Picking up good vibrations

Recently I've been helping with the construction and testing of extremely sensitive instruments that should (hopefully) be launched into space. I think it is extremely cool that something I've been working with will end up 1.5 million kilometres from the Earth, so I thought some of you might be interested to hear about it.

The particular instruments I'm testing are radio amplifiers and are actually amongst the lowest noise amplifiers ever built at the radio frequencies involved. Noise - imagine the hiss between radio stations on an analog radio set - is something that astronomers have to battle with a lot because astronomical objects are often very faint and they get lost in the noise. To deal with noise from different sources there are different techniques e.g. for CCD cameras you can do a flat field, a bias frame and stack lots of images.

All electronic devices have a noise associated with them because the electrons that go whizzing around the circuits have a temperature. For small particles, temperature is related to how much they jostle about. The higher the temperature, the more they jostle and the larger the noise. To reduce the jostling, the circuits are cooled down. The receivers I'm working on get cooled down to almost the temperature of liquid helium (which is about -269°C/-452°F) and that makes the noise very low indeed. Mind you, it will have to be to produce brilliant scientific results.

To reach this kind of quality level, space hardware has to be top notch and boy that sure does take a mammoth amount of effort. Everything has to be checked, double checked and checked again a few more times just to be sure that it works perfectly. So far these amplifiers have taken several years to build and I've been involved with the testing process full-time over the last two months.

A couple of days ago we took part of the instrument down to a facility near Oxford to perform a vibration test. For this test the instrument is firmly attached to a large computer-controlled bench that can shake at a whole range of different rates. If fact it can vibrate at lots of different frequencies simultaneously - our range was from a few Hertz to a couple of kilo-Hertz. The bench is programmed to simulate what the electronics will experience during the real rocket launch. In fact, we only simulated 'half a launch' as the test was only performed for one minute. Still, one minute was pretty nerve-racking especially when the amplifiers experienced the equivalent acceleration of 77-g at one point! They could have literally shook to pieces.  Thankfully they survived in one piece and after re-testing back in the lab they were shown to still be working. Phew.

Now we just have to make the rest of them.

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Posted in astro blog by Stuart on Wednesday 23rd Nov 2005 (21:27 UTC) | Permalink
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