STSAT-1 Observes comet C/2001 Q4

FAR-ULTRAVIOLET OBSERVATIONS OF COMET C/2001 Q4 (NEAT) WITH FIMS/SPEAR

Authors:

Lim et al

Abstract:

We present the results of far-ultraviolet observations of comet C/2001 Q4 (NEAT) that were made with the Far-Ultraviolet Imaging Spectrograph on board the Korean satellite STSAT-1. The observations were conducted in two campaigns during its perihelion approach between 2004 May 8 and 15. Based on the scanning mode observations in the wavelength band of 1400-1700 Å, we have constructed an image of the comet with an angular size of 5°×5°, which corresponds to the central coma region. Several important fluorescence emission lines were detected including S I multiplets at 1429 and 1479 Å, C I multiplets at 1561 and 1657 Å, and the CO A1Π-X1Σ+ Fourth Positive system; we have estimated the production rates of the corresponding species from the fluxes of these emission lines. The estimated production rate of CO was Q CO = (2.65 ± 0.63) × 1028 s–1, which is 6.2%-7.4% of the water production rate and is consistent with earlier predictions. The average carbon production rate was estimated to be QC = ~1.59 × 1028 s–1, which is ~60% of the CO production rate. However, the observed carbon profile was steeper than that predicted using the two-component Haser model in the inner coma region, while it was consistent with the model in the outer region. The average sulfur production rate was QS = (4.03±1.03) × 1027 s–1, which corresponds to ~1% of the water production rate.