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To make a long story short, it was a long day of work, but we seem to be back on the sky with a telescope behaving as it should...
The new encoder assembly was installed back where the encoder used to be before the earthquake (West). Not much luck there: it was not really possible to put back the encoder roller in nice alignment with the horseshoe. As the structure supporting the
encoder assembly had been severely bumped, the new assembly was moved on the East side stand where it got in nice contact. Time to use the telescope from the control system (TCS) to check if the new encoder was sending some information back. It was and
the telescope was then moved all around through TCS, while the telescope was closely watched in the dome for unusual noises. It moved very smoothly!
Next step required the sky, and it started after sunset with a hole in the clouds but not enough time to really take useful images before the fog came in. Fortunately, humidity went down and the sky cleared up. We were able to take a first image and
check the pointing. We were of by a few tens of arc-seconds, not a surprise as the absolute encoders are likely to have moved with respect to the telescope itself. So far, so good. Now, had the telescope been bent, or some of the optics put of alignment,
or... by the earthquake? Subsequent pointing all around the sky were as good as usual once the initial offsets had been removed. So, nothing really changed and the telescope was back as good as before.
All functionalities of MegaPrime were checked and MegaPrime guiding is doing well. However, we found that the tracking rate was not too good: again, not a surprise as the encoder roller is not exactly the same as before. Conversion factor between bits and
arc-seconds was fine-tuned and should now be good enough. Fog came back and we decided to give the telescope back to science (where it belongs) so that they could use any clear sky to come :)
The last item to be checked once the sky is clear again with a decent seeing is the image quality over the MegaCam field. More on this when the weather cooperates.
MegaCam is operational again! Electronic boards were checked yesterday afternoon and the camera was switched on. By the end of the day, images were checked and all chips are alive and well! As of this morning, MegaPrime looks very happy! WIRCam is now cold
and needs now to be checked... more news later!
The new encoder assembly is now at the summit. Time to mount it. Stay tuned!
One more day of hard work and only good news to report! In Waimea, a new encoder assembly has been assembled and is ready to go to the summit tomorrow morning. More troubleshooting of the computers needed for image archiving and data processing narrowed
the remaining potential problems to only a couple of machines.
On the instrument side, Pueo, the Adaptive Optics Bonnette, has been thoroughly checked and is in good shape. The vacuum of the MegaCam cryostat is holding well and the camera is cold! The electronics board have still to be checked before
switching the electronics on.
The telescope structure was carefully examined and a few loose or bent bolts found on the way were either replaced or tightened. No way to really know if it comes from the earthquake or not... The earthquake clips were also checked and look good. The Right Ascension and Declination pins and
brakes were carefully checked: they are working well.
The telescope hydraulics has been restarted: the gap at the hydraulic pads with pressure on is nominal. The telescope was moved in Right Ascension by hand very slowly over 40 degrees and its motion was found to be very smooth, with no sign of anything bad in the gearbox: a
real relief! The teeth on the drive gear of the horseshoe that were in contact with the gearbox at the time of the earthquake were examined and they look fine. The horseshoe areas that were in contact with the pads at that time are clearly
scratched and show an excursion along the RA axis of around 3.5 cm, similar to the one we can infer from the shaving on the encoder housing (see picture from yesterday below). A similar excursion is seen on the South journal of the RA axis. These surfaces
will be cleaned up tomorrow, but there is no apparent damage bad enough that it would prevent a smooth motion of the telescope.
The Declination encoders were inspected and they look good. The final check will be done once they are really exercised.
Tomorrow, the new encoder assembly will be installed and the telescope moved through its control system. Weather permitting, the shutter should be fully opened: so far, it was checked only open half-way. The MegaCam electronics will be checked. If there is no bad surprise, the telescope could be ready to go with MegaPrime for tomorrow night, with likely the first half of the night spent
checking that pointing and tracking are good and that the telescope is behaving normally. The rest of the night could go to science... So, stay tuned!
At the headquarters, the main remaining issue is related to the computers running the Elixir pipelines and the archives. Some of the machines were badly shaken, and the system is not back and operational yet. A quick fix could be made available quickly if needed, while troubleshooting of the current system is underway.
At the summit, the dome has been realigned and is now back and operational. The dome shutter is working well too. On the telescope side, some checks were made on the overall structure, and so far nothing bad was found on the horseshoe itself. The smashed encoder assembly and the spare one were brought down in the shop in Waimea. The base plate of the assembly is being machined to allow the remounting of the encoder assembly on a different location on the horseshoe track so that the encoder roller avoids the area smashed as the time of the earthquake. The work should be completed soon and the assembly ready to go on the telescope by the middle of the day tomorrow.
WIRCam has been pumped and is now cooling down happily. MegaCam shutter and jukebox are working well. The focal plane has been visually checked through the cryostat window and appears to be intact. MegaCam is being pumped and so far there does not seem to be any leak. Electronics board will be checked before switching the camera on again.
ESPaDOnS looks good in the coudé room.
Tomorrow, the telescope hydraulics will be started as soon as more checks of the structure have been completed. Then the telescope will be moved by hand, carefully cranking the gear box. This remains one of the main question marks: the telescope moved up and down along the RA axis by a couple of centimeters and we don't know how well the gears in the gearbox handled that. Another big question mark concerns the declination encoder: How well did it handle this big shake? It will be looked at once the RA axis has been cleared up. So, stay tuned for more news tomorrow. We don't expect to have anything operational for at least three more nights: even if we can put the telescope back together quickly, engineering will be needed on the sky to check telescope pointing and tracking. If the gearbox or the declination axis have issues, that could take longer!
Looking at the headquarters, you would hardly believe that something happened. Thanks to the hard work of all the Waimea staff not involved in summit work, the offices are now nice and clean. The computers are back on again, and the observatory is again linked to
the world through the Internet. The library looks much better (but for its ceiling), and for now the large conference room is off-limit. The ceiling will have to be redone.
At the summit, the adjustment of the dome is moving ahead nicely. It already moved by 120 degrees and should be operational again tomorrow by the end of the day. The destroyed RA encoder was dismounted, as was its spare. Most of the computers
hosting instruments and data flows are back and working. Telescope main mirror looks good, as does M2 (which is on the floor). Too early to know how MegaPrime is doing. So far, not so bad!