Since last week included a holiday we will include activities from the last two weeks.

This week we had a software engineer from Austin visiting to commission the Metrology loops in software. The includes the distance measuring interferometer, the tip-tilt sensor and guiding with the CAT. The team was able to accomplish all of these at a single azimuth but problems with the alignment of the CAT stopped further exploration of the performance of the system. We will test the alignment of the CAT on Sunday so that further commissioning can continue.

In the previous blog post we mention the discovery of some loose bolts. The source of the “loosening” is still a mystery but we installed an accelerometer to look for significant jarring events on the tracker. This week we took it down and looked at the data. The most serious events were those of the installation and removal. Even forced Emergency Stops did not produce large accelerations.

Commissioning of the Strip and Wash Room continues. The room heater and make-up air were tested and found to work but needs small tweaking with regards to the indicator lights on the controls. Other members of the team are working on the Safety Protocols document. They believe that commissioning will be completed by January 5th and that we should resume mirror swaps in the primary at that time.

This week one large project has been completed. Phase I of the Dome Sealing and Conditioning was completed with the last of the dome “hair” seals being refurbished. With the completion of Phase I we have sealed the vents on the ring wall, refurbished the seals at the base of the dome, sealed the leaky dome nodes and replaced all of the louver seals. We note that this last rainy season we did not have any leaks in those locations. Phase II involves sealing the dome shutter and will require some engineering.

The technical teams at the HET continue to make progress on various projects such as continuing installing the VCS Safety System components; installing a differential thermostat and a parallel temperature acquisition system in the K-Hut to monitor inside and outside temperatures over the weekend; and test fitting the PFIP Electric Box Frame Weldment Assembly. One pending item that was accomplished was to replace the structure drive wheels. These wheels were showing considerable wear and we replaced them before a failure could occur.

The Anemometer project has made some progress this week. All of the units were calibrated and the system was run over night on Wednesday and Thursday. Some problems were found in shared memory flags in the database but these were cleared up and we should be able to start collecting data and looking at how to best visualize and utilize this new data set to minimize dome seeing induced by turbulence.

In the coming week we will be down a large number of staff. Three of the operations team who are traveling to Texas A&M to speed along the final assembly and testing of the 2nd VIRUS enclosure. Three other people from the operations team (including the blogger) will be traveling to Germany for the HET Board of Director’s Meeting. Much of the last two weeks was spent in preparing reports and presentations for this meeting.

Work continues on various aspects of the new tracker. In the electrical room one of our E. techs installed a new
Phase Control Modification circuit for the LER Servo Driver cabinets and successfully tested its operation. This will be critical if we were to loose just one phase of power. One of the other E. techs and a programmer from one of our partners in Germany have started working on the VIRUS enclosure PLC for monitoring the sensors within the enclosure. They tested each sensor and mute switch; all worked as expected. End to end testing will be done next week. Meanwhile the mechanical team worked on the Platforms for the first Virus Enclosure. It took several days but all of the platforms are now in.

After the interruptions due to weather and the problems of the loose screws from last week we are finally back on sky this week. Night operations commissioning started with the first data sets for structure and tracker sag models. This is done with the small celestron telescope mounted on the tracker. After the engineering tasks were complete,
the telescope operator was able to find all of the mirrors (with some assistance of the mirror team who sited some of them in from the catwalk). Mirror alignment for the full array is now near 0.5″.

Work continues on the commissioning of the strip and wash room. We finished working on the PID control of the strip/wash room exhaust fan. Fan will now respond to pressure setting change requests from within the strip/wash room and regulate the pressure to previously established set points. This will allow the team to switch from positive pressure while washing or drying mirrors to negative pressure when doing acid stripping.

We reviewed spectrograph room temperature data and discovered that we have dropped below the cooling temperature settings of the Mitsubishi thermostats/control heads, this is largely due to the thermal pulse moving through the ground produced by our <20 F temperatures last week. We have designed a new experiment to determine the optimum method to hold the 16 C setpoint during periods where both heating and cooling are required. We hope this new methodology will work. If not then we will need a PID controller which will require significant more work.

Our electrical tech began work on Virus enclosure this week. We will be installing all of wiring and breakers in the enclosure. One of our telescope operators is working with one of our programers to sort out the remaining problems with the wiring to the anemometers. The next step will be to set the zero point of the wind vein in the software which requires them to point the anemometers in a known direction and note the position read out. We also installed a new digital rain gauge this week. We will now be able to record when we have rain events in the weather archive. Work on the TCS continues and some bugs in the RA and DEC offsets were found and removed. Offsetting in X,Y, rho are still to be done.

This was supposed to be the last week for work on the Facility Thermal Management Project. Veliz Construction finished the back stairway past the K-hut to the liquid nitrogen slab. This was a requirement by the people who will be filling the liquid nitrogen tank. A fair amount of time was spent putting insulation around pipes, cleaning up the site and small projects. The consulting engineers from El Paso came out on Thursday to generate the punch list of remaining items for the contractors.

For our large project which we call “Facility Thermal Management project” Veliz Construction began the mounting of the access stairway that serves the LN2 tank. ARC was onsite to continue the pipe insulation and insulation protection. Weathers Electric landed the Advantage Chiller power line into the HET main panel and replaced the 400 amp fuses in the the 112 KVA transformer disconnect panel with 350 amp fuses. Weathers Electric made the final connections for the new telescope Advantage Glycol chiller 3 phase power. This glycol chiller will help us cool the tracker motors and keep all of the electronics in the tracker at ambient temperature.

We continue to work on the VIRUS Safety system which will have alarms for dealing with the large liquid nitrogen tank behind the control room. It senses liquid nitrogen flow and oxygen levels around the facility. It is a fairly fast system that will take more than another week to complete its installation.

This week we began cleaning up the spectrograph room including moving around the large air tanks to make more room for the HRS insulation and the HPF enclosure, which will show up the 2nd week in November. Our goal is to hold the inside of the HRS enclosure to a very tight tollerance so we are current experimenting with RTD temperature sensors for the Spectrograph room to monitor how tightly we can control the temperature with the new air conditioning system recently installed.

This week we had some night time engineering work using the CAT (Celestron Alignment Telescope). This small telescope is mounted in some V-blocks near the center of the tracker where the future corrector will go. This small telescope will allow us to test guiding metrology and TCS software on the sky. This week we spent the time trying to align the telescope parallel to the rho axis, moving it to the center of the rho axis and then finding the offsets to align it along the central optical axis of the primary. Once done we were able to take a quick image of an open cluster, NGC 869, and confirm the plate scale and orientation and do some preliminary analysis of the newly installed TCS commands for rho, theta, phi, RA and DEC offsets. We have some debugging to do but this is a big step forward and will allow us to get valuable feedback before the corrector arrives in January.

For the Facility Thermal Management Project, Veliz construction spent the week preparing and finally pouring the concrete pad for the large liquid nitrogen tank which will feed VIRUS and eventually the HPF.

Veliz Construction pours the LN2 concrete slab

Weathers Electric began working on the Krabben hut exhaust fan wiring after ARC installed the fan early in the week. Veliz Construction also finished the cinder block wall around the new Mitsubishi compressors out in the remote thermal area.

One of the engineers from Austin came out this week to work on the tracker mount model using the laser tracker. They were able to run several long tests at night and will start the analysis of the data.

The work to clean and rejuvenate the hair seals continues. The newest
technique involves removing the seal clean it and then reinstall it such that the hairs are not curled the opposite direction as before. We are about one third complete with this effort.

Our new Opto-mechanical technician started today. She joins us from Austin and has already driven the JLG above the mirror and done an inspection of the coating tank in the clean room.

We received the work platforms for the VIRUS enclosures. These go on the inside of the enclosure but outside the truss. We found that the top set of platforms are to wide and will have to be modified.

This week has been fairly slow largely because we are cleaning up after last weeks VIRUS enclosure installation and because we have had many large rain storms.

In the Mirror Strip and Wash room we are making some modification to make it more user friendly and preparing for commissioning of the acid stripping process once the contractors have the acid vapor duct in place and the fan working. This should be ready to start sometime in the next two weeks.

Veliz Construction finished the Liquid Nitrogen slab backfill and sleeving for water line that must run under this slab. ARC also started the installation of the K-Hut exhaust fan. Weathers Electric continues running conduit between the pipe vault and the indoor breaker panel to support power lines to the dry cooler, Advantage Chiller and convenience outlet.

ARC Mechanical working with the Mitsubishi rep, tested out the HVAC system and it is now fully functional. This means we now have new air conditioning capability in the lower electrical room where all of the new tracker electronics are located as well as more powerful cooling capability in the spectrograph room. This will allow us to put the High Resolution Spectrograph in a cold bath which will help us keep a more constant temperature and improve velocity stability. Air conditioning has also been restored to the HET offices and the clean room.

Next week we will repeat of the 97-pt laster tracker test measuring only the hexapod control point, and a repeat of the 21-pt grid, measuring the control point as well as tip-tilt of the hexapod. This will provide an independent verification of the mount model imposed several weeks ago by the software and telescope controls group.