Variability of the HCN (3–2) line over time in comet C/2001 Q4 (NEAT) obtained by the AOSA (left panel), AOSB (middle panel), and CTSB (right panel) spectrometers from UT 7.92–8.05 May 2004. All the spectra have been interpolated smoothly between data points for clarity. The CTSB spectra have been resampled to a 380 kHz resolution per channel with a rectangular window function. Each individual spectrum represents a 6-min scan excluding the spectra, where the system temperature of the receiver deviates more that 1-σ from the mean system temperature. The sampled color scale corresponds to the time of the observation and runs from blue to red.