SALTICAM returns!

Sutherland's been getting Huge amounts of rain over the past couple of months & it's occasionally led to some flooding.  A spectacular waterfall appeared behind Valhalla (Vic & Annie's home) back in February.

That & subsequent deluges have led to the place being temporarily renamed Mudvalla.  No sooner had the green stuff been cleaned out of the pool & put up in the trees, when the mud came rushing in...

Not enough to cramp the style of the natives though - boys will be boys!

We even got some archery lessons thrown in, thanks Keith!

Meanwhile, up at the hostel, Anthony took a break from writing software for automating his PCON software ATP.  He set up his camera on a tripod to stake-out the home of a very cute little rodent & then with a long-distance remote trigger was able to nail these Fantastic shots of the little guy :)

Later, Darragh, Dave C, Denys & Amanda arrived from Cape Town with SALTICAM & dozens of other boxes, bits & pieces, including the Atmospheric Dispersion Compensator (ADC).  Welcome back SCAM!

Everything was unloaded into the spectrometer room, ready to be unpacked & assembled tomorrow...

Installing the RSS beamsplitter

The optic that's suffered the most as a result of the RSS lens fluid nightmare is the beamsplitter.  This incredibly intricate assembly's made up of 18 UV calcite prisms arranged in a 3x3x2 array, with coupling fluid filling the gaps between the pairs of prisms.

Calcite is a birefringent crystal & thus splits light up into 2 linearly polarised components, known as the ordinary & extraordinary rays.  The fact that RSS is designed to operate all the way down to the atmospheric cut-off means that UV-transmissive calcite's required & that's extreeemely rare.  In fact, these crystals were mined in a really dodgy part of Mexico & the individual chunks are amongst the largest specimens in the world.

The prisms all had to be precisely aligned so that they produce a clean pair of images, rather than a jumble of variously offset versions.  Happily, this all looks good!

Although it does manage to produce some rather funky effects - here's a light bulb shining down on its surface at an angle.  Spot the dispersion due to the prisms & the reflections off the various surfaces.

As happened with the collimator optics, an air bubble appeared in the lens fluid & this had to be herded out of the optical path.  A small amount of air was probably trapped within the network of channels inside the frame that holds the whole thing together.  While traveling up to altitude, the bubble grew & migrated out of its hiding place...

Tipping, tilting & tapping the frame eventually chased the bubble up into the fluid storage bladder at the top of the frame, where it ought to stay. 

While the beamsplitter was away having its lens fluid replaced & then being repaired, a chunk of aluminium was installed in its place.

This served to protect the huge front element of the spectrograph camera that otherwise would've been scarily exposed to all the mechanical interventions going on nearby.

So - time to insert the beamsplitter!

Note the yellow rope in the background that's doubled when seen through the optic...

It just wouldn't be a real SALT instrument without the obligatory limited-space/tortured-access issues!

Nothing Peter can't handle though...

Once it was safely mounted we could test the pneumatics that lift & lower the beamsplitter.  When not doing polarimetric observations, the beamsplitter will be stowed above the beam.

A slitmask with a set of pinholes was inserted into the beam & an image taken.  The frame showed the pinhole pattern repeated (albeit in the form of slits) & off-set in the vertical, indicating that all is well.  Obtaining an image with a narrowband filter in the beam confirmed that the small slits are due to dispersion by the prisms.

All 91 segments back in the array!

Lots of jobs are going on all over the facility, including  fixing up some wiring on the cherry-picker to make power available up there, particularly while doing mirror work. 

All the mirror segments that had been removed before the SAC was brought down had been re-coated & the last of them went back into position a couple of days ago.

Here it is, showing up its dirtier neighbours...

So for the first time in almost 2 years, we have a complete primary mirror array!

Very cool to see & much fun to photograph :)

The recently cleaned & re-installed segments still need to be pistoned (adjusted in Z) to get them to fly in formation with the rest - this will be done next week.

Meanwhile - up at the top end, Dummy PFIS (the weight simulator for the spectrograph) was brought down from the tracker, along with the stage assembly that carried the camera we used to check the IQ after the SAC was put back up.

Then the rotating structure (RS) part of the payload could be removed & put back in the spectrometer room.  It's getting a few more mods made while it waits for SALTICAM, which is due to come up from Cape Town on Sunday.

Regarding Henry

Things are really ramping up at SALT & there's much to report so the "commissioning blogger" is settling in for a few weeks.  The trip up included an encounter with a magnificent young martial eagle just outside Matjiesfontein, about the best omen one could wish for!  Then, closer to Sutherland - a black-breasted snake eagle put in an appearance as well :)

My traveling companion for the day was Henry - a stowaway scorpion that had successfully made it down to Cape Town in Hamish's luggage a few weeks ago.  Apart from the protestations of the rest of the Whittal family, Henry had a good time over there (enjoying 24-hour IT support & being fed juicy green bugs regularly), however - it was time for him to go back home...

First though, he needed to be re-integrated into the Sutherland social scene so it was off to Perlman's for a couple of drinks.  Somehow he missed his ride back up the hill so was forced to spend the night with Vic & hence only made it back here in time for the glycol party the next afternoon.  Anyway, after a beer & some champagne, it was time to go.  Henry was most excited about his new home & we all (other than Adelaide!) wish him well :)

Upgrading the tertiary glycol system

Last week one of the huge jobs at SALT was the long-sought tertiary glycol system upgrade.  This is the system responsible for cooling most of the igloos, the tracker & the top hex - the places that need to be kept within +/- 2 degrees of ambient.

The old system was inadequate & so it was always a juggling act to get enough glycol to the places that needed it most at a given time.

Not to mention the awful leaky pipes & general mess of it all...

Pipes run underground from the utility building (the place our glycol calls home), across to the dome.

 

Where they pop up in the spectrometer room.

From there they go up to the telescope floor (below the structure) before branching off to the igloos & the top end of the telescope.

Serious manual labour was the order of the week as all the old pipes had to be cut up & removed before the new ones could be installed.

This involved some spectacularly hard-to-reach places that left everyone aching & grumbling for days about their now-apparent decrepitude.

&, of course, plenty of glycol ended up all over the place...

An impressive heap of old pipes & junk now adorns the area between the dome & the utility building, perhaps to serve as a warning to any other sub-systems that just aren't quite making it.

E-Bay time?

Or maybe these could work as a nest site for a colony of carmine bee-eaters?

The boys chose a tasteful shade of blue for the new PVC pipes.

These now run aross the roof of the spectrometer room, instead of around the perimeter.

Before popping up below the telescope pier.

The whole ensemble's subtly accented with charcoal coloured corners & connectors...

Just Splendid - wouldn't you say?!

Once everyone had regained most of their mobility, a celebration was in order - extra credit going to Eben for leading a hugely successful mission.

Although we managed to miss the "real" fun of SALT's 2nd best ever team-building exercise, Ockert, Henry (see next post) & I were privileged to get to enjoy the glycol-inspired festivities - thank you chaps! :)

As usual, Sutherland obliged with a beautiful sunset & a great night was had...

Science Papers for 2010

Despite the limited operations at SALT over the last few years, there were still a number of science papers published by SALT in the past year primarily focusing on time domain astrophysics. These included papers on near Earth asteroids, cataclysmic variables, and other time varying stars and can be found on the SALT publications list.

Tomek Kwiatkowski lead three papers on observations of near Earth asteroids. These observations allowed the measurement of their rotational period and the amplitude in the light variations of the objects. An example of SALT observation of a near Earth Asteroid is given below.

Studies of cataclysmic variables were the main topic of most papers from 2010. SALT observations were part of the multi-site monitoring project of the accreting white Dwarf SDSS J161033.64-010223.3 (V386 Ser) as reported by Mukadam et al. Patrick Woudt and collaborators presented observations of outbursts in VW Hyi. Revnivtsev et al. present evidence for truncated disks in seven intermediate polars that was partially based on SALTICAM slotmode observations. Stephen Potter and collaborators present multi-site observations of INTEGRAL polar IGRJ14536-5522 that includes SALTICAM data. Further observations of transients objects include observations of classical T Tauri stars by Günther et al. They find no evidence for sub-minute periodicity in these objects.

Finally, Ido Finkelman along with SALT collaborators present additional results from SALT observations of spherical galaxies to measure the extragalactic extinction law. Below, are some of their B-R color maps based on SALT images for some of their elliptical and lenticular galaxies. The white areas indicate the dust lanes that appear in these galaxies.

Finkelman et al. 2010, MNRAS, 409, 727