The Viking Mission to Mars

                             James E. Tillman

                      Viking Meteorology Science Team
                                    and
                    Director, Viking Computer Facility
                         University of Washington
                           Seattle, Wash., 98195


		  	      Keynote Address
		Prime Computer Users Group National Meeting
			    Orlando, Fla. 1984


1 Introduction



The  planet Mars  has often  stimulated the  imagination and  curiosity of
mankind.   With  the  following material,  I  hope  to  show some  of  the
intriguing aspects  of the planet,  as observed from Earth,  aspects which
generated a strong desire to observe and explore the surface.  These Earth
bound observers have long known  that Mars has seasonal changes, with dust
storms and a varying polar cap.  As its atmospheric and surface conditions
most resemble  those of Earth, when  compared to the other  planets in our
solar  system, the  possibility of  life and  its relation  to terrestrial
forms, provided a  major portion of the scientific  impetus for the Viking
Mission  to  Mars.   The Viking  Mission  to  Mars  was the  most  complex
scientific  exploration  of  any  planet  other than  Earth  conducted  by
mankind.  In the sophistication  of the remotely operated instrumentation,
it  surpasses even  the Apollo  Lunar  Missions.  Due  to the  exceptional
effort of  its engineering, management, operations  and scientific staffs,
it exceeded by far the design goals and expected lifetimes of the systems.
For example, Lander 1, the Thomas Mutch Memorial Station, ceased operation
after 2,245 sols ( 2,306 days ) on Mars, which should be compared with its
designed lifetime  of approximately 120 sols.  In  the following segments,
some  of  the  highlights  of  the  Viking exploration  of  Mars  will  be
presented.  Some of the interesting  aspects of our use of Prime computers
for the  Viking program will  be discussed as  well as our  acquisition of
hardware for and  development of the computer driven  display, "The Viking
View of  Mars" for  the Smithsonian National  Air and Space  Museum.  This
permanent exhibit  presents text, graphics  and images for the  public and
should be on display during this meeting.

2 Mars
      2.1 Observations of Mars from Earth


   Several characteristics of Mars have contributed to our interest in it
   since  prehistoric  times.  It  has  a reddish  color,  it  is easy  to
observe,
   its motions are not a simple circular orbit and, since the invention
   of the telescope, it has been observed to undergo significant seasonal
   changes.  Seasonal changes of major interest are its development of
   polar caps, the differences in its albedo, or contrast, on a day to day
   and year to year basis, and the identification of linear features on
   the surface as "canale", singular ( Father Secchi ), about 1869 and
   "canali", plural ( Schiaparelli ) about 1877.  Percival Lowell seems to
   have pushed the linear features to the extremes of artistic endeavor
   and speculation, in that in 1908 he published a book "Mars as the Abode
   of Life" wherein he speculated that the canals were the work of
   "intelligent creatures, alike to us in spirit, though not in form."
   The possibility of life, but at a far more primitive level than that
   envisioned by Lowell, was a major aspect of the Viking Mission.
   Although we have not detected life on the planet, it has the
   environmental characteristics most similar to Earth and consequently,
   most likely of the other planets or moons to support life.  However, as
   meteorologists, our observations from the surface of Mars have provided
   information, conclusions, new phenomena and speculations far beyond my
   hopes or even dreams at the beginning of the mission.


   Scintillation in the atmosphere due to temperature variations, limits
   the resolution of Earth based astronomical observations such that
   telescopes of a few inches diameter provide as high resolution as can
   be simply obtained: larger telescopes are constructed to view dimmer
   objects.  However, Earth based observations are valuable in that we do
   not currently have any active spacecraft at Mars and we have found
   important year to year differences in this climate of Mars.  They
   supplement our Mariner and Viking observations by providing data on the
   seasons in which dust storms form and some information as to their
   extent and intensity.  Since Mars is too far from earth for useful
   observations most of the year, these data can not be very continuous,
   even if the weather were always cooperative.


   2.2 Pre Viking spacecraft observations



   The first close observations of Mars by NASA spacecraft began with the
   Mariner 4 fly by in 1965 which took 21 photographs.  Each photo
   contained 240,000 bits of data, transmitted to Earth at 8.33 bits per
   second.  Mariner 4 showed craters and a thin haze in the Carbon Dioxide
   atmosphere.  Two later Mariner flyby's in 1969, mainly revealed only a
   cratered terrain without major geological features.  However, the
   observations of the Mariner 9 orbiter soon changed the perception of
   Mars.  During approach, a small dust storm in the southern hemisphere
   developed into an intense global dust storm, injecting dust to heights
   well above 30 kilometers.  At the most intense period, only a small,
   low contrast feature could be seen.  Once the dust cleared, this
   feature was revealed to be a volcano, Olympus Mons, whose top was 29
   kilometers above mean Mars level!  Other interesting features were the
   chain of three other volcanos almost as high as Olympus Mons and a
   canyon system 5,000 kilometers long, up to 200 kilometers across and up
   to 7 kilometers deep.  Since the diameter of Mars is only 53% that of
   earth, these large canyons and volcanos seem even more dramatic.  At
   its base, the diameter of Olympus Mons is more than 500 kilometers.  In
   the next section, some of the highlights of the Viking Mission to Mars
   will be covered.


3 The Viking Mission to Mars



The Viking  Mission was the  most ambitious planetary  exploration program
undertaken by NASA or by any agency.  In terms of its scientific goals and
complexity, it even  surpassed the Apollo Lunar missions,  although not in
cost or operational complexity.  Its success was due to reasonable support
in  the early  and  middle stages,  to  excellent management,  and to  the
dedication  of its  staff, contractors  and vendors.   There  are numerous
instances in my own experience where I requested assistance from a vendor,
( Prime received many of these  ), and tasks that normally took weeks were
somehow accomplished  in hours or  days.  For example, during  our upgrade
from a Prime  300 to 400 CPU, we  were able to have a  government ADP plan
approved within several weeks of submission.


   3.1 Mission design



   The initial mission design consisted of a 90 day nominal mission using
   two identical spacecraft systems.  Each spacecraft consisted of a
   orbiter-lander pair, with the orbiter providing imaging of surface,
   some science measurements, and high rate communications support for the
   lander during the nominal mission operations phase.  Operations were
   planned around a nominal 90 day mission where one spacecraft would
   reach Mars roughly a month prior to the other: both spacecraft would
   operate simultaneously after the landing.  Early in the mission design
   review process, reviewers from the Mercury, Gemini, Apollo and other
   projects, favorably commented on the mission design but indicated it
   would not be possible to operate both spacecraft with the staff and
   facilities available, even though the mission operations staff was
   roughly 1,000 full time individuals.  A plan was developed to operate
   the first Lander for approximately 45 sols, ( a sol is a Martian day of
   24 hours and 37 minutes ) and then to reduce its activity to a minimum
   while landing and operating the second lander for a similar period.  In
   this manner, the flight control teams were able to maintain reasonable
   10 to 11 hour work days!

   Launch was scheduled for the summer of 1975, followed by an 11 month
   cruise to Mars.  Landing was scheduled for July 4, 1976, summer in the
   northern hemisphere and due to the low temperatures on Mars, the system
   was not required to operate through the winter.


   3.2 Early use of Prime in the Viking Mission



   Since testing by the Viking Meteorology Instrument System, VMIS, was
   inadequate due to the small wind tunnel constructed to simulate Martian
   pressures and its CO2 atmosphere, we decided to perform additional
   testing at NASA Langley Research Center during the summer of 1975.  The
   original plan was to replace the paper tape punch of the TRW VMIS test
   set with a tape drive and use it for the tests.  The proposal to
   accomplish that and associated work was $200,000 and I proposed that we
   develop a test set at UW which could both gather and reduce data in
   real time.  After preparation of a lengthy proposal and an extensive
   evaluation, a Prime 300 was selected during the summer of 1974 to be
   used for wind tunnel testing of the VMIS.  Hardware interfaces to
   simulate the lander computer were developed, software written and the
   system checked out between its delivery in September 1974 and its
   shipment to LRC in June of 1975.  I chose RTOS as an operating system,
   a mistake, since hindsight proved that DOS/VM, ( later Primos III ),
   would have been a better choice due to our low data rates and its
   greater software maturity.


 

   The system had to function properly, and reliably, from the
   beginning of testing as some flight qualified hardware was only
   made available after launch and the NASA is generally scheduled
   several years in advance. The Transonic Dynamics Tunnel, 
TDT,
   has a diameter of 16 feet, generates wind speeds from 10
   MPH to transonic and can provide pressures from 1% to 100 % of
   atmospheric.  Another index of its capabilities, is that it is
   powered by a 20,000 HP motor which draws 1,000,000 watts at our
   lowest testing speeds.  During 1974, a specific two week time slot
   was assigned to us at no cost, in this facility whose testing cost
   was $4,000 per hour.  The cost of the computer system was less than
   10% of the value of the test time.  Initial testing was begun in
   June 1975 in a facility especially designed for us and was
   interrupted so that we could take part in the launch at Cape
   Kennedy.  After launch, the Flight Spare VMIS was made available
   for testing and we moved to the TDT.  Testing was successful, and
   as expected, we had to upgrade our software while our instruments
   were on the way to Mars.  This was somewhat unusual, since all
   other software were essentially in their final form for training
   exercises at JPL between launch and Mars encounter.  The system was
   moved back to UW in November of 1975.

   Once it was determined that our complex software would have to undergo
   significant changes, we found that adequate time would not be available
   on the JPL Univac 1108 systems ( an extra 1108 was installed for
   Viking ) and we studied the possibility of providing support at UW on
   the Prime for users at Martin Marietta, Denver, NCAR, Boulder, TRW,
   Redondo Beach, JPL, Pasadena and UW.  Since it was clear that the P300
   would be overloaded, discussions were initiated with Prime as to
   possible solutions.  The architecture of the soon to be completed P400
   was discussed with J.  W.  Poduska as well as its probable performance
   and availability.  A presentation was made to the Viking Project
   management to purchase a 60 mbyte disk drive and the new CPU as soon as
   it became available and to provide the software development facility at
   UW.  The proposal was accepted, and we began 24 hour/day operation in
   November of 1975 which continues at the present with the exception of
   one week for the installation of air conditioning.  In April of 1976,
   we received delivery of Serial # 2 of the P400 CPU's.



   3.3 Mission operations during the Primary Mission


   Mission Operations at JPL became intensive after launch of the
   spacecraft.  In the normal course of events, the VMIS system would not
   be operated more than a few times during cruise to check its basic
   functionality and we would have mainly been involved in training for
   Mission Operations.  However, drift was detected in the Lander 2
   temperature system and the system was activated a number of times to
   determine the magnitude and nature of the drift.  Although the cause of
   the drift was not discovered, we developed corrections for the early
   mission measurements.


   In June of 1976, we shipped the system to JPL for Mission
   Operations.  It arrived at 8 A.M.  and with the assistance of
   movers, we installed it and were operational by noon.  The system
   was mainly used for science analysis, using a version of our
   Mission Operations meteorology software. The project's Mission
   Operations software was configured to produce a meteorology tape
   after some preliminary processing for use on Prime, prior to the
   more extensive data reduction segment of the program.  When the
   first data were relayed from the lander tape recorder, we obtained
   this tape and produced the first meteorology data from the surface
   of another planet, Mars, on our system.  Since it was summer in the
   tropics at our landing site, the wind was light and variable, much
   the same as on earth under similar conditions.


   The project director was James Martin of NASA Langley Research Center
   and the success of the mission was due in a large part to the
   competence and dedication of Jim and his staff.  A number of possible
   landing sites had been selected prior to Mars encounter on the basis of
   the previous Mariner 9 mapping and Earth radar data.  It was the
   function of the site selection group to choose an acceptable and safe
   site from the previously selected sites.  At least a week in orbit
   around Mars was planned for this activity and it was desired to land on
   July 4, 1976, the bicentennial.  However, engineering prudence
   sometimes delays plans and desired timelines.  The Viking orbiters were
   capable of resolving objects larger than about 40 meters and, in the
   ideal case, one would use observations of roughness elements larger
   than this and extrapolation to estimate the chance of spacecraft
   disturbing boulders.  However, all cases are not ideal and earth based
   radar data was required to supplemented the orbiter images.  Although
   the radar can not measure individual small features, they can estimate
   the size distribution of boulders, etc in large areas which are smaller
   than can be resolved in the images.  The combined data indicated that
   the previously chosen sites were not safe and the Fourth of July passed
   as the search went on.  The search could not go on indefinitely due to
   due to the cost of maintaining 1,000 of us at Mission Operations and
   due to the fact that the second spacecraft was rapidly approaching and
   would have to occupy the resources of the flight operational staff.
   Another site was selected on the basis of radar and orbiter data and
   landing was initiated.  Due to the one way propagation time of 18
   minutes from Mars to Earth, the landing sequence had to be automated.
   The entry and landing procedure consists of three phases.  First, the
   lander separates from the orbiter and retro rockets cause it to enter
   the atmosphere, protected by its heat shield.  At about 6,400 meters,
   the heat shield is jettisoned and the parachute is deployed.  Finally
   at about 1,200 meters, the parachute is jettisoned and the retro
   rockets are ignited with the descent being under control of the
   lander's Guidance and Sequencing Computer, GCSC, radar altimeter and
   inertial reference unit.  The first landing was completely successful,
   witnessed by many thousands of staff and families at JPL and by
   millions throughout the world.


   The second landing proceeded 44 sols later with fewer problems in the
   site selection process.  Although Lander 1 was to be placed in a low
   activity mode for Lander 2's arrival, we managed to schedule continuous
   meteorological data collection from both landers.  To have both landers
   and orbiters functioning successfully, was the result of good design,
   management and planning.  This is not to imply that there were not a
   few "cliff hangers" such as the Biology Instrument and the GCSC's
   plated wire memory, but the final results were more than satisfactory.
   At the end of nominal mission operations, the Prime system was moved
   back to UW in November of 1976.


   3.4 Science


   An idea of the complexity of the scientific instrumentation can be
   gained by considering the experiments.  The major individual ones are:


   1) three biology experiments,


   2) organic analysis,


   3) a gas chromatograph-mass spectrometer serving both organic and
   atmospheric analysis,


   4) stereo black and white and color fascimilie imaging system


   5) seismology


   6) meteorology


   7) other supporting components and experiments such as the soil sampler
   arm used to feed the experiments and to determine soil properties.  To
   appreciate the stringent engineering requirements, one should also be
   aware that the complete lander operated on an average power of 50 watts
   and had to be sterilized at 130 degrees Celsius for two 24 hour
   periods.  These simultaneous requirements, mandated innovative and
   careful design as well as somewhat higher than normal development and
   component cost.  Another indication of the success is that the
   proceedings from only two of the special Viking conferences weigh 8
   pounds and contain 1368 pages: this is only a small portion of the
   Viking generated research publications.


   As to specific results, the consensus is that no evidence for life was
   found even though the biology experiments reacted in a strongly
   positive way.  The reason for the reaction is that the Martian sols
   contain compounds that liberate oxygen in the presence of water.


   The atmosphere is composed of 95% CO2, small amounts of nitrogen and
   oxygen, as well as traces of Argon, hydrogen and other gases.  In the
   field of meteorology, we found that fronts on Mars were more similar to
   those on Earth than we expected.  However, in one instance at Lander 2,
   ( Lander 1 was at 22 degrees north while Lander 2 was at 48 degrees
   north ) six or seven fronts passed by at almost identical time
   intervals and strengths, as measured from the pressure data: on earth,
   we rarely see such regularity.  Since we were able to continue
   operation for more than three Martian years, we were able to observe
   year to year similarities in many meteorological phenomena as well as
   differences.  Major atmospheric, and over long time scales, geological,
   process are the global dust storms which decrease the daily average
   temperature on the order of 14 degrees Celsius or approximately 25
   degrees Fahrenheit.  As the dust remains in the atmosphere for many
   tens of sols, the effect was thought to be similar to that discussed in
   Nuclear Winter: Global Consequences of Multiple Nuclear Explosions,
   _______________________________________________________________________
   R.P. Turco, O.B. Toon, T.P. Ackerman, J.B.  Pollack and Carl Sagan,
   _______________________________________________________________________
   Science, 23 Dec.  1983, pp 1283-1292.
   _____________________________________


   An interesting, and as yet unexplained characteristic of the dust
   storms, is that some years have major storms while others do not.  For
   example, Year 1 had two, years two and three had none and the beginning
   of year four had one.  We do not know about the rest of year four due
   to the landers' failure during this fourth year storm, the most intense
   observed from the surface of Mars.  Another unusual feature is the
   discovery of transient dust storms, which seem to repeat at the same
   time of year, and which indicate a mode of global oscillation in the
   atmosphere of Mars.


   Many other interesting, and important, atmospheric processes have been
   studied on Mars.  One is the year to year similarity in the formation
   and sublimation of Mars' polar caps.  Mars has an inclined axis of
   rotation of 25 degrees Celsius, similar to Earths, which produces a
   large annual temperature range.  Due to its low temperatures and carbon
   dioxide atmosphere, around 20% of the atmosphere condenses, in the form
   of "dry ice" each year with surprisingly precise repeatability each
   year despite the variation in dust storm intensity and number from year
   to year.  A difference is the erosion of soil from year to year.
   During the third year, between sols 1720 and 1756, ( there are 669 sols
   per Martian year ) piles of dust placed by the soil sampler moved as
   well as small pebbles.  These were probably accompanied by local dust
   storms but why did they not move in previous years and why was there no
   global dust storm this year?  We hope that analysis of the data that we
   presently have will provide some insight into these questions in
   addition to numerical modeling of the processes.


   Martian meteorology is important, as well as interesting, in that its
   atmosphere resembles that of Earth more closely than any of the other
   planets, or moons, in our solar system which have atmospheres.  By
   testing our physical and numeric models of atmospheric motion, climate,
   etc.  on Martian observations as well as terrestrial ones, we can
   refine them to better explain and predict the effects of changes or
   differences in the variable parameters.  For example, the effect of
   major amounts of dust on the atmosphere are sometimes easier to
   understand Mars, than on Earth, since it swamps the other
   meteorological variables at times.  However, there are no funds if FY85
   for Mars Data analysis!

  

4 Real time operations at the Viking Computer Facility



One of the  main problems with the Viking Mission  was its success!  Prior
to landing, I suspect that most of us would readily have traded the chance
of  a  multi-year  mission  for   a  guaranteed  90  day  mission  without
hesitation.  It  the end of  the nominal mission  we were faced  with four
healthy spacecraft  and an excellent  flight operations team.   During the
next year or so, we at UW were content to continue receiving data from JPL
in  processed science  form even  though  we had  operational software  to
obtain  meteorology data from  the meteorology  Front End  Processor, FEP,
tapes produced by  the JPL UNIVAC 1108 system.  However, if  we were to be
able to obtain meteorology data in  the future, it was clear that we would
have to implement  some of the operational software  which handled the raw
spacecraft data stream from the  Deep Space Network, DSN, since the flight
operations IBM 360/75's were certain to be decommissioned soon.  A minimal
set  of this  software  was implemented  on  the VCF's  Prime  for use  in
obtaining meteorology results from  the meteorology science data format in
the raw data stream and  pressure from the engineering data format.  While
implementing this  capability, changes  were made in  the data  format and
block lengths by NASA, which we  included as options.  In January of 1981,
we began processing data on  a weekly basis, including a comprehensive set
of  engineering parameters  for the  operations  team at  JPL.  Data  were
provided to JPL by dial up access  or by mail.  In the next few months, we
expanded the engineering processing, including plotting selected, and then
all,  engineering parameters.  Prior  to our  conversion of  the software,
data were plotted by hand at JPL if at all.


Around  that time,  it  became clear  that  the lander  might continue  to
function for  many years  and dedicated, part  time, Viking  staff members
initiated a  program to recondition the two  dead nickel-cadmium batteries
of the four  on Lander 1.  To assist in the  rapid turnaround required for
this effort to be successful, I  proposed that we implement a direct, real
time link  between JPL and the VCF  since the previous method  was to mail
tapes from JPL to UW.  This was accepted and after several iterations, the
communications       configuration      of       Figure       3-8,      Telecommunications
and Data Acquisition  System Support for the Viking  1975 Mission to Mars,
The Viking Lander  Monitor Mission May 1980 to March  1983, D. G. Mudgway,
JPL publication 82-107  was implemented.  The synchronous NASA
communications codes  were decoded and  input to an  AMLC port on  the VCF
using an  Intel system.  First testing  of the system  was accomplished on
May 14, 1982 and our  permanent installation was implemented in October of
1982.  The only special provisions made  on the Prime end were to increase
the  size  of the  AMLC  buffer  to around  1,000  bytes  to preclude  the
possibility of  buffer overflow.  Since the  data rate from  Mars to Earth
was 1,000  bits/sec, there was no need  to assign a high  priority to this
task.  With  our real time capability,  we were able  to provide immediate
analysis of  the battery conditioning  results for planning  the following
sequences in a timely manner.

 5 Development  of the Smithsonian
National Air and Space Exhibit



Prior to the  establishment of the real time link,  we had been displaying
lander images on  our AED 512 image processor.  Once  the planning for the
link was initiated,  Dr Farouk El-Baz of the  Smithsonian National Air and
Space Museum was  consulted as to whether the Museum would  like to have a
weekly picture "Live from Mars",  provided we could obtain the donation of
an  image  processor.   After a  commitment  of  AED  to donate  an  image
processor  I requested that  Prime donate  a used  system for  the Museum.
After long  negotiations with  the various parties,  and Stan Kent  of the
Viking Fund  providing maintenance funds,  a system was  donated including
two  Prime  microcoded  MPC  4   controllers,  to  allow  high  speed  DMA
communications between Prime and the image processor.


Microcode for  the MPC  4 was  written by Noel  Cheney of  the Atmospheric
Sciences Department at UW, while we continued to operate 24 hours/day.  To
minimize impact  to users  and disruption of  our continuous  weather data
collection and  processing, initially the  testing of MPC 4  microcode was
done between 7 and 8:30 AM.  To make the development of this code possible
under such constraints, Dr.  Harold Edmon  of the VCF wrote a debugger for
microcode development as well as  a routine to down load microcode without
cold or warm starting the system.  User interfaces for the MPC 4 and image
processing software were written by James Synge of the VCF.  William Guest
processed and generated the meteorology  graphics that are included in the
display and Neal Johnson provided in Viking data processing.  The sequence
of  text, graphics  and  images that  are  presented at  the Museum,  were
developed  by  Dr.   Ted  Maxwell  of  the  museum,   Rachel  Tillman  and
me.  Finally, I  designed the  overall system  as well  as  convincing the
interested parties to donate the required resources.


Subsequent to our development  of  the  display,  which  requires  only  a
special cable  and  our  microcode  to drive the AED, we have developed an
expansion capability which permits multiple AED's to  be  driven  by  one
port with  a  small  interface box, which supports up to three local image
processors and provides line drivers to another  similar  interface.   The
next interface  can  be  located  thousands  of  feet  away and in turn can
support several image processors.  While this does violate our "commercial
hardware only" policy it does allow high speed and significant flexibility
with minimal additional hardware.  I  hope  that  such  features  will  be
provided as off the shelf items in the near future by Prime or others.


Unfortunately, schedules and other complications delayed  the  opening  of
the exhibit  until  after  our loss of the lander.  However, during one of
our routine real time downlinks from Mars, we  processed  and  transmitted
the weekly  image to the Smithsonian system via Primenet within an hour of
receipt of the data by  our  facility  as  a  simple  demonstration  which
required no  software  changes  on  our part.  Primenet was routinely used
between NASM and UW during our joint  development  and  debugging  of  the
display.


While the loss of the "Live from Mars" aspect, lessens
the excitement, the display was never planned to include more than a
small amount of the latest data, due to the once a week transmission.
Also, the fact that the data are transmitted at Mars noon coupled with
the 37 minute difference in day length, guarantee that the majority of
the downlinks would not have been live during public hours.  I would
recommend that you take advantage of the opportunity to view the
exhibit, at the Museum due to the other historical items associated
with the display and during this meeting.  In the Smithsonian, it is a
permanent exhibit buried upstairs in the "Exploring the Planets"
gallery, which requires diligence to find.

 


 

The Viking Mission to Mars was  the  most  sophisticated  and  interesting
planetary missions  ever  executed.  The enclosed table summarizes some of
the operational parameters and it should be remembered  that  the  landers
both lasted  through  winters with temperatures of -118 degrees Celsius and
Lander 1, the Thomas Mutch Memorial Station, lasted 2,245 sols, roughly 20
times its design life.  Such  performance  is  a  proper  tribute  to  the
spacecraft designers and operators, as well as the Project management!  As
a follow  on,  I  suggest  that  we begin planning for a manned mission to
Mars, inviting and encouraging all nations to take part. 

Figure 1

Viking Lander "As Built" Performance Capabilities. NAS1-9000, June 1976. Martin Marietta Corp., Denver Division, Denver, CO 80201

Figure 2 Mission Operations Communications including Real Time. NASA Deep Space Network >> Jet Propulsion Laboratory >> University of Washington >> Smithsonian National Air & Space Museum, Washington DC. From "Telecommunications and Data Acquisition System Support for the Viking 1975 Mission to Mars, The Viking Lander Monitor Mission May 1980 to March 1983", D. G. Mudgway, JPL publication 82-107. ______________________________________________________________________ ______________________________________________________________________ Parameter V0-1 V0-2 ______________________________________________________________________ Number of days from launch to end of mission 1813.98 1049.52 Number of orbits of Mars 1488.0 706.1 Number of pictures recorded in orbit 36,622 16,041 BILLION data bits played back from 357.7 161.3 the tape recorders (including lander relay data) Tape travel across recorder heads, km 2955 1397 Number of commands sent by the Network 269,500 Number of tracking passes supported by the Network 7,380 Hours of tracking time provided by the Network, 56,500 _________________________________ Table 1. General Viking Orbiter Statistics ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ Event Viking 1 Viking 2 ______________________________________________________________________ Launch Aug. 20, 1975 Sept. 9, 1975 Arrival June 19, 1976 Aug. 7, 1976 Landing July 20, 1976 Sept. 3, 1976 Site Chryse Planitia Utopia Planitia Coordinates 22.3 N, 48.0 47.7 N, 225.8 Orbiter in orbit 1,509.9 days 718.8 days Lander active on surface 2,245 days 1,316.1 days End lander operations Nov. 13, 1982 April 11, 1980 End orbiter operations Aug. 7, 1980 July 25, 1978 Orbiter photos 51,539 Lander photos More than 4,500 Photo coverage 97% of planet with resolution of 300 m (1,000 ft) or better. 25% of planet with resolution of 25 m (82 ft) or better. Lander weather reports: more than 1 million Orbiter infrared observations: more than 1 million Orbiter weight: 2,325 kg Lander weight: 571 kg Orbiters built by Jet Propulsion Laboratory Lander built by Martin Marietta Aerospace Project managed by NASA Langley Research Center ____________________ TABLE 2 ______________________________________________________________________ ______________________________________________________________________

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