Chromospheric Helium-I Imaging Photometer (CHIP) to observe the Sun at 1083.0 nm

The Chromospheric Helium-I Imaging Photometer (CHIP) is a filtergraph that records the full disk of the Sun across the neutral Helium emission line at 1083.0 nm. The centerpiece of the instrument is a tuneable Lyot filter composed of liquid crystal variable retarders (LCVRs) devised to observe the full disk of the Sun at multiple points across the 1083.0 nm Helium-I emission line at a cadence of 3 minutes. The filter has a free spectral range of 2.35 nm and a spectral resolution of 0.135 nm. Seven spectral positions from 1082.74 nm thru 1083.31 nm are recorded within 2 seconds The CHIP field-of-view (FOV) is approximately 1.8 solar radii across with a CCD pixel size of 2.29 arcseconds. CHIP operated from September 29, 1996 until August 2, 2013.

CHIP data products consist of: 1) full disk Helium 1083 nm line center images with 1024 x 1024 pixels in fits and gif format with filenames containing ‘chp.hsh’; 2) full disk Helium 1083 nm ‘doppler’ images with 1024 x 1024 pixels in fits and gif format with filenames containing ‘chp.bsh’. The Doppler images are produced by combining the 7 spectral positions across the line from 1082.74 nm in the far blue wing to 1083.31 nm in the far red wing. The low spectral resolution (0.135 nm) limits the integrity of the Doppler reconstructions.

All CHIP data are available on the MLSO web page and can be used to identify and track solar prominences, filaments and their eruptions, chromospheric waves produced by flares and CMEs, coronal holes, sunspots, active regions and variations in chromospheric structure over the solar cycle.