Engineering cameras are those that provide data on satellite platform performance, such as the state of deployables, or the progress of a rendezvous maneuver. The requirements for these engineering cameras typically differ from those of prime payload cameras.
Firstly, satellite buses are often designed around, or tailored to, the prime payload. In contrast, engineering cameras should impose minimal requirements on the platform. This means minimal size, weight, and power consumption. Additionally, the command and data interface should be common and widely available, such as RS422/485.
While Earth observation cameras have a clear target, engineering cameras are required to image subjects at different distances which occupy different fields-of-view. Examples include capturing the state of deploying solar sails, the unfurling of antennas, and even satellite selfies. Therefore, it is beneficial for engineering camera products to offer a range of lens options, or a standardized lens mount such as M12 or C-Mount. The option for optical filters, especially neutral density filters, may also be useful to engineering cameras having to image in high dynamic range environments.
If intending to image rapidly moving targets, such as spring loaded deployables, a global shutter image sensor may be preferable to the more common rolling shutter type. Global shutter image sensors expose the whole image at once, while rolling shutters expose each line sequentially, which can lead to image artifacts.
A final consideration is onboard memory, which is typically less important for an engineering camera, compared to a primary payload camera. Transferring an image over a serial bus, such as RS422, can take tens of seconds, so onboard memory may be required for capturing rapid image sequences. Onboard memory may also be useful if the engineering camera is expected to operate autonomously for a period of time, such as capturing a timelapse while the platform processors are busy with other tasks.
Engineering cameras are indispensable tools for satellite performance monitoring, providing unique imaging capabilities for diverse mission needs. By focusing on minimal platform requirements, versatile lens options, advanced sensor technology, and onboard memory considerations, these cameras ensure reliable operation across various scenarios. As satellite technologies continue to evolve, engineering cameras will play an even greater role in supporting mission success through innovative design and adaptability.
