The equipment on the ING Seeing Tower needs to be protected from bad weather and the remote-controlled Dome is the first line of defence. The Dome itself is vulnerable to ice and snow, and also to high winds. The priority is therefore to avoid opening in windy or icy conditions and prevent accidental opening during storms, by clamping the top clam shells shut.

This page is to clarify weather conditions under which the ING Seeing equipment can be safely operated and to list safety rules for the protection of personnel.

Protecting Equipment - Recommendations

• Wind: Maximum wind is 50 km/h, on the JKT anemometer. This was reduced from 60 km/h in January 2021.
  • It is not necessary to close the DIMM dome immediately after seeing one measurement above 50 km/h.
  • Wind speed exceeding 50 km/h more than twice during half an hour (approximately) is probably a better recommendation for closing the DIMM dome.
  • This must be decided by the operator and carried out manually.
  • At winds above 40 km/h, approx. RoboDIMM should be parked and not used, to avoid losing pointing.
  • R2D2 is more resistant to wind. If TNG online data is updating, R2D2 should be safe to use. If data are frequently interrupted or higher than 1.5 arcseconds, R2D2 should be shut down and the dome closed.
  • Wind Gust is peak wind speed over a shorter time, but if this frequently exceeds 70 km/h, R2D2 may lose data, in which case the dome should be closed.
  • The WHT anemometer is sheltered from certain wind directions and is not a reliable indicator of wind speed. Use the JKT data.
• Maximum relative humidity: 80% (on the seeing tower hygrometer). The tower PLC is programmed to close automatically above 90% RH but the operator can close earlier to give full attention to the safe operation of WHT.
• Minimum temperature: 2 deg Celsius. (Increased from 0 deg in Jan 2021). The dome should not be opened below this temperature and should be closed if it is reached while open. This must be done manually by the OSA, as there is no automatic closure for low temperatures. This is to avoid damaging the motors while operating in resistance to ice.
• Lightning: due to the installation of surge protection in the electrical distribution board of the DIMM tower, it is no longer considered necessary to take preventive measures in the case of electrical storms. There is no need to shut down or plug out PCs. It may help to disconnect network cables internally.
• Forecast of Ice or Storm: if icy or stormy conditions are expected, clamps can be applied to the inside of the dome. This releases strain on the drive belts and avoids damage through accidental opening. The emergency stop button in the Dome should be pressed when clamps are in place.
  • During weekdays clamping should be carried out by daytime staff, preferably by request from OSA, who should be aware of the weather forecast. This will allow clamping well before conditions become hazardous for dome access.
  • During weekends the OSA should follow rules (below) for access to Dimm Tower.
  • Two clamps are provided in the Tower and should be applied over the metal plates as shown in the photo (below).
  • The clamp can be closed over the plates by sliding the mobile part of the clamp upward until both sides are touching the plates.
  • The red handle should be tightened clockwise until the black insulation is squeezed by about 1 cm.
• Following Ice or Storm (Jan 2021)
  • Experience shows that a night below 2 degrees C or heavy rain can make the rubber seals, on the edges of the dome shells, stick together. This can stop the dome motors from opening the dome, and could lead to it opening unitentionally later.
  • When weather permits opening again, the first opening should be carried out locally from the tower, usually by day staff (see rules below) to check whether the seals are sticking.
  • The OSA should ask daytime staff to do this check and report back.

  

  Protecting ING Personnel - Rules

  • The Tower must not be accessed without informing another member of staff who is on site, no matter the weather or daylight conditions.
  • Note that the Lone Worker Alarm does not work outside the telescope buildings and is not a valid safety measure for work on the DIMM tower. Therefore a mobile phone or radio is needed, to be contactable by the other staff member while outside.
  • If the walkway or steps to the Tower are likely to be affected by ice, you must never attempt to access them.
  • In other bad weather conditions (wet or very windy), extra caution should be exercised when accessing the Tower, and only then to carry out essential tasks related to the preservation of the equipment (see above).
  • The trap door should always be closed when working in the Seeing Tower.
  • Care should be taken not to collide with RoboDIMM when entering the tower from the trap door.
  • When working alone on the tower, tell the observer the number of the IP phone (605) on the tower, so that they can contact you in case of a problem. The IP phone in the control room can be contacted on 452 from the tower.
  • Always carry a torch and take care not to snag on cables while moving around in the dark on the Seeing Tower.
  • Be aware that the emergency stop buttons on the tower will disable the dome shell motors.