Irregular shaped passive samples can be accomodated near the center of the carousel. The outside three rows of active sample will be measured by OPM optical instruments. These samples are mounted on calorimeter sample holders for the calorimetric determination of solar absorptance and total emittance. The integrating sphere, the TIS Coblentz sphere, and one of the two VUV detectors are positioned above the carousel and view the samples through the holes in the emissivity plate as the carousel is rotated to position each sample for measurement. The OPM contains three types of environmental monitors.
Radiometers monitor the solar and earth irradiance.
The two TQCM contamination monitors and the AO monitor are mounted on either side of the exposed portion of the carousel and have the same view of space as the exposed test samples. The two radiometers are located on the carousel. OPM also has a Sensor Monitoring Subsystem that controls the AO monitor, data, temperatures, and voltage. The purpose of the carousel assembly is to rotate the flight test samples into the proper position to enable measurements by the OPM instruments. Because of the criticality of the carousel drive, there is a redundant stator winding on the stepper motor and a redundant set of position sensors.