Controlling the atmosphere in Antarctica

Furthering its studies into global atmospheric change by implementing a new VHF radar at the Davis station, Antarctica, is one of many key initiatives the Australian Antarctic Division's (AAD) Atmospheric Sciences Division has scheduled in for this summer.

Yet as researchers pool their concentration into deploying the radar and exploring the atmosphere, the division's technicians are hard at work crafting unique IT control systems which not only run the equipment, but also manage the volumes of information being generated.

The new VHF radar is designed to measure wind conditions in the lower and higher atmospheric layers by registering the wind turbulence present in each atmosphere. In particular, its primary purpose is to read polar mesosphere summer echoes (PMSE) operating on the 55MHz frequency - a collection of wind velocity waves unusually high in both the Arctic and Antarctic regions, which only occur during summer. The mesosphere layer is the outermost layer of the atmosphere, sitting between 80 to 90km away.

Research scientist Damien Murphy says the new VHF radar will work on a similar control system to that already in place for the MF (medium frequency) radar at the Davis Station. The MF instrument measures the middle atmospheric layer and waves operating across the 2MHz band to define wind conditions.

In order to record information from the MF radar, the team, along with South Australian developer ATRAD (Atmospheric Radar Systems) developed two PCs: one Windows NT-based system attached to the radar, and another Linux-based machine, which analyses the data retrieved by the radar and transforms it workable information.

The NT-based machine is interfaced with the radar via a National Instruments login card featuring two drivers. The signals generated and sampled by the radar using its three antenna points are then transferred using this interface. At the end of each data collection period, which is about two minutes, the machine is left with data from a number of time series featuring varying echo strengths.

These data series are then handed over to the second Linux PC using FTP. The Linux machine is also used to set the parameters for the first PC, including changing the height of the range of samples being retrieved by the radar, the gain of each of the radar's receivers, and the number of pulses sent out by the radar into the atmosphere, Murphy said.

Data can be displayed in a variety of formats, some of which are sent through to both the AAD and ATRAD Web sites every couple of hours.

Full credit for the development of both systems should go to ATRAD, Murphy said.

Murphy says the new VHF control system will be largely similar to the MF system currently in place. Work to construct the radar will start in the next two to three weeks, with the control system PCs expected to ship to Antarctica in late November. The team hopes to have the VHF radar fully operational by the end of January.

The control system has also been designed so that the division can look at and control the radar data from its head office in Kingston, Tasmania.

"The way the system is designed, we can reprogram data from anywhere with the Internet," he said.

Despite the harsh climate, Murphy says the PCs weather conditions in the icy region well. Aside from being housed in a heated building, the only other measure taken to insure the equipment operates effectively is by attaching the PCs to UPS in case of a power failure.

Alongside its studies into global atmospheric changes this season, the AAD's atmospheric division will also be conducting specific research into the depletion of the ozone layer, in conjunction with the Bureau of Meteorology. This will involve the use of the AAD's existing Lidar (light detection and ranging) instrument.

The Lidar instrument was developed in Australia by the AAD and the University of Adelaide and first used in Antarctica at the Davis station in 1997. Now a permanent fixture at the station, the Lidar instrument utilises laser technology to record atmospheric conditions. It emits green laser pulses into the atmosphere, which are then scattered by molecules and aerosols in the atmosphere.

According to the AAD, this process allows scientists to "obtain high resolution measurements of temperature, density, wind velocity and aerosol concentration" from the lower stratosphere (at an altitude of 10km) to the mesosphere.

In order to run and operate the instrument, the AAD has attached it to a control system consisting of a mixture of standard and in-house IT applications and infrastructure.

Andrew Klekociuk, a research scientist in the atmospheric sciences program, says the Lidar instrument controls are based on a combination of applications produced by four PCs networked to a central workstation.

The team uses LabVIEW on the PCs to control and process system information. LabVIEW is an applications software program that National Instruments developed, which lets the team create their own control applications and graphical user interfaces for interacting with the Lidar instrument, he said.

The four PCs are built around an alpha workstation, which uses interactive data language (IDL) to then analyse and display data retrieved by the PCs from the Lidar instrument. IDL was developed by Research Systems and is mainly used by astrophysicists to retrieve data from scientific equipment.

As the central control agent, the workstation also tells the PCs what information to retrieve by generating and deploying jobs. These jobs are transmitted through TCP/IP and run in a loop between the PCs, with data collection occurring at about 10 minute intervals. Klekociuk said the process can be set to any time cycle, but that 10 minutes was reflective of the period of time that atmospheric waves naturally occur.

Once the jobs have been issued and raw data is recorded, the information is passed back to the workstation, which then binds the files together and collates the information into an interface the operators can interpret and interact with.

From these files, the operator can study the raw data on laser movement versus the altitude and spectrum of light, measure temperatures through the spectrometer, and take notes of various other log data information.

Klekociuk says the team is storing pretty much anything, as the information can be useful to analyse if future problems occur.

Information is then saved in NetCDF format, a standard method of representing scientific data originally developed by NASA. Because it is an internationally recognised format, the department can ship data conveyed in NetCDF around the world, Klekociuk said.

"We have just sent files to the Jet Propulsion Laboratory in the US to check algorithms we used in setting up the laser for example," he said.

Like the MF radar, the Lidar controls system can also be manipulated remotely.

Klekociuk says while the system's technology is "frozen" in 1998, the software and applications can be upgraded as required. At this stage though, the team doesn't need to fix what's not broken, he said.

"We've chosen applications that are widely used, and stable," he said.

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