Space debris increasingly becoming a real problem. We’re not quite at Kessler’s Syndrome yet, but with the increased interest in sending objects into space, there’s a real possibility that it could happen in the not-too-distant future.
Many potential solutions have been proposed to solve the problem, but they all face a similar problem in the first step: how to track the debris they are trying to clear. Enter a new idea from Iranian researchers – to use a new type of radar to detect and track space junk before it becomes a hazard.
The new type of radar is called Inverse Synthetic Aperture Radar, or ISAR. As you might expect from the name, it’s the opposite of Synthetic Aperture Radar (SAR). SAR has become much more important lately, especially by satellites trying to collect data from the Earth, especially terrain data that could be useful for geospatial mapping.
The SAR uses the movement of its platform (i.e. a satellite) to recreate a larger “synthetic” opening by using the area covered by the platform as it moves relative to the object she image as aperture size. It might sound confusing, but think of it as a way to take multiple images of an object from different angles and then reconstruct a single three-dimensional image from those combined images.
UT video on the space debris problem.
ISAR works in the opposite direction. In it, the measured object is the one that moves relative to the detector. In this case, the detector is stationary on the ground while the moving object (i.e. space debris) is actively measured.
There are several advantages to this technique. Using ISAR would allow scientists and engineers to detect both the orbital path and spin value of even tiny pieces of debris. It is essential to understand these characteristics to understand if they pose a threat.
An additional problem with using ISAR to detect space debris is that many objects are exceptionally small and therefore do not reflect much light. The research team in Iran circumvented this problem by using a compression detection technique. Basically, compressive sensing takes a bit of data (like a limited number of radar shots of an object with longer exposure times) and attempts to extrapolate intermediate data that might have been missed based on correlations between data it actually has.
UT discusses whether we will be able to clean up all space junk in orbit.
Compressive sensing is as much an art form as it is a science, but the team’s results were reasonable in terms of consistently getting good results from a simulation they ran using their idea. It’s not quite the same as collecting debris data in the real world, but it’s a step in the right direction.
They are also not the only ones working on this problem and have many references to other researchers working on similar techniques. The domain has garnered enough interest that it will most likely be adopted more widely by those interested in defending the Earth from all the trash we throw into its atmosphere. Companies developing their business models on how to clean up this space junk should take note.
It might even be an interesting thought exercise to develop a system on a moving platform capable of having an extraordinarily large opening for other objects that also move relative to it. It would be an impressively complex mathematical problem, but it could be useful in the fight to save us from ourselves.
This article was originally published on Universe today by Andy Tomaswick. Read the original article here.