MacDirectory Magazine

Warren Manser

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INTERVIEW TD > As per above - SkyCube is passively stabilized. We have no control over its orientation. We expect it to tumble slowly (about one turn every 25 minutes) as it orbits the Earth. We can tell it which cameras to turn off/on, and what/when to broadcast. We can also tell it when to inflate the balloon, which will end the mission and bring the satellite down at the end of its useful lifetime. MA > Taking about mission lifetime, what measures have been taken, if any, to avoid SkyCube running into the thousands of small space trash that currently orbits Earth? This could potentially end your mission. TD > None - it has no propulsion or active stabilization system. This is no different from many other CubeSats or even many larger satellites - basically, we're banking on the very high probability that nothing big enough to harm the satellite will, in fact, actually hit it during its useful lifetime. Honestly this is not a bad bet. In the entire history of the space age, there is exactly one (ONE) instance of satellites hitting each other. Having said that, though, the space debris problem is real, and serious. That one collision in 2009 (between an active Iridium communication satellite and an inoperative Russian spy satellite) created thousands of bits of shrapnel traveling at hypersonic speeds, many of which are still zipping around up there. The danger is that those bits of shrapnel will hit other satellites, and create more shrapnel, and cascade into an even bigger problem. The only way to avoid this scenario is to reduce the number of large objects in orbit, which could potentially hit each other and generate more shrapnel. The small shrapnel will eventually fall out of orbit due to atmospheric drag - we just have to remove the possible sources of new shrapnel before they generate more. And we're doing just that. SkyCube's space balloon isn't just to make the satellite visible - its second purpose is to de-orbit our satellite quickly (through atmospheric drag) at the end of the mission. We are the first CubeSat mission to deliberately de-orbit itself at end of mission, and we want to set a present for future missions. MA > But, what if for some remarkable reason, a collision is anticipated? TD > I suppose, if we detected that SkyCube were on a collision course with another satellite, we could inflate our balloon early, and change our orbit just slightly enough (via atmospheric drag) to avoid the collision. Honestly, the chances of that scenario taking place are all but zero. Nevertheless, it's comforting to know that we could actually do something about it if it did occur. MA > I'm unclear about SkyCube's mission duration. Why will it orbit Earth for only three weeks? Do you feel this project duration outweigh the cost and development time spent? TD > Actually that's not quite right. If we never inflated the balloon, the satellite would have an orbital lifetime on the order of years, not weeks. We're planning to leave it up for 90 days, taking pictures and "tweeting" before we inflate the balloon. If things go well, we may leave it up there a bit longer. Our FCC authorization actually gives us up to six months. After we inflate the balloon, the orbit is expected to decay in less than three weeks. Sometime during that period, it will re-enter the atmosphere, and vaporize harmlessly, many miles above the Earth's surface. SkyCube will be the first CubeSat to deliberately de-orbit itself at the end of its mission, with the express purpose of avoiding space debris. Please note, though, that if we never inflated the balloon, SkyCube would also eventually de-orbit itself, though it would take years instead of weeks - and thus be a correspondingly greater space- debris hazard. We don't want to leave "space junk" up there when our mission ends. MA > Some believe that launching SkyCube is a great marketing tool to get users to download and use SkySafari. Is this a valid point? TD > Well - if folks end up using SkySafari as a result of learning about SkyCube, we sure won't complain! But the larger purpose is to get people interested in space, to get them to look up, and to get a sense of personal ownership and involvement in a mission that they can see with their own eyes. MA > And what makes you feel there is a lack of awareness now? TD > The weekend before last I was camping with a few friends in their mid-20s, who all happen to be hardware/software engineers at Nvidia. All are very bright guys, and none of them has ever looked through a telescope. All of them grew up in big cities, inundated by Star Trek, and Sci-Fi channel - but none of them had ever actually looked through a telescope. I brought along my 5" Celestron NexStar 5i, which is as much a "toy" of a telescope as SkyCube is of a satellite. We looked at Saturn, the Ring Nebula, the Lagoon, Albireo, Mizar, and a few other objects of complete- beginner quality. We saw a few satellites pass overhead. And none of them had had any idea you could see satellites with your naked eye. It's that lack of awareness that we're trying to fix. Space isn't just something out there you can read about on the NASA website. It's something you can touch. I got tired of just dreaming and writing apps about space. I decided to go. And SkyCube became the realization of that dream. I'd like to share it with as many people as I can. MacDirectory 105

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