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The Metric Camera (MC) experiment, which is a standard Zeiss 30/23 aerial camera 
with 30 cm focal length and 23 x 23 cm format, will be operated through a window 
in the manned module. From the anticipated altitude, these pictures will cover 
an area of 190 x 190 km, with a ground resolution of approximately 20m. The 
mission will be nine days duration and three film cassettes providing a total of 
1650 frames will be carried. The principal objective is to determine the appli- 
cability of such photographs for topographic mapping at scales as large as 
1:50,000. 
The second Earth observation instrument aboard Spacelab is the Microwave Remote 
Sensing Experiment (MRSE). This consists essentially of a parabolic reflector, 
a sub-reflector, and a feed horn. The instrument can operate as a two-frequency 
Scatterometer to measure ocean wave spectrum, as a passive thermal radiometer to 
measure surface temperature with sensitivity of +/-1° K, or as a synthetic aper- 
ture radar providing 25m ground resolution over a 9 km swath. 
There will be subsequent Spacelab missions with various objectives such as life 
Sciences and materials processing. One of these has been designated for Earth 
and atmospheric observations but a final selection of instruments has not been 
made. 
Shuttle mission STS-11 at 296 km altitude and 28.59 inclination has the primary 
mission of launching three communication satellites. It will also carry the 
Large Format Camera (LFC) built by NASA. The essential parameters of the camera 
are a 30.5 cm focal length with a 23 x 46 cm format. The camera has automatic 
exposure sensors and forward motion compensation, permitting use of high reso- 
lution fine grain film. The magazine has capacity for 2400 frames. A ground 
resolution of 10 to 15m can be obtained from the nominal Shuttle altitudes. By 
using 80 percent forward overlap, a base-height ratio of 1.2 can be obtained, per- 
mitting contours of 20m interval to be compiled. An Attitude Reference System 
(ARS) is also being built for addition to the LFC. This will consist of two 
stellar, cameras of 152 mm focal length operating on a single 70 mm film web. The 
cameras will be directed horizontally when the LFC is looking vertically and will 
be aimed 459 fore and aft of the normal to the flight path. The lock angles 
between the ARS cameras and the LFC will be determined by calibration. The mid- 
point of exposure of the star cameras will be synchronized with the LFC exposure. 
Post-flight mensuration of the star photographs will permit determination of the 
three attitude angles for the LFC with a precision of about +/-5 arcseconds. 
The LFC/ARS will be mounted on the Multi-Purpose Experiment Support Structure 
(MPESS) shown in Figure 2. This is conceived as a standard payload which can 
be carried in the cargo bay of any Shuttle mission with substantial Earth-viewing 
time. 
Shuttle mission STS-17 is presently scheduled for August 1984 at 296 km altitude 
and 57° inclination. Its principal objective will be to carry the OSTA-3 Earth 
observation payload. The primary instrument will be a new imaging radar, identi- 
fied as SIR-B, which will have a folding antenna mounted on a cargo bay pallet. 
The radar will operate in L-band, with an incident angle variable from 15° to 65°, 
and corresponding swath widths of 30 to 55 km. The ground resolution will vary 
from 30 to 110m depending upon the look angle. The 46 megabit/second digital data 
will be transmitted via TDRSS, but a back-up optical recording on film will also 
be provided. 
The second instrument in the OSTA-3 payload will be the LFC/ARS. Initially it 
was planned to mount this on the same pallet which will carry the SIR-B, but later 
developments make it probable that the same MPESS structure used on STS-11 will be 
employed.