The actuators are back on the unit!

By the end of the day (Wed Jun 26 - 21:00 local time), all the actuators were back on the unit.

A great job by Michael Wagner and Juan-Carlos Guerra! 

As the insertion depth of the actuators is slightly changing as more are added, this depth will be checked for each actuator now that they are all installed.

Below are a few pictures of the whole process...

Staged actuators ready to go...

Another ~150 to go...

The overall setup: the clean actuators are nicely laid out on the table, the adaptive secondary unit is in the back, and the fresh shell (TS4) can be seen on the left quietly waiting to go back on the unit.

TS4 on the mountain!

A short post to let you know that the thin shell number 4 made it to the mountain. It is in one piece, quietly waiting to be integrated to the AdSec unit in the clean room.

TS3 is now in Tucson. It will be stored there waiting for a decision on its fate, which will be taken at a later date: there are more pressing matters to attend to at this moment in time!

Thin Shell #4 starting its journey...

Today, the thin shell  number 4  (TS4) is leaving the Mirror Lab Sunnyside coating facility, where it was stored following its aluminization a couple of months ago.

Here are the main steps of its journey:

• Jun 18: loading at Sunnyside and travel to the MGIO base camp in Safford
• Jun 19: travel to the summit with UAPD escort (access road freshly graded). TS4 unpacked and checked, TS3 packed...
• Jun 20: travel from the summit to Sunnyside with TS3

If you wonder how does TS4 look like, here are a couple of pictures...

G. Brusa looking at the freshly coated shell

 The back of the shell with its magnets...

More cleaning done...

- All the actuators have been removed and the actuator holes have been cleaned successfully with the exception of the one initially damaged during the Arcetri glycol incident which seems irrecoverable. 

- The actuators have been cleaned with isopropyl alcohol (coil tip, board, spring contacts and DB-side contacts). The actuators have been visually inspected to select those with problems. Fifteen have issues, with six of them to be replaced by spares. The others will be repaired.

   A rusted actuator tip. The rust can be easily removed in thickness by brushing the tip and no damage is shown on the copper (rust comes from magnets).

- Preparation is being made for the transportation of the recently aluminized thin shell #4 (TS4) from the Sunnyside Mirror Coating Lab to the mountain next week. The access road to the observatory will be graded just before the transportation to offer the shell a ride as smooth as possible.

- In parallel, work is done to accommodate TS4, which is not a real twin of the current shell.

A planning of the many steps to come will be available on June 17th.

The long road to recovery

From Thursday's, it was found that the actuator contacts in the actuator holes of the reference body showed significant oxidization where there were problematic actuators.   

On Friday, a number of apparently good actuators were removed to check if that oxidization was present there as well.  Approximately 10% of them showed damage and extrapolating that to the complete shell means that operational performance would be impacted.   

Thus, the decision has been made to remove all the actuators, inspect the contacts and clean where necessary.  We should end up with contact oxidization cleaned, distribution boards cleaned and remounted as well as the astatic levers and cables etc.. at the end of the visit of our Arcetri colleagues (A. Riccardi and M. Xompero).

Reinstallation of the actuators, component checkout and reintegration of the shell, check out of all the boards and contacts,adjustment of the membrane shim, installation of TS4 board (currently in transit from Arcetri to LBTO), shell cleaning. shell mounting to the reference body, initial tests of reassembled unit, check-out of the AdSec unit in the lab on the installation mount to verify system performance, installation of the AdSec unit into the hub and the hub back onto DX, alignment of the AdSec unit and calibration with the 4D interferometer to build a new interaction matrix, system alignment calibration with retro-reflector for both FLAO and LBTI systems, and on-sky commissioning are some of the tasks to accomplish in the weeks to come. What a list!

Stay tuned as we walk this long road to recovery...

Assessing and cleaning...

Another good day (Thursday, June 6) of work in the clean room around the disassembled AdSec-DX.

On the reference side

- Distribution boards. The back of the boards with contamination on the front did not show any problem. Boards were successfully cleaned (ultrasound bath). See before-after picture below.

 

- Actuators. Of the 40 actuators showing signs of rust, only one showed contamination on the actuator board and another one was found with a single spring contact.Both will be replaced. 

-   - Holes in the reference. For 15 of these 40 actuators, the hole in the reference showed some sign of contamination (white or black contaminant or oxidation).

On the shell side

- Attempts were made to remove the white contaminant on the back of the shell with alcohol, acetone and distilled water, to no avail, as seen on the before/after cleaning picture below.

- Preparation is made for the transport of the spare shell to the observatory.

Assessing the status of the shell

On Wednesday (June 5), most of the work was devoted to an assessment of the damage on the shell.

•  Twenty magnets are rusted and another twelve slightly rusted.

•   For more than thirty actuators, at least 25%of the capacitive sensor area on the shell lost its coating, resulting in the loss of continuity even for an AC signal.

 The performance of the shell will be affected severely, especially due to the clustering of the actuators exhibiting coating losses shown seen below.

It is therefore likely that we will use our spare shell, TS#4, freshly aluminized and still in Tucson... Meanwhile, the current shell, TS#3, will be cleaned up and used to check the electronics of the secondary system.

• Distribution boards were examined for possible water damage. Ten spots have been identified and boards will be cleaned and tested. There is only a limited supply of spare boards, so hopefully most of them will still work...

Involved on Mt Graham: A. Riccardi, J.-C. Guerra, M. Wagner, M. Xompero

A first look at the "dropped" shell

Today, the shell was lowered and safely "dropped"... Initial observations show some rusted magnets, indicating that water came in from the top, and some damaged capacitive sensors. 

A more thorough investigation of the shell reference body/actuator status will be made over the next few days. More to come...

 

 

 The "dropped" shell

 

Close-up on rusted magnets

 

 

Contaminant seen here at the edge of the shell 

Kudos to our team of the day... G. Brusa, J.C. Guerra, M. Montoya, and R. Sosa