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29 April, 2000

T5 Hut and the Science Technician 2 Question 70: How can killer whales kill other whales that are as large as or larger than they are? Continued from 4/28/00... The station's gamma ray counter measures radiation levels in the small, solid parcticles suspended in the atmosphere (aerosols). Filter paper is used to trap these aerosol parcticles from the station's relatively pristine air over three-day periods. Then the filter paper is run through the counter and compared to a neutral sample (a Coleman lantern wick). This week there has been lots of dirt from the station in the filter. The filter needs to be even further away from the station and the ships that dock there. Currently a good west wind will blow dirt kicked up from station activity right into the filter, contaminating the sample with non-aerosol parcticles. The counter's measurements are used to look for radioactives from two sources: 1) natural, which includes upper atmosphere X-ray or UV high-energy photons that produce isotopes with short half lives; and 2) manmade, from nuclear devices detonated in the atmosphere. Since aerosols float in the atmosphere for around six months, the counter is truly looking at worldwide monitoring (including some northern hemisphere areas) of radioactivity levels. Palmer Station monitors the yearly ozone hole over Antarctica by measuring UV radiation. The level of UV radiation is measured every 15 minutes during daylight, scanning the entire spectrum between 280 and 605 nm one wavelength at a time. The hole appears as an increase in the 290-320nm range of UVB. Ozone season is mid-August to late October. The UV monitor's sensor is mounted on the roof of the hut and attracts Snowy Sheathbills. There have been problems with the birds pecking it and sitting on it--which can damage or block the sensor. The science tech is currently trying to find an effective avian deterrent unit. The science technician also deals with air sampling, data maintenance for the VLF project (see 4/20 journal), collecting various types of satellite information for NOAA, NASA, and SCRIPPS, and local signal correction for Global Positioning Systems (GPS). Currently the satellite-based GPS's signals have an error programed into them. At midnight on 1 May the U.S. government will reduce that intentional error. This error is called a selective availability degradation, and it is meant to limit the precision of GPS signals so they can't be used against U.S. interests. U.S. military, Coast Guard and other groups have equipment to receive a signal that corrects local GPS error so they know exactly where they are. Without the error, a single receiver could correctly identify a location with an accuracy of 10 meters (within a tennis court size area). With the error, the best a single GPS receiver can do is locate an area within the size of a football field. The science tech maintains the station's very accurate backpack-mounted GPS unit. It receives corrections to cancel the error, giving it high quality data accurate to within 1 meter. The researchers use the unit to map the size of the penguin colony over time. All the researcher has to do is walk around the limits of the colony, and a signal from the backpack goes into the carry-along hard drive every 15 seconds, logging the backpack's position accurately. This information is later transformed into a yearly map. The backpack unit has also been used to track the ice edge retreat of Anvers Island's glacial sheet, currently estimated to be around 10 m per year. Answer 69: In general, toothed whales eat fish and squid, but there are differences. Arnoux's beaked whale, a deep diver, eats mostly squid, while as much as 50% of the diet of the southern bottlenose whale is krill. Less is known about the long-finned pilot whale and the hourglass dolphin, but fish and squid appear to make up most of their diet.


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