Publication of our Earth photos raised an incredible interest among our fans, especially in the comments section of our posts and articles. Many of you have pointed out the low resolution of the presented pictures and boasted having better cameras in your smartphones. So, what is the deal with PW-Sat2 cameras? Was it a cost-saver, sloppiness or maybe a conscious design design? Let’s find out!
The main purpose of the two cameras on board our satellite is to register the deployment of the deorbit sail. Two lenses set in the direction of this experiment enable us to check whether the essential mission of PW-Sat2 proceeded as it has been planned.
The devices we use are commercially available board cameras that had to originally meet our requirements – including dimension and mass constraints. They consist of a simple optical system (up to 116° and 76°) and a detector that allows to take JPEG photos with a resolution of up to 640×480 pixels. Images are saved on our on-board memory in one of the several resolutions. Usually we ask the satellite to take one small and one bigger image one after another, then the smaller one is sent to Earth.. Photo files are relatively large, which is why pre-collected thumbnails allow us to decide which of the bigger files are worth downloading in subsequent communication windows and which can be rejected showing for example pure black frame (our cameras are not sensitive enough to capture stars – that’s the domain of two Polish scientific satellites – BRITE-PL operated by Space Research Center).
Highest quality images are so big that we had to spend 3 whole communication sessions downloading them and we only have 6 such sessions per day at best. PW-Sat2 uses radioamateur UHF/VHF bands for communication with ground. Using higher frequencies would allow us to send the data much faster, but at a cost of making the mission significantly more complex. Appropriate device cost more, consume more power and require fine attitude control, making the satellite bigger, heavier and obviously, more expensive to launch.
Our satellite consumes significantly less power than a usual smartphone in your pocket. Using the smartphone camera onboard a satellite would be a bad idea, it would only be a matter of days before the camera’s image sensor would be severely damaged by cosmic radiation. Devices chosen to fly on PW-Sat2 have a very big pixels (5×5 μm) making them much more resistant to highly energetic particles damage. To decrease risks, cameras with a documented flight heritage only were considered.
Besides the confirmation of the deployment of our deorbit sail, as you may have seen recently, cameras are also able to take pictures of the Earth. However, due to the fact that the satellite is constantly rotating on orbit, it is difficult to predict what will be captured in the photo. Luckily our planet looks amazing in each picture we take.
Today we would like to share a little surprise again – a first movie (or a GIF to be precise) recorded by PW-Sat2 on orbit. This is a sequence of 24 overexposed frames recorded around 30 seconds apart. This sequence could potentially be used to determine the satellite’s rotation speed. Although, we are still not sure if it will be sufficient for this task, we are doing our best to use the resources available on board and our time on orbit to the limit, experimenting and learning as much as possible.