SALT |

Our first look inside!

LucianB — Mon, 30 May 2022 17:10:00 +0000

The instrument was cold (at -40C) when Melanie & I got here on Sunday evening. After a focus sequence to establish how much detector tilt is needed, the team decided to warm everything up over night, in order to make the mechanical adjustments the next day. That meant that we could get inside the enclosure & see the fully assembled instrument on Monday afternoon! Words can’t really do it justice, so here’s a bunch of photos instead…

The optics are truly spectacular – kicking out much of the visible light

& the last lens of the collimator

The fibres enter the collimator on the right, the grating is near the middle of this view & the camera is to the left. The camera assembly articulates on the curved rail in the foreground.

It takes a fairly wide angle to get the whole lot in!

Funky views everywhere you look

The test integration cable (TIC) plugging into the collimator

The TIC represents the full extent of the final IFU, but it’s only partially populated with fibres. It has a few fibres arranged singly (to mimic the sky fibres) & others in small groups, as per the nominal spacing of the fibres in the science cable.

The 8 V-groove blocks at the left-hand end were made with the SAAO mechanical workshop’s wire-cutter

Mike gave us the grand tour & then made the detector tilt adjustments, while Kurt tuned up the orientations of the various cameras inside the enclosure.

Mike’s in there somewhere…

No – that’s not exasperation, just concentration!

With the adjustments made, & the enclosure cooling down again overnight, it was time to take in the magnificent (albeit Freezing cold) evening!

A busy Saturday in the spectrometer room

LucianB — Sat, 28 May 2022 08:02:07 +0000

The NIR team put in a loooong Saturday – tackling various tasks & snapping some particularly cool photos of the instrument that now contains all of its optics.

The TIC light feed was aligned, so that light can be injected into the instrument.

That then allowed them to align the collimator, to centre the fibre spots on the detector. After installing the grating they could check the (warm) camera optical alignment using neon arc spectra. At best focus there was <100 microns of focal plane tilt, so that was good enough to go cold without making any further adjustments (other than a 1 mm re-spacing of the dewar gap for cold operation).

Some plastic shrouds were installed to shield the instrument from the air flow within the enclosure.

Here you can see where the TIC attaches to the collimator

& there was plenty of other prep to be done ahead of cooling the system down, including hooking up air purge lines for the optics.

Spot the mildly dispersed Kurt, seen here through the 950 l/mm VPH grating! The silver vacuum hose is permanently attached to the dewar so that it can be pumped on at any stage, without having to warm everything up first. It had to be carefully suspended so that it stays out of the way of the camera that articulates according to the grating angle selected.

A number of night-owl cameras were also installed within the enclosure – these are really handy as they can be used to spy on the mechanisms while the system’s cold.

Various views of the instrument from inside the cold enclosure

The cooling process was started at about 10pm, so it should be down to -40C by dinner time tomorrow…

In goes the collimator + test integration cable!

LucianB — Fri, 27 May 2022 11:34:34 +0000

The team’s making excellent progress in getting the instrument integrated within the thermal enclosure. Today they got the collimator optics installed…

Collimator lens barrel attached

Here you can see where the pseudo-slit will attach to the collimator optics.

Entrance slit on the collimator

The test integration cable (aka the TIC) was routed through the enclosure wall & attached to the collimator.

Test integration cable (TIC) in place

The light feed system was also set up on an ad hoc lab bench (that closely resembles a particle board box!). The light source on the left feeds a liquid light guide that plugs into the gold-coloured integrating sphere before entering the TIC.

Light feed for the TIC

They also took a test image with the detector still warm to confirm that it’s alive & well. Noisy of course, but fine – so then the cooling was started & it should get down to temperature sometime tomorrow.

Installing the camera optics & detector

LucianB — Thu, 26 May 2022 09:49:29 +0000

The instrument PI – Marsha Wolf – arrived in SA over the weekend & went up on Monday. She got straight into the fray & we soon realised that some of the best parts of the integration process would take place during the SALT Board meeting that’s happening this week… To maximise the torment, the team began installing the big optics today! First of all – huge relief to find that the contents of the various crates were none the worse for wear after having made the trip from Cape Town to Sutherland on the back of a large bakkie!

Here comes the camera barrel!

Kimwipes at the ready…

Whew – it still fits

Now for the detector package

Hope they remembered to remove the white card that was taped on the front

Huge progress getting all that done today & then they still got the dewar pumping down over night….

We have a complete camera & detector!

Meanwhile, down in Cape Town we had to bid farewell to SALT software stalwart Deneys Maartens, after 14 years of fantastic work. Very sad to see you go Deneys, but we wish you everything of the best in your new adventures – please keep in touch! We miss you already

Nope, no speech…