We designed a low-cost flight instrument that images the full solar disk through two narrow band filters at the red nd blue 'wings' of the solar potassium absorption line. The images are produced on a 1024 X 1024 charge-coupled device with a resolution of 2 arcsec per pixel. Four filtergrams taken in a very short time at both wings in the left and right states of circular polarization are used to yield a Dopplergram and a magnetogram simultaneously. The noise-equivalent velocity associated with each pixel is less than 3 m/s. The measured signal is linearly proportional to the velocity in the range +/- 4000 m/s. The range of magnetic fields is from 3 to 3000 Gauss. The optical system of the instrument is simple and easily aligned. With a pixel size of 12 micrometers , the effective focal length is 126 cm. A Raleigh resolution limit of 4 arcsec is achieved with a 5-cm entrance apertures, providing an f/25 focal ratio. The foreoptic is a two-component telephoto lens serving to limit the overall optical length to 89 cm or less. The mass of the instrument is 14 kg. the power required is less than 30 Watts. The Compact Doppler Magnetograph can be used in space mission with severe mass and power requirements. It can also be effectively used for ground-based observations: large telescope, dome or other observatory facilities are not required.

Date Published: 2 November 1998
PDF: 10 pages
Proc. SPIE 3442, Missions to the Sun II, (2 November 1998); doi: 10.1117/12.330262

Published in SPIE Proceedings Vol. 3442:
Missions to the Sun II
Clarence M. Korendyke, Editor(s)