Multispectral imager

Orbiting Earth at an altitude of 510 km, the satellite carries a multispectral camera that images in the visible to near-infrared part of the electromagnetic spectrum. Benefiting from the previous Φsat-1 experiment, the camera uses a dedicated processing unit that allows the various onboard AI applications to run effectively.

The small onboard multispectral camera is able to take images in eight different bands at the same time with a ground sampling distance of about 5 metres.

Square images measuring about 20 x 20 km captured by each band are generated and stored in the onboard memory over many orbits, about 15 orbits a day. These images are then radiometrically corrected, aligned and geolocated before being made available to the onboard applications.

This onboard pre-processing constitutes one of the distinctive features of the Φsat-2 mission.

Images acquired are processed onboard and then transmitted back to Earth at least four times a day.

Another key aspect of the mission is its added ability to handle multiple applications, all targeting different goals. The concept of onboard applications was pioneered by another ESA mission called OPS-SAT, which developed a way to organise and use these applications on a satellite. Φsat-2 extends this approach to Earth observation via its dedicated version of the NanoSat MO Framework software that allows onboard application to be created.

As well as allowing users to run, manage and update the Apps directly from the ground, the NanoSat MO Framework also allows advanced features such as ‘chaining’ so that different applications can run sequentially.

Over its life in orbit, the mission will go through different phases; initially to confirm the proper functioning of the satellite and then a calibration phase dedicated to the instrument.

Then, during normal operations, acquisitions will be determined based on specific requests from the users. AI application providers are also expected to complete an in-orbit fine tuning of their models that were initially trained with synthetic data.

Data provided by the Φsat-2 mission will be open and freely available.

There is a set of four primary applications:

• Cloud detection
• Street mapping
• Marine vessel detection
• Deep compression