Performance and thermal-vacuum testing of terrestrial cameras in pocketqubes

Due to their low mass pocketqubes are relatively inexpensive to launch. This makes them ideal for the creation of large constellations in low Earth orbit and a sufficiently large constellation would be able to perform measurements over the same area multiple times per day. Equipping these pocketqubes with cameras would increase the chance of cloud free images and would allow scientists to study dynamic processes which happen on sub-daily timescales. A camera in a pocketqube would have a spatial resolution of about 40 meters which would be sufficient for, for example, ocean color measurements or measuring land related variables, such as vegetation extent or land use, which allows biologiststo better study conservation efforts. The economics of pocketqubes requires that the development cost and production cost per pocketqube must be comparable to the launch cost. For this reason it is preferable to use commercial off the shelf over purpose built cameras. to test whether or not those commercial off the shelf cameras would survive in space, environmental testing is required. The launch environment, consisting of the accelerations and vibrations experienced during launch, and the thermal-vacuum environment potentially have the largest immediate impact on a camera and should be tested for. Other environmental effects in low Earth orbit, such as atomic oxygen, UV radiation, ionizing radiation, et cetera, are damaging over time but might only require analysis rather than extensive testing. Due to limited resources only a thermal-vacuum test was conducted. For this test two cameras, the See3CAM_CU30 and a generic ELP H264 720p usb camera, were selected. These cameras were subjected to a thermal-vacuum test by placing the cameras inside a vacuum-oven in which the cameras were exposed to a vacuum while being heated to a temperature of 50∘퐶. Because the vacuum-oven was not suitable to test the cameras at temperature below room temperature a thermal-ambient test was also conducted in which the cameras experienced four cycles of heating up and cooling down to the expected in-orbit temperature extremes of 50∘퐶 and −5∘퐶 respectively. Before, in between, and after the thermal-ambient and thermal-vacuum tests a performance test was conducted to identify changes to the cameras. These performance tests measured the modulation transfer function, change in color representation, change in full well capacity, change in average dark signal, change in chromatic aberrations, and change in image distortion.Both cameras still functioned after the thermal-ambient and thermal-vacuum tests and showed no significant outgassing. Both cameras also showed no change in the distortion and chromatic aberration after the conducted tests indicating that the lenses survived the thermal-vacuum environment withoutdetectable changes. After the thermal-ambient test, conducted prior to the thermal-vacuum test, only the See3CAM_CU30 showed some minor changes in its color representation. The ELP camera was unaffected. After the thermal-vacuum test the See3CAM_CU30 only showed again some minor changes in the color representation. The ELP camera became unusable. It experienced a large change in color representation and showed significant performance deterioration in the full well capacity and average dark signal. This indicates the camera overexposing all its images. However, a test measuring the effective integration time at various camera settings before and after the experiments showed thatthe camera integration time is unlikely to have been affected.Both cameras still functioned after the thermal-vacuum experiments. However, the fact that the ELP camera, and to a lesser extent the See3CAM_CU30, experienced performance degradation shows the necessity for good and rigorous performance testing of commercial off the shelf cameras beforeusing them in pocketqubes. Although the See3CAM_CU30 showed potential it is too early to conclude whether or not it can survive in space for any length of time. In order to determine this at least a test is required demonstrating its ability to survive the mechanical environment experienced during launch.Aerospace Engineerin