218 
77b 200 225 250 275 300 325 350 375 400 425 
ALTITUDE (kilometers) 
Figure 1.—Ground resolution expected from Large Format Camera 
(LFC) operated in low Earth orbit with various film types. 
Currently under construction is an attitude reference system (ARS) for 
use with the LFC. This will consist of two stellar cameras looking 
towards the horizon and directed 45° fore and aft of the normal to the 
ground track. Each camera will have a lens of 150 mm focal length, and 
a film format of 70 x 70 mm. The cameras will be exposed for 25 msec 
centered about the exposure time of each LFC frame. The ARS cameras 
will be rigidly attached to the LFC so that there will be no problem of 
changing alignment during flight. The locking angles between the ARS 
and LFC reference coordinate systems will be determined by stellar cali 
bration procedures. By postflight measuring of the identified stellar 
pattern, it will be possible to determine the attitude of each LFC frame 
with an accuracy of + 5 arc seconds about each of the three rotation 
axes. 
The LFC with ARS is presently planned for flight on Shuttle missions 
STS-11 in January 1984 and STS-17 in August 1984. The latter mission, 
which will be at 300 km altitude, will also carry a new Shuttle Imaging 
Radar (SIR-B) and several other experiments which were operated on 
STS-2. The flight configuration of the cargo bay pallet for this 
mission is shown in figure 2.