🚀 go-pugleaf

On Tue, 07 Aug 2012 14:04:19 -0700, Jon Kirwan <jonk@infinitefactors.org>
wrote:

>On Tue, 7 Aug 2012 12:42:56 -0700 (PDT), George Herold
><gherold@teachspin.com> wrote:
>
>>On Aug 7, 3:19 pm, Jon Kirwan <j...@infinitefactors.org> wrote:
>>> On Tue, 7 Aug 2012 05:23:52 -0700 (PDT), dp <d...@tgi-sci.com>
>>> wrote:
>>>
>>>
>>>
>>>
>>>
>>> >On Aug 7, 5:11 am, Jon Kirwan <j...@infinitefactors.org> wrote:
>>> >> ...(Most of my work was in the
>>> >> visible, near UV, and near IR -- but for very different
>>> >> applications.) I still have some decent setups here and I've
>>> >> designed some devices that can be made for only a few
>>> >> dollars, and wavelength calibrated for $8 more, so that high
>>> >> school students could actually built their own real-world
>>> >> equipment that could genuinely "do science" and meet
>>> >> calibration standards. No intensity calibration, though,
>>> >> sadly. That costs money to do. (Unless you have a suggestion
>>> >> about how to do it on the cheap?)
>>>
>>> >Oh no, I could not possibly have a suggestion. My spectrometers
>>> >don't seem to have an overlapping wavelength range with yours,
>>> >mine are xray/gamma. I am practically clueless when it comes to
>>> >those in the UV and below range, mine generally count single
>>> >photons.
>>>
>>> For all those reasons, that is why I would LOVE to see the
>>> "optics" (and the schematics, as well.) Totally new area for
>>> me to learn about. In my region, it's all about electron
>>> transitions -- and no molecular dissassociation.
>>>
>>> I'd expect you'd count single photons at those energies --
>>> just one probably creates quite a shower to deal with. I'd
>>> like to know, in practice, how one measures the energy.
>>>
>>> Also, in space there is a serious problem with "brown crud",
>>> which is smashed, charged particles that come from the
>>> satellite's own fabrication scattered into space, which
>>> because it is charged comes back to the spacecraft at some
>>> later time, but sticks elsewhere (not where you want it.) I
>>> don't know if there is a problem with this on Mars -- there
>>> is an atmosphere of sorts. But I'm curious just the same if
>>> there is an accumulation problem and how it is dealt with.
>>>
>>> >Efficiency calibration is costly on those for gamma, too,
>>> >though - the calibration source costs thousands. The rest, hm,
>>> >has become much less expensive since the release of the
>>> >netmca-3 (one can still spend tens of thousands on it but
>>> >does not have to any longer).
>>>
>>> Now THAT I totally believe. I probably couldn't afford it.
>>> But I still could learn.
>>>
>>> >I would be curious what gamma spectrometry the thing is
>>> >carrying on board, too (if any, but likely so). Unlikely
>>> >HPGe, but then who knows, Mars is a cold place, they may
>>> >have figured some practical way to cool things down to
>>> >about liquid nitrogen.
>>>
>>> Well, they certainly don't have much atmospheric pressure to
>>> worry about.
>>>
>>> Which reminds me of another thing. How do they convect the
>>> internally generated heat away. I recall hearing about
>>> multiple power systems, operating around 32V at near 2A. More
>>> than one. This power must be convected/conducted away -- no
>>> way they want to radiate it. I wonder if they push it
>>> (costing more heat) towards a vane or arm and drag it around
>>> on the surface to get rid of it?
>>
>>The atmosphere won't help much.
>>
>>Why not?  Thermal conductivity of air is pretty much constant till you
>>get below 1 Torr or so.  Wiki says the mean pressure on mars is about
>>0.1 psi, which is ~5 torr.
>
>Good point.
>
>What triggered my comment is remembering that heat buildup
>was most certainly a problem during broadcasts with the high
>gain antenna system towards Earth. They can't operate it
>continuously, if I recall correctly. Made me wonder about the
>rest. I had also remembered the case of satellites and "knew"
>that the Martian atmosphere could be as little as a few tens
>of Pascals. So I projected that heat accumulation may be a
>problem. Apparently, it isn't.
>
>I gather your point. To understand it more fully, I need to
>think more closely about mean-free-path, I guess. Thanks.
>
>>Re spectrometer calibration:  We had this "black body" source. (from
>>Ortec?)  That could be used for intensity calibration.  PITA though.
>
>The problem for students is that they cannot afford the $800
>it takes to get a $8 tungsten bulb calibrated. (It can cost a
>lot more than that, too.) Then they need to set up a careful
>station for making the calibration. It's just plain too
>expensive to do. And I don't know a way around it. Wavelength
>calibration is CHEAP!! $12 buys a merc-argon calibration
>lamp, which fires up with the Argon first (for about a minute
>or two where you get some very nice Argon lines in the longer
>wavelengths) and then the Mercury kicks in and dominates with
>it's lines. A couple of well-timed snapshots and you've got
>enough (with software) to completely calibrate your pixel
>positions in a cheap ($10) megapixel camera.
>
>I'd LOVE to figure out a cheap intensity calibration setup,
>though. So would a lot of other people, I suppose.
>
>>But maybe you could do something on the cheap with a tungsten light
>>bulb.
>
>But that's the problem. I can get a cheap tungsten lamp. They
>are VERY CHEAP. In fact, the EXACT SAME ONE I would buy,
>calibrated, is dirt cheap uncalibrated. It is the calibration
>data that comes with a newly calibrated lamp that costs so
>darned much. It needs to be traceable to standards. And you
>pay for that. Plus, you need an expensive power supply to
>operate it (0.1% current control is standard.) And it ages,
>too. Within 100 hours or so, it's drifted enough that it
>needs recalibration.
>
>Thanks,
>Jon


It may be possible to start with a selection of calibrated LED sources
(kind of like the near IR ones used for light source & light meter used
for fiber optic cable measurements).  With a nice selection of say a dozen
wavelengths in the range of interest, it may become reasonably feasible.
With a decent calibration cycle as well.

Internet patent dated 7 August, 2012, all rights reserved.

?-)