CTIO Weather Station renewal E. Bustos La Serena, Aug. 28th 2009

Summary Current system on Tololo is a temporary solution build after lightning strike on Sept. 2008 The Weather Tower (24m) needs a replacement urgently More reliable measurements are required Haga clic para agregar notas

Background Wind speed is one the most important weather measurements for telescope operations. The reliable measurement under bad weather conditions is a must. According with our experience on Site Testing, mechanical wind sensors are not reliable under snow and rain conditions on astronomical sites and on observatories. They have to be check once per month and usually they have to be replaced almost every winter because are destroyed or damaged by dust or rusted. The ultrasonic wind sensor technology has demonstrated to be very reliable and usually these sensors don’t need service in years. The state-of-the-art of weather sensors is the smart sensors technology. These are sensors with embedded communication protocols and they can be connected directly to the computer without a logger. This is an advantage when a calibration or a quick check is required and when software interface is developed.

Background Nowadays weather multi-sensors are been developed. These units can measure virtually all weather variables in one unit. A single operator can install a new unit in minutes by connecting just one cable. CTIO requires a new weather station tower soon, because the tower used as a temporary location has to be removed in 2 months because a new telescope will be installed in the Columbia Dome. By other hand, the current CTIO weather tower reached the end of its life and it can’t be used anymore. The current tower altitude is 24 meters, but only the last 12 meters are actually above the Tololo summit. In order to research Blanco Dome condition, the weather sensors have to be at least at the altitude of the Blanco Primary Mirror. So the new tower must be more than 12m above the summit.

Sensors proposed System with no moving parts Redundancy for wind measurements Smart sensors: embedded serial protocol without dataloggers & accessories. Low power consumption (suitable for solar power) Easy installation and maintenance: one bolt clamp, installation without extra cables. Haga clic para agregar notas

WXT520: multiparameter transmiter Temperature Pressure R. Humidity Wind speed and direction Rain Haga clic para agregar notas Vaisala WXT520

WS425: Ultrasonic Wind Sensor Very reliable and free of maintenance for years. With heater option for better behavior under snow conditions Haga clic para agregar notas Vaisala WS425

New Tower A new 40 meters tower is needed: Sensors will be at the same height of Blanco Primary mirror (~24 meters) CTIO Telescopes visibility is not blocked: 1m Tel. minimum observation angle will be ~27o 28 meters effective height (not 12m) Haga clic para agregar notas

40m Tower

40m Tower

Power and Communications Wireless communications Reduce installation and maintenance costs Reduce effects of lightning strikes Solar Power System (optional) Low installation costs Reduce effects of lightning and surge events Solar panels and cabinet available

Cost WXT520: multiparameter sensor(*) 2500 WS425: ultrasonic wind sensor (**) 2850 Surge protectors for sensors 650 Wireless communication equipment 900 Grounding system + sensor/communications housing 1300 Acquisition Computer (rack-mounted) Total 10700 Solar power system (***) 2600 Total with the optional Solar Power System 13300 Haga clic para agregar notas (*) including accessories (**) including accessories and a wind field verifier (***) includes AGM batteries, load regulator (PV panels and battery housing are already available)

Work time estimation 1 man/week for specification and purchasing 4 man/week for tower installation by contractors 1 man/week for cabling and sensor installation 1 man/week for interface development and web integration Haga clic para agregar notas

Comparative chart Monitor Sensors Pty. Is the Australian brand of equipment used on site testing by CTIO and TMT, they are in use in LSST site and SOAR. Both the wind speed and the wind direction sensors are mechanicals There are 2 types of anemometers: AN2 and AN3. They are smart sensors and the communications is based on a custom serial protocol Monibus. To transform in a RS232 protocol an interface is required. The rainfall sensor has moving parts. RM Young is the brand used by the CTIO Weather Station. Those sensors listed were selected because they have similar specs with the used and proposed sensors. Not all the sensors are 都mart� so in case of the 41282 Temperature/Humidity sensors and the 50202 precipitation gauge they require a logger. Both the B. Pressure sensor 61202 and the Ultrasonic Wind sensor 85004 have serial communication. Monitor Sensors Pty. has been used by CTIO & TMT Site Testing RM Young is the brand used by CTIO in the old weather station.