When a natural disaster strikes or a national security emergency breaks out, every minute counts. In many cases, satellite imagery is a key tool for first responders.
But it can take a satellite in low earth orbit 100 minutes to make one of the many passes needed to provide global coverage. Larger satellites can provide continuous coverage of greater areas but require higher altitudes and still only cover roughly one-third of the Earth.
In critical, fast-moving situations, space operators can find themselves challenged by the stubborn inflexibility of satellite positioning, which, despite numerous technological advances, still requires satellites to rotate or orbit into viewing range to image an area.
Engineers as The Aerospace Corporation are testing a new approach that uses atmospheric drag to provide dynamic satellite re-positioning, enabling on-demand responsiveness to situations on the ground.
This new concept, known as Project Rollercoaster, is an alternative to the current, static method of satellite imaging and leverages maneuvering and the atmospheric drag of low Earth orbit (LEO) to rapidly and efficiently alter satellite ground tracks.
“The idea is you could deploy one of these Rollercoaster vehicles, use a chute and safely change your orbit so that you could image an area of interest much more responsively than you could have otherwise,” said Travis E. Swenson of Aerospace’s Flight Design and Optimization Section.
The Project Rollercoaster methodology is divided into three sequential phases: burn, drag, and coast.
To initiate the process, a small maneuver is executed to lower perigee which alters the satellite ground track, giving the spacecraft access to higher density atmosphere. Next, the satellite deploys panels or chutes to further modify its ground track using drag.
Lastly, the drag devices are stowed or jettisoned, and the satellite continues to orbit until the target flyover is achieved. This enables global visibility access within a significantly reduced timeframe, and with greatly reduced fuel requirements.
The technology required for Project Rollercoaster has already been demonstrated via CubeSats, and computer simulation has upheld its feasibility.
“If you want to get eyes on the ground, this will enable you to get there in a very short timeline.”
If successful, the Project Rollercoaster method could allow for prompt surveying of natural disasters, provide intelligence during a national security emergency, and serve a host of other applications.
Rollercoaster could also facilitate targeted ocean re-entry of spacecraft, substantially reducing instances of land impacts while also enabling the orbit rephrasing required to avoid spacecraft collisions.
This could ultimately enable the targeting of specific landing zones and the reduction of re-entry footprints. Aerospace’s Flight Design and Optimization Section, in collaboration with iLAB, is already exploring the application of atmospheric lift to target flyovers at specific local times, and the possibility of achieving repeated passes over a target area.
Another advantage to Project Rollercoaster is that it allows for a flexible mission architecture. For example, a number of relatively inexpensive small satellites could be stored onboard a Cygnus cargo spacecraft until called into action to provide rapid assessments of dynamic situations.
“If you want to get eyes on the ground, this will enable you to get there in a very short timeline”, said Swenson.