Secondary calibration standards referenced to primary gravimetric standards were prepared in the laboratory and shipped to the sites. In 1991, the systems were modified for sampling every half hour. Calibration and environmental samples were alternated to increase the environmental sampling frequency from three hours to one hour. Since the establishment of these programs, many new compounds have been added to the list of those measured and analyzed by the HATS group.
CATS systems are now in place at all five of the RITS field sites.
As of October 2000 the RITS system at Barrow has been completely shut down, while the systems at Niwot Ridge and South Pole continue to run all available channels. At Mauna Loa and Cape Matatula, two of the three available RITS channels have been turned off. Those parts of the RITS program still in operation remain so because of unreconciled discontinuities between the RITS and CATS measurements. In order to insure the best possible transition from RITS to CATS, the RITS systems will not be shut down completely until all such issues have been resolved. Our current aim is to have the RITS program offline by the time South Pole closes for winter in February 2001.