Update for the week that was

Going out on a limb here publishing a very cool pic that the PI unsuspectingly shared last week...  But we all know that it's easier to get forgiveness than permission, so "Sorry" Marsha!

The quintessential PI selfie 😎

Here's a high-level summary of what the NIR team's been up to this past week:

Kurt worked with Jeff on the monitoring of flow sensors for purge lines & actuators, then added purge air to the cryotiger lines as they exit the enclosure & insulated them.  He also spruced up the turbo pump vacuum system & he's updating labels on all control system components. 

With the instrument warm, Mike adjusted the camera-dewar interface to improve the optical alignment & then cooled the enclosure again on 30 May.  Marsha subsequently took data for diagnosing the overall optical alignment, including frames to help analyse the grating alignment.

On 31 May she did a focus run with the grating at an angle of 25-deg & the camera at 50-deg.  This was followed by a set of scattered light data with only the sparsely spaced fibres in TIC illuminated.  Matt found the scattered light to be ~1% of the peak, which is good news.

Over the next 2 days, Marsha took a set of stray light data inside the enclosure at different spectrograph setups.  These were done with the spectrometer room lights off to prevent light from getting into the TIC fibres.  She stepped every 2-degrees in grating angle (4-degrees in camera articulation) over the range of 25-49 degrees on the grating, & did a focus run at grating = 39-deg, camera = 78-deg.  There was nothing visually noticeable, but quantitative analysis is yet to be done.

On 3 June she did a focus run at grating = 49-deg, camera = 98-deg & collected data for measuring the position of the grating Littrow ghost at grating angles of 25, 38 & 49 degrees.

The next day she took an image of the fibre slit without the grating, for comparison to the same image when warm, & also did a focus run in imaging mode (no grating, camera = 0-deg).

On 5 June Marsha spent the day analysing all the alignment data collected over the previous week, & trying to model it in Zemax.

Today she took sets of data for read noise measurement, for the different readout modes (correlated double sampling, up-the-ramp group & Fowler sampling), as well as for gain measurement for both preamp gain settings (faint & bright modes).

The camera articulation detent started acting up when articulating from 50-deg to 76-deg - it looks to have reached 75-deg & had a detent error (likely due to an air leak in the system).  They worked with Jeff using the low level software controls, but the detent will not engage, so they'll need to take a look at this when the instrument's warm again.  Marsha had planned to take more scattered light data at high angles, & a reference set of spectra through the whole spectral range.  But since they can't articulate the camera for these setups, they're inclined to start warming the enclosure in the morning.  Good timing for Ant, who arrived up there this evening!

The run of great weather continues up there

With the instrument to be warmed up soon, expect a wave of SALT staff tourists - all eager to see what's inside the wicked new enclosure in the spectrometer room!