3 
tables were selected primarily because of their straightness charac 
teristics and because they minimize "sticktion" or stick-slip motion 
which is necessary to permit zero positioning of the tables without 
excessive hunting or loss of correlation. Each carriage is floated 
on a thin film of low pressure air (about 5 lb.). The base upon 
which the carriages are floated consists of a base and rails which 
are assembled to form a channel. The y-carriage, which is floated 
on the base, also has a channel in which the x-carriage is floated. 
Both carriages have precisely machined pads on the bottom and side of 
each carriage against which the air acts to provide the cushion for 
floating and guiding the tables. The x and y tables are driven by 
a steel tape and friction pully. 
A Ferranti moire fringe metering system is used to provide the 
measuring capability. Ten-inch, 250 lines/mm gratings are used to 
give the one micron read-out. The table servo drive system in the 
fine mode consists of an anti-backlash worm gear reduction clutch, 
and a magnetically detented stepper motor. In the coarse of rapid 
slewing mode the tables are translated at a rate of approximately 
0.3 in/sec using D-C servo motors. In the fine mode, the motors 
are geared so that each step causes a table translation of approxi 
mately 0.6 microns and maximum speed of 120 microns/second. Manual 
control is provided by a joy stick. The signal provided from this 
joy stick controls the drive velocity so that the displacement of 
the joy stick in any direction from its center position will control 
the table drive speed in that direction. A button on top of the 
joy stick can be depressed intermittently to give single step motion. 
The marking system consists of a die (two for each table) which 
produces the desired mark on the emulsion, a heating element to 
maintain the die temperature at approximately 300° F., guidance 
bushing to provide linear vertical travel of the die, logic to trans 
late the table to its proper position under the die and a vertical 
drive to raise and lower the die (See Figure 5). The marking dies 
are fabricated to produce concentric circular marks on the emulsion. 
Several sizes of dies have been produced for test purposes. Each 
produced die has two concentric circles, an outside circle or "flag 
ging" mark 2mm in diameter and an inner circle or dot of varying 
dimensions (See Figure 6). For instance, the inside circle may be 
a dot of 25 or 50 microns or a circle having an inside diameter of 
50, 75, 100, 200, 500 microns. When the requirements for the com 
plete map compilation system have been finalized one die size will 
be selected. Since the marking system bushing is held stationary