Viking '75 Science Test Lander, Detail photographs of the Science Test Lander from Viking '75 Options

[Tom Dahl]

Recently I spent an enjoyable afternoon photographing the Viking '75 Mars Lander
which is on display at the Virginia Air and Space Center in Hampton VA. Based on
many details, I am sure this is the so-called Science Test Lander (STL) which
was installed in the NASA/JPL "sandbox" during the missions. I have uploaded 277
detail photos (totaling nearly 2GB) to a Picasa Web album.

(As far as I know, the best/only way to download them all is to install and
execute Google's free Picasa application for Windows PCs. Note a quirk with the
Picasa Web magnifier tool: on large images such as these, the full resolution
usually is not loaded right away when you activate the magnifier. If you wait
ten seconds or so, usually the full 4K-pixel version will become available via
the navigator pop-up in the corner. Sometimes it never does, however.)

The STL in its current museum display configuration has two very interesting
attributes. First, the insulation blankets and cloth covers which normally
surround the fuel tanks, associated plumbing, and roll-control thrusters has
been removed. I happily captured a fair number of photos of the exposed (and
complex!) fuel-system plumbing, valves, wiring, and thrusters.

Second, the lander's bottom cover plate has been cut open in the 30-inch square
area normally covered by the Terminal Descent Landing Radar (TDLR) box. The TDLR
is not installed; instead it is mocked-up on two side with tall white flanges. I
would like to see an accurate TDLR someday (the Smithsonian's Proof Test Capsule
is also missing a TDLR), so it's a bit of a shame not to find one here. However,
the trade-off is wonderful -- the large opening in the bottom allows a peek at
the lander's interior! It is not really possible to see visually inside, due to
geometry of the museum display, but a carefully-positioned camera can get some
views. :-)

The STL body is essentially empty, but a few interesting details are present.
The dacron-covered insulation blankets lining the interior sidebeam walls are
there, restrained with authentic vertical nylon ties. The Equipment Plate is
installed, which is a large hexagonal aluminum plate spanning the interior about
five inches down from the lander's top cover plate. (The computer, batteries,
science instruments, radios, etc. were bolted to and hung from the bottom of the
Equipment Plate.) The plate is partially painted black (for thermal control) in
areas which were not to be covered by mounted components, and this is visible.
The thin coolant-loop tubing which snakes around the underside of the Equipment
Plate is there. The three cylindrical struts from which the TDLR was to be hung
are there. The Thermal Switches to which the Radioisotope Thermoelectric
Generators were mounted are there, and I managed to capture a peek at the
flexible copper "Contactor" of one of them.

The STL has somewhat simplified external wiring, and the externally-mounted
electronics units on sides 1 and 3 are simple wood mock-ups. This includes the
Inertial Reference Unit, the two Radar Altimeter Electronics units, and the
Valve Drive Amplifier. The three Terminal Descent Engines are also mostly wood
mock-ups, however TDE #2 (on the "front") has an authentic top plate and gold
thermal shield.

I was able to take a number of detail measurements, which will eventually be
incorporated into plans I've barely begun to create. All in all, I was very
happy to have made the trip to see this lander.
-- Tom

[Tom Dahl]

I recently discovered some new (to me) information about the origin of the Viking lander known as the "Science Test Lander" (STL). There is an article titled Viking That Will Never Fly in the August 11 1975 issue of the Langley Researcher newsletter. Accompanying the article is a photograph (reproduced below) of the STL with the caption:

Engineers Leonard V. Clark of VPO (Viking Project Office) and Vernon P. Gillespie of SED (System Engineering Division) discuss the status of the Viking Science Test Lander being fabricated by personnel of SED and FID (Flight Instrumentation Divisions). This full-scale working model of the Viking Lander will be shipped to JPL (Jet Propulsion Laboratory) in Pasadena, California, in late August for utilization during Viking Flight Operations.

The article essentially confirms in my mind that the circa-1975 STL is a distinct unit from the Proof Test Capsule (now in the Smithsonian National Air and Space Museum) which was assembled earlier by Martin Marietta in Denver and used extensively in numerous test programs during lander development. The full text of the article reads as follows:

Viking That Will Never Fly

Not all the Viking Landers will see the light or life on Mars. While its two sisters mated with Orbiters, speed to Mars, the third capsule will sit complacently here on Earth, content to be viewed and tested as a working model.

The third Viking Lander is called the Science Test Lander (STL). It is a full-scale model that will be used during the period of Flight Operations at Jet Propulsion Laboratory (JPL) in Pasadena, California.

The STL is an exact duplicate in appearance and geometry of the Flight Landers. A particular emphasis has been placed on fidelity of the top deck of the Lander where the Mars surface sample inlets to the principle science instruments (biology, GCMS (Gas Chromatograph/Mass Spectrometer) and XRFS (X-ray Fluorescence Spectrometer) are located.

An important feature of the Lander model is its operational subsystems, namely, a pair of facsimile cameras and a surface sampler. The cameras will be operated to scan 360 degrees to take panoramic pictures of the area around the Lander. They can be used in a special "line scanning" mode to detect motions. Its color filters can perform chemical minerology investigations on the surface near the Lander.

The surface sampler can be commanded to reach out its retractable ten foot arm, scoop up the Mars surface samples and deposit the grains into the mini-laboratories that will perform the experiments.

The model has been assembled at Langley using an assortment of surplus hardware from the many test programs that preceded the building of the flight Lander components. The STL will be shipped to JPL in late August. It will be installed by Langley staff in the Atrium adjacent to Von Karman Auditorium. The Atrium, enclosed by floor to ceiling glass viewing windows, was reconstructed and powered to house the working model in a suitable surrounding. The facility will be operational by October. The Surface Sampler Team of the Viking Science Group is responsible for the operational phase. By testing and studying this working capsule, the crew will be able to understand, command and control the other two Landers for their performance and data return.

The facility will initially be used to provide camera and surface sampler data for the Lander Simulation System, and to support Flight Team Test and Training exercises. Later, the STL will be used extensively by the Imaging and Surface Sampler Teams to develop an instrument performance data base, to develop command sequences for nominal and off-nominal situations, and to develop and verify flight commands.

Sometimes called the "Kiwi" or "Gooni Bird" by the joking staff, who nonetheless are proud to be its guardian, the STL will provide an interesting close-up display during its working hours to the fascinated viewers.

Edited to add some more information: I was re-reading a set of Viking Mission Status Bulletins that I acquired a while ago, and came across a definitive statement in the cover story of No. 36, about Lander 1's early surface sampler locking-pin troubles. The story includes the following statement clearly indicating the independent status of the STL and PTC:

The situation was quickly evaluated, and tests were made to duplicate and determine the nature of the problem using the science test Lander at JPL and the proof test Lander at Martin Marietta in Denver.