Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/JPLNEWS1/0334.PR

Text File | 1993-04-21 | 4KB | 76 lines

OFFICE OF PUBLIC EDUCATION AND INFORMATION
JET PROPULSION LABORATORY, CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIFORNIA.  TELEPHONE [phone]

          The National Aeronautics and Space Administration
launched two Mariner unmanned spacecraft in November, 1964, taking
the first step by the United States in the exploration of Mars.
          The first of these, designated Mariner III, was
launched November 5 by an Atlas D/Agena D launch vehicle from
Cape Kennedy.  Because its protective covering, or shroud, failed
to jettison shortly after launch, Mariner III's solar panels did
not deploy and Mars trajectory was not attained.  The spacecraft
is now in perpetual orbit around the sun.
          Twenty-three days later, Mariner IV enclosed in a newly
designed and fabricated shroud, was launched successfully on a
228-day mission to Mars.  The rapid failure analysis and
resulting modifications were necessary because a Mars launch
opportunity lasts only a few weeks and occurs only once every 25
months.
          On December 5, 1964, Mariner IV performed a mid-course
maneuver that altered its flight path.  The maneuver changed the
spacecraft's fly-by distance from 151,000 miles in front of Mars
to about 5700 miles behind the planet and changed the arrival
date from July 16, 1965, to July 14, 1965.
          The Mars mission was undertaken by NASA because the
planet is of great scientific interest and offers the best oppor-
tunity in our solar system for shedding light on the possibility
of extraterrestrial life.  The Mariner mission, however, was not
designed to provide answers to the question of life on Mars.

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          The mission to Mars is the first in which American
spacecraft have been launched on a flight path away from the
sun.  (Mission objectives now being met include providing
engineering experience on the operation of a spacecraft during a
long-duration flight.)  When Mariner IV flys by Mars, the
spacecraft will be more than 134 million miles from Earth and
will have flown some 325 million miles in its arcing path around
the sun.
          The Mariner program is directed by NASA's Office of
Space Science and Applications which assigned project management
to the Jet Propulsion Laboratory of the California Institute of
Technology in Pasadena, California.  JPL designed, built and
tested the spacecraft and is conducting space flight operations
and tracking associated with the mission.
          Eight scientific investigations aboard Mariner are
provided by scientists representing eight universities and two
NASA laboratories.  Six of these were designed to operate
throughout the entire mission, the other two only at the planet.
          If the spacecraft is still functioning at Mars, its
television camera system will take and record as many as 21
black-and-white, still pictures of the planet's surface for
transmission to Earth.  Analysis of Mariner's flight path
indicates that the pictures, made in overlapping pairs, will
cover a narrow, 4000-mile arc from the Amazonis Desert in Mars'
northern hemisphere to the Aonius Sinus, more than 40 degrees
below the equator, where the shadow line separates day and night.

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          The other planetary experiment, occultation, needs no
instrumentation other than the spacecraft transmitter.  As Mariner
IV curves behind Mars following the picture sequence, its radio
signal will be bent by the Martian atmosphere and will change in
frequency and strength.  Analysis of these minute changes can
indicate the density and scale height of the atmosphere.  This
data is important in planning future Mars missions in which a
landing capsule would penetrate the atmosphere.




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