajectory to
Mars.  The three Deep Space Communications Complexes, located
in Goldstone, Calif., Madrid, Spain and Canberra, will
provide the air-to-ground links communication links with the
spacecraft in Mars orbit.  At its maximum distance from
Earth, the time required for a signal to be sent to the
spacecraft and be returned to Earth (called the round trip
light time) will be approximately 40 minutes.

     Communications links which tie together all elements of
the project team on Earth are provided by the NASA
Communications Network (NASCOM) and the Program Support
Communications Network (PSCN).

    NASA's Office of Space Communications provides the
overall program management for the communication system.  The
STDN and NASCOM networks are managed by GSFC.  The PSCN is
managed by the Marshall Space Flight Center, Huntsville, Ala.
The DSN is managed by JPL, in concert with Spain and
Australia.

SALIENT FACTS ON SPEED AND DISTANCE

Speed in Earth orbit
 (with respect to Earth)           17,300 mph (7.73 km/s)

Speed at TOS burnout
 (with respect to Earth)           25,700 mph (11.5 km/s)

Average speed during cruise
 (with respect to Sun)             56,000 mph (25.0 km/s)

Speed before Mars orbit insertion
 maneuver (with respect to Mars)   11,800 mph (5.28 km/s)

Speed after Mars orbit insertion maneuver
(with respect to Mars)             10,200 mph (4.56 km/s)

Speed in mapping orbit
 (with respect to Mars)             7,500 mph (3.35 km/s)

Distance traveled between Earth and Mars        450 million miles
                                                (7.24 x 10^8 km)

Distance from Earth at Mars arrival         210 million miles
                                               (3.4 x 10^8 km )

Distance from Earth during      Min:  62 Mmi (108  km)
 mapping phase                  Max:  230 Mmi (3.7 x 108  km)

Time for command to reach spacecraft    Min:   5.5 minutes
 during mapping phase                   Max:   20.5 minutes

Maximum acceleration on spacecraft (postlaunch)  0.1 G
 (occurs during transfer to low orbit)

Navigation target diameter at Mars     300 miles (480 km)
 (less than 1/10 of planet diameter)


SCIENCE OPERATIONS

     The Mars Observer mission operations at the Jet
Propulsion Laboratory will be supported by NASA's Deep Space
Network (DSN) and the JPL Advanced Multimission Operations
System.  The 34-meter (111- foot), high-efficiency
subnetwork, the newest of the DSN antenna subnets, will
provide daily uplink and downlink communications with the
spacecraft at X-band frequencies of 8.4 gigahertz.  The 70-
meter (230-foot) antenna network also will provide periodic
very-long-baseline interferometry and real-time, high-rate
telemetry and radio science support to the mission.

     The DSN facilities are located in Pasadena and
Goldstone, Calif.; Canberea, Australia; and Madrid, Spain.

     The instrument scientists will remain at their home
institutions, from which they will access Mars Observer data

------------------------------

End of Space Digest Volume 15 : Issue 166
------------------------------