The Imager for Sprites and Upper Atmospheric Lightning (ISUAL). Issue 8 (3rd August 2016)

• Record Type: Journal Article
• Authors: Frey, H. U.; Mende, S. B.; Harris, S. E.; Heetderks, H.; Takahashi, Y.; Su, H.‐T.; Hsu, R.‐R.; Chen, A. B.; Fukunishi, H.; Chang, Y.‐S.; Lee, L.‐C.
• Is Part Of: Journal of geophysical research. Volume 121:Issue 8(2016:Aug.)
• Page Start: 8134
• Page End: 8145
• Publication Date: 2016-08-03
• Subjects: ISUAL -- TLE -- sprites -- elves -- space‐based observation; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2016JA022616
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: The Imager for Sprites and Upper Atmospheric Lightning (ISUAL) was the first specifically dedicated instrument to observe lightning‐induced transient luminous events (TLE): sprites, elves, halos, and gigantic jets from space. The Imager is an intensified CCD system operating in the visible wavelength region with a filter wheel to select from six positions with filters. The Imager has a 5° × 20° (vertical times horizontal) field of view. The spectrophotometer (SP) is populated with six photometers with individual filters for emissions from the far ultraviolet to the near infrared. An array photometer with two channels operating in the blue and red provides altitude profiles of the emission over 16 altitude bins each. The Associated Electronics Package (AEP) controls instrument functions and interfaces with the spacecraft. ISUAL was launched 21 May 2004 into a Sun‐synchronous 890 km orbit on the Formosat‐2 satellite and has successfully been collecting data ever since. ISUAL is running on the nightside of the orbit and is pointed to the east of the orbit down toward the limb. The instrument runs continuously and writes data to a circular buffer. Whenever the SP detects a sudden signal increase above a preset threshold, a trigger signal is generated that commands the system to keep the data for about 400 ms starting from ~50 ms before the trigger. Over its lifetime of ~11 years the system recorded thousands of TLE and also successfully observed aurora and airglow. Key Points: ISUAL is the first dedicated science instrument for comprehensive, long‐term, and global transient luminous event observations from space Instrument includes CCD Imager, spectrophotometer, and array photometer for spatial and spectral characterization of TLE Operations aim at separating pure lightning from lightning accompanied by TLE