Mass Properties

Here are some details from today's weight session in the old mirror coater room.

-  Used a calibrated load cell in line with the crane rigging to measure weight, and appropriate tare weights have been removed in the numbers presented here.
-  Measurements here are for a fully assembled instrument, including the support triangles, mounting plate, cal source, and eBox.  No cryos on board (wet instrument might be 10-15 lbs. heavier)


-  Installation weight, including SI Cart, weighed with all four wheels off the ground, is 1331 lbs.
-  Cart weight, all four wheels off the ground, is 368 lbs. (from the October measurement).
-  Weight of full-up SI, minus cart: 963 lbs.

-  Installation weight borne by the two forward wheels: 422 lbs. (211/wheel).
-  Installation weight borne by the two aft wheels:  914 lbs. (457/wheel).

-  Weight of full-up SI, minus cart, measured at forward ring: 365 lbs.
-  Weight of full-up SI, minus cart, measured at aft ring: 588.3 lbs.

(Single-end weight measurements do not exactly add to the four-wheel suspended numbers due to minor differences in the fulcrum points for each measurement which have not been accounted for.)

-  'Paper test' shows contact patches of 1.25 sq. in. at aft cart wheels, and 0.86 sq. in. at forward wheels.  This gives a mean contact pressure of 457/1.25 = 366 psi aft and 211/0.86 = 245 psi at the forward wheels.  No problem with the floor loading ICD :)

-  Counterweight rack, fully populated and with all cables in place weighs 317 lbs. (no waiver required!)

Fast frame times

During CD14, we looked at how well we can do fast read outs.  The criteria we set, somewhat arbitrarily, was <5% difference from a 1 second frametime.  We were imaging echelon orders so that we had fairly high photon rates.  Normalizing each SUTR difference so the peak is 1, I subtracted the 0.25, 0.33 and 0.8 seconds from 1.0 second frames.  They all look pretty good to me.

New vignetting in hi-med at echelon 10,echelle 17

After recentering the slit, decker and filter in camera mode (at low res), I noticed that we are now vignetting when in high-med. This was not the case at 23T/4T, and I'll prove it with another set of images when Bob is done with his tests today.

For now,
Here is the SDF, medium res mode: (Vechelle=3.5480V, 4.7um filter)

And here is the SDF, high-med mode (Vechelle=3.5244V, 4.7um filter)

 Since the Q0 line has not changed position I don't believe we have changed steering. And I verified that both flip stops are being reached. Maybe this is due to a clip at the roof mirror between the two chambers? I recall hitting them high during alignment, and now that the focus is deeper in the echelon chamber, the beam could be too big for that spot on the roof mirror (?)

Med-res pinhole data at 8-17 turns on echelle mirror

Nothing quantitative now, but here is rinse subtracted pinhole spectra in medium mode of the Q-branch, dialed over the 100-300 column region.

18a filter

I used the data for the 18a filter taken way back in early Feb(?).  We were comparing the transmission looking at room for the 18a+KBr blocker with and without the ZnSe window in the lens wheel in front.  The concern is that 18a without a blocker had light leaks preventing observations from around 16 to 17.5 microns (see post from May 2012).  The money plot is below showing first the relative transmission in good settings with (red) and without (white) the ZnSe blocker in the lens wheel and (bottom) the transmission as a function of wavelength.  Key takeaway is that with ZnSe, we can get to 16.5 microns.  I suppose a possible problem is that the atmosphere doesn't cut out until 15.5, so we'd like to go even shorter.  Still, 16.5 is better than 17.5 (gives us access to H2 J=3-1 at 17 microns).

Still need to look at UKIRT filter, although I fear it will be somewhat similar in short wavelength cutoff.  Time to order a small ZnSe window to replace the KBr that is currently sandwiched with the 18a.  Also time to start looking at filter for the 15.5-16.5 region.