Preliminary Results of Polar Season Measurements by the Hot Oxygen Doppler Imager (HODI)

The Hot Oxygen Doppler Imager (HODI) is a fixed-gap Fabry-Perot interferometer which was deployed during the 2022-2023 polar night observing season to the Kjell Henrikson Observatory (KHO) on Spitsbergen at Longyearbyen. The HODI ICOS-make etalon is 15cm in diameter and was combined with an apochromatic lens assembly from Keo Scientific to focus the outer rings of the pattern. HODI was deployed with a 732 +/- .5 nm optical filter whose bandpass allowed for the transmission of both thermospheric O+ doublet (731.904,732.012 (Whiter et al., 2014)) emission lines as well as the Lamb-split mesospheric OH line at 731.62 (Phillips et al., 2004). One of the two Lamb-split OH peaks is isolated from the O+ doublet while the second is collocated. Isolated OH measurements free from the O+ doublet taken at the Jenny Jump Observatory (JJO) in New Jersey before deployment to KHO allowed for a linear relationship between these peaks to be determined. This relationship was utilized to extract the OH contamination from the O+ peak. We present in this poster the algorithm for OH removal as well as first results of the analysis of HODI O+ doublet winds and temperatures taken over Svalbard which included a joint experiment between the EISCAT incoherent scatter radar at Longyearbyen and HODI. Initial results show low, moderate, and high intensity regimes for the O+ doublet. These regimes likely represent times when the O+ is excited by EUV solar radiation (low intensity), soft electron drizzle (<~200 eV), or neither are present (i.e. low solar zenith nightside measurements with minimal precipitation). The case of both being present is certainly likely during dayside measurements. Our algorithm performs well in moderate intensity regime. During what is assumed to be electron drizzle excitation the O+ peak intensity overcomes the isolated OH peak and invalidates the algorithm. It may be possible to ignore the OH contamination at such times due to the drastic intensity differences (~6 O+/OH intensity). Ion temperatures recovered are nominally of the order of ~1200 Kelvin and commonly show gradients in the zonal directions. Future work involves theoretical investigations of how much error ignorance of this contamination will introduce into the recovered winds and temperatures. Analysis of the mesospheric OH winds, temperatures, and intensities may also allow for the creation of a local empirical representation of these parameters above KHO. The intensities of this model would be calibrated with the Silver Bullet (Sigernes et al., 2003) and HiTIES (Whiter et al., 2014) instrument datasets. This model would be utilized to remove the OH contamination as well as be distributed to the larger scientific community and instrument operators at KHO.