A Canadian satellite proves small is beautiful


Space satellites, typically, are big, expensive beasts, which is one reason we all cringe when one fails to achieve orbit, as happened on February 24 with NASA’s $280 million Orbiting Carbon Observatory (OCO).

Complex satellites like the OCO, which was intended to monitor atmospheric carbon dioxide, are of course absolutely necessary for some tasks.

But satellites don’t have to be big and expensive to do useful work, a fact proved beyond a doubt by a much, much cheaper and smaller satellite marking the one-year anniversary of its successful launch next month.

Best of all, it’s Canadian.

Called the Canadian Advanced Nanospace eXperiment 2 (CanX-2), it masses only 3.5 kilograms (compared to 447 kilograms for the OCO, which was pretty typical), and is roughly the size of a milk carton. Best of all, it was roughly 100 times cheaper to build than a traditional satellite with the same capabilities.

Those capabilities are pretty impressive, too, for something you could put in a shopping bag. It can’t compare to the OCO, of course, but it does contain an atmospheric spectrometer, developed at York University, that provides measurements of airborne greenhouse gases, with a resolution high enough to identify local variations in greenhouse-gas emissions.

The GPS Signal Occultation Experiment, which comes from the University of Calgary, uses the constant radio signals from the Global Positioning System to more accurately model the Earth’s atmosphere, by measuring how much those signals are refracted (bent) as they are blocked from CanX-2’s receivers by the atmosphere.

Better modeling of the atmosphere will help enhance GPS accuracy, which can sometimes suffer during periods when there are auroras and other disturbances in the electrically charged outer layer of the atmosphere known as the ionosphere.

The experiment is very cleverly piggy-backed on the satellite’s own use of the GPS system to provide precise updates to ground control about its position in orbit.

Another experiment, from the University of Toronto, is testing the efficiency of a special treatment designed to reduce atomic oxygen erosion in materials exposed to space. (On Earth, oxygen is most often found as a molecule of two oxygen atoms. Atomic oxygen consists of single atoms of oxygen. Formed by the sun’s energy breaking apart ordinary oxygen molecules at the edge of space, these solitary oxygen atoms are very reactive–anxious to latch on to other molecules–and that makes them very corrosive.)

Also on board is a network communications experiment from Carleton University, a test of a new way for low-Earth-orbit satellites to communicate with ground stations and other satellites–kind of like an outer-space Internet.

Dr. Robert E. Zee, director of the Space Flight Laboratory at the University of Toronto, which developed the satellite, notes that it is likely the smallest satellite to ever perform these kinds of scientific experiments–particularly the atmospheric monitoring experiments–from orbit.

But the significance of CanX-2 goes beyond the science instruments to the design of the satellite itself. In particular, it boasts an amazing miniature attitude control system.

Spacecraft, like aircraft, have to be stabilized along three axes. The CanX-2 uses sun-sensors to measure its attitude, and maintains it using, and I can’t resist quoting this, “a momentum bias system with three orthogonal vacuum-core magnetic torque coils and a reaction wheel.”

That means–I think–that it keeps wheels spinning along in each of the three axes. As anyone who has found it easier to balance on a moving bicycle than a stationary one knows, a spinning wheel resists being tipped. The resistance of the spinning reaction wheels therefore keeps the spacecraft stable in all three axes.

And as if all that wasn’t enough, there’s also a power system–22 solar cells feeding both the spacecraft and a rechargeable battery for use when it’s in shadow–two on-board computers, a communications system, and even a propulsion system that uses cold gas (sulfur hexafluoride) as a propellant.

There are many more tiny satellites in the works at Space Flight Laboratory. Through its student apprenticeship program with the University of Toronto, it’s also training the satellite engineers of the future.

Judging by the success of the CanX-2 system, the future is shaping up to be faster, smaller–and cheaper.

Permanent link to this article: https://edwardwillett.com/2009/03/a-canadian-satellite-proves-small-is-beautiful-2/

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