Re: [APML] OT: M17 in near-IR

[Wei-Hao Wang <whwang@gmail.com>]

Hi Jason,

Thank you for the comments. 

I'd never read Photonic so I don't know if it is the same detector discussed
in this magazine.  The detector we are using is HgCdTe Astronomical Wide 
Area Infrared Imaging (HAWAII) array made by Rockwell.

I don't know the detail about the pupil stop of ULBCAM.  What I wrote is 
based on what I was told by the instrumental team and I don't really have a 
deep understanding on this.  As a user, I tend to care less about the design 
details.

Probably IR detectors have a longer history than CCD.  However, on 
astronomical applications, it is true that overall optical instruments (based on
CCDs) are more mature.  I have been using a 100 Mega pixel CCD camera
since 2001.  The state of art is a 340 Mega pixel CCD camera.  We will have
Giga pixel CCD cameras in just one or two years.  On the other hand, the 
largest near-IR camera is the one I used to take this M17 picture and it only 
has 16 Mega pixels.  Perhaps this is because it is hard to make large near-IR
arrays, or because it is hard to put many near-IR arrays together to form a 
large mosac camera.  I don't know.  

Wei-Hao


On Tue, 7 Sep 2004 09:40:19 -0700, Lane, Jason R <jason.lane@navy.mil> wrote:
> Hi Wei-Hao,
> 
> Is this the same detector array discussed in the article in July 04 Photonics magazine?  It is pretty impressive stuff.  I'm jealous that you get to play with it :)  While a new field for astronomers, IR systems technology has been around for much longer (since the late 40s) than CCD systems and is considered a more mature field.  I think CCD was originally a spin-off of IR development.
> 
> I am interested in your statement about why the pupil stop would require much more complicated optics.  If the baffle design and FOV of the FPA is properly designed, then you should be fine with only cooling the closest baffle (aka the cold shield) and probably the filter.  If the baffle (stop/shutter) and filter are included in the dewar, then it may not be as complicated.  Of course, this would depend on how the FPA is cooled, and you may have additional special requirements which add to the complication.  What kind of cooling system is it?  I'd assume closed-cycle like a Stirling Fridge or Thermo-electric ie Peltier)?
> 
> Cheers,
> Jason
> 
> 

-- 
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Wei-Hao Wang  :)

Institute for Astronomy at University of Hawaii

Address:                       
2680 Woodlawn Drive         Personal Website:
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