Subject: Re: Cleanliness requirements for Solar-B stuff Date: Fri, 30 Jul 1999 14:58:24 +0100 From: Barry Kent To: Matthew Whyndham CC: j.lang@rl.ac.uk Hi Matt - The vu-graphs I presented in Japan (March 99) detailed how to design clean and how to put together a contam control plan. After the summer I hope to be able to do just that and put together an EIS contamination control plan. As the vu-graphs explained in principle this is not too big a deal- and mostly comes down to a clear plan and solid enforcement of protocols. 1) We need to establish a budget - we do this by a) establish a tolerable degradation in performance - this will be a science driven statement ie over the whole mission by how much are you prepared to see the perfomance fall.****This drives everything else***** b) model the various optical elements to determine what level of what contamination causes this level of performance decay (we have the software to do this) 2) Assign the performance decay to the varous phases of the project; maybe a good starting point is 60% pre launch (most contaminating environments but also best control), 40% in orbit (best environment but probably less easy to control). 3) Further divided the pre launch phase into the standard build / test phases and assign budget to each. 4) Asses what levels you now have to measure - is it possible, is it controlable. XPS is probably most sensitive general applicable test at around the 10ng/cm2 sensitivity. (We can do it at RAL) 5) Take an inventory of designed components, and materials. 6) Identify sources and targets of contamination. 7) Can design be influenced to minimise effect of sources and minimise sensitivity of targets - eg exclude known crappy materials, keep contamination source well away from sensitive components, keep crappy components cold keep sensitive items warm. 8) Devise component cleaning plan - the CDS one should be fine but I will check to make sure. 9) Devise build, test environment conditions based on 3 10)Devise monitoring protocols 11) Keep an eye on what other instruments / spacecraft are doing to ensure they don't compromise our good work! What is your deadline for this document? (Whatever you say it is unlikely to be finished much before end Sept and it need answer to 1 above to even start - although I can start by assuming 10% decrease in performance (throughput, resolution which is worse) Does any of this help??? Cheers Barry At 16:01 20/07/99 +0100, you wrote: >Dear Jim and Barry, > >Our cleanroom manager just had a converstaion with me about the >cleanliness requirements for Solar-B. I have previously told him that >the requirements, particularly for molecular contamination may be >quite tough. We need to get this on a firmer basis obviously. >Probably we should derive a surface contamination requirement that >we can measure against. > >XMM-OM had a requirement of 100 ng/cm^2 and ~20 ng/CM^2 was acheived. >I'm not sure how this was derived. The measurement was >done by transmission through a witness window over 200-300 nm. > >So, how can we come up with a contamination budget for components, >and how are we going to measure the real world contamination? > >-- >Cheers, Matt-> >----------------------------------------------------------------------- >Matthew Whyndham MSSL/UCL Department of Space and Climate Physics >mwt@mssl.ucl.ac.uk Holmbury St. Mary, Surrey, RH5 6NT >+44 (0)1483 204131 +44 (0)1483 274111 Fax: 278312 > > Solar-B EIS : http://www.mssl.ucl.ac.uk/Solar-B/ >----------------------------------------------------------------------- > B.J.Kent Space Instrumentation Division Rutherford Appleton Laboratory Chilton, Didcot OXON, OX11 0QX United Kingdom Tel (+ 44) (0)1235 44 6364 Fax (+ 44) (0)1235 44 5848