RADICALS

The University of Alberta has contracted SFL Missions Inc. for development of the RADICALS small satellite to study the transport of space radiation into Earth’s atmosphere and its impact on climate. The RADiation Impacts on Climate and Atmospheric Loss Satellite (RADICALS) mission is being designed by a consortium of Canadian universities and SFL Missions, led by the University of Alberta, and funded by the Canada Foundation for Innovation, Government of Alberta, and Canadian Space Agency.

Built on the space-proven SFL DEFIANT bus, RADICALS will leverage SFL’s flexibility in attitude control approaches and require the spacecraft to spin end-over-end as it travels in a near-polar orbit around Earth. This will enable its suite of multiple instruments to collect continuous measurements of the full angular distribution of space radiation which rains down into the Earth’s atmosphere, these 360-degree directional measurements being essential for quantifying the energy input with unprecedented accuracy.

RADICALS will carry three multi-sensor instrument suites – an X-ray Imager (XRI), High Energy Particle Telescope (HEPT), and Magnetometers (MAGS), with a total of 11 sensors.

“The primary design objective of RADICALS is creating a spacecraft that is spin stabilized and magnetically quiet,” said SFL Missions Director and CEO Dr. Robert E. Zee. “Mission specifications will also require us to accommodate and coordinate among 11 onboard sensors.”

The RADICALS science team will analyze the measurements collected by the small satellite to better characterise space weather, and to understand the effects that space radiation has on the atmosphere, and ultimately its role in the Earth’s climate system. Energetic particles are usually trapped by the Earth’s magnetic field, bouncing back and forth along the field lines. At times of heightened space weather activity, electromagnetic waves in the near-Earth space environment can scatter some of these trapped energetic particles into the atmosphere.

The RADICALS mission will discover the dominant processes which transport these energetic particles into the atmosphere, assess how and when this occurs, and establish their role in coupling the space environment and the Earth’s climate system. Energetic particles from the sun can also enter the Earth’s atmosphere and will be monitored by the RADICALS as it passes over the North and South Poles.

The SFL Missions team was one of the pioneers that introduced high-performance Attitude Determination and Control System (ADCS) technologies to the nanosat and microsat communities. For RADICALS, the team is developing a Quiet ADCS mode that does not use torquers and wheels, subsystems which emit magnetic energy that could interfere with the measurements being made by the sensitive instruments.

The need for RADICALS to spin while also remaining stable and magnetically quiet will require implementation of a spacecraft design called a Thomson Spinner, which will maintain spacecraft stability as it turns perpendicular to its orbital path at a steady rate of at least two rotations per minute. A benefit of the Thomson Spinner is that for extended periods it requires no active control that would create magnetic interference with payload sensors.

RADICALS will, however, include magnetic torquers and reaction wheels for activation periodically to correct the small satellite’s alignment to maintain the quality of the science measurements.