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http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal

This is a great story. Thanks, Andrew!


Andrew Resnick wrote:
> Search the CONFOCAL archive at 
> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal Ok, here goes.  
> I apologize in advance for the length; it's just a sign of how committed 
> I was to the project.
> 
> Let me first say that this project (the Light Microscopy Module, LMM) 
> was an incredible experience for me, and I learned an amazing amount of 
> stuff from some truly world-class engineers and technicians.  In my 
> opinion, the failure of this project was due to the fear of NASA and 
> contractor managers to make timely and unpopular decisions.  At it's 
> peak, the LMM contractor team numbered about 50, there was another 10 
> NASA technical folks and the Principle Investigator (PI) teams added 
> another 5 or 10 post-docs and grad students.
> 
> Here's some background: around 1998, NASA approved a group of 
> experiments involving colloids and fluids for spaceflight on the 
> International Space Station.  The first step in the process is for NASA 
> to write a set of "requirements" for each experiment.  A "requirement" 
> is some capability that the flight instrument must have in order to 
> produce valid and useful scientific results.  For example, a requirement 
> may be "obtain 30 images per second".  How these requirements come about 
> is an interesting story in itself, but in the end, NASA provides a list 
> of requirements as part of a contract bid- contractors look at the 
> requirements list and come up with a proposal to build *something that 
> meets the requirements* at a certain cost.  NASA then awards the 
> contract to whomever it chooses.
> 
> I was hired by the contractor in late 1999, when a contract was being 
> generated to fly a microscope. That is to say, the contractor management 
> convinced NASA management that a microscope was *something that met the 
> requirements* for 4 flight experiments.  Three of the experiments 
> involved imaging and manipulating colloidal emulsions, while the fourth 
> was a fluid heat transfer experiment, and the need was to image the 
> wetting boundary.  There were approximately 300 pages (single spaced) of 
> requirements.  At the time, none of us knew anything about microscopes 
> specifically.
> 
> To summarize the early planning stage, what was needed was a completely 
> automated, tricked-out microscope.  Not motorized, but *automated*.  
> Once we invented this particular instrument, quite a bit of excitement 
> was generated throughout NASA, for obvious reasons.  It's cool, for one 
> thing. Really sci-fi. The project rapidly blew up , attracting the NASA 
> bio community as well.  Lots of color drawings were made and distributed 
> around.  Websites were created.
> 
> At the time, we knew of no imaging system that will *automatically* 
> focus on an unknown target within any sort of reasonable timeframe, and 
> maintain focus as the sample is moved around.  We knew of no microscope 
> system that will optimize (and automatically adjust) DIC shear for 
> contrast.  We knew of no microscope system that will automatically align 
> the phase rings in a phase contrast system.   We knew of no imaging 
> system that would automatically establish Kohler illumination.  I still 
> am not aware of any microscope that will do any of this. If I am wrong, 
> I would certainly like to know about it.  When we did the project, we 
> had to motorize the condenser turret and components, the epi- DIC prism, 
> polarizer, and waveplate, the tube lens turret and Bertrand lens, the 
> viewing prisms, all kinds of stuff.  And any existing motors that did 
> not meet NASA specs had to be removed and replaced, the gears de-greased 
> and re-greased with NASA approved grease, the chassis de-painted, bolts 
> changed, wiring re-done, integrated circuits had to be replaced with 
> radiation-hardened components.  I've disassembled and reassembled 
> irises, stage slider bearings, and entire microscopes. Irises are the 
> worst, by far.
> 
> We obtained from the manufacturer complete blueprints for the microscope 
> and lenses.  Complete lens specifications and drawings.  Let me tell 
> you- those high NA immersion apochromats are absolute marvels.
> 
> Here's how I would characterize the design phase: Imagine you work for 
> GM, and GM wants a spiffy new car. You head the team that is in charge 
> of the engine. LMM is the engine- the whole car is a larger structure 
> that supplies the LMM with electricity, coolant, saves data, etc. etc.  
> So you are to design an engine to certain specifications- torque, 
> horsepower, compression ratio, whatever. Problem: you don't know how 
> much room you have in the hood.  You don't know where the transmission 
> or exhaust will connect.  You don't know where the electrical 
> connections are. You don't know anything except the engine 
> requirements.  Your first step may be to decide on the piston 
> arrangement- how many?  inline? V? rotary? In any case, off you go.  And 
> as problems arise, you work to solve them. There will be meetings with 
> the electrical team to decide where the alternator belt will go. 
> Meetings with the fuel supply group to determine how much gas is 
> needed.  This goes along reasonably well until someone claims that the 
> car will not meet "car specifications"- maybe not enough miles per 
> gallon. Who's fault is that- the transmission team or the engine team? 
> Maybe it's the body design- too much drag or weight? Design teams now 
> compete to show the other team is at fault. Money and time is wasted 
> trying to meet unrealistic and arbitrary requirements.
> 
> Now we come to the safety concerns- astronauts are rare and delicate 
> flowers, after all- touch temperatures (no convection to draw off heat) 
> have to be below a certain value, the equipment must withstand "kick 
> loads"- astronauts may kick off the microscope to propel themselves (!), 
> anything breakable (including the samples and arc bulbs) has to be 
> enclosed 3x.... chemicals, etc.  There were "leak paths" that had to be 
> plugged- the objective turret head was re-designed, we thought about 
> enclosing the immersion objectives with latex at some point, it's insane 
> what has to be done in the name of 'safety'.  There was a 200+ page 
> document with a list of safety concerns: for example, we calculated at 
> most 2000 ml of immersion oil was required over the life of the 3 
> colloid experiments- so one question was "what happens if all 2000 ml is 
> dispensed at once?"  Each concern required at least 3 pages of reply- a 
> plan, a backup plan, a backup to the backup, and then a test, validation 
> and verification procedure to ensure that one of the three plans would work.
> 
> Then the microscope is launched (up to 9 g's) in pieces and assembled 
> on-orbit, without gravity loading things or keeping them in place.  
> This, after sitting in Florida in a non-environmentally controlled crate 
> for several months.  And the space station is incredibly (mechanically) 
> noisy.  And there are huge thermal swings, some from the microscope and 
> light sources- and the fans we needed to move the heat off add to the 
> vibrational environment.  This is why the microscope needed to be able 
> to align the optical elements.
> 
> Remember, there is no user interface- it's all done by software.  We had 
> no access to "diagnostic" images to determine if there is a problem.  
> There was no astronaut interface- no eyepiece, no computer screen to 
> view what was being acquired. Again, imagine writing down instructions 
> on how to set up a microscope from the box, giving the instructions to 
> an undergraduate who has never done that before, and having the 
> expectation that everything will work perfectly the first time (because 
> you only get one chance to run the experiment- once the experiment is 
> over, all you get is a stack of data tapes with all your images when the 
> shuttle is able to bring them down).    In reality, it's even worse than 
> that- you don't get to write the instructions, someone unfamiliar with 
> how microscopes work writes down the instructions, occasionally asking 
> for your input.
> 
> Confocal was (surprisingly) the easy one- we used a Yokogawa spinning 
> disk- incredibly rugged, and the issue of "finding focus" is 
> eliminated.  Confocal imaging would have met the overwhelming majority 
> of imaging requirements for the colloid experiments.
> 
> Oil immersion is do-able, actually- the oil preferentially clings to the 
> glass and objective, and we found some non-wetting coatings we could 
> apply to control where the oil went.  The trick is dispensing the oil 
> without bubbles.  We proved this out by flying a microscope on the 
> KC-135 "vomit comet".  That was awesome.
> 
> And the data- we estimated 1 TB of information was going to be generated 
> *per day* (the requirements were 30 frames/sec, 1k x 1k 12-bit images) 
> for 12 months.  Where does the data go? Downlinking provided about 5 MB 
> at best per day, IIRC.
> 
> Here's an example of what is right about NASA technical folks- one of 
> the PIs wanted to fly about 1500 samples.   How on earth could we 
> accommodate this? The solution was wafer-scale integration of sample 
> cells- a glass disk 1 mm thick, just like a huge microscope slide, was 
> bonded to a silicon wafer, which was then ground down to 100 microns 
> thickness, so we could image the whole thickness.  The silicon was 
> etched in the pattern we needed: rows and columns of holes shaped like 
> '=0=', each hole/cell holding about 50 microliters of colloid. Each hole 
> got a small magnetic stir bar, a fraction of a mm long, so each sample 
> could be freshly mixed prior to imaging.  Then, a glass plate was bonded 
> to the top and ground down to 150 microns thick: a # 1 1/2 coverslip. 
> The silicon provided an excellent reflective surface- i.e. something to 
> focus on, and we could pack in about 300 cells per sample tray.   We 
> knew the exact position of everything, and the exact thickness of 
> everything, so we solved quite a few problems in one fell swoop.  Of 
> course, there is then the problem of filling and sealing 1500 
> 50-microliter cells (each with different compositions- and the 
> composition had to be verified somehow) that have to maintain their 
> integrity for months, but we put that back onto the PI.
> 
> Anything that goes up in space is using 10-year old technology at best.  
> For gears and fans, that's not a big deal.  But it is for cameras. And 
> data interlinks. And software.  Again, going back to the car analogy, 
> once the piston layout is designed, a lot of things are constrained. And 
> as the project moves along, it's harder and harder to change the piston 
> layout.  Once a particular microscope was selected, we could not go back 
> and even update to a newer model- we bought 5 sets of everything to 
> ensure we had spare parts.
> 
> In the end, the NASA expectations (as sold to the PIs) were totally 
> unrealistic, and the budget was likewise ridiculous.  NASA management 
> honestly believed that we could simply buy what we needed, that there 
> were no problems to be solved.  There was no money for testing and 
> evaluation, among other things.  I really thought, until I left 5 years 
> later, that we could deliver something that would meet about 80% of the 
> requirements.  Unfortunately, management's only input was to 
> periodically yell "failure is not an option!" and so we spent 80% of our 
> time on the least important 20%.
> 
>