We tested the movement of the dichroic and fold mirror both at Zenith and horizon using the DichroicServiceController
. Few times one optic or the other failed to exit from limit switch (both working or parking). In these cases we checked that the O0 output was properly activated.
In the afternoon we started to setup and align a flat mirror that identifies the axis of the LUCI rotator. We used the laser tracker head to shine a laser beam onto the mirror reflecting it on the dome wall:
Around 17:00 local time, with the Handover from ARGOS day time activities to the Telescope night time operation LBC red moved into the deployed DX ARGOS swing arm. The T-gusset of the ARGOS swing arm got damaged.
Detailed information can be found here:
See also Gustavo's email of 25/04/2015:
This evening we had an incident where the DX Cal Swingarm was left inadvertently deployed at handover.
At the beginning of night operations, the TO proceeded to deploy the DX LBC swingarm and it collided with the ARGOS swingarm, resulting in damage to tip of the swingarm (the "gusset").
There was no indication to the TO that the ARGOS swingarm was deployed, and it was me who realized that nobody had retracted the swingarm.
After parking the ARGOS swingarm, we took the telescope to horizon and Wolfgang and I went up to assess the damage. The gusset was badly bent. Wolfgang removed the optics unit and the harbor. There was no apparent damage to the optics unit, but a more thorough inspection should take place.
Also, tomorrow we will do a closer inspection of the swingarm itself.
Attached are pictures showing the damage to the gusset, taken during our inspection.
Jeff and Elliott also checked LBC, and did not find any issues, other than some scratches on the surface of the LBC hub.
As usual in these incidents, there was a chain of events that caused the collision:
- Failure of the ARGOS team to retract the Cal swingarm after being done with its use.
- Failure to notice that the Cal swingarm was deployed before handing over the telescope to Operations.
- Most important, failure of the interlock system, which should have prevented the deployment of the LBC swingarm.
This last cause is the most critical, as we rely on the interlock being the last line of defense. We will certainly investigate why the interlock did not work as expected, and will fix it.
The incident has been reported internally at the LBT by the TO (Geno) as IT#5549 (https://lbt.issuetrak.com/CSIssue_View.asp?IssueNbr=5549). Further developments will be reported there.
I'm sorry to be the bearer of these bad news. Hopefully we will be able to come up with a solution that minimizes the impact to the commissioning.