also need to be considered. Rosetta is beyond the orbit of Jupiter and it’s very cold. Te sensor has to be able to survive these low temperatures – deep space missions tend to be at -100°C for extended periods. One other problem is ice potentially building
up on the sensor or other instruments. Jerram explained that, even though space is a vacuum and ice shouldn’t be an issue, it can happen because of the big differences in temperature, even from one side of an instrument to the other. He elaborated: ‘Some things that sit in the sunlight can get quite hot and give out gases, whereas those parts out of the sunlight get very cold. If there is any residual water vapour it can condense on the cold parts. So actually, rather perversely, ice build- up can be an issue.’ To overcome this, the materials used have to be
strictly regulated and specifications are in place to decide how much outgasing is allowed from a component. As the sensors e2v send out are
Rosetta is beyond the orbit
of Jupiter and it’s very cold. The sensor has to be able to survive these temperatures
made of silicon this is not too much of an issue. However, Jerram said that adhesives used to stick the sensor to its packaging can be a particular problem and that specific glues are chosen for their low outgas properties. Every kilo sent into space increases the cost
The area of Barnard 33 (Horsehead nebula) and NGC 2023
said: ‘All the visible image sensors are made by e2v, two were made in Chelmsford, and the other three were made in Grenoble.’ To survive the harsh environment of space,
systems designers have to consider a number of potentially harmful phenomena. Jerram outlined the main issues: ‘Tere are all sorts of radiation in space, from gamma rays to protons to x-rays, and also a type of radiation known as heavy ions. Tere is quite a lot of radiation that can cause concern so you have to ensure that whatever you have designed is radiation hard and this requires a lot of testing. You have to think a bit about shock and vibration – particularly during the launch, as this is quite a violent period. However, most image sensors are mechanically robust enough to deal with this.’ Jerram explained that temperature extremes
www.imveurope.com @imveurope
of the mission. On Philae, the sensors and the packaging sent were quite small, so the overall effect on the system wasn’t too noticeable. Whereas for Gaia, another ESA project e2v worked on, the focal plane was one metre by a half metre with 106 sensors. Here, the packaging is very important, and a specialised material called silicon carbide was used, which is lightweight and has good thermal conductivity. He said: ‘If you are flying any sort of imager into
space it has to have a high resolution, but it costs you a fortune to put a lens on the system and it can’t be very big. You have to make extremely sure that every single little particle of light you gather is detected at the output. We effectively have to have 100 per cent detection efficiency and a wide spectral band. Tey are more optical instruments than just imagers.’ In order to satisfy the required criteria, the
budget for these space projects is of a different order to more terrestrial applications. Jerram observed: ‘In total, our business here has around 300 people that mostly do space missions; we
Matrox Design Assistant 4 lets you effectively put together vision solutions for all your inspection needs.
www.matrox.com/da4/imve
Matrox Design Assistant vision software
It inspects it all.
Thierry Legault
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48