Global ultraviolet imager (GUVI): measuring composition and energy inputs for the NASA Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission

Abstract

The Global Ultraviolet Imager (GUVI) on the NASA Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission will determine the variability in thermospheric composition, and its response to auroral inputs as well as measuring those inputs. GUVI is the result of twenty years of work in designing large field of regard far ultraviolet (1 10 -1 80 nm) imagers for spaceflight. These systems are based on the concept of a horizon-to-horizon "monochromatic" imager. The field of view of a spectrograph is swept from horizon to horizon using a scan mirror. The spectrograph uses a grating to spectrally disperse the light. A two-dimensional detector is used to record spatial and spectral information simultaneously. Images are obtained at discrete wavelengths without the use of filters; this reduces if not eliminates much of the concern about instrumental bandpasses, out-of-band rejection, and characterization of filter responses. Onboard processing is used to bin the spectral information into "colors" thereby reducing the overall data rate required. The spectral bandpass is chosen to lie in the far ultraviolet so that the sunlit and dark aurora can be imaged. We review the instrument's as delivered performance and the TIMED science requirments. TIMED will be launched May 18, 2000 and will inaugurate the Solar-Terrestrial Connections program at NASA.

Thermospheric Density and Wind Determination from Satellite Dynamics

“…The TIMED (Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics) mission, launched in December 2001, carries the GUVI (Global Ultraviolet Imager) instrument [Paxton et al, 1999], as part of a suite of instruments to study the charged and neutral particles in the altitude range of 60-180 km, and the influence of solar radiation on this region. The GUVI instrument images the dayside airglow in the upper atmosphere in order to derive temperature and composition profiles.…”

“…These recent missions have also introduced calibration techniques to account for the effects of instrument degradation. Such missions include UARS [Reber et al, 1993], launched in 1991, SOHO [Domingo et al, 1995], launched in 1995, TIMED [Paxton et al, 1999], launched in 2001 and SORCE [Rottman, 2005], launched in 2003.…”

On the solar cycle variation of the winter anomaly

“…They were measured by the Global Ultraviolet Imager (GUVI) instrument [Paxton et al, 1999] that flew on board the thermosphere-ionosphere-mesosphere electrodynamics (http://www.timed.jhuapl.edu/WWW/index.php) satellite. This paper will use these data to describe the evolution of the winter anomaly from 2001 to 2011, and provide a possible explanation for this solar cycle variation of the winter anomaly.…”

Estimation of electron densities in the lower thermosphere from GUVI 135.6 nm tomographic inversions in support of SpreadFEx

“…These wavelength intervals nominally correspond to H + 121.6 nm, O + 130.4 nm, O + 135.6 nm, and N 2 Lyman-Birge-Hopfield bands 140 to 150 nm and 165 to 180 nm. The instrument consists of a scan mirror feeding a parabolic telescope and Rowland circle spectrograph, with a wedge-and-strip detector at the focal plane (Paxton et al, 1999).…”