Instrument Calibration of the Interface Region Imaging Spectrograph (IRIS) Mission

J.-P Wülser,C Madsen,S Mckillop,N Schanche,P Bryans,S Jaeggli,M Wiesmann,W Liu,R Timmons,T Tarbell,S Brannon,C Kankelborg,P Testa,P Boerner,S Freeland,S Saar,B De Pontieu,J Prchlik

doi:10.1007/s11207-018-1364-8

Abstract

The Interface Region Imaging Spectrograph (IRIS) is a NASA small explorer mission that provides high-resolution spectra and images of the Sun in the 133 – 141 nm and 278 – 283 nm wavelength bands. The IRIS data are archived in calibrated form and made available to the public within seven days of observing. The calibrations applied to the data include dark correction, scattered light and background correction, flat fielding, geometric distortion correction, and wavelength calibration. In addition, the IRIS team has calibrated the IRIS absolute throughput as a function of wavelength and has been tracking throughput changes over the course of the mission. As a resource for the IRIS data user, this article describes the details of these calibrations as they have evolved over the first few years of the mission. References to online documentation provide access to additional information and future updates.

Highlights

Background Properties the Interface Region Imaging Spectrograph (IRIS) telescope rejects most of the incoming solar IR–V, a small portion is passed to the entrance of the spectrograph and slit-jaw imager
The IRIS telescope rejects most of the incoming solar IR–V, a small portion is passed to the entrance of the spectrograph and slit-jaw imager
A second contributor is light that is first reflected off the slit-jaws toward the slit-jaw imager and back to the slit-prism by one of the NUV filters in the filter wheel

Summary

Introduction

Background Properties the IRIS telescope rejects most of the incoming solar IR–V, a small portion is passed to the entrance of the spectrograph and slit-jaw imager. A second contributor is light that is first reflected off the slit-jaws toward the slit-jaw imager and back to the slit-prism by one of the NUV filters in the filter wheel Most of this light is reflected back out through the telescope, but a residual fraction enters the spectrograph again through imperfections in the light trap around the slit. The background does seem to be present in the NUV channel as well, but it is more difficult to separate from the bright and highly structured spectrum around the Mg II lines. It is less prominent because of the lower gain setting of the NUV camera amplifier

Objectives

Results

Discussion

Conclusion