Viking Missions to Mars by pengxiang

VIEWS: 6 PAGES: 24

									Viking Missions
    to Mars


                                   Viking 1 launched
                                        August 20, 1975


                                   Viking 2 launched
                                     September 9, 1975
  Titan 3 Centaur Launch Vehicle
                Mission Objectives
1) Obtain high resolution photographs of the Martian surface
2) Characterize the structure and composition of the atmosphere and surface
3) Search for evidence of life




                                                                      IKONOS



    Resolution - A measure of the smallest detectable object
      Viking: 150 x 300 meters (8 meters at selected locations)
      IKONOS (Non-military “spy” satellite): 0.6m (best available)
Earth to Mars
          It took nearly 10 months to
          reach Mars. Like a
          quarterback on the run,
          throwing a pass to a moving
          receiver... You have to know
          where Mars will be and throw
          the “ball” to that spot - that’s a
          309 MILLION mile trajectory
          with almost NO room for error.
          ...OR... In golf, it’s like going
          for a hole in one from Los
          Angeles to Houston, Texas!
          After the landing, depending
          on the locations of Earth and
          Mars, it can take up to 22.3
          MINUTES to send a radio
          command to the spacecraft.
                    Earth to Mars
                                               Orbit     Transit     Power
                                 Launch                                        Orbits
                                             Insertion    Days       Down
                      Viking 1   8/20/1975   6/19/1976     304     8/17/1980   1400+

                      Viking 2   9/9/1975    8/7/1976     333      7/25/1978    706




Compare the time that it took the two vehicles to reach Mars orbit...

   Why did it take 29 additional days for Viking 2 to reach Mars?
              ... Go to the ORBITS TABLE to see why...
The Spacecraft
   The spacecraft consisted of two parts - the
   ORBITER (upper section) and the LANDER
   (lower, ball shaped section).
The Spacecraft
   The spacecraft consisted of two parts - the
   ORBITER (upper section) and the LANDER
   (lower, ball shaped section).

   During the trip to Mars, the ORBITER controlled
   the trajectory based on commands from earth.
The Spacecraft
   The spacecraft consisted of two parts - the
   ORBITER (upper section) and the LANDER
   (lower, ball shaped section).

   During the trip to Mars, the ORBITER controlled
   the trajectory based on commands from earth.

   Once in orbit around Mars, the ORBITER
   photographed the planet surface to assess the
   pre-planned landing sites. The landing site was
   changed based on the images received.




             See what the Orbiters saw...
Viking 1 Orbiter Imagery




                 Central Tithonium Chasma
                 Landslide lobes can be
                 seen on the 6 km deep
                 canyon floor. Some
                 layering is visible on the
                 south wall. The image is
                 ~90 km across. North is at
                 ~11:30.
                 (Viking Orbiter 064A22)
Viking 1 Orbiter Imagery


                  Yuty crater in Chryse Planitia

                  The 18 km diameter crater is
                  surrounded by complex ejecta
                  lobes, one of which partly
                  covers an older crater. North
                  is at about ~1:00.


                  (Viking Orbiter 003A07)
               Viking Orbiter 1 and 2 Mosaic




A color mosaic showing Candor Chasma which is part of the Valles Marineris
system. This oblique view is looking from the north over the 800 km wide chasm.
The walls and floor show evidence of erosion and mass wasting and complex
geomorphology. (Viking Orbiter NJ05S070-912A)
                      The Spacecraft
                                The spacecraft consisted of two parts - the
                                ORBITER (upper section) and the LANDER
                                (lower, ball shaped section).

                                During the trip to Mars, the ORBITER controlled
                                the trajectory based on commands from earth.

                                Once in orbit around Mars, the ORBITER
                                photographed the planet surface to assess the
                                pre-planned landing sites. The landing site was
                                changed based on the images received.

Once a site was selected, the LANDER was detached from the ORBITER... Retro
rockets were fired to begin the descent... A parachute was used to slow the fall.
During the descent, the LANDER opened up (deployed) for the final landing.
The LANDER then fired its own retro rockets to soften the actual touch-down.
The Lander
             This drawing shows
             the deployed Lander
             with the numerous
             instruments used to
             photograph, sample,
             and analyze its
             surroundings.

             The Lander was
             stationary - it could
             not move to other
             locations.
Landing Sequence
Landing Sequence
                           Orbit     Transit     Power
             Launch                                        Orbits
                         Insertion    Days       Down
  Viking 1   8/20/1975   6/19/1976     304     8/17/1980   1400+

  Viking 2   9/9/1975    8/7/1976      333     7/25/1978    706


                                     It took 6 to 13 minutes
                                         for the landers to
                                       reach the surface of
                                           Mars... Why?
                                     The answer lies with
                                       the Orbit Table...
                                       Both vehicles had
                                       unique orbits and
                                         landing sites
The Viking has Landed...
                                        Orbit         Transit     Power
                            Launch                                          Orbits
                                      Insertion        Days       Down
              Viking 1   8/20/1975    6/19/1976         304     8/17/1980   1400+

              Viking 2     9/9/1975   8/7/1976         333      7/25/1978    706




                Landing       Loss of     Life Span
                   Date        Signal       (Days)
   Lander 1     7/20/1976    11/13/1982      2307

   Lander 2     9/3/1976      4/11/1980     1316
                Landing Sites




   In this distorted view of Mars, you see the Viking and
Pathfinder (1997) landing sites - imagine just how LITTLE we
       have been able to explore of the actual surface!
                Landing Sites




In June and July, 2003, two missions (Spirit and Opportunity)
                    were launched to Mars.
    In January, 2004... WHERE will the new ROVERs land ?
                             Viking 1 Lander




The first panoramic image of Chryse Planitia taken on 23 July 1976, three days after
Viking 1 landed. The meteorology boom is at the center of the image and to the left
is the support for the high-gain dish antenna. The bright area to the left is the late
afternoon Sun in the west. The bright horizontal lines in the sky are not clouds,
they are caused by internal reflections in the camera housing. Features on the
horizon are about 3 km away. The dark rock at the center of the frame, nicknamed
"Big Joe", is about 3 meters across and 8 meters from the lander. The center of the
frame shows fine grained material forming a small dune field. The material forms
horseshoe shaped scour marks and wind tails around the rocks, which are about 10
cm across.
(Viking 1 Lander, P-17428)
                            Viking 1 Lander




The sampling arm dug a number of deep trenches in the "Sandy Flats" area of
Chryse Planitia as part of the surface composition and biology experiments. The
digging tool on the arm (at lower center) could scoop up samples of material and
deposit them into the appropriate experiment. Some holes were dug deeper to study
soil which was not affected by solar radiation and weathering. The boom holding the
meteorology sensors is at left.
(Viking 1 Lander, 11D128)
    Viking 2 Lander


This image shows patches of ground frost at the
Utopia Planitia. The image was taken at 12:32 local
time in late northern winter. The frost layer is
extremely thin, only a few hundredths of a mm thick.
The frost persisted at temperatures higher than the
freezing point of carbon dioxide, and so must be
water ice or some combination of water and carbon
dioxide ice.
The view is looking SWW. The colors have been
distorted to enhance the contrast.
(Viking 2 Lander, 22E169)
Viking 2 Lander

             Looking back across the
             Lander, dark boulders are
             prominent against the
             reddish soil. The landing
             site, Utopia Plantia, is a
             region of fractured plains.
             The site is about 200 km
             south of Mie crater, and may
             be on top of one of the
             crater's ejecta blankets.
             The largest rocks are about
             half a meter in size. The
             view is approximately to the
             southwest.
             (Viking 2 Lander, 22A158)
                      Accomplishments
•   Photographs from the landers and orbiters surpassed expectations in quanity and quality.
    The total exceeded 4,500 from the landers and 52,000 from the orbiters. Viking's orbiters
    mapped 97 percent of the Martian surface.
•   The infrared thermal mappers and the atmospheric water detectors determined that the
    residual north polar ice cap (that survives the northern summer) is water ice, rather than
    frozen carbon dioxide (dry ice) as once believed.
•   Barometric pressure varied at each landing site on a semiannual basis, because carbon
    dioxide, the major constituent of the atmosphere, froze to form an immense polar cap,
    alternately at each pole. The carbon dioxide formed a great cover of snow and then
    evaporated again with the coming of spring in each hemisphere. When the southern cap
    was largest, the mean daily pressure observed by Viking Lander 1 was as low as 6.8
    millibars; at other times of the year it was as high as 9.0 millibars. The pressures at the
    Viking Lander 2 site were 7.3 and 10.8 millibars. (For comparison, the surface pressure on
    Earth at sea level is about 1,000 millibars.)
•   Martian winds generally blew more slowly than expected. Scientists had expected them to
    reach speeds of several hundred miles an hour from observing global dust storms, but
    neither lander recorded gusts over 120 kilometers (74 miles) an hour.
               Other Significant Discoveries
•   NO LIFE HAS BEEN DETECTED ON MARS -- The surface contains no
    organic molecules that were detectable at the parts-per-billion level -- less,
    in fact, than soil samples returned from the Moon by Apollo astronauts.
•   The surface is a type of iron-rich clay that contains a highly oxidizing
    substance that releases oxygen when it is wetted.
•   Nitrogen, never before detected, is a significant component of the Martian
    atmosphere, and enrichment of the heavier isotopes of nitrogen and argon
    relative to the lighter isotopes implies that atmospheric density was much
    greater than in the distant past.
•   The greatest concentration of water vapor in the atmosphere is near the
    edge of the north polar cap in midsummer. From summer to fall, peak
    concentration moves toward the equator, with a 30 percent decrease in
    peak abundance. In the southern summer, the planet is dry, probably also
    an effect of the dust storms.
•   While the permanent north cap is water ice, the southern cap probably
    retains some carbon dioxide ice through the summer.
              Other Significant Discoveries

•   The density of both of moons is low -- about two grams per cubic centimeter
    -- implying that they originated as asteroids captured by Mars's gravity.


•   Measurements of the round-trip time for radio signals between Earth and
    the Viking spacecraft, made while Mars was beyond the Sun (near the solar
    conjunctions), have determined delay of the signals caused by the Sun's
    gravitational field. The result confirms Albert Einstein's prediction to an
    estimated accuracy of 0.1 percent -- 20 times greater than any other test.

								
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