The Multi-angle Imaging SpectroRadiometer (MISR) optical bench, which houses the instrument's nine cameras, is temperature-controlled by an electronic heating system. As the system pulses on and off, the camera electronics picks up a tiny signal. This effect is greatest when the spacecraft is on the night side of the planet. On 12 February 2000, before the instrument cover opened for the first time, this heater signal was captured in 41 seconds of "dark current" data that are displayed here as an image. The vertical stripes are a tiny bit brighter, about 0.3%, than the typical background level, and are apparent only because the contrast has been greatly enhanced. As the bench warms up on the orbit day side, the pulse widths narrow and the "jail bars" disappear.