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spacelab module. It must be secured in Storage racks during 
takeoff and landing. During operation the astronauts must mount 
the camera to the optical window and remove it from there. While 
astronaut time is at a premium a more efficient camera operation 
is achieved by providing signals from the payload operations con- 
trol center in Houston via communication satellites to the one on 
board computer, which gives these commands at Specified times to 
the camera. It would of course be desirable to take as many photos 
during the Spacelab 1 mission as possible. 
However there are some basic limitations on this first spacelab 
flight such as mass and energy limiting the experiment to 3 films, 
that is a total of 1650 photos. The scenes which can be photo- 
graphed still depend on other factors such as the timeline having 
to be shared with other experiments particularly with regard to 
orientation of the spacelab. 
The last timeline worked out from NASA and ESA permits the targets 
shown in fig. 2. Three films can be exposed over these targets at 
60$ overlap. The actual sites will be shifted after calls for 
experiment proposal answers to countries wishing to participate 
in the experiment will be received. ESA has sent out these docu- 
ments to the governments concerned. Whether an experiment wish 
can be accomodated will also be determined whether a satisfactory 
timeline can be agreed taking into consideration the Spacelab 
orientation requirements of other experiments. Should it not be 
possible to include such cooperation wishes into the first mission, 
the would be included in plans for future European missions. 
The 23 x 23 cm photos can be evaluated in standard mapping equip- 
ment. Weather conditions will most likely eliminate the possibility 
to photograph some of the targets. In this case an 80$ overlap 
will be taken over the good weather areas. The metric camera ex- 
periment must be seen in the contact of past photographic and 
other past space missions, as well as in the light of future 
missions or proposals. The criterion to be used for mapping capa- 
bility is resolution. While there are diverging views and standards 
to measure and to compare resolution, it may also be difficult 
to justify the validity of the table of comparison on resolution 
shown in fig. 3. Determinations have been made at different con- 
tracts; but well known to photogrammetrists is the difference 
between pixel size and photographic resolution. In order to com- 
pare both, pixel size must at least be multiplied by 2 x Kell 
Factor (which is V2). Depending upon the type of film chosen, we 
hope to achieve a ground resolution of at least 25 m over the 
whole 23 x 23 cm format; this is a conservative estimate based 
on a contrast of 1:1,5. With this it becomes clear that Spacelab 1 
will deliver area covering photos in the range of the highest 
resolution obtained from orbits thus far. 
AS potential films highly sensitive emulsions are selectable, 
since exposures of 1/1000 or 1/500 sec. will be used only to 
avoid image motion. 
The actually most suitable films will be determined by test 
flights from high altitude in a cooperative program agreed upon 
between the French and German Space agencies. The attainable 
ground resolution has been estimated with the aid of modulation