Calibration and Data Analysis for the SOLIS-VSM


The Vector Spectromagnetograph (VSM) instrument of the Synoptic Optical Long-term Investigations of the Sun (SOLIS) project will provide a unique 25-year record of synoptic solar observations with daily full-disk photospheric vector and high sensitivity longitudinal magnetograms. In addition, the VSM will produce daily full-disk chromospheric longitudinal magnetograms along with various He I 1083 nm parameter images. The VSM is being prepared for installation at a temporary site in Tucson for a comparison period with observations from the Kitt Peak Vacuum Telescope (KPVT). After the cross-calibration period, the VSM will replace the KPVT spectromagnetograph at Kitt Peak. We outline the various VSM data products, with emphasis on the calibration and data reduction efforts.

The data transmission and storage resources are such that the reduction of VSM data will be performed at the observing site on Kitt Peak. Reduced data products will be transmitted via a DS3 link from Kitt Peak to the National Solar Observatory’s digital archive in Tucson. During a typical observing day, three full- disk photospheric vector magnetograms will be available over the Internet in two stages: first, as a ``quick-look’’ product within 10 minutes of data acquisition, and then as a full Milne- Eddington (ME) inversion product within 12 hours of each observation. The quick-look parameters will include estimates of the magnetic field strength, azimuth and inclination based on Auer, Heasley, House (1977, Solar Physics 55, p. 47). The high- precision vector products will be determined with the High Altitude Observatory ME inversion technique implemented by Skumanich and Lites (1987, ApJ, 322, p.473). The flexible design of the VSM data handling system can incorporate future improvements under consideration (e.g., principal component analysis).

This research was supported in part by the Office of Naval Research Grant N00014-91-J-1040.

AAS/Solar Physics Division Meeting #34