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Here are some of the articles that have been recently posted to the PASSCAL website:

Batteries for Year Round Polar Programs

Rechargeable batteries:

Rechargeable batteries are used for projects using solar and/or wind charging systems. PASSCAL's Polar Group has used SunXtender AGM batteries by Concord succesfully for many deployments. These batteries, aside from being reliable, offer several advantages. They are sealed and non-spillable, which makes then safer and easier to handle in the field; they have a low self discharge rate, which is important for a low power system, with extended periods of time between charges (arctic conditions); and they are exempt of DOT HazMat requirements (49 CFR Section 173.159) provided that they are shipped in their original package or in a package that satisfies the requirements of 49 CFR 173.159(d).

Vaults for Summer Only Polar Programs

For summer only deployments, either short-period seismometers and geophones or broadband seismometers are typically installed. In the case of short-period sensors or geophones, a “vault” is not required and the instrument is often buried in the snow at a shallow depth and reasonably leveled.  If broadband seismometers are used, a vault needs to be built to hold the instruments. This involves more work as the sensors have to be accurately oriented, leveled and protected from wind noise and thermal changes.  For a detailed description of broadband seismic vaults for polar environments, see the Specialized Polar Equipment section.

Cold-rated Guralp CMG-3T Sensor

The Cold-rated Guralp CMG-3T seismometer is described in detail in the Polar section article "Sensors for Year Round Polar Programs".

Station Enclosure for Summer Only

For summer only deployments, special and costly, heavy insulation is not needed since the temperature at that time of the year remains high enough that the electronic equipment and batteries will continue to operate normally without a heat source.

The PASSCAL Polar Group's summer only enclosures are made of molded,  heavy-duty, lightweight polyethylene on the outside and have closed cell foam liner inside, cut to accommodate the equipment and batteries.  They were designed with portability in mind and their outside dimensions are 24 in x 21 in x 11 in.

To ease deployment, the case was designed to contain all the equipment necessary as long as the sensor is an L28 or smaller.  At the site, only the seismometer needs to be installed and the solar panel needs to be mounted on top of the case.

Solar for Summer Only Enclosure

Summer Only Solar Panels

10W or 20W of solar power are usually sufficient for summer only experiment depending on a typical seismic station load.

IRIS PASSCAL's Polar Group uses both the Suntech STP010 (10W) and the STP020 (20W).  They are both efficient, monocrystalline silicon solar panels and have strong frames.  A mount was designed in house and manufactured specifically for these panels to attached them directly to our  “summer only” enclosures.

Power Box Equipment for Summer Only Enclosure

Solar Charge Controllers

The Solar Charge Controller is responsible to properly charge the batteries when solar energy is available.  The GenaSun GV-4 controller, which is used for summer only experiments,  is a very efficient charge controller that uses the MPPT (Maximum Power Point Tracking) to maximize the power available at the solar panel, increasing the efficiency by 10 to 30% over traditional solar regulators.  It also uses very little power in low or no light conditions.

DASes for Summer Only Polar Programs

Refraction Technology RT-130

The Reftek RT-130 is a 24bit, low power, robust and very portable seismic data recorder.  It is well suited for deployment in harsh climate environment and is easy to program and retrieve data in the field.  It can have 3 or 6 channels and records data on Compact Flash (CF) cards.

Vaults for Year Round Polar Programs

Seismic Sensor Vaults

The type of seismic sensor vault and the amount of sophistication it requires, is dependent on the type of seismometer.  A geophone does not require a “vault” per se, it can be buried in dirt or snow and be kept reasonably level in the process. A sensitive broadband seismometer requires a quiet, temperature stable and level vault.  In the Antarctic two main styles of vaults are used for broadband seismometers:  the rock vault and the snow vault.

The Rock Vault

In rocky environments where digging is nearly impossible, a weatherproof enclosure with a rigid bottom, typically aluminium, is secured to the ground.  The seismometer is then set inside, oriented properly and leveled.

To reduce noise caused by wind, and to thermally stabilize the vault and protect the instrument from flying debris, a double walled dome is placed on top of the vault and anchored to the ground as well.

Power Box Equipment for Year Round Polar Programs

The Extreme-Cold Temperature Power Management Module for Year Round Use

PASSCAL's Polar Group specifically designed a power management module to control the charging and manage the power system in extreme-cold temperature environments. There are two main parts in the power box:  The solar charge controller and the power switcher.  The solar charge controller, as the name implies, takes care of the proper and efficient charging of the batteries when solar energy is available.  The power switcher takes care of switching from the rechargeable batteries to the primary batteries when the rechargeable batteries' voltage dips below a threshold, and switches from the primary batteries to the rechargeable batteries when the rechargeable batteries' voltage gets high enough from solar charging.  Both the charge controller and the power switcher were tested successfully for operation at -55C after having been subjected to -70C for several hours.