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--- uc:uc20240206_february_6_2024 [2024/02/12 21:36]
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 General  updates: Jamey thanked to Kevin and other APO users for stopping by the APO booth at the January 2024 AAS meeting; it was nice to meet folks in person after only knowing them through Zoom. The weather at APO has been terrible in December-January. The DSSI team will be here this month, and we are looking ahead to a class visit from CU next month (thanks for CU and OU for being proactive and doing the early planning for their class visits in March and April, respectively). We have been seeing some seasonal motion errors on the  3.5m. The 0.5m has an issue with syncing the time; we are still working on it. The new slits for KOSMOS arrived; after making some small adjustments they are now mounted and available for use.
-Snow on the roof issue: The recent winter weather has impacted our ability to open, even during clear nights, due to the accumulation of snow on the enclosure roof. [If we open the enclosure when there is snow on the roof, it will fall down onto the telescope.] There are heaters on the edges of the dome building (not across the top), which we use to help melt the snow. However, the main mechanism for snow removal is sunshine; if it's not sunny -- which has been the case after the recent snow storms -- the snow on the roof won't melt. Previously we have had staff members go onto the roof while wearing safety harnesses to shovel it off. This raised safety concerns from NMSU's Environmental Health and Safety (EHS) office during their annual safety training. An EHS representative is coming to site this week to inspect and discuss the situation; we may need to modify the hook points used for attaching the people wearing harnesses. We are looking at other options as well, e.g. using long poles to reach the snow, or possibly adding more heaters (but we need to be careful about ruining dome seeing). We recently put in cameras so we can see the snow on the roof and know how much there is. The heaters have to be shut off at -2 C. If we operate them when the temperatures are near freezing then we run the risk of building up ice from the snow melt. This makes it less likely to have snow blowing onto the telescope but more likely to cause damage if that ice falls. This is also why we sometimes have wintertime opening restrictions where the wind speeds must be low. If the winds are below our normal limit but still above that special wintertime/snow limit then we must stay closed, which we recognize is frustrating for users. One person asked if it would be possible to add some sort of structure with sloped sides onto the existing roof? Jamey replied that this would require not only changing the roof but also the doors (to accommodate the additional weight), so it would likely be cost prohibitive. The bottom line is that we recognize that these closures are frustrating for our users, and we are committed to identifying a strategy that can help us remove the snow fairly soon after it falls while ensuring the continued safety of our staff and telescope.
+Snow on the roof issue: The recent winter weather has impacted our ability to open, even during clear nights, due to the accumulation of snow on the enclosure roof. [If we open the enclosure when there is snow on the roof, it will fall down onto the telescope.] There are heaters on the edges of the dome building (not across the top), which we use to help melt the snow. However, the main mechanism for snow removal is sunshine; if it's not sunny -- which has been the case after the recent snow storms -- the snow on the roof won't melt. Previously we have had staff members go onto the roof while wearing safety harnesses to shovel it off. This raised safety concerns from NMSU's Environmental Health and Safety (EHS) office during their annual safety training. An EHS representative is coming to site soon (their visit last week was postponed due to inclement weather) to inspect and discuss the situation; we may need to modify the hook points used for attaching the people wearing harnesses. We are looking at other options as well, e.g. using long poles to reach the snow, or possibly adding more heaters (but we need to be careful about ruining dome seeing). We recently put in cameras so we can see the snow on the roof and know how much there is. The heaters don't work well at temperatures below -2 C. If we operate them when the temperatures are near freezing then we run the risk of building up ice from the snow melt. This makes it less likely to have snow blowing onto the telescope but more likely to cause damage if that ice falls. This is also why we sometimes have wintertime opening restrictions where the wind speeds must be low. If the winds are below our normal limit but still above that special wintertime/snow limit then we must stay closed, which we recognize is frustrating for users. One person asked if it would be possible to add some sort of structure with sloped sides onto the existing roof? Jamey replied that this would require not only changing the roof but also the doors (to accommodate the additional weight), so it would likely be cost prohibitive. The bottom line is that we recognize that these closures are frustrating for our users, and we are committed to identifying a strategy that can help us remove the snow fairly soon after it falls while ensuring the continued safety of our staff and telescope.
 ARCES issue: ARCES had a failure in its autofill system that caused it to warm up, taking it out of service for several weeks. We are pumping it down right now and then will cool it. The earliest possible date that it will return to service is likely around February 16, but it could extend beyond that. The dewar is a big volume to pump down and the cooling will be rather delicate. It has been at least a decade since we have done this in wintertime. We have all of the replacement parts for fill system in hand and they are ready to be installed.
-DIS issue: The DIS red channel has had an electronics failure, with all pixels reading the same value. There are no immediate plans to repair it; we have tried every intervention we can do from the outside of the instrument to recover the red camera and not met with any success. We currently don't have the in-house expertise to do an internal repair. This raises the broader issue of when (not if) to decommission DIS. As the oldest instrument on the 3.5m, it continues to show its age and perform sub-optimally. Recall that the acquisition of KOSMOS was intended as a stop-gap measure that would provide continued capability for long-slit optical spectroscopy while Ocotillo is being developed and built. Nearly all former DIS users have migrated to KOSMOS, but there remain a few DIS holdouts. **UC reps: please tell your users that we need to understand what capabilities KOSMOS lacks that makes some people still want to use DIS.** If it is a resolution issue (either the desire for higher or lower resolution than what is offered by KOSMOS), we still have several slots remaining in the wheel that holds the grisms for KOSMOS. If people want/need different resolution, in principle we could fulfill this need with the addition of one low-res grating that would get the entire spectrum in one shot, and two higher-res gratings. Russet noted that we do now have a complete set of 1.25" slits (low, center, and high position) which are better matched to the site seeing, so users can now optimally sample the site seeing. **Nancy will follow up with Sarah to get some ROM estimates of costs for additional grisms.**
+DIS issue: The DIS red channel has had an electronics failure, with all pixels reading the same value. There are no immediate plans to repair it; we have tried every intervention we can do from the outside of the instrument to recover the red camera and not met with any success. We currently don't have the in-house expertise to do an internal repair. This raises the broader issue of when (not if) to decommission DIS. As the oldest instrument on the 3.5m, it continues to show its age and perform sub-optimally. Recall that the acquisition of KOSMOS was intended as a stop-gap measure that would provide continued capability for long-slit optical spectroscopy while Ocotillo is being developed and built. Nearly all former DIS users have migrated to KOSMOS, but there remain a few DIS holdouts. **UC reps: please tell your users that we need to understand what capabilities KOSMOS lacks that makes some people still want to use DIS.** If it is a resolution issue (either the desire for higher or lower resolution than what is offered by KOSMOS), we still have several slots remaining in the wheel that holds the grisms for KOSMOS. If people want/need different resolution, in principle we could fulfill this need with the addition of one low-res grating that would get the entire spectrum in one shot, and two higher-res gratings. Russet noted that we do now have a complete set of 1.25" and 20" slits (low, center, and high position) which are better matched to the site seeing, so users can now optimally sample the site seeing. **Nancy will follow up with Sarah to get some ROM estimates of costs for additional grisms.**
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