ECE 432: Intro to Signal Processing

[Caelan Fletcher 0]

ECE 432: Intro to Signal Processing

A log by Lt. Caelan Fletcher

 

A few notes:

1) If anyone does this for a living, sorry for butchering your science! This problem happened to me during a class project, but I embellished more than a little bit to make it fit the sim.

2) The grid is supposed to be tinier than it looks...and art isn't my strong suit.

 

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‘Gather round, kiddoes…’Fletcher had assembled the think tank in the Engineering conference room. Not to think – that part was already done. It was hard to call it a moment of genius, as Caelan rarely had anything that could be described as an inspired thought, but nonetheless, he had discovered the source of their computer woes – and class was about to start.

 

‘This…’ He displayed an image of the Earth on the conference room viewer. It was back to basics, it seems. ‘…Is a planet.’

 

A few groans emerged from the crowd of densely packed engineers. A few ‘we know’s and ‘get on with it’s along with a few more colorful phrases could be picked out, but Fletcher simply plastered a grin on his face, enjoying torturing his colleagues with some remedial training, ‘S’pretty damn obvious what it is. Anyone could tell. Right?’

 

Nods of varying levels of enthusiasm were returned. ‘…This…is how the computer processes the image.’ Over top the original image, a grid was laid down. Even 24th century hadn’t managed to do away with the pixel in its entirety.

 

 

‘All o’yeh know that the computer splits the image up into tiny bits, or at least you did back in Signal Processing during your cadet years.’ Dr. Uzuki had left a rather…vivid impression on Fletcher (when he chose to attend the class)…and he expected most of the other engineers would feel similarly. Judging from the mixed expressions of discomfort and outright fear (as one might who still suspects a pop quiz on Fourier Transforms could show up at any moment), he was correct.

 

‘But space has got a lot of stuff in it…useless stuff…’

 

‘Like this meeting?’ Lieutenant Alenko chimed in, crossing his arms in a show of contempt.

 

‘No…’ Fletcher kept his tone cool, making a mental note to buy Mrs. Alenko a rather strong drink the next time he ‘bumped’ into her, ‘…like stars, hundreds of thousands of light years away. Orbiting trash, asteroid fragments, comet dust…stuff you find all over.’

 

‘That’s why we filter our sensor scans…otherwise we’d blow the ship’s memory space in a month of sensor sweeps. Do any of you remember how we do that?’

 

Most of the engineers made a convincing impression of petrified wood, but one eager beaver in the room waved his arm to let everyone in the quadrant know that he knew the answer. ‘We average the signal! Organize the surrounding pixels, and take the median! Right?!’

 

Fletcher nodded toward the ensign, smirking at his almost Scott-like enthusiasm, ‘Mmhmm…you take the median. Pick a pixel. Look at the eight other squares around it, and average the color. It’s why we can make sense of the sensor sweeps…sharpens the image. And once there’s enough contrast…the computer can recognize what it sees.’

 

‘But what happens if you look at more than just those eight squares? What if you look at…twenty-four? Forty-eight? Eighty? Four hundred forty? Two thousand six hundred?’ Fletcher pointed to the image once more. Most of the pixels were black, and only a small fraction had the azure tones of the Earth’s surface. ‘What’ll happen if you take the average of that?’ Caelan wasted no time waiting for an answer, placing the next image up on the viewer.

 

 

The empty grid that appeared was met with several confused looks, darting between the viewer image and Caelan for an explanation, ‘Space is pretty empty. If you have a hundred black pixels for every blue one, and you take the average…you’ll get a grid of all black. This is the same image – it’s just after the computer filtered it. This is how the defense grid’s computer would see the planet Earth, as of twenty minutes ago.’

 

Another ensign, brow furrowed, raised the question all of the engineers shared, ‘But it recognized enemies before…why not now?’

 

Caelan grinned, reveling as he could finally share his moment of revelation, ‘Because one of your morons, or someone upstairs, eff’ed up our filter function.’ Shooting a look toward each engineer in the room, Fletcher attempted to pinpoint a culprit…not that he truly suspected any of them. Afterall, it was primarily he and Scott that had worked on the grid – particularly on the programming. None the less, it was amusing to watch them squirm.

 

‘It’s a low security point in the code – no real log of who changes it. Modify by the filter factor by a couple powers of ten, and you can blind the computer, more or less. And we’ll be none the wiser – since we usually see the unfiltered images on the viewscreens. The filtering is just so the computer can save space, and so it can tell the difference between a horse’s ass and Lieutenant Alenko…small difference though that may be…’

 

Alenko was just about to issue a cry of protest, though Fletcher continued on, cutting him off, ‘I returned the filter factor back to its normal level – the grid can see things like normal again. Chances are the ship we missed was electromagnetically silent…so we had no way to catch it.’

 

‘If anyone wants to claim it…accident or not…let me know. I haven’t told Jorahl yet, but that’s going to change in about five minutes unless someone owns up.’ Silence. ‘No one? Hrm…figured as much. Very well – class dismissed!’

 

Fletcher watched the engineers shuffle out of the room, some looking more befuddled than others. They weren’t lying. This wasn’t a mistake they’d have made…and chances are, it wasn’t a mistake anyone made. He had no interest in getting caught up in the hoopla of the mutiny taking place on board, but the chances of this being unrelated were slim at best. It wasn’t for him to decide, fortunately – Jorahl would be making the call on that.

 

Tap-tap. ‘Caelan to Jorahl – let’s chat…’