Excerpted from: Electronic Journal of the ASA, Vol. I, No. VIII
MARS 1994
By Andrew J. LePage
For decades the track record for the Soviet Union's program of
unmanned exploration of the planet Mars has been less than impres-
sive. Several early spacecraft never reached an Earth parking orbit.
Three others are known to have never made it beyond Earth orbit.
Three more probes failed enroute to Mars. One craft failed in its
attempt to orbit the Red Planet. Three orbiters, while successful
in accomplishing their main tasks, returned less information than
hoped. Four landing attempts either crashed, missed the planet
entirely, or ceased functioning soon after touchdown. Most
recently, PHOBOS 2 failed before it was able to complete its
rendezvous mission with the Martian moon Phobos.
The Soviets have proven that they are capable of better things
in the field of planetary exploration, however. Ten unmanned probes
have successfully landed on the hellish world of Venus. Four other
spacecraft were placed into orbit around the cloud-shrouded planet.
Two of these orbiters made high-resolution radar maps of Venus'
northern hemisphere. Their data on the planet's surface will not
be surpassed until the United States' MAGELLAN spacecraft goes into
Venusian orbit in August of 1990. Two more Soviet probes placed
balloons in the Venusian atmosphere, while the main buses of these
spacecraft flew on to study Comet Halley. After their impressive
string of accomplishments with the VENERA and VEGA programs, the
Soviets felt they had the technology, confidence, and international
savvy to attempt their first new missions to Mars since 1974.
Starting in the early 1980s, the Soviets slowly developed a
ambitious program to explore the Red Planet. A totally new, modular
spacecraft bus was designed to replace the twenty-year-old second
generation planetary bus that the Soviets used in their VENERA
program. The two PHOBOS spacecraft launched in the summer of 1988
towards Mars were the first phase in the Soviet's new Mars initiative,
becoming the first to make use of this new spacecraft design.
Unfortunately, they were also the first to uncover a number of its
design deficiencies - the result of hurried planning and lack of
communication between the spacecraft manufacturer and the mission
scientists.
The Soviets have already stated that the next missions to use
this third generation planetary bus will have upgraded computers,
an omnidirectional antenna for receiving emergency commands, an
autonomous attitude recovery capability, and improved backup
batteries installed. These improvements, along with much better
overall mission planning, should prevent the failures experienced
by the PHOBOS 1 and 2 spacecraft.
In late 1989, the Soviet government approved a three hundred
million ruble (about 450 million dollar) program called MARS 1994.
The goal of the MARS 1994 mission is to place two spacecraft in orbit
around Mars which will deploy landers and balloons to make direct
measurements of the Martian surface. The orbiters will employ their
own instruments to make remote observations from space. Like the VEGA
and PHOBOS missions, the Soviets intend to make this a cooperative
scientific program which will involve France, many Eastern European
nations, and the United States. While most of the spacecraft's
instruments and many of the mission details remain to be determined,
a fairly clear picture of the MARS 1994 mission is emerging, thanks
in part to the new "openess" of the Soviets.
In September of 1994, two six metric ton (13,000-pound) spacecraft
based on the PHOBOS design will be sent into space on separate PROTON
launch vehicles. The two spacecraft will enter highly elliptical
polar orbits around Mars after an interplanetary voyage of slightly
less than one year. After attaining an initial orbit, the vehicles
will settle into an orbit with an inclination of about one hundred
degrees and a period of twelve hours. Their orbits will range from a
high point of twenty thousand kilometers (12,000 miles) to a low point
of two hundred to five hundred kilometers (120 to 300 miles) above
the Martian surface. While in orbit, the spacecraft will continue
observations begun six years earlier by PHOBOS 2. About two hundred
kilograms (440 pounds) of instruments will be carried, including an
imaging system with a maximum resolution of about one meter (39.37
inches) and a collection of other instruments to remotely probe the
Martian surface properties and composition, observe the atmosphere,
and make various measurements of the elusive Martian magnetic field.
Some time after the spacecraft have entered orbit around Mars,
each will deploy a package towards the surface. Each package will
likely contain four spike-like penetrators and a highly novel balloon.
The landing sites have not been chosen yet, but the selection would
be based on data obtained by the VIKING orbiters, PHOBOS 2, and the
MARS OBSERVER (currently scheduled to be launched by the United
States in 1992), as well as the MARS 1994 orbiters themselves. It
is expected that the landing sites will be much more interesting
than the VIKING landing sites. Those sites were chosen in 1976
because they were considered to be "safe" for making a "blind"
landing. Unfortunately, "safe" also means "dull". Areas that
included interesting features such as volcanoes, channels cut by
water, canyons, and other exotic terrains are much rougher. The
VIKING landers would have most likely been destroyed during a landing
attempt in one of the places. Penetrators, on the other hand, are
very rugged and balloons can fly over most obstacles. These inherent
advantages should open up a much wider range of potential landing
sites that are far more interesting than the two examined to date.
The design and capabilities of the penetrators has yet to be
finalized. Each will weigh a few tens of kilograms and be capable
of burying themselves into solid rock. The only experiment selected
so far has been a seismometer for transmitting information about Mars'
surface movements for some as yet undefined period of time. It is
also likely that simple meteorological measurements such as temperature
and pressure will be made. The penetrator design should be announced
sometime in 1990.
At this time the balloon package is much better defined and
numerous tests have already been conducted with it. The balloon
package will consist of a twenty-meter (66-foot) tall balloon supplied
by the French CNES (Centre National d'Etudes Spatiales, the National
Center for Space Studies), with a four-kilogram (nine-pound) pano-
ramic camera package hanging below and a four-kilogram (nine-pound)
instrument-laden "snake" supplied by The Planetary Society dangling
at its base. The balloon will be divided into two parts: A helium
filled upper portion and a lower portion filled with the ambient
Martian atmosphere. At night the balloon will have enough buoyancy
to hold itself and the camera package above the Martian surface while
the "snake" lies on the ground. In this way, the camera package can
make images of the ground below with a resolution of less than one
millimeter (0.04 inch), while the instruments in the "snake" make
measurements of the composition and physical properties of the nearby
soil and rocks.
In the morning, the balloon will absorb the Sun's rays and heat
the cool Martian air inside its lower portion. The air will begin
to expand, whereafter the balloon will generate enough additional
buoyancy to lift the "snake" off the ground. The balloon will then
rise at a speed of about one meter per second (39.37 inches per
second) to an altitude of two to four kilometers (1.2 to 2.4 miles),
where it will ride on the Martian winds. The camera package will be
relaying images of the planet's surface to the Soviet MARS orbiters
and to a specially installed receiver on the American MARS OBSERVER,
which should still be functioning after two years in orbit. It may
also be possible to use Earth-based radio telescopes to track the
balloons, as was done with the balloons deployed in the dense
Venusian atmosphere by the VEGA spacecraft in 1985. Using VLBI
(Very Long Baseline Interferometry) techniques, it should be possible
to determine the balloons' locations and clock the wind speeds in
various parts of the Martian atmosphere.
Once the Sun "sets", the air inside the balloon will cool, causing
the balloon to slowly sink to the ground. Once the "snake" comes in
contact with the surface, the balloon will drop no further and the
"snake" will be able to make more surface measurements in yet another
location. When the Sun "rises" the next morning, the balloon will
heat up and the process will repeat. Using this novel method for
locomotion, the balloon can travel a few hundred kilometers a day,
studying widely separated locations and obtaining numerous high
resolution images that will complement the orbiters' images.
According to current estimates, each balloon should be capable of
ten such cycles and cover a few thousand kilometers before too much
helium leaks from the balloon, making it impossible to hold itself
off the ground at night.
If this mission proves successful, it should vastly increase our
knowledge about the planet Mars. The penetrators scattered over eight
sites should give new information on the level of geological activity
on Mars and indications of the planet's internal structure. The two
balloons should give us data on the composition of as many as twenty
widely scattered sites, return highly detailed swaths of images of
the Martian surface several thousand kilometers long, and yield much
information on the Martian winds.
If the quality of the data returned by the Mars orbiters is
comparable to that briefly returned by PHOBOS 2, the amount of data we
may receive and what it tells us could be staggering. When combined
with the data returned by the penetrators and balloons, scientists
should have a much better understanding of Mars' surface properties
and composition on a global scale, a better picture of the atmosphere
and its motions, and a much more detailed knowledge of the Martian
water inventory. All this information should give scientists and
engineers an excellent foundation to plan future missions to the Red
Planet, including soil sample return missions and manned expeditions.
If the Soviets can overcome their legacy of Mars mission failures,
the MARS 1994 mission stands to make a key contribution to our
understanding of the Red Planet in the closing years of this century.
References:
Blamont, Jacques, "Exploring Mars by Balloon", THE PLANETARY
REPORT, The Planetary Society, May/June 1987, pages 8-10.
Friedman, Louis D., "The Mars Balloon", THE PLANETARY REPORT,
The Planetary Society, September/October 1988, pages 7-11.
Wilson, Andrew (Editor), INTERAVIA SPACE DIRECTORY 1989-90,
Jane's Publishing, pages 151-152.
"Soviet Space Program Strife Threatens Mars Mission Plans",
AVIATION WEEK & SPACE TECHNOLOGY, May 22, 1989, pages 18-21.
"Time, Cost Constraints Force Soviets to Alter 1994 Mars Mission",
AVIATION WEEK & SPACE TECHNOLOGY, August 28, 1989, page 22.
"A New Soviet Plan for Exploring the Planets", SCIENCE,
October 13, 1989, pages 211-212.
"Mars '94 Takes Shape", SPACEFLIGHT, The British Interplanetary
Society, November 1988, page 417.
About the Author -
Andrew J. LePage is a member of the Boston Group for the Study
of the Soviet Space Program (Krasnaya Orbita). In addition to his
interests in astronomical and space related topics, he has been a
serious observer of the Soviet space program for over a decade.