Selection of FUV auroral imagers for satellite missions

Abstract

A survey of previously flown and recently designed FUV auroral imagers is presented in conjunction with selection criteria to optimize the potential scientific impact of future satellite‐based FUV auroral observations. The selection of the appropriate suppressive imager is ultimately broken down to four field‐of‐view categories: (1) less than 10°, (2) 10° to 16°, (3) 16° to 24°, and (4) greater than 24°. The determination of the field of view follows as a necessary consequence of the orbit of the satellite, which is often imposed by the mission. The first category of imagers has a wide range of available choices, the second and third categories have a couple of options each where a distinction is made between narrow and wide aggregate filter bandwidth, and the fourth category is limited to on‐axis designs introduced by the authors. High‐resolution imaging is possible up to 50° field of view with the class of imager design first presented in this paper.

Photon Counting Imaging with Low Noise and a Wide Dynamic Range for Aurora Observations

“…The intensity of LBH aurora radiation in polar dayglow conditions is usually greater than 10 k Rayleigh. Meanwhile, the intensity in Earth’s polar caps can be as low as 100 Rayleigh [ 8 , 11 ]. To accurately obtain the aurora morphological distribution over time and space, the detection system must accommodate not only intense radiation, but also weak signals with a wide dynamic response [ 12 ].…”

Auroral Structure and Dynamics From GOLD

“…Therefore, it is possible to use the ratio of the intensities of the shorter wavelengths to the longer wavelengths (within the FUV band) to estimate the altitude at which the emissions are coming from and hence the characteristic (average) energy of the precipitating electrons (Unick et al, 2016). The total intensity of the aurora within these bands is considered to be proportional to the total electron flux (Unick et al, 2016); however, it is not as straightforward as it is with the 427.8 nm N + 2 emissions (Rees & Luckey, 1974) in the visible (Murphree, 1998). Quantifying the total energy influx into the aurora and the average energy of the precipitating electrons is fundamental to characterizing the aurora and its effects on the thermosphere, including ionospheric conductivity.…”

“…The atmospheric absorption of these FUV auroral emissions is also dependent on wavelength and (within the GOLD passband) the shorter wavelengths are more absorbed than the longer wavelengths. Therefore, it is possible to use the ratio of the intensities of the shorter wavelengths to the longer wavelengths (within the FUV band) to estimate the altitude at which the emissions are coming from and hence the characteristic (average) energy of the precipitating electrons (Unick et al, ). The total intensity of the aurora within these bands is considered to be proportional to the total electron flux (Unick et al, ); however, it is not as straightforward as it is with the 427.8 nm N emissions (Rees & Luckey, ) in the visible (Murphree, ).…”

Data‐derived optimization of sensitivity requirements for upcoming auroral imaging missions

“…The scientific productivity of a satellite‐borne auroral imaging camera depends on the characteristics of the mission orbit as well as camera performance parameters; such as spatial and temporal resolution, the spectral band, the sensitivity, and the field of view [ Unick et al , ]. In the preceding paper on the subject [ Uritsky et al , ], we have presented a statistical analysis of short‐living auroral forms observed by the Ultraviolet Imager (UVI) on board the POLAR spacecraft [ Torr et al , ].…”