Satellite Operations & Formation Flying
UNSW Canberra Space has designed, manufactured, flown, and operated five satellites across four missions.
Our latest mission to date, the M2 mission, was launched in March 2021 and consists of two identical small satellites, M2-A and M2-B. These highly complex spacecraft demonstrated several Australian firsts (including the first image of the Earth by an Australian satellite) and even a world first in propellant-less formation flying.
Being in a low Earth orbit, the M2 mission averages about six usable ground station passes per day (when the satellites are in view of the antennas), with each pass each lasting about 10 minutes. The role of our trained operators is to prepare the necessary transmission plans, schedule them during passes and monitor the satellites’ health status. Our operators use in-house developed operations software and infrastructure that are tailored to the specific needs of our space missions. While our satellites do not require constant monitoring (in part due that they are not in sight for the greater fraction of a day), regular adjustments and monitoring are required particularly for propellant-less formation flying.
Traditionally, satellites alter their orbit using either chemical or electrical propulsion systems. By using a technique called “differential drag”, M2-A and M2-B can be made to accelerate or decelerate along their orbit track, and thus enable the distance between the two to be fine-tuned by the operators without onboard propulsion. Differential drag rests upon the simple idea that if one satellite is presenting its largest surface area (high drag mode) in the direction of its orbit track while the other is travelling with its smaller side facing forward (low drag), the two are affected by Earth’s faint atmosphere in orbit, differently.
Somewhat counterintuitively, when in high drag mode, the satellite will tend to accelerate. This is because the increased drag causes it to lose altitude, creating a shorter orbit period. Conversely, in low drag, the satellite doesn’t lose altitude as much and will maintain a longer orbit period. Daily adjustments of the drag modes of each satellite have allowed us to control and tune the separation between the two satellites.
Experimenting with this differential drag technique has also allowed us to push the detection boundaries of ground antennas and telescopes to new limits, particularly during SACT (Sprint Advanced Concept Training) exercises. (SACT are global Space Domain Awareness exercises that are run three times per year and includes participants from the USA, France, Canada, the UK, and Australia.)
Paper
Brown, M., Peters, E. G. W., Dilkes, M., Jefferson, R., Lambert, A., Saleem, R., & Bateman, T. (2023, September). Autonomous Close Proximity Differential Drag Control of Low Earth Orbit Small Satellite Formations using an Inter-Satellite Radio Frequency Link. In Proceedings of the Advanced Maui Optical and Space Surveillance (AMOS) Technologies Conference (p. 82).