Calibrated H i Lyman α Observations with TRACE

Abstract

Since shortly after launch in April 1998, the Transition Region and Coronal Explorer (TRACE) observatory has amassed a collection of H i Lα (1216 A) observations of the Sun that have been not only of high spatial and temporal resolution, but also span a duration in time never before achieved. The Lα images produced by TRACE are, however, composed of not only the desired line emission, but also local ultraviolet continuum and longer wavelength contamination. This contamination has frustrated attempts to interpret TRACE observations in H i Lα. The Very Advanced Ultraviolet Telescope (VAULT) sounding rocket payload was launched from White Sands Missile range 7 May 1999 at 20:00 UT. The VAULT telescope for this flight was a dedicated H i Lα imaging spectroheliograph. We use TRACE observations in the 1216 A and 1600 A channels along with observations from the VAULT flight to develop a method for removing UV continuum and longer wavelength contamination from TRACE Lα images.