This past week we had a large fraction of the Austin engineering and software groups visiting the telescope. This gave us an opportunity to make rapid improvements in the Telescope Control System and start getting the telescope ready for the installation of the first spectrograph.

With the removal of the Deployable Wave Front Sensors we were able to re-enable the guide probes and continue with their commissioning. Despite rather poor weather much of the week, the big milestone reached was the ability to now guide on the guide probes.

The software and engineering teams remain at the HET this next week and if we have some clear skies we will continue the push on commissioning of both the guide probes and refinement and characterization of the mount model.

We have big news this week. We have officially declared first light on the wide field upgrade for the HET. Please see:

Upgrade HET Sees First Light

This is the first light image from the 29th of July. The image quality is 1.3″ and we were only an arcminute from the target of interest.

Now that verification of the WFU corrector optics is complete we can get started on operational aspects of the new HET. This next week we are collecting data with the guide probes which will allow us to start the software commissioning of the guide probes next week.

We have cleared out the temporary clean room we installed in our loading bay so we can now have access from the mirror lab to the HET dome floor. This means that the mirror team will start doing mirror re-coating in the near future.

Other interesting news comes from our big hail storm in the past month. It broke many car windows damaged a few of the residents’ roofs and below we show the damage to the HET dome. Thankfully no leaks that we can detect.

In the big hail storm of 2015 that fully covered the road in several inches of hail the HET dome took a bit of a beating.

Since the last blog posting we had our most senior telescope operator retire. We wish her well in all of her next adventures. In the mean time we have posted the position and it is open now, probably for two more weeks.

Telescope Operator Position now Open

Despite nearly a month of heavy smoke, fog, rain and hail we have completed our tests with the Deployable Wave Front Sensors (DWFS) on the Focal Plane Assembly (FPA). In these tests we were putting geostationary satellites on the various DWFS units across the FPA. While the final report on the image quality of the Corrector optics are still pending we do know that the image quality is good enough to move on to the next stage of commissioning. We will likely leave the central DWFS unit in place to allow us to check and re-optimize the image quality as we make further changes to the mount model. Below is an image of what a single bright star looks like through the DWFS unit. You can see that the light is broken up into small sub-aperatures (not each mirror) and then the distribution of those spots, ie. how evenly they are spaced, can tell you about the deformations of the optical system. The Corrector is the area in the center without the spots. The tracker rails run from 2 o’clock to 8 o’clock where the lower X work platform is still installed.

On the staffing side of operations the good news is that we are fully staffed. We have a new electrical engineer and a optical technician starting this past week and a telescope operator joined us the week before. The bad news is that one of our other telescope operators has decided to retire as of the 14th of this month. We will be posting the position in the coming week.

The mirror team has begun an intensive inspection and repair regiment for the primary mirror actuators and electronics. They have found a number of damaged connectors and replacement of these connectors seems to have improved reliability considerably.

We have successfully tested the cooling of the first VIRUS enclosure. The cooling is accomplished by bringing in glycol that is only slightly cooler than the dome ambient temperature and then additional cooling from a small thermo-electric cooler is added when needed. This test was accomplished with no VIRUS units installed but artificial heat loads induced. We will have to wait to see how the system performs under the full load of the VIRUS units.

This week the visiting engineers from Austin aligned the Video Alignment Telescope (VAT) to the corrector optics and then aligned the corrector to the the center of the primary mirror. This sets our axis for making all trajectories. We will now set the distance from the primary to the VAT. Work will continue over the weekend and we will then turn the VAT around and measure the angle from the VAT up to the CCAS instrument. This last will be night work. So far things are progressing on schedule.

The big news this last week is that the Prime Focus Instrument Package (PFIP), the Lower Instrument Package (LIP) and Focal Plane Assembly (FPA) were installed. We are now in the process of getting electricity, glycol and air to these systems. We have started testing the subsystems in place such as filter wheels and guide probes. This is a bit tedious and sometimes requires careful book keeping as we bring together separate systems into one coherent telescope. This next week we hope to have the Austin WFU optics team come out to align the Corrector optics to both the PFIP mechanical system and the HET primary mirror optics. If that goes smoothly this next weekend we may be aligning the corrector to the CCAS tower optical system. All of these alignment tasks are accomplished with the Video Alignment Telescope (VAT) which is an auto-collimating camera which we have designed a mount that allows it to be mounted either pointed down towards the primary mirror or up towards the PFIP, FPA and CCAS tower and sky.

To get ready for this transition to more night work we have a 2nd telescope operator (TO) training with the TO who has been working with the engineers for the past 9 months. At the beginning of next month we will be ready for 1st light through the corrector and will start to require all 3 TOs and some of the Resident Astronomers to work all night long.

One very exciting test that we were able to conduct this past week was to actually test our oxygen sensors that have been installed to look for spills from the liquid nitrogen system which might displace some oxygen. This liquid nitrogen system has flow sensors that if it detects a spill will be able to shut down the flow fairly quickly but with a flow rate of 4 gallons per minute this could still be quite a few gallons spilled on the dome floor. We conducted a test using 40 gallons of liquid nitrogen in a large insulated dewar. Spilled in what we considered to be the most dangerous location (inside the pier of the telescope on the dome floor). The liquid nitrogen quickly turned to cold vapor upon hitting the floor and we found that only the first 1-2 inches reached critical values while oxygen values at 1 meter above the floor stayed above warning values for the entire test. The test reassured the operations staff that the oxygen sensors do work and the risks are minimal except in the most contrived and unrealistic scenarios.

The big news for us this week is the lift of the wide field corrector to the top of the telescope. This involved removing the old test mass and the hexapods. The hexapods were serviced and put back on. The corrector was sealed up, rolled out of the clean tent into the dome floor and then lifted up to the top of the telescope. See the attached pictures.

The lift of the Wide Field Corrector begins. The Corrector has its side plates mounted so no optics are visible.

The corrector now at the top of the crane is lowered into the tracker. The blue and silver hexapods sticking up are only a small obstacle.

In addition the the installation of the corrector some work with the laster tracker was done and we determined the position of the base of the hexapods and see how much they may need to be shimmed to get into proper position for the corrector. At the same time we confirmed the distance to the CCAS instrument from the primary mirror and found it to be well within specifications for this corrector’s design focal distance.

Overall a great week with a major milestone passed. We now will start the PFIP installation as well as all of the plumbing and wiring connections to the new components.

Not much to report this week as we prepare for the lift of the corrector. Since the corrector is going to have all of its covers on and it may be years until we actually have this view of it again I thought I would post this picture showing the 4 elements (M2 can not be seen as it is under M5. Note the reflections of the straight support members are severely bent showing the curvature of the mirrors.

An image of the Wide Field Corrector with its covers off in the temporary clean tent in the HET loading bay. The Wide Field Corrector will live on the tracker and takes the beam of the HET, corrects for spherical aberration and brings it to focus.

The WFU corrector has passed its initial tests in the clean room setup in the loading bay. This was done ahead of schedule and the corrector will be closed up and mounted on the tracker over the coming weeks. The worked involved people from Austin and the optics team and we are grateful for the long hours and careful work they did this week.

The HET Board Meeting was held on the previous week and the board was very impressed with the progress that had been made and the plans for the recommissioning. It was a great event and the board did not ask for any significant changes to the direction that the HET is going.

We continue to make progress in the testing and development of the telescope control system. We have conducted tests to implement new pointing zero points and are working on the tip and centroid tracker sphere. Having done these tests before the corrector is in place will give us a chance to look for potential problems and solutions before we even see first light.

At the end of this last week the test weight at the top of the telescope was removed and with it the CAT. This means we will have no more on-sky tests until the corrector is mounted and ready for commissioning.