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Abstract-The det~tabi~~ty ofamp~itud~ modulation and spat% frequency modulation ofsuprat~resh~~ld sine-wave gratings was measured at retinal eccentricities ranging from 0 to 30 deg. The main conclusions to be drawn from the experimental results are: (I) for this visual task it is not possible to bring peripherai sensitivity to the same level as fovea1 sensitivity by scaling the stimuli with the inverse of the cortical magnification factor M. (2) Increasing the number of cycles in the carrier grating improves modulation detectability. For gratings in the periphery this holds up to the largest stimulus size used (6-l cyclrs). In earlier investigations it has been shown that for central vision the improvement ends at about I6 cycles.

Focal is a facility designed to perform optical tests on payloads in a thermal vacuum space environment. The vacuum chamber is a vessel of horizontal cylindrical shape having 5 m (16.4 ft) diameter and 6 m (19.7 ft) length. The vacuum limit is about 1 nbar. Inside the vessel an optical table ensures a stability better than 10 μg. A thermal environment is simulated by shrouds specific to each experiment. The thermal facilities allow the feeding and control of 10 independent shrouds at 10 different temperatures between 170K (-153°F) and 370K (206°F) with a stability of 0.1 K (0.18°F). This facility has been used for the thermal vacuum and thermal balance tests of the ESA Hipparcos astrometry payload.