SCANDI – an all-sky Doppler imager for studies of thermospheric spatial structure

Abstract

Abstract.A new all-sky Fabry-Perot Interferometer called the Scanning Doppler Imager (SCANDI) was built and installed at Longyearbyen in December 2006. Observations have been made of the Doppler shifts and Doppler broadening of the 630 nm airglow and aurora, from which upper thermospheric winds and temperatures are calculated. SCANDI allows measurements over a field-of-view (FOV) with a horizontal radius of nearly 600 km for observations at an altitude of 250 km using a time resolution of 8 min. The instrument provides the ability to observe thermospheric spatial structure within a FOV which overlaps that of the EISCAT Svalbard radar and CUTLASS SuperDARN radars. Coordinating with these instruments provides an important opportunity for studying ion-neutral coupling. The all-sky image is divided into several sectors to provide a horizontal spatial resolution of between 100-300 km. This is a powerful extension in observational capability but requires careful calibration and data analysis, as described here. Two observation modes were used: a fixed and a scanning etalon gap. SCANDI results are corroborated using the Longyearbyen single look direction FPI, and ESR measurements of the ion temperatures. The data show thermospheric temperature gradients of a few Kelvins per kilometre, and a great deal of meso-scale variability on spatial scales of several tens of kilometres.

Neutral thermospheric dynamics observed with two scanning Doppler imagers: 1. Monostatic and bistatic winds

“…Recently, instruments have been deployed which combine all‐sky fore‐optics with separation‐scanned Fabry‐Perot etalons to enable measurement of spectral line profiles of upper‐atmospheric optical emissions from many tens of locations across the sky, simultaneously [ Conde and Smith , 1997, 1998; Griffin et al , 2008; Anderson et al , 2009; Aruliah et al , 2010]. These scanning Doppler imagers (SDI's) have the distinct advantage of sampling the wind field at many tens of locations simultaneously, and are thus able to resolve horizontal spatial structures at high resolution (down to scales of around 100 km or less when observing the 630.0 nm line) without serious distortion due to temporal variation of the wind field.…”

The phases and amplitudes of gravity waves propagating and dissipating in the thermosphere: Application to measurements over Alaska

“…Errors in line‐of‐sight (LOS) wind determination have decreased significantly with the switch to imaging CCD detectors in recent years [ Aruliah et al , 2005; Ford et al , 2006, 2008; Meriwether et al , 2011; Makela et al , 2011]. The advantage of these imaging FPI observations over imaging all‐sky FPI observations [e.g., Conde and Smith , 1995; Conde et al , 2001; Aruliah et al , 2010] during times of auroral activity is the ability to detect small Doppler shifts with errors of only several ms −1 in a given direction. The field‐of‐view (FOV) of FPI observations of the thermospheric region is narrow, typically ∼1°.…”

First observation of thermospheric neutral wind at Chinese Yellow River Station in Ny-Ålesund, Svalbard

“…Aruliah et al [19] mentioned that the high viscosity soothes out small-scale structures. By comparison, the winds of OI 557.7 nm in Figure 4 behave in a more disorderly manner most of the time while winds of OI 630.0 nm in Figure 5 display a tendency for eight-hour cycles with good agreement.…”