NOTE 20211227: On the 25th Dec 2021, the authorities have declared finished the eruptive process of the volcano in La Palma, but the experts have noted that the activity underground still goes on and the emergency state is still on, so we should continue with the procedure below in which some of the conditions have been relaxed according to the current situation.
NOTE 20211220: The volcano is still active (at a low level), so for a few more days we should continue to follow the procedure below which has been modified according to the current situation.
The possibility of presence of volcano ash in the ORM may change in short time scales. During the time the volcano is active, and until the situation comes back to normal, it will be necessary to continuously monitor the general conditions in La Palma and in particular at the ORM, previous, during and after the observing night, for deciding if and when to open and closing the INT dome, avoiding that the telescope and instruments are affected by the volcano ash.
Below there is a guideline to operate the INT while the volcano is active. Please read it thoroughly before operate the INT. Note that some weather limits and operations constraints have changed from normal operations.
This guidelines will be edited as needed and modifications will be notified by email, but please revisit this page previously to your observing night. Do not hesitate to ask if you have any question.
This guideline was made with the contribution of T&I (Diego Cano, Roberto Martinez and Carlos Martin) and astro-group staff.
- Overview
- Criteria used by the TO when deciding whether to open the dome
- When to close the dome
- How to open the dome
- How to close the dome and telescope
- Other useful information
1. Overview
- Until the situation is more stable no visitor astronomers are allowed in the INT. The observations, whenever is possible to open the dome, will be carried out by the INT students. The PIs are being informed by Cecilia. So far, there are service observations are planned until the end of Jan 2022.
- The INT may open every night (weather and ash allowing), still following the volcano protocol as described in this page.
- The students who are in the roster every night (as seen in the on-line Schedule) should plan go to the INT. Note that NO email will be send authorising the telescope to be opened daily. Communication will only be send, if for some exceptional reason, no student should go to ORM.
- A TO must be at the ORM. Only if observations are canceled for a long time, the presence of a TO in the ORM can be re-examined.
- The INT will only open if there is an INT student to do the observations.
- The INT will be opened only after the explicit authorisation of the TO.
- The decision for opening the dome should be biased towards the precaution side: If there is any doubt about whether to open or not, it should not to be opened.
- The dome should be closed if any of the criteria for opening the dome (described in the following section) are no longer satisfied.
- If ash falls during the afternoon or night report it should be reported in the usual FR database (stating if the dome was open or closed during the event). The dome must not be opened again until the ops-team have reviewed the situation and any required cleaning activities have been carried out (these will be logged in the fault report).
2. Criteria used by the TO when deciding whether to open the dome
If you are at the ORM, and the TO is evaluating to open the INT, it is because there was no previous warning that prevents to open it. But the conditions may change, therefore, we must rely on the assessment on site at every moment. Below is a guideline for the checks the TO must do before opening. The TO needs to explicitly authorise the opening of the INT. The INT students should not open without the TO's explicit consent.
The TO will decide about open the dome taking into account the following:
- Check the FR database and the INT log book for information about the previous events and day works at the INT.
- Check the real time conditions on site:
- Check the wind direction at ORM.
The volcano is still active (at a low level), we should continue to close the INT dome when there is a strong wind from the south (to allow any remaining airborne ash to dissipate).
But in the cases where the wind is from the south with speeds of only a few km/h (less than 10 km/h), then the dome could be open as long as we check regularly while the telescope remains open that ash is not reaching the ORM and the INT (check the water-bottle "ash detectors",
the dust meters, the surfaces in the INT terrace, activity at the other telescopes,
etc.), and in the case of any doubt, as always, close the dome.
- Check the dust monitors, the INT and WHT should measure concentrations in suspension below 25 ug/m^3 and the TNG below 50 ug/m^3.
Note: GTC dust monitor shows short lived peaks above 50 ug/m^3. These probably indicate local dust stirred up by strong winds. This should be ignored if all the other indicators in this page are fine.
- Check the 'ash detector detector' device ( a plastic bottle inside a brick) on the left side of the INT terrace (accessing from the door in the control room). This device will be checked and cleaned daily to detect new volcanic ash fall. If ash is detected there before opening do not open the dome and report it in a FR. The dome cannot be opened again until the revision by the OPS-mechanical team has been done and/or the requested cleaning operation of the dome is completed.
During the night the INT student and the TO (until goes to bed) have to monitor the conditions continuously. The TO will also monitor them until goes to bed. As usual, the TO should communicate to the INT student when goes to bed. After the TO final call the responsibility to have a closed check of the conditions relies on the INT student. During the night if the INT student is doubting about the presence of ash at the ORM ,first should close the dome and then contact the TO.
The dome should not be reopened without the TO explicit authorisation.
In the same way, if the TO went to bed when the dome had not been opened yet,
the dome should not be opened by the INT student without the TO explicit authorisation.
It is very important to keep on checking the conditions during the night. Besides the above mentioned checks, you also can go outside and check with a torch if no ash is visible in the torch beam. Also feel if the air is clean.
3. When to close the dome
• The dome should be closed if any of the criteria for opening the dome are no longer satisfied.
The TO or the INT student (if the TO has already gone to bed) is responsible for monitoring the conditions.
• If, for any reason, you have any doubt about the safety of the telescope.
• If you see other telescopes are closing.
If you close due to the presence of ash do not open again that night.
Remember that in the current situation, safety of the telescope and instrument is more important than loosing observing time.
4. How to open the dome
- Before opening the telescope rotate the dome a few degrees (~ 50 deg) in both directions so possible loose particles may fall.
Turn on the speakers and pay special attention to unusual noises when rotating the dome. Do not keep rotating if sound is not familiar (ask the TO for advice).
- Point the dome shutter in the opposite direction to the prevalent wind (with the shutter downwind). E.g. if the wind is coming from the North the shutter should be in the south (dome ~ 180 deg).
- For IDS set Mount PA at 180 degree to reduce the cryostat spilling LN2 when the telescope is in access park.
Note: Even with the Mount PA at 180 deg it can be spill of LN2 from the IDS cryostat (specially if it was filled not long ago) threrefore, it is important to keep a safe distance from the cryostat when the telescope is moved to access park.
- Set the telescope in access park position.
- Open the shutter. Then open the petals.
Pay special attention to unusual noises when opening the shutter and petals. If you notice unusual sounds ask the TO for advice.
- DO NOT open the south doors during the whole night.
- DO NOT turn on the dome fans during the whole night.
- Do not use the lower shutter.
5. How to close the dome and telescope
- Point the dome shutter in the opposite direction to the prevalent wind (with the shutter downwind). E.g. if the wind is coming from the North the shutter should be in the south.
- Set the telescope in access park position.
- Close the petals. Then close the shutter.
- Please go to the dome and double check that the shutter is properly closed (e.i. no light is filtering horizontally in the dome shutter aperture).
- Leave the shutter in the opposite direction to the prevalent wind (with the shutter downwind). E.g. if the wind is coming from the North the shutter should be in the south.
6. Other useful information
