Skype the Tub

More alignment images, this time via iPhone and Skype.

Taped an iPhone to the tub-side of the 41-inch flange, positioned so that its camera could look in toward the instrument's KRS-5 window without obscuring too much of the TAAS beam.  Surprising that Skype works in the closed up tub, but whaddyaknow.

Pictures below correspond to ~diametrically opposed positions on the 'mystery' aperture corresponding to the dotted green line two posts back, just where the TAAS image starts to clip on it.

It seems conclusive that the  mystery aperture is in fact the black ring holding the window in its mount.  Why this isn't exactly concentric with the flange opening (dotted red line two posts back) is something to ponder....

About the TAAS/EXES images

If we put a 0.5 degree artificial 'sag' in the TAAS/EXES instrument at the SI flange, effects similar to what you're seeing show up as illustrated in the attached composite image from Zemax models.  It's not clear to me that the magnitude of the effect is the same as what you're seeing, or that the direction of the sag is the same.  Or it might be something else altogether!

The obvious things I see are the beam displacement at the cold stop and at the detector.

The sketch at the bottom shows what TAAS/EXES looks like with a 5.0 degree 'sag' at the SI flange to show you the sense of the tilt that I induced.

More Alignment

We continued to investigate the irregularity of the field of view. A webcam was dropped inside the EXES/TAAS junction and yesterday's pattern was repeated. The webcam took pictures of the pattern relative to the hole in EXE's 41-inch flange. These images were then composited and aligned with yesterday's results. Two more dotted perimeters were also added. The red perimeter indicates the edge of the 41-inch flange hole, while the green perimeter is an extrapolation of whatever is restricting the field of view in the lower left of this image. The blue perimeter is, as it was yesterday, the s/d/f perimeter.The centers of each circle are color-coded accordingly. This image confirms that the assembly has coaxial alignment issues.

TAAS Field of View Measurement

We carried out a search procedure to ascertain the exact size and shape of the TAAS field of view as seen from EXES.  We selected the largest aperture opening available to us on TAAS, 5 mm, and positioned it at various points where we saw the TAAS aperture clipped in the FOV.  Each exposure was saved as an image file, which we later compiled into one image. The resulting image is shown here, along with a dotted line showing the observed position of the s/d/f wheel aperture.  The observed FOV did not appear to be perfectly round, nor did the bootstrapped TAAS boresight center position (the dim white circle near the center of the image) correspond to neither the center of the FOV nor center of the s/d/f/ aperture (the overlaid red dot). We will continue to investigate why these patterns are non-concentric.

TAAS/FLCS Startup

We had a repeat session with Al Howard on using the TAAS with the FCLS-- this time we wrote things down...

Turning on the hardware
      a) first turn on the temperature controller
      b) then, turn on the amplifier
 At any time, turn on computer and TAAS motor controller box.

Software/files for running TAAS.
------------------------------------------
TAAS_Aperture.vi
When started, the aperture motors automatically home after a 10-15 second delay. Afterwards, select the aperture size and it will automatically be slewed into place in front of the light source.

FCLS.vi
         a) press "HOME"- entire FCLS stage will move
         b) press "LOAD" and select "FCLS X-Z Slides Aligned2" -- this is the best bore-site representation of the SOFIA telescope, transferred from DAOF TAAS using one of the SOFIA instruments.

Robofocus
The value of the focus is given in steps.
The button "A/R" toggles whether the focus is given in absolute or relative step numbers. It defaults to display relative, but absolute is far more useful, so select "absolute" as soon as you open the program.
The step numbers can be converted to absolute focus position by converting steps to mm with the excel spreadsheet,  "FCLS #2 Focus Calibration Curve 02-14-2011.xls", also located on the desktop.


FCLS #2 Focus Calibration Curve 02-14-2011.xls
find the distance from the mounting flange to the TAAS focus using the conversion from steps to mm given in this spreadsheet. Negative mm values mean the focus is inside TAAS; positive mm values mean the focus is on the instrument side of the flange.

Other notes:
The beam is thought to be close to f/10.


The light source is located inside a glass envelope. The temperature is controlled with a PID loop, and heated by a long, horizontally-oriented filament. The filament is likely to be the only thing producing light in visible bands: for example, if the temperature setpoint of the black body is suddenly turned down, the filament will completely shut off, and the spot on the bare MUX will disappear until the temperature of the glass envelope falls below the new set point and the amplifier turns on again.


Current Performance:
Currently,  with the bare mux in place in the warm instrument,we see a ~ 70 pixel spot, regardless of the aperture selected or the focus position.